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Title: The Cambridge natural history, Vol. 08 (of 10)
Editor: S. F. Harmer
Author: Hans Gadow
Editor: Sir A. E. Shipley
Release date: June 21, 2024 [eBook #73885]
Language: English
Original publication: London: Macmillan and Co, 1909
Credits: Keith Edkins, Peter Becker and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK THE CAMBRIDGE NATURAL HISTORY, VOL. 08 (OF 10) ***
Transcriber's note: Text enclosed by underscores is in italics (_italics_).
A single underscore introduces a subscript (CO_2), and a caret a
superscript (B^1).
Page numbers enclosed by curly braces (for example: {25}) have been
incorporated to facilitate the use of the Alphabetical Index and other page
references in the text.
* * * * *
THE
CAMBRIDGE NATURAL HISTORY
EDITED BY
S. F. HARMER, Sc.D., F.R.S., Fellow of King's College, Cambridge;
Superintendent of the University Museum of Zoology
AND
A. E. SHIPLEY, M.A., Fellow of Christ's College, Cambridge; University
Lecturer on the Morphology of Invertebrates
VOLUME VIII
[Illustration]
MACMILLAN AND CO., LIMITED
LONDON . BOMBAY . CALCUTTA
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NEW YORK . BOSTON . CHICAGO
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TORONTO
_Frontispiece._ PHYSICAL FEATURES OF THE WORLD AFFECTING THE GEOGRAPHICAL
DISTRIBUTION OF AMPHIBIA AND REPTILES.
AMPHIBIA AND REPTILES
By HANS GADOW, M.A. (Cantab.), Ph.D. (Jena), F.R.S., Strickland Curator
and Lecturer on Advanced Morphology of Vertebrata in the University of
Cambridge.
MACMILLAN AND CO., LIMITED
ST. MARTIN'S STREET, LONDON
1909
_First Edition 1901_
_Reprinted 1909_
{v}PREFACE
Linnaeus had but a poor opinion of the Amphibia and their describers, or he
would not have called the former "pessima tetraque animalia," nor would he
have dismissed the latter with the terse remark: "Amphibiologi omnium
paucissimi sunt nullique veri." That was, however, nearly 150 years ago;
and at the present time there are fewer difficulties in writing a book on
Amphibia and Reptiles. Those who care for the study of Amphibia and
Reptiles–the Herpetologists, to give them their scientific title–have never
been numerous; but most of them have been serious students. One reason for
the fact that this branch of Natural History is not very popular, is a
prejudice against creatures some of which are clammy and cold to the touch,
and some of which may be poisonous. People who delight in keeping Newts or
Frogs, Tortoises or Snakes, are, as a rule, considered eccentric. But in
reality these cold-blooded creatures are of fascinating interest provided
they are studied properly. The structure of animals is intimately connected
with their life-habits; and this correlation is perhaps more apparent in
Amphibia and Reptiles than in any other class. The anatomist who studies
internal and external structure is as much struck with the almost endless
variety in details as he who takes the trouble to observe the living animal
in its native haunts, or at least under conditions not too unnatural. He
will agree with V. von Scheffel's Toad "that those above seem to have no
{vi}notion of the beauties of the swamp"–brilliantly coloured Newts engaged
in amorous play, concert-giving Frogs, and metamorphosing Tadpoles. The
motto assigned to the Reptiles seems singularly appropriate when we
consider that poisonous snakes have been developed from harmless forms, and
that many kinds of reptiles have lost limbs, teeth, and eyesight in the
process of evolution.
The present work is intended to appeal to two kinds of readers–to the
field-naturalist, who, while interested in life-histories, habits, and
geographical distribution, beauty or strangeness of forms, is indifferent
to the homologies of the metasternum or similar questions;–and to the
morphologist, who in his turn is liable to forget that his specimens were
once alive.
A great portion of the book is anatomical and systematic. It was necessary
to treat anatomy, especially that of the skeleton, somewhat fully, since it
has long been recognised that it is impossible to base a scientific
classification upon external characters. The reader familiar with
Vertebrate anatomy has a right to expect that questions of special
morphological interest will be dwelt upon at length. Those who have no
anatomical foundation must be referred to one of the now numerous
introductory manuals on the subject.
The account of the Amphibia is more complete than that of the Reptilia. It
was possible to diagnose practically all the recent genera; and this has
been especially done in the Anura, in order to show how in an otherwise
very homogeneous group almost any part of the body, internal or external,
can be modified in kaleidoscopic variety. The same could not be done with
the Reptilia. Their principal groups,–called sub-classes in the present
work, in order to emphasise their taxonomic importance in comparison with
the main groups of Birds and Mammals,–differ so much from each other that
it was decided to refrain {vii}from attempting a general account of them.
Moreover, the number of species of recent lizards and snakes is so
bewildering, the genera of many families being but tedious variations of
the same theme, that only those forms have been described which are the
most important, the most striking, or which the traveller is most likely to
come across. The student who wishes to go farther into systematic details
must consult the seven volumes of the _Catalogue of Reptiles in the British
Museum_ (London, 1889-1896). Mr. G. A. Boulenger, the author of this
magnificent series, has rendered the systematic treatment of recent
Amphibia and Reptiles an easy task. During many years of the most friendly
intercourse I have profited on countless occasions by his ever-ready
advice. Although he has kindly read the proofs of the part dealing with the
Amphibia it would be unfair to associate him with any of its shortcomings
or with contestable opinions, for which I alone am responsible.
Cope's large work on the Crocodilians, Lizards, and Snakes of North America
(_Rep. U.S. Nat. Mus. for 1898_ (1900)) has unfortunately appeared too late
to be used in the present work.
The drawings on wood were, with few exceptions, made by Miss M. E. Durham,
mostly from living specimens–a procedure which has to a great extent
determined the selection of the illustrations.
Since both the metric and the English systems of measurements have been
employed, it may be well to state for the convenience of the reader that
the length of a line of the text is four inches or approximately ten
centimeters.
I have frequently and freely quoted accounts of previous authors instead of
paraphrasing them. Especial thanks are due to Messrs. Longmans, Green, and
Co., and to Messrs. Murray, {viii}for their courteous permission to make
several long quotations from Sir J. E. Tennent's _Ceylon_, and from H. W.
Bates' _Naturalist on the River Amazons_.
Lastly, a remark about my Editors. Instead of being a source of annoyance
they have rendered me the greatest help.
H. GADOW.
CAMBRIDGE, _December 19, 1900_.
{ix}CONTENTS
PAGE
PREFACE v
SCHEME OF THE CLASSIFICATION ADOPTED IN THIS BOOK xi
PART I. AMPHIBIA
CHAPTER I
CHARACTERS AND DEFINITION—POSITION OF THE CLASS AMPHIBIA IN THE
PHYLUM VERTEBRATA—HISTORICAL ACCOUNT OF THE CLASSIFICATION OF
AMPHIBIA 3
CHAPTER II
SKELETON OF URODELA AND ANURA—SKIN—COLOUR-CHANGING MECHANISM—
POISON-GLANDS—SPINAL NERVES—RESPIRATORY ORGANS—SUPPRESSION
OF LUNGS—URINO-GENITAL ORGANS—FECUNDATION—NURSING HABITS—
DEVELOPMENT AND METAMORPHOSIS 11
CHAPTER III
NEOTENY—REGENERATION—TEMPERATURE—GEOGRAPHICAL DISTRIBUTION 63
CHAPTER IV
STEGOCEPHALI OR LABYRINTHODONTS—LISSAMPHIBIA—APODA 78
CHAPTER V
LISSAMPHIBIA (_CONTINUED_)—URODELA 94
CHAPTER VI
LISSAMPHIBIA (_CONTINUED_)—ANURA 138
PART II. REPTILIA {x}
CHAPTER VII PAGE
DEFINITION AND CHARACTERS—POSITION OF THE CLASS REPTILIA IN THE
PHYLUM VERTEBRATA—CLASSIFICATION—SKULL AND VERTEBRAE 277
CHAPTER VIII
PROREPTILIA—PROSAURIA—THEROMORPHA 285
CHAPTER IX
CHELONIA—ATHECAE—THECOPHORA 312
CHAPTER X
DINOSAURIA—CROCODILIA 412
CHAPTER XI
PLESIOSAURIA—ICHTHYOSAURIA—PTEROSAURIA—PYTHONOMORPHA 473
CHAPTER XII
SAURIA—AUTOSAURI OR LACERTILIA—LIZARDS 491
CHAPTER XIII
SAURIA (_CONTINUED_)—OPHIDIA—SNAKES 581
INDEX 651
{xi}SCHEME OF THE CLASSIFICATION ADOPTED IN THIS BOOK
CLASS AMPHIBIA.
Sub-Class. Order. Sub-Order. Family. Sub-Family.
STEGOCEPHALI (p. 78)
STEGOCEPHALI LEPOSPONDYLI (p. 80)
BRANCHIOSAURI (p. 80).
AISTOPODES (p. 81).
STEGOCEPHALI TEMNOSPONDYLI (p. 81)
STEGOCEPHALI TEREOSPONDYLI (p. 83)
LISSAMPHIBIA (p. 84)
APODA (p. 84)
COECILIIDAE (p.89).
URODELA (p. 94)
AMPHIUMIDAE (p. 97).
SALAMANDRIDAE (p. 102)
Desmognathinae (p. 102).
Plethodontinae (p. 103).
Amblystomatinae (p. 109).
Salamandrinae (p. 115).
PROTEIDAE (p. 132).
SIRENIDAE (p. 136).
ANURA (p. 138)
AGLOSSA (p. 143).
PHANEROGLOSSA (p. 152)
DISCOGLOSSIDAE (p. 152).
PELOBATIDAE (p. 160).
BUFONIDAE (p. 166).
HYLIDAE (p. 185)
Amphignathodontinae
(p. 188).
Hylinae (p. 189).
CYSTIGNATHIDAE (p. 209)
Hemiphractinae (p. 210).
Cystignathinae (p. 211).
Dendrophryniscinae
(p. 224).
ENGYSTOMATIDAE (p. 225)
Engystomatinae (p. 225).
Dyscophinae (p. 235).
Genyophryninae (p. 236).
RANIDAE (p. 237)
Ceratobatrachinae
(p. 237).
Raninae (p. 238).
Dendrobatinae (p. 272).
CLASS REPTILIA (p. 277).
PROREPTILIA (p. 285). _Eryops_ (p. 286). _Cricotus_ (p. 287).
Sub-Class. Order. Sub-Order. Family. Sub-Family.
PROSAURIA (p. 288)
MICROSAURI (p. 288).
PROSAURI (p. 290).
PROTOROSAURI (p. 290).
RHYNCHOCEPHALI (p. 292).
THEROMORPHA (p. 300)
PAREIASAURI (p. 304).
THERIODONTIA (p. 306).
ANOMODONTIA (p. 309).
PLACODONTIA (p. 311).
CHELONIA (p. 312)
ATHECA (p. 333)
SPHARGIDAE (p. 333).
THECOPHORA (p. 338)
CRYPTODIRA (p. 338)
CHELYDRIDAE (p. 338).
DERMATEMYDIDAE (p. 341).
CINOSTERNIDAE (p. 342).
PLATYSTERNIDAE (p. 345).
TESTUDINIDAE (p. 345).
CHELONIDAE (p. 378).
PLEURODIRA (p. 388)
PELOMEDUSIDAE (p. 390).
CHELYDIDAE (p. 399).
CARETTOCHELYDIDAE (p. 404).
TRIONYCHOIDEA (p. 404)
TRIONYCHIDAE (p. 404).
DINOSAURIA (p. 412)
SAUROPODA (p. 418).
THEROPODA (p. 420).
ORTHOPODA (p. 424)
STEGOSAURI (p. 425).
ORNITHOPODA (p. 426)
CERATOPSIA (p. 430).
CROCODILIA (p. 431)
PSEUDOSUCHIA (p. 432).
PARASUCHIA (p. 433).
EUSUCHIA (p. 434)
TELEOSAURIDAE (p. 450).
METRIORHYNCHIDAE (p. 451).
MACRORHYNCHIDAE (p. 451).
GAVIALIDAE (p. 451).
ATOPOSAURIDAE (p. 453).
GONIOPHOLIDAE (p. 453).
CROCODILIDAE (p. 454).
PLESIOSAURIA (p. 473)
NOTHOSAURI (p. 476)
MESOSAURIDAE (p. 476).
NOTHOSAURIDAE (p. 477).
PLESIOSAURI (p. 477)
PLIOSAURIDAE (p. 477).
PLESIOSAURIDAE (p. 478).
ELASMOSAURIDAE (p. 478).
ICHTHYOSAURIA (p. 478)
ICHTHYOSAURI (p. 483).
PTEROSAURIA (p. 484)
PTEROSAURI (p. 486)
PTERODACTYLI (p. 486).
PTERANODONTES (p. 487).
PYTHONOMORPHA (p. 487)
DOLICHOSAURI (p. 489).
MOSASAURI (p. 489).
SAURIA (p. 491)
LACERTILIA (p. 491)
GECKONES (p. 502)
GECKONIDAE (p. 507)
Geckoninae (p. 507).
Eublepharinae (p. 512).
Uroplatinae (p. 512).
LACERTAE (p. 513)
AGAMIDAE (p. 515).
IGUANIDAE (p. 528).
XENOSAURIDAE (p. 536).
ZONURIDAE (p. 536).
ANGUIDAE (p. 537).
HELODERMATIDAE (p. 540).
LANTHANOTIDAE (p. 541).
VARANIDAE (p. 542).
XANTUSIIDAE (p. 547).
TEJIDAE (p. 547).
LACERTIDAE (p. 549).
GERRHOSAURIDAE (p. 559).
SCINCIDAE (p. 559).
ANELYTROPIDAE (p. 564).
DIBAMIDAE (p. 564).
ANIELLIDAE (p. 564).
AMPHISBAENIDAE (p. 565).
PYGOPODIDAE (p. 567).
CHAMAELEONTES (p. 567)
CHAMAELEONTIDAE (p. 573).
OPHIDIA (p. 581)
TYPHLOPIDAE (p. 593).
GLAUCONIIDAE (p. 594).
ILYSIIDAE (p. 594).
UROPELTIDAE (p. 595).
BOIDAE (p. 596)
Pythoninae (p. 598).
Boinae (p. 601).
XENOPELTIDAE (p. 605).
COLUBRIDAE (p. 606)
Aglypha (p. 606)
Acrochordinae (p. 606).
Colubrinae (p. 607).
Rhachiodontinae (p. 622).
COLUBRIDAE
Opisthoglypha (p. 623)
Dipsadomorphinae
(p. 623).
Elachistodontinae
(p. 625).
Homalopsinae (p. 625).
COLUBRIDAE
Proteroglypha (p. 625)
Elapinae (p. 626).
Hydrophinae (p. 635).
AMBLYCEPHALIDAE (p. 637).
VIPERIDAE (p. 637)
Viperinae (p. 638).
Crotalinae (p. 644).
PART I
AMPHIBIA
"'s scheint, dass die hier oben keine
Ahnung haben von dem Sumpf und
Seiner Pracht."
The "plattgedrückte Kröte,"
SCHEFFEL'S _Trompeter von Säkkingen_.
{3}CHAPTER I
AMPHIBIA
CHARACTERS AND DEFINITION–POSITION OF THE CLASS AMPHIBIA IN THE PHYLUM
VERTEBRATA–HISTORICAL ACCOUNT OF THE CLASSIFICATION OF AMPHIBIA
A bird is known by its feathers, a Beast by its hairs, a Fish by its fins,
but there is no such obvious feature which characterises the Amphibia and
the Reptiles. In fact, they are neither fish, flesh, nor fowl. This
ill-defined position is indicated by the want of vernacular names for these
two classes, a deficiency which applies not only to the English language.
All the creatures in question are backboned, creeping animals. Those which
are covered with horny scales, and which from their birth breathe by lungs
only, as Crocodiles, Tortoises, Lizards, and Snakes, are the Reptiles. The
rest, for instance, Newts or Efts, Frogs and Toads, are the Amphibia. Their
skin is mostly smooth and clammy and devoid of scales; the young are
different from the adult in so far as they breathe by gills and live in the
water, before they are transformed into entirely lung-breathing,
terrestrial creatures. But there are many exceptions. _Proteus_ and _Siren_
the mud-eel, always retain their gills; while not a few frogs undergo their
metamorphosis within the egg, and never breathe by gills. If we add the
tropical limbless, burrowing Coecilians, and last, not least, the
Labyrinthodonts and other fossil forms, the proper definition of the class
Amphibia,–in other words, the reasons for grouping them together into one
class, separated from the other backboned animals,–requires the examination
of many other characters.
{4}So far as numbers of living species are concerned, the Amphibia are the
least numerous of the Vertebrata. There are about 40 limbless, burrowing
APODA; 100 URODELA or tailed two- or four-footed newts, and about 900
ANURA, or tailless, four-footed frogs and toads; in all some 1000 different
species. Few, indeed, in comparison with the 2700 Mammals, 3500 Reptiles,
nearly 8000 Fishes, and almost 10,000 Birds. But we shall see that the
Amphibia have not only "had their day," having flourished in bygone ages
when they divided the world, so far as Vertebrata were concerned, between
themselves and the Fishes, but that they never attained a dominant
position. Intermediate between the aquatic Fishes and the gradually rising
terrestrial Reptiles they had to fight, so to speak, with a double front
during the struggle of evolution, until by now most of them have become
extinct. The rest persist literally in nooks and corners of the teeming
world, and only the Frogs and Toads, the more recent branch of the
Amphibian tree, have spread over the whole globe, exhibiting almost endless
variations of the same narrow, much specialised plan. The greatest charm of
the Anura lies in their marvellous adaptation to prevailing circumstances;
and the nursing habits of some kinds read almost like fairy-tales.
CHARACTERS OF THE AMPHIBIA.[1]
1. The vertebrae are (_a_) acentrous, (_b_) pseudocentrous, or (_c_)
notocentrous.
2. The skull articulates with the atlas by two condyles which are formed
by the lateral occipitals. For exceptions see p. 78.
3. There is an auditory columellar apparatus, fitting into the fenestra
ovalis.
4. The limbs are of the tetrapodous, pentadactyle type.
5. The red blood-corpuscles are nucleated, biconvex, and oval.
6. The heart is (_a_) divided into two atria and one ventricle, and (_b_)
it has a conus provided with valves.
7. The aortic arches are strictly symmetrical.
8. Gills are present at least during some early stages of development.
9. The kidneys are provided with persistent nephrostomes.
10. Lateral sense-organs are present at least during the larval stage.
11. The vagus is the last cranial nerve.
12. The median fins, where present, are not supported by spinal skeletal
rays.
13. Sternal ribs and a costal or true sternum are absent.
14. There is no paired or unpaired medio-ventral, copulatory apparatus.
15. Development takes place without amnion and allantois.
None of these characters is absolutely diagnostic, except 1 (_c_), and
this applies only to the Anura and most of the Stegocephali.
{5}Numbers 1 (_b_), 1 (_c_), 2, 3, 4 and 12 separate the Amphibia from
the Fishes.
Numbers 1, 6 (_b_), 7, 8, 9, 11, 13, 15 separate them from the
Reptiles, Birds, and Mammals.
Number 2 separates them from the Fishes, Reptiles, and Birds.
Number 5 separates them from the Mammals.
Number 6 (_a_) separates them from the Fishes (excl. Dipnoi), Birds and
Mammals.
We can, therefore, very easily define all the Amphibia, both recent and
extinct, by a combination of the characters enumerated above. For instance,
by the combination of numbers 2, 3 or 4 with either 7, 8, 9, 11, 13 or 15.
_Amphicondylous Anamnia_ would be an absolutely correct and all-sufficient
diagnosis, but it would be of little use in the determination of adult
specimens; and the tetrapodous character is of no avail for Apoda.
_Amphicondylous animals without an intracranial hypoglossal nerve_ is a
more practical diagnosis.
In the case of living Urodela and Anura the absence of any scales in the
skin affords a more popular character; it is unfortunately not applicable
to the Apoda, many of which possess dermal scales, although these are
hidden in the imbricating transverse rings of the epidermis; and the
frequent occurrence of typical scales of both ecto- and meso-dermal
composition in many of the Stegocephali forces us to discard the scales, or
rather their absence, as a diagnostic character of the class Amphibia. The
same applies to the mostly soft, moist, or clammy, and very glandular
nature of the skin.
THE POSITION OF THE CLASS AMPHIBIA IN THE PHYLUM VERTEBRATA.–There is no
doubt that the Amphibia have sprung from fish-like ancestors, and that they
in turn have given rise to the Reptilia. The Amphibia consequently hold a
very important intermediate position. It was perhaps not a fortunate
innovation when Huxley brigaded them with the Fishes as _Ichthyopsida_,
thereby separating them more from the _Sauropsida_ (= Reptilia and Aves),
than is justifiable,–perhaps more than he himself intended. The
connecting-link, in any case, is formed by the Stegocephali; all the recent
Orders, the Apoda, Urodela, and Anura, are far too specialised to have any
claims to the direct ancestral connections. The line leading from
Stegocephali to fossil Reptiles, notably to such Proreptilia as _Eryops_
and _Cricotus_, and even to the Lepospondylous Prosauria, is extremely
gradual, and the steps are almost imperceptible. Naturally, {6}assuming
evolution to be true, there must have lived countless creatures which were
a "rudis indigestaque moles," neither Amphibia nor Reptilia, in the present
intensified sense of the systematist. The same consideration applies
equally to the line which leads downwards to the Fishes. But the great gulf
within the Vertebrata lies between Fishes and Amphibia, between absolutely
aquatic creatures with internal gills and "fins," and terrestrial,
tetrapodous creatures, with lungs and fingers and toes. On the side of the
fishes only the Dipnoi and the Crossopterygii come into consideration.
The piscine descent of the Amphibia is still proclaimed by the following
features.–(1) The possession by the heart of a long conus arteriosus,
provided with, in many cases, numerous valves, or at least (Anura) one
series at the base, another at the beginning of the truncus where the
arterial arches branch off; (2) the strictly symmetrical arrangement of
these arches; (3) the trilocular heart is still like that of the
Lung-fishes or Dipnoi; (4) the occurrence of as many as four or even five
branchial skeletal arches in the larval stage; (5) the glottis is supported
by cartilages which themselves are derivatives of posterior visceral
arches; (6) the development of the vertebrae (Stegocephali and Urodela)
from four pairs of arcualia, and the formation of the intervertebral joints
by a split across the intervertebral ring of cartilage: this feature is
unknown in Reptilia, but it occurs also in _Lepidosteus_, most probably
also in _Polypterus_; (7) the hypoglossal still retains the character of a
post-cranial or cervical spinal nerve; (8) the presence of lateral
sense-organs; (9) the possession of external gills is of somewhat doubtful
phylogenetic value, although such gills occur amongst fishes only in Dipnoi
and Crossopterygii. It is not unlikely that in the Amphibia these organs
owe their origin to entirely larval requirements, while the suctorial mouth
of the larvae of the Anura and many fishes has certainly no ancestral
meaning, but is a case of convergent development.
The usual diagnoses of the Amphibia contain the statement that they, or
most of them, undergo a metamorphosis, or pass through a larval stage. The
same applies to various fishes; while, on the other hand, the larval (not
ancestral) stage has become permanent in the Proteidae and Sirenidae; and
lastly, we cannot well speak of larvae in the viviparous _Salamandra atra_.
{7}THE EVOLUTION OF AN ADEQUATE CLASSIFICATION OF THE AMPHIBIA has been a
long process. Even their recognition as a class, separate from, and of
equal rank with that of, the Reptilia, was by no means generally accepted
until comparatively recent times. A historical sketch of the laborious,
often painful, striving for light, in France and Germany, then in England,
and lastly in America, is not without interest.
The term _Amphibia_ was invented by Linnaeus for the third class of
animals in his famous "Systema Naturae." It comprises a very queer
assembly, which, even in the 13th edition (1767), stands as follows:–
1. REPTILES PEDATI, with the four "genera" _Testudo_, _Draco_,
_Lacerta_, and _Rana_. _Lacerta_ includes Crocodiles, Lizards, and
Newts!
2. SERPENTES APODES.
3. NANTES PINNATI. Elasmobranchs, Sturgeons, Lampreys, and various
other fishes.
Laurenti, 1768, in a dissertation entitled "Specimen medicum, exhibens
Synopsin Reptilium ...," uses Brisson's term, REPTILES, and divides them
into:–
REPTILIA SALIENTIA, these are the Anura.
GRADIENTIA, namely the Urodela and Lizards.
SERPENTIA, the Snakes and the Apoda.
Brongniart, 1800, "Essay d'une classification naturelle des Reptiles,"[2]
distinguishes:–
CHELONII, SAURII, OPHIDII, BATRACHII; the last for the Frogs, Toads,
and Newts.
Latreille, 1804, "Nouveau Dict. Hist. Nat." xxiv.,[3] accepts the four
Orders of Brongniart's "Reptiles," but clearly separates the fourth
Order, "BATRACHII," from the rest by the following, now time-honoured,
diagnosis: _Doigts des pattes n'ayant pas d'ongles; des branchies, du
moins pendant un temps; des métamorphoses_. But there is not one word
about "Amphibia" in opposition to "Reptilia."
Duméril, 1806, "Zoologie analytique" (p. 90), and "Élémens de l'histoire
naturelle," 1807, divides the "Reptiles batraciens," or "Batracii," into
ECAUDATI and CAUDATI; he also introduces the terms "ANOURES" and
"URODÈLES" as their equivalents; but since these terms appear in the
French form purists do not admit their having any claim to recognition!
Oppel, 1811, "Die Ordnungen, Familien und Gattungen der Reptilien,"
establishes the term APODA for the Coeciliae, and recognises their
affinity to the Ecaudata and Caudata by removing them from the Snakes.
De Blainville, 1816, "Prodrome d'une nouvelle distribution du règne
animal"[4]–
AMPHIBIENS SQUAMIFÈRES. [The Reptilia.]
" NUDIPELLIFÈRES s. Ichthyoides. [The Amphibia.]
{8}Merrem, 1820, "Tentamen systematis Amphibiorum."
PHOLIDOTA. [The Reptilia.]
BATRACHIA: _APODA_.
_SALIENTIA_.
{ Mutabilia [with metamorphosis, _e.g._
_GRADIENTIA_ { Newts.]
{ Amphipneusta [Perennibranchiate Urodeles.]
F. S. Leuckart, 1821, "Einiges ueber die fischartigen Amphibien."[5]
MONOPNOA. [The Reptilia.]
{ with temporary gills: Ecaudata + Caudata pt.
DIPNOA. [The Amphibia] { with permanent gills: "Proteidae," _Menopoma_
{ and _Amphiuma_.
Latreille, 1825, "Familles naturelles du règne animal." The Vertebrata
are divided into _Haematherma_ and _Haemacryma_. These terms for warm and
cold-blooded creatures were later on amended by Owen to _Haematotherma_
and _Haematocrya_. The latter are divided by Latreille as follows:–
REPTILIA. Still including the Coeciliae amongst the Snakes.
AMPHIBIA { Caducibranchiata.
{ Perennibranchiata.
PISCES.
Wagler, 1830, "Systema Amphibiorum."
TESTUDINES, CROCODILI, LACERTAE, SERPENTES, ANGUES, COECILIAE, RANAE,
ICHTHYODI.
RANAE I. _AGLOSSA._
" II. _PHANEROGLOSSA_: 1. Cauda nulla. [The Anura.]
" " 2. Cauda distincta. [The Salamandridae.]
ICHTHYODI I. _ABRANCHIALES._ _Menopoma_ [_Cryptobranchus_] and
_Amphiuma_.
" II. _BRANCHIALES._ [The Perennibranchiate Urodela.]
J. Müller, 1831, "Beiträge zur Anatomie ... der Amphibien."[6]
GYMNOPHIONA, DEROTREMATA, PROTEIDAE, SALAMANDRINA, BATRACHIA.
J. Bell, 1836, Todd's "Cyclopaedia of Anatomy and Physiology," Art.
"Amphibia."
AMPHIPNEUSTA, the Perennibranchiate Urodeles; ANOURA, URODELA;
ABRANCHIA, _Menopoma_ and _Amphiuma_; APODA.
Stannius, 1856, "Handbuch der Zootomie: Anatomie der Wirbelthiere." (2nd
ed.)
AMPHIBIA MONOPNOA. The Reptilia.
AMPHIBIA DIPNOA. 1. URODELA. _PERENNIBRANCHIATA._
_DEROTREMATA_: _Amphiuma_ and _Menopoma_.
_MYCTODERA._[7]
{9} 2. BATRACHIA. _AGLOSSA._
_PHANEROGLOSSA_: Systomata =
Engystomatidae.
Bufoninae. Without manubrium sterni.
Raninae. With manubrium.
Hyloidea. With adhesive finger-discs.
_GYMNOPHIONA._
Gegenbaur, 1859, "Grundzüge der vergleichenden Anatomie."
AMPHIBIA as a separate class, equivalent to that of the REPTILIA, are
divided into the four Orders: _PERENNIBRANCHIATA_, _SALAMANDRINA_,
_BATRACHIA_, and _GYMNOPHIONA_. In the second edition of the
"Grundzüge" (1870) they are divided into _URODELA_, _ANURA_, and
_GYMNOPHIONA_.
Huxley, 1864, "The Elements of Comparative Anatomy."
MAMMALS.
SAUROIDS, subsequently changed into SAUROPSIDA = Reptilia + Aves.
ICHTHYOIDS, " " ICHTHYOPSIDA = Amphibia + Pisces.
Haeckel, 1866, "Generelle Morphologie."
Amphibia. A. PHRACTAMPHIBIA s. Ganocephala = Labyrinthodonta + Peromela
[Apoda].
B. LISSAMPHIBIA s. Sozobranchia = Sozura [Urodela] + Anura.
Cope, 1869.[8]
STEGOCEPHALI, GYMNOPHIDIA, URODELA, PROTEIDEA, TRACHYSTOMATA, ANURA.
Huxley, 1871, "A Manual of the Anatomy of Vertebrated Animals."
Amphibia I. SAUROBATRACHIA [v.d. Hoeven's term] s. URODELA
1. Proteidea.
2. Salamandridae.
II. LABYRINTHODONTA.
III. GYMNOPHIONA.
IV. BATRACHIA s. ANURA.
Boulenger, 1882, "Catalogue of the BATRACHIA GRADIENTIA s. CAUDATA and
BATRACHIA APODA," divides the Caudata simply into: _SALAMANDRIDAE_,
_AMPHIUMIDAE_, _PROTEIDAE_, and _SIRENIDAE_.
1882, "Cat. Batrachia Salientia s. Ecaudata," see p. 140.
Cope, 1890, "Synopsis of the Families of Vertebrata."[9]
CLASS BATRACHIA.
Sub-Class I. STEGOCEPHALI.
Order 1. Ganocephali: _Trimerorhachis_, _Archegosaurus_.
2. Rhachitomi: _Eryops_.
3. Embolomeri: _Cricotus_.
4. Microsauri: _Branchiosaurus_, _Hylonomus_, etc.
{10} Sub-Class II. URODELA.
Order 1. Proteidae: _Proteus_.
2. Pseudosauria. [All the rest of the Urodela +
Coeciliidae.]
3. Trachystomata: Sirenidae.
Sub-Class III. SALIENTIA.
P. and F. Sarasin, 1890, "Zur Entwicklungsgeschichte der Ceylonesischen
Blindwühle, Ichthyophis glutinosa."[10]
Sub-Class I. ARCHAEOBATRACHI s. STEGOCEPHALI.
II. NEOBATRACHI.
Order 1. _URODELA._
_a_. Salamandroidea. [The Urodela.]
_b_. Coeciloidea = Amphiumidae + Coeciliidae.
2. _ANURA._
The classification adopted in this volume is as follows:–
CLASS AMPHIBIA.
Sub-Class I. Phractamphibia.
Order I. Stegocephali Lepospondyli.
Sub-order 1. Branchiosauri.
Sub-order 2. Aistopodes.
Order II. Stegocephali Temnospondyli.
Order III. Stegocephali Stereospondyli.
Sub-Class II. Lissamphibia.
Order I. Apoda.
Order II. Urodela.
Order III. Anura.
Sub-order 1. Aglossa.
Sub-order 2. Phaneroglossa.
{11}CHAPTER II
SKELETON OF URODELA AND ANURA–SKIN–COLOUR-CHANGING MECHANISM–
POISON-GLANDS–SPINAL NERVES–RESPIRATORY ORGANS–SUPPRESSION OF LUNGS–
URINO-GENITAL ORGANS–FECUNDATION–NURSING HABITS–DEVELOPMENT AND
METAMORPHOSIS
SKELETON OF THE URODELA
THE VERTEBRAL COLUMN.–The number of vertebrae is smallest in the
terrestrial, greatest in the entirely aquatic forms, and is exceptionally
large in the eel-shaped _Amphiuma_. In the following table the sacral
vertebra is included in those of the trunk.
Trunk. Tail.
_Siren lacertina_ 22 35 +
_Necturus maculatus_ 19 29
_Proteus anguinus_ 30 28 +
_Cryptobranchus alleghaniensis_ 20 or 21 24 +
_C. scheuchzeri_ 21
_C. japonicus_ 22 22 to 26
_Amphiuma means_ 63 35 +
_Amblystoma tigrinum_ 17 or 16 32 +
_Salamandra maculosa_ 17 27
_Triton cristatus_ 17 36
_Triton taeniatus_ 14 or 15 36 +
_Triton palmatus_ 14 23 to 25
_Salamandrina perspicillata_ 15 32 to 42
_Spelerpes fuscus_ 16 23
The vertebrae of the Urodela and those of the Apoda differ from those of
all the other Tetrapoda[11] by possessing no special centra or bodies. That
part which should correspond with the centrum is formed either by the
meeting and subsequent complete co-ossification of the two chief dorsal and
ventral pairs of arcualia {12}(tail-vertebrae), or entirely by the pair of
chief dorsal arcualia. There is consequently no neuro-central suture.
Moreover, the central region of each vertebra is strongly pinched in
laterally, widening towards the ends. Another feature of the vertebral
column of the Urodela is the possession of a considerable amount of
intervertebral cartilage, by which the successive vertebrae are held
together. This cartilage does not ossify, and it either remains continuous,
serving in its entirety and owing to its flexibility as a joint, or it
becomes more or less imperfectly separated into a cup and ball portion, the
cup belonging to the posterior end of the vertebra. Such joints are called
opisthocoelous, and occur in the Desmognathinae and Salamandrinae. In the
adult the cup and ball frequently calcify, and the chorda dorsalis or
notochord is completely destroyed. Those vertebrae between which the
intervertebral cartilage remains unbroken, are called amphicoelous, since
in them, most obviously in macerated or dried skeletons, the vertebrae
appear hollowed out at either end. In such amphicoelous vertebrae a
considerable amount of the chorda always remains, running in an unbroken
string through the whole length of the vertebral column. Towards adult life
the chorda becomes constricted, and is ultimately squeezed out or
destroyed, in the middle of the vertebra, by the invasion of cartilage from
the chief arcualia. This intravertebrally situated cartilage has been
described erroneously as chordal cartilage.
The development of the vertebrae proceeds as follows. First appear a pair
of basidorsalia and a pair of basiventralia (Fig. 1, 1, B.D, B.V), blocks
of cartilage, imbedded in and resting upon the thin sheath of the chorda
dorsalis. Next appears a pair of interdorsal blocks, immediately behind the
basidorsals; and somewhat later appears a pair of interventral blocks.
These four pairs of cartilages or "arcualia" each meet, above or below the
chorda, and form semi-rings, which again by extending upwards or downwards
fuse into complete rings, in such a way that the interdorsal and
interventral elements form the intervertebral mass spoken of above. The
basidorsals fuse with the basiventrals, and form the body of the vertebra,
the fusion being effected chiefly by the calcification and ossification of
the lateral connecting portion of the skeletogenous layer. The basidorsalia
form the neural arches with their unpaired short spinous or neural, and the
paired anterior and posterior zygapophysial processes. Concerning the
{13}basiventralia we have to distinguish between the trunk and the tail. In
the latter they produce a pair of ventral outgrowths or haemapophyses,
which ultimately enclose the caudal blood-vessels. In the trunk the
basiventral blocks of cartilage are suppressed; they appear in the early
larvae, but disappear during or even before metamorphosis.
[Illustration: FIG. 1.–1-5, Five successive stages of the development of a
caudal vertebra of a newt; 6-7, the second and the first cervical vertebra
of _Cryptobranchus_; 8-9, side view of the constituent cartilaginous blocks
of a caudal vertebra (8) and a trunk-vertebra (9) of _Archegosaurus_ as
typical examples of Temnospondylous quadripartite and tripartite vertebrae.
The cross-hatched parts indicate the articular facets for the ribs. The
anterior end of all the vertebrae looks towards the right side. _af_, In 7,
articulating facet for the occipital condyle; _B.D_, basidorsal piece or
neural arch; _B.V_, basiventral piece or ventral arch; _Ch_, chorda
dorsalis, or notochord; _I.D_, interdorsal piece; _I.V_, interventral
piece; _I.V.L_, intervertebral ligament; _N_, spinal nerve–these are
numbered I, II, III in 6 and 7; _R_, rib; _T_, in 7, rib-like tubercle on
the first vertebra.]
Towards the end of the tail the vertebrae diminish in size, and their
constituent cartilages assume a more and more indifferent shape, until they
become confluent into a continuous rod of cartilage, resembling in this
respect the Dipnoi and Holocephali. A periodical revival of this rod, at
least of its connective tissue, appears in the tail-filament of the male
_Triton palmatus_ during the breeding-season.
The first vertebra, called the atlas, because it carries the head, is
remarkable for the possession of an odontoid process. The latter is formed
by a pair of cartilages and represents part of a vertebra, the dorsal
portion of which seems to have been added to the occipital part of the
cranium.
{14}All the trunk-vertebrae, with the exception of the atlas, carry ribs,
at least vestiges thereof. Owing to the early disappearance of the
basiventral cartilages the capitular portions of the ribs are much reduced,
and are mostly represented by strands of connective tissue only. The ribs
develop therefore occasionally at some distance from the vertebral column,
and that portion of the rib which in the metamorphosed young newt looks
like the capitulum is to a great extent really its tuberculum. Witness the
position of the vertebral artery, which still indicates the true foramen
transversarium. The homologies of these parts are still more obscured by
the fact that a new process grows out from the rib, by which the latter
gains a new support upon a knob of the neural arch. Thus an additional
foramen is formed, sometimes confounded with the true transverse canal. The
meaning which underlies all these modifications is the broadening of the
body, the ribs shifting their originally more ventral support towards the
dorsal side. The whole process is intensified in the Anura; it is an
initial stage of the notocentrous type of vertebrae. The transverse
ossified processes of the adult are often much longer than the vestiges of
the ribs themselves, and are somewhat complicated structures. They are
composed first of the rib-bearing cartilaginous outgrowths of the neural
arches; secondly, of a broad string of connective tissue which extends from
the ventro-lateral corner of the perichordal skeletogenous layer to the
ribs.
[Illustration: FIG. 2.–Transverse section through a trunk-vertebra of a
larva of _Salamandra maculosa_, enlarged. The right side shows the actually
existing state, while on the left side the rib and its attachments are
restored to their probable original condition. _A_, Vertebral artery within
the true transverse canal; _B.V_, remnant of the basi-ventral cartilage;
_Ch_, chorda dorsalis; _Sp.c_, spinal canal; *, the false transverse
canal.]
The SHOULDER-GIRDLE is extremely simple. It remains almost entirely
cartilaginous, and the three constituent elements are not separated by
sutures. Ossification is restricted to the base of the shaft of the
scapula, and may extend thence over the glenoid cavity. The coracoids are
broad, loosely overlap each other, and are "tenon and mortised" into the
triangular or lozenge-shaped {15}cartilaginous sternum, which latter has no
connection with the ribs. The precoracoid is a large, flat process,
directed forwards, not meeting its fellow; it is absent in _Siren_.
The humerus articulates with both radius and ulna, and these two bones of
the forearm remain separate. The elements which compose the wrist and hand
exhibit an almost ideally simple arrangement, slightly varied by the
frequent fusion of two or more neighbouring carpalia into one, and by the
reduction of the number of fingers. Most frequently the intermedium and the
ulnar carpal element fuse together, and there is more often one centrale
instead of two. The wrist and hand of the Urodela represent, however, no
longer the entirely primitive pentadactyle type, owing to the loss of one
finger together with its metacarpal and carpal element. Comparison with the
Anura makes it probable that the Urodela have lost the pollex, their four
fingers being consequently the 2nd, 3rd, 4th, and 5th. _Siren_ has four or
three fingers; _Proteus_ has only three fingers and three large compound
carpal cartilages. In _Amphiuma_, with either three or two fingers, the
ulnare, intermedium, and carpale are fused together, the radiale with the
neighbouring carpale. The number of phalanges in the four-fingered species
is generally 2, 3, 3, 2 respectively.
The PELVIC GIRDLE.–The ilium stands vertically to the vertebral axis,
slanting slightly forwards and downwards. It is attached by means of a rib
to only one vertebra, and this ilio-sacral connection is acetabular in its
position, _i.e._ it lies in the same transverse plane with the acetabulum,
in other words vertically above it. The ventral portion of the pelvis is
formed by one large continuous mass, the united pubo-ischia, the anterior
or pubic portion of which extends forwards in the shape of a broad triangle
(_Necturus_) or as a slender, stalked, Y-shaped cartilage, the epipubis,
which is often movably jointed at its base. The lateral portion of the
pubic cartilage is always perforated by the nervus obturatorius.
Ossification is restricted to the ischium and to the middle of the shaft of
the ilium. The acetabular fossa for the femur is closed. The tibia and
fibula remain separate. The foot is still more primitive than the anterior
extremity, as the majority of Urodela possess the full complement of five
toes, with 2, 2, 3, 3, 2 phalanges respectively. Concrescence of the
tarsalia applies most frequently to the fourth and fifth distal {16}and to
the two centralia; exceptional, for instance, in _Cryptobranchus
japonicus_, are as many as three centralia, but this is an individual, even
a one-sided variation, as shown for instance by a specimen in the Cambridge
Museum. Loss of the fifth toe occurs sporadically in genera of different
groups, namely, in _Salamandrella_, _Batrachyperus_, _Salamandrina_,
_Necturus_, _Manculus_, _Batrachoseps_. In _Amphiuma_ the number is reduced
to three or two; in _Proteus_ to two; and in _Siren_ the hind limbs, with
their girdle, are altogether absent. Lastly, in some species of _Spelerpes_
and _Batrachoseps_ both fore and hind limbs have become so small as to be
practically without function, parallel cases being found among various
Scincidae and other Lizards.
The HYOID APPARATUS is still very primitive in many, especially in larval,
Urodela. Besides the hyoid there are as many as four pairs of branchial
arches, which, however, decrease in size and completeness, so that the last
two have lost their connection with the median copular piece, and become
attached in various ways to the second branchial arch. This is the
arrangement apparently in all larvae, but four pairs of branchials persist
in the adult _Siren_, _Amphiuma_, and _Cryptobranchus alleghaniensis_. The
whole branchial apparatus is reduced to three pairs of arches in _Necturus_
and _Proteus_, to two in the adult _Cryptobranchus japonicus_ and in the
Salamandridae. Of considerable interest is the vestige of a fifth pair of
arches in the larvae of _Triton_ and _Salamandra_, in the shape of a pair
of tiny cartilages, which lie in front and on each side of the opening of
the trachea, and give rise to the formation of the laryngeal cartilages,
better developed in the higher Vertebrata.
The following are noteworthy characters of the SKULL OF URODELA. The
articulation of the skull with the vertebral column is not always effected
entirely by the two condyles of the lateral occipital bones, but the median
basal cartilage often possesses a pair of facets for the odontoid-like
process of the first vertebra; such additional facets are perhaps best
developed in _Cryptobranchus_ and in the Salamandrinae.
The middle portion of the primitive cranium, from the exit of the optic
nerve to the ethmoid cartilage, is formed by a pair of separate bones, the
orbito-sphenoids. The parietal and frontal bones remain separate. One or
more periotic bones exist, besides the prootic, in the aquatic families.
{17}A pair of prefrontal bones is present in most Salamandridae, e.g.
_Salamandra_, _Triton_, _Amblystoma_, especially in the larva, and in
_Cryptobranchus_; these bones are absent in _Amphiuma_, _Necturus_,
_Proteus_, and _Siren_.
[Illustration: FIG. 3.–Skulls of various Urodela. 1, _Salamandra maculosa_,
ventral view, and 2, dorsal view; 3, Axolotl stage of _Amblystoma_; 4,
adult stage of _Amblystoma_; 5, _Salamandrina perspicillata_ (after
Wiedersheim); 6, _Salamandra maculosa_, dorsal view of the lower jaw. _A_,
Articulare; _C_{1}_, _C_{2}_, outer and inner occipital condyles; _Ch_,
choana or posterior nasal opening; _d_, dentary; _E_, ethmoid; _F_,
frontal; _LO_, lateral occipital; _M_, maxillary; _N_, nasal; _No_,
nostril; _OS_, orbito-sphenoid; _P_, parietal; _Pf_, prefrontal; _Pl_,
palatine; _Pm_, premaxillary; _Po_, prootic; _PS_, parasphenoid; _Pt_,
pterygoid; _Q_, quadrate; _S_, angulo-splenial; _Sq_, squamosal; _St_,
stapes; _Vo_, vomer; II, VII, X, exits of the optic, facial, and
glosso-vagus nerves.]
The lacrymalia are still separate in some Amblystomatinae, e.g. _Ranidens_
and _Hynobius_. A pair of nasalia are generally present, but are absent in
_Necturus_, _Proteus_, and _Siren_. The parasphenoid is furnished with
teeth in the Plethodontinae and Desmognathinae.
Separate palatine bones exist in _Necturus_ and _Proteus_, and in the larva
of _Amblystoma_, but in the adult form they fuse with the vomers, producing
the vomero-palatines characteristic of the majority of Urodela.
{18}The pterygoid bones are most fully developed, so as to reach the
vomero-palatines, in the Amblystomatinae, in _Necturus_, and in _Proteus_;
they are reduced, so as to leave a gap, in _Cryptobranchus_, and still more
in the Salamandrinae; they are absent in _Amphiuma_ and in _Siren_.
The quadrates are directed forwards in _Necturus_, _Proteus_, and _Siren_,
while in the other Urodela they extend transversely and almost
horizontally. The hyomandibular remnant, the so-called operculum, is small,
and forms a plate which fits into the fenestra ovalis, extending as a
ligamentous process upon the quadrate.
The quadrato-jugal elements are reduced to ligaments. In many Salamandrinae
the large orbito-temporal space is divided into an orbital and a temporal
fossa by an arch which is formed by the meeting of two corresponding
processes from the squamosal and frontal bones respectively. This bridge is
rarely bony (_Salamandrina_, _Triton_), mostly ligamentous;–apparently a
reminiscence of the Stegocephalous condition. The two premaxillary bones
are liable to fuse into one, for instance in _Cryptobranchus_, generally in
adult Tritons. They are most reduced, and are toothless, in _Siren_.
The two maxillary bones are absent only in _Necturus_, _Proteus_,
_Typhlomolge_, and _Siren_. Their posterior end is frequently free, loosely
connected by ligaments with the pterygoid in _Cryptobranchus_; or with the
distal portion of the quadrate, and in this case either just touching it
(_Tylototriton_), or forming a broad junction (_Pachytriton_).
Each half of the lower jaw consists of a dentary, articular and
angulo-splenial. The splenial remains as a separate element in _Siren_; in
others only during the larval period. There are no mento-Meckelian
elements.
SKELETON OF THE ANURA
THE VERTEBRAL COLUMN.–The distinctive peculiarities of the vertebrae of the
Anura are that they are notocentrous, and that about a dozen of them are
modified and fused into an os coccygeum. The whole column is the most
specialised found in the Vertebrata; and various stages are rapidly hurried
through and obscured caenogenetically during the embryonic development.
Paired cartilages appear on the dorsal side of the thin chordal sheath, and
whilst tending to enclose the spinal cord in a {19}canal, their bases grow
head- and tail-wards into what will ultimately become the intervertebral
region. This extension of cartilage leads to a fusion with that of the next
following pair of arches, so that the axial column at this early stage
consists of a right and left longitudinal ridge of cartilage which sends
off dorsal processes, neural arches, in metameric succession. Next, the
intervertebral cartilage increases in such a way as to constrict the chorda
either laterally (_Rana_) or obliquely from above downwards and inwards
(_Bufo_, _Hyla_). We recognise in this cartilage the interdorsalia. Ventral
arcualia are late and much obscured. There is scarcely any cartilage which
could represent the interventralia, the intervertebral cartilage being
almost entirely made up of the interdorsalia. These fuse together and form
a disc or nodule, which later fuses either with the vertebra in front, and
in this case fits into a cup carried by the vertebra next behind
(procoelous vertebrae), or the knob is added to the front end of the
vertebra, fitting into a cup formed by the tail end of the vertebra next in
front (opisthocoelous vertebrae). Much later than the two longitudinal
dorsal bands there appears on the ventral side an unpaired band in which
appear metamerically repeated swellings of cartilage, likewise unpaired.
These swellings become confluent, in a way similar to that which produced
the dorsal bands, and form the unpaired ventral band of cartilage, the
hypochordal cartilage of some authors. The swellings in this band,
equivalent to the basiventralia, become semilunar in a transverse view,
their horns tending upwards towards the basidorsal cartilages, but there is
no actual meeting. Both dorsal and ventral elements are, however, joined
together and form the chief portion of the vertebrae, owing to the rapidly
proceeding calcification and later ossification of the all-surrounding
"membrana reuniens" or skeletogenous layer so far as that is not
cartilaginous.
Procoelous vertebrae exist in the overwhelming majority of Anura;
opisthocoelous are those of the Aglossa, the Discoglossidae, and of some
Pelobatidae. The systematic value of this pro- or opistho-coelous character
has been much exaggerated. We have seen that the centra of the vertebrae of
the Anura are formed entirely by the interdorsal elements, hence the term
"notocentrous," and these centra sometimes remain in adult specimens of
_Pelobates_ as separately ossified and calcified pieces, {20}not fused with
the rest of the vertebrae. This important discovery has been made by
Boulenger, but Stannius had previously mentioned a specimen of _Pelobates_
in which the second and fourth vertebrae are biconvex, the third, sixth,
and eighth biconcave. Moreover, since the sacral vertebra, generally the
ninth, in all the Anura is invariably biconvex, the eighth being biconcave
in the procoelous families, opisthocoelous like the remaining seven
vertebrae in the other families, it is not difficult to imagine that in the
Anura the production of pro- or opistho-coelous vertebrae depends simply
upon the centra or articulating knobs happening to fuse either with the
hind or the front end of the vertebrae. This must of course ultimately be
determined by a mechanical problem of motion.
A second type of the vertebrae amongst the Anura is the epichordal type, an
exaggeration in degree of the notocentrous tendencies of the more usual
perichordal arrangement. It shows, namely, the almost complete suppression
of all the ventral cartilaginous elements, so that the chorda remains for a
long time on the ventral surface of the axial column in the shape of a
flattened longitudinal band. These two types are not unconnected. The
suppression of the ventral elements applies most typically to the trunk
region, while hypochordal cartilage exists in the anterior cervical
vertebrae, and above all in the coccyx. Typically epichordal are the
vertebrae of _Pipa_, _Xenopus_, _Bombinator_, _Pelobates_, _Discoglossus_
and _Alytes_. It is significant that the epichordal often coincide with
opisthocoelous vertebrae, and still more suggestive is the fact that
_Bombinator_ is eminently aquatic, _Pipa_ and _Xenopus_ entirely so, having
lost the tympanum, at least externally. The epichordal feature is not
necessarily indicative of relationship. It has probably been developed
independently in various groups, in correlation with a resumption of
aquatic life. Various genera of Pelobatidae and most likely some
Cystignathidae, e.g. _Pseudis_, will not improbably connect the two types
and their several correlated features, for instance, the frequent reduction
of the tympanic cavity.
The os coccygeum has retained rather primitive features in so far as much
dorsal and ventral cartilage is developed; but this has almost entirely
lost its metameric arrangement, and the posterior half of the coccyx is
formed chiefly by the ventral mass of cartilage, while the dorsal elements
are more or less reduced. {21}Only two vertebrae, generally the tenth and
eleventh of the whole column, are clearly visible, each being composed of a
pair of dorsal and a pair of ventral cartilaginous blocks. The sacral
vertebra articulates with the coccyx by one or two convexities, but in the
Aglossa, in some Pelobatidae, and a few others, the coccyx is fused with
the sacral vertebra. Beyond the first and second component vertebrae of the
embryonic coccyx, the cartilage is continued in the shape of two dorsal,
and one ventral, bands, which soon fuse with each other. Dorsally this
cartilage surrounds the spinal cord; the latter degenerates towards the end
of the tadpole-stage, leaving, however, the empty spinal canal. The chorda,
completely surrounded by cartilage, persists into the post-larval stage,
but is destroyed long before the creature attains maturity. Ultimately the
whole coccyx ossifies.
The tail proper, namely that portion which is absorbed during the
metamorphosis, remains throughout its existence in an apparently primitive
condition. The chorda dorsalis and the spinal cord extend through its whole
length, surrounded by continuous connective tissue without any cartilage;
in fact it represents a piece of typical vertebral column before the
appearance of cartilage. The reduction of this swimming organ begins at the
hind end.
The vertebral column of the adult.–The first vertebra (we will call it the
atlas since it carries the skull) is not, as in the Urodela, provided with
an odontoid process. It articulates by two cups with the condyles of the
occiput. In some Anura it co-ossifies, rather incompletely, with the second
vertebra, regularly in the fossil _Palaeobatrachus_, often in
_Ceratophrys_, _Breviceps_, and occasionally in _Pelobates_, _Bufo_,
_Rana_, and _Xenopus_. This is, however, no justification for looking upon
the first vertebra as a complex of two vertebrae, although the atlas is
frequently very thick and broad, and even carries, in the Aglossa,
considerable lateral wings or diapophyses. Those of the trunk-vertebrae are
often very long, acting thereby as substitutes for ribs which are absent,
except on the second, third, and fourth vertebrae of the Discoglossidae,
and on the second and third of the Aglossa. In the adult Aglossa these ribs
fuse with the processes which carry them.
The diapophyses of the sacral vertebra carry no ribs, the ilia being
attached to them directly. They are either cylindrical {22}as in the
Ranidae and Cystignathidae, or they are more or less dilated as in all the
other families, most strongly in the Pelobatidae and the Aglossa. In some
members of the large sub-family of the Cystignathidae the otherwise
cylindrical diapophyses are slightly dilated.
[Illustration: FIG. 4.–Dorsal view of the sacral or ninth vertebra (9),
with the attachment of the ilium, of (1) _Rana temporaria_, (2) _Bufo
vulgaris_, showing the whole coccyx and pelvis, (3) _Pelobates fuscus_, as
examples of cylindrical and of dilated sacral diapophyses. (About nat.
size.) _a_, Acetabulum; _c_, coccyx; _i_, ilium; _z_, anterior
zygapophyses.]
The sacrum is formed by the ninth vertebra, but there are a few interesting
exceptions. _Pelobates_, _Pipa_, and _Hymenochirus_ possess two sacral
vertebrae; and, neglecting individual abnormalities, these three genera
form the only exception amongst recent Amphibia. In the three genera the
coccyx is fused with the second sacral vertebra, and such a fusion occurs
elsewhere normally only in _Bombinator_ with its single sacral vertebra.
The morphologically oldest condition is normally represented by
_Pelobates_, the sacral vertebrae being the tenth and ninth. One case has
been recorded by Boulenger of _Bombinator pachypus_ "with eleven segments,"
the last carrying the ilium. Individual lop-sided abnormalities have been
described in _Bombinator_ and _Alytes_, where the right ilium articulated
with the tenth, the left ilium with the ninth vertebra. This shifting
forwards of the ilium to the extent of one metamere has been continued
further in _Pipa_, in which the sacrum is formed by the ninth and eighth
vertebrae, their diapophyses fusing on either side into extra broad
wing-like expansions. In old specimens of _Palaeobatrachus fritschi_ the
seventh vertebra is in a transitional condition, the ilium being carried by
the ninth and eighth, and slightly also by the diapophyses of the seventh
vertebra; and in _P. diluvianus_ the {23}diapophyses of all these vertebrae
are united into one broad plate to which the ilia are attached. Lastly, in
_Hymenochirus_ the first sacral is the sixth vertebra, and this creature
has thereby reduced the pre-sacral vertebrae to the smallest number known.
This shifting forwards of the iliac attachment implies the conversion of
original trunk into sacral vertebrae, and the original sacral vertebra
itself becomes ultimately added to the urostyle. The second sacral, the
tenth of _Pelobates_, the ninth of _Pipa_, and the tenth on the right side
of the abnormal _Bombinator_, are still in a transitional stage of
conversion. In Discoglossidae the tenth is already a typical post-sacral
vertebra, and is added to the coccyx, but it still retains distinct, though
short, diapophyses. In the majority of the Anura the tenth vertebra has
lost these processes, and its once separate nature is visible in young
specimens only. In _Bombinator_ even the eleventh vertebra is free during
the larval stage. In fact the whole coccyx is the result of the fusion of
about twelve or more vertebrae, which from behind forwards have lost their
individuality. We conclude that originally, in the early Anura, there was
no coccyx, and that the ilium was attached much farther back; and this
condition, and the gradual shifting forwards, supply an intelligible cause
of the formation of an os coccygeum. The fact that the sacral vertebrae of
the Anura possess no traces of ribs as carriers of the ilia, is also very
suggestive. The ilia have shifted into a region, the vertebrae of which had
already lost their ribs. By reconstructing the vertebral column of the
Anura, by dissolving the coccyx into about a dozen vertebrae, so that
originally, say the twenty-first vertebra carried the ilia, we bridge over
the enormous gap which exists between the Anura and Urodela. That whole
portion of the axial continuation behind the coccyx, more or less
coinciding with the position of the vent, is the transitional tail.
The disappearance of both notochord and spinal cord, and the conversion of
the cartilaginous elements into a continuous rod in the case of the os
coccygeum, find an analogy in the hinder portion of the tail of Dipnoi and
Crossopterygii, and in the tail-end of most Urodela, portions which are not
homologous with the os coccygeum. The term urostyle should be restricted to
such and similar modifications of the tail-end, and this latter happens to
be lost by the Anura during metamorphosis.
{24}Strictly speaking, or rather in anatomical parlance, the Vertebrate
tail begins with the first post-sacral vertebra. In the Anura that portion
of the whole tail has retained most cartilage, and has become the
coccygeum, which is required as a "backbone" for the often enormous belly.
This requirement is an outcome of the great shortening of the trunk proper
(if the trunk be defined as ending with the pelvic region), and this
shortening of the trunk is again intimately connected with the jumping
mechanism, enlargement of the hind-limbs, elongation of the ilia, and
throwing the fulcral attachment forwards as much as possible. The
pre-acetabular ilio-sacral connection is carried to the extreme in the
Anura.
The SHOULDER-GIRDLE and "sternum" are more complete than in the Urodela,
there being also a pair of clavicles, fused with the precoracoidal bars.
The whole apparatus presents two types. In the arciferous type the
coracoids and precoracoids retain a great amount of cartilage in their
distal portions, and these cartilages (the epicoracoids of some authors)
overlap each other movably on one another, the right usually lying
ventrally upon the left. The epicoracoidal cartilage of each side, by
connecting the distal end of the coracoid with the precoracoid of the same
side, forms an arc, hence "arciferous." In the firmisternal type the
epicoracoidal cartilages are much reduced, and, instead of overlapping,
meet in the middle line and often fuse with each other, forming thereby a
firm median bar, which connects the ventral ends of the precoracoids with
those of the coracoids. This type is morphologically the higher and more
recent, and passes in the larval stage through the arciferous condition. It
is restricted to the Ranidae, Engystomatinae, and Aglossa. Although these
two types afford an excellent distinctive character for the main divisions
of the Anura, they are to a certain extent connected by intermediate forms
in such a way, that, for instance, in _Bufo_ and among Cystignathidae in
_Ceratophrys_, the two opposite epicoracoidal cartilages begin to unite at
the anterior end.
In many Engystomatinae the precoracoids together with the clavicles are
much reduced, sometimes to thin ligaments, being in this case mostly curved
back and lying closely against the coracoids; or they may be lost
completely. Very rarely the precoracoidal bars are actually much stronger
than the coracoids, {25}and the median symphysial bar of cartilage is lost;
this is the case in _Hemisus_.
The scapula is always large and curved into transverse, dorsally broadening
blades, the dorsal greater portion of which, the so-called supra-scapula,
does not ossify but calcifies.
[Illustration: FIG. 5.–Ventral views of the shoulder-girdles of various
Anura. (Slightly enlarged.) 1, _Bombinator igneus_, and 2, _Bufo vulgaris_,
as examples of the arciferous type; 3, adult, 4, metamorphosing _Rana
temporaria_ showing change from the arciferous into the firmisternal type;
5, _Hemisus guttatum_; 6, _Breviceps gibbosus_; 7, _Cacopus systoma_. (5,
6, 7, after Boulenger.) Cartilaginous parts are dotted; ossified parts are
left white. _Cl_, Clavicle; _Co_, coracoid; _E_, epicoracoidal cartilage;
_H_, humerus; _M_, metasternum; _O_, omosternum; _P_, precoracoid; _Sc_,
scapula; _S.S_, supra-scapula.]
It is very doubtful if the Anura possess a true sternum, if by sternum we
understand a medio-ventral apparatus which owes its origin to the ventral
portions of ribs. The so-called sternal apparatus of the Anura consists of
two pieces. One, anterior, variously named episternum, presternum, or
omosternum, rests upon the united precoracoids and extends headwards, being
either styliform or broadened out. Sometimes it is partly ossified, with a
distinct suture at its base; this is the case especially in the
Firmisternia; in many Arcifera the omosternum remains cartilaginous and is
continuous, without a sutural break, with the cartilage of the
precoracoids, indicating thereby its genetic relation to the
shoulder-girdle. Hence _omosternum_ is the {26}preferable name. It is
frequently much reduced, even absent, for instance in most Bufonidae and in
the Engystomatinae. The posterior so-called sternal part may be termed
_metasternum_. It forms the posterior counterpart of the omosternum. It is
attached behind to the epicoracoidal cartilages, or fusing with them forms
their posterior continuation. It appears mostly in the shape of a style,
which is frequently ossified, and broadens out behind into a cartilaginous,
partly calcified blade. In the Discoglossidae only it diverges backwards
into two horns, assuming a striking resemblance to the typical xiphisternum
of the Amniota. In young Anura the metasternal cartilage is intimately
connected with the pericardium, an indication of its being derived not from
ribs but from the shoulder-girdle.
The glenoid cavity is always formed by the coracoids and by the scapula,
but the precoracoid often takes part in its formation, for instance in
Bufonidae, Hylidae, and Discoglossidae.
In the FORE-LIMB the humerus has a crest, stronger in the males than in the
females; it assumes extraordinary strength in some Cystignathidae, notably
in the male _Leptodactylus_. Radius and ulna are fused into one bone. The
carpalia are originally nine in number: radiale, ulnare, two centralia, and
five carpalia distalia, the fifth of which is reduced to a tiny nodule or
to a ligamentous vestige. The primitive condition still prevails in the
Discoglossidae. In most of the other Anura the fourth and third distal
carpalia, in any case very small, fuse with the enlarged ulnar centrale;
the radial centrale comes, in the Bufonidae and Pelobatidae, into contact
with the radius, so that the forearm articulates with three elements as in
the Urodela, but with this difference, that the intermedium of the Urodela
has been lost by the Anura. There are five metacarpalia and five fingers,
but the elements of the first or thumb are nearly vestigial, so that the
pollux is reduced to one or two nodules, scarcely visible externally. The
normal number of the phalanges of the second to fifth fingers is 2, 2, 3,
3. The distal phalanges are generally straight, either pointed or expanded
or with Y or T-shaped ends; but in the Hylidae, in _Hylambates_ amongst the
Ranidae, and in _Ceratohyla_, one of the Hemiphractinae, the terminal
phalanges are produced into curved claws which support the adhesive
finger-discs. There are, however, many genera of different families, which
possess finger-discs and have no claw-shaped {27}phalanges. The Hylidae,
and many of the climbing members of the Ranidae with adhesive discs,
possess an extra skeletal piece intercalated between the last and last but
one phalanges of the fingers and toes. This piece, a mere interarticular
cartilage in _Hyla_, is in the following Raninae developed into an
additional phalanx, so that their numbers are 3, 3, 4, 4 in the hand and 3,
3, 4, 5, 4 in the foot: _Cassina_, _Hylambates_, _Rappia_, _Megalixalus_,
_Rhacophorus_, _Chiromantis_, _Ixalus_, and _Nyctixalus_. All the other
Ranidae are without this additional phalanx, irrespective of the presence
or absence or size of digital expansions.[12]
The PELVIC GIRDLE looks like a pair of tongs (see Fig. 4, p. 22). The ilium
is enormously elongated and is movably attached to the sacral diapophyses.
This connection is always pre-acetabular in position. The ilium and ischium
co-ossify completely, and make up nearly the whole of the pelvis; the pubis
is very small, and remains cartilaginous unless it calcifies. It rarely
possesses a centre of ossification, for instance in _Pelobates_, where the
osseous nodule is excluded from the acetabulum, recalling certain
Labyrinthodonta, whose ossa pubis likewise do not reach that cavity. The
latter is open or perforated in young Anura and remains so in the
Discoglossidae, but in the others it becomes closed up as in the Urodela.
The ventral halves of the pelvis, besides forming a symphysis, closely
approach each other, just leaving room for the passage of the rectum and
the urino-genital ducts.
The HIND-LIMBS are in all cases longer than the fore-limbs. The femur is
slender, the tibia and fibula are fused into one bone. The tarsus is much
modified by the great elongation of the two proximal tarsalia (there being
no intermedium) into an astragalus and a calcaneum, both of which fuse
together distally and proximally, or completely as in _Pelodytes_; in the
latter case the limb assumes a unique appearance, since it consists of
three successive and apparently single bars of nearly equal length. The
other tarsal elements, especially the more lateral ones, are practically
reduced to pads. The Anura have thereby acquired two well-marked joints,
one cruro-tarsal, the other tarso-metatarsal; this shows a high stage of
specialisation in comparison with the Urodelous and Stegocephalous type of
still undefined joints.
{28}The Anura possesses five well-developed toes with normally 2, 2, 3, 4,
and 3 phalanges, and the rudiments of a sixth digit, the so-called
prehallux, which consists of from two to four pieces, including the one
which represents its metatarsal. This prehallux, as a vestige of a once
better developed digit, is exactly like the elements on the radial side of
the wrist, which, we are certain, are the remnants of a once complete
finger, namely the pollex. The only weighty difficulty against its
interpretation as a prehallux lies in the fact that hitherto no six-toed
Stegocephali have been found; but the fact that there are no Stegocephali
known with more than four fingers could be used as an argument against
there being a pollex-vestige in recent Anura with just as little reason.
The SKULL of the Anura differs from that of the other recent Amphibia in
the following features:–
The orbital region of the primitive cranium remains cartilaginous, but
further forward the cranial cavity is closed by the unpaired sphenethmoid,
which forms a ring round the anterior portion of the brain-cavity, hence
called "os en ceinture" by some anatomists. The frontals and parietals fuse
into one pair of fronto-parietal bones, and these again can fuse together
in the middle line; as in Aglossa and _Pelobates_. The palatal portion of
the palato-quadrate cartilage is complete, reaching forwards to the sides
of the ethmoid region. The curved arch, formed by this cartilage, is
covered by the following bones: (1) the quadrato-jugal, reduced to a thin
splint which connects the quadrate and squamosal with the posterior end of
the maxilla; (2) the pterygoid, always strong, extending from the distal
inner corner of the quadrate to the maxilla, sometimes also to the
palatine, and with a broad, median process to the parasphenoid, this
process covering ventrally most of the otic region; (3) the palatines,
which vary considerably in shape and size; they are placed transversely and
meet in the middle line; in _Bombinator_ and _Pelodytes_ they are absent.
The quadrates are directed transversely and backwards, in conformity with
the wide gape of the mouth. The squamosal is always well developed,
covering the whole of the quadrate on its outer side; it has a forwardly
directed process which ends freely in _Rana_, meets a corresponding process
of the maxilla and forms a bony arch with it in _Discoglossus_,
_Pelobates_, and others, or {29}is scarcely developed at all, for instance
in _Bufo_. In _Pelobates cultripes_ the squamosal is very wide and forms a
junction with the fronto-parietals, thus producing a broad bridge across
the temporal fossa.
The nasal bones are large and meet in the middle line. Frequently they
leave a space between them and the diverging anterior portion of the
fronto-parietals, through which gap appears part of the dorsal surface of
the ethmoid cartilage. A fontanelle between the frontals occurs in most
Hylidae, many Cystignathidae, some few Bufonidae, in _Pelodytes_ amongst
the Pelobatidae, and in the Discoglossidae.
The tympanic cavity is bordered in front, above, and below by the squamosal
and quadrate, behind by the musculus depressor mandibulae, internally by
the otic capsule, and by the cartilage of the cranium between this and the
lateral occipital bone. The cavity communicates, however, by the wide and
short Eustachian tube with the mouth, the passage being bordered anteriorly
by the pterygoid, posteriorly by soft parts. Partly imbedded in these soft
tissues is the styloid process or stylohyal, which is attached to the
cranium, mostly behind the otic region, and is continued downwards into the
anterior horn of the hyoid. The whole partly cartilaginous, ligamentous,
and osseous string is, in fact, the entire ventral half of the hyoid arch,
while the dorsal half or hyomandibular portion of this, the second visceral
arch, is modified into the columellar or auditory chain. The inner end of
this chain, the stapes, is inserted into and around the fenestra ovalis of
the otic capsule, while the outer end is somewhat T-shaped, and is loosely
attached to or near the upper rim of the tympanic ring and to the middle of
the tympanic disc. In many Anura this terminal bar can be seen from the
outside. The middle portion of the columellar chain is ossified, the rest
remains cartilaginous. But the whole chain exhibits various modifications
in different genera, especially in the number and the extent of the
processes sent out by the outer cartilaginous portion; these are attached
in various ways to the tympanum and its rims. The tympanic disc is carried
by a cartilaginous ring, which rests against a special process sent out by
the quadrate, and is probably itself a differentiation of this element.
In some very aquatic genera, but also in _Pelobates_, the {30}tympanic
cavity is much reduced, for instance in _Bombinator_, _Liopelma_. In
_Batrachophrynus_ not only the cavity, but also the Eustachian tubes are
suppressed. In the Aglossa only the two tubes are united into one short but
wide median canal, opening at the level of the pterygoids on the roof of
the mouth.
The lower jaw is remarkable for the possession of mento-Meckelian
cartilages, absent only in the Aglossa and Discoglossidae. At first they
are much longer than the rest of the jaw; during the larval life they
indeed form the functional jaw, and they are now covered with horny sheaths
instead of teeth. Owing to the absence of teeth on them, these
mento-Meckelian cartilages are later not invested by bone, although in many
Anura they ultimately ossify, either retaining their separate nature or
fusing partly with the dentary bones. The bulk of the lower jaw, the
Meckelian cartilage, becomes invested by the dentary, a small articulare,
and an inner angulare, while a splenial element is absent. The dentary
itself is mostly reduced to a small dentigerous splint, while the angulare
forms by far the greater part of the bony jaw.
Teeth are more restricted in their occurrence than in the Urodela. On the
jaws they always stand in one row. With the exception of the
Hemiphractinae, Amphignathodontinae, Ceratobatrachinae, and Genyophryninae,
no recent Anura carry teeth on the lower jaw, and even in these genera they
are mostly much reduced in size and firmness, having all the appearance of
vanishing structures. The premaxillae and maxillae are frequently furnished
with teeth, except in the Dendrobatinae, Genyophryninae, Engystomatinae,
Dendrophryniscinae, Bufonidae, _Pipa_, and _Hymenochirus_. The vomers
mostly carry a series of teeth on their posterior border; when these teeth
are absent, as in many species of _Bufo_, a kind of substitute sometimes
occurs on the palatines in the shape of a row of tuberosities. The
palatines carry teeth in Hemiphractinae. The parasphenoids are rarely
toothed, _e.g._ _Triprion_, _Diaglena_, _Amphodus_, and occasionally in
_Pelobates_.
A few Anura possess peculiar substitutes for teeth in the anterior portion
of the lower jaw, namely, a pair of conical bony processes, sometimes
rather long, but always covered by the dense gums, or investment of the
jaws; _e.g._ _Lepidobatrachus_, several Rana, _e.g._ _R. adspersa_, _R.
khasiana_, _R. kuhli_, and _Cryptotis brevis_.
{31}Cranial dermal ossifications are developed in some species of _Bufo_,
still more in the Hemiphractinae, and above all in _Pelobates cultripes_
and in the Cystignathoid genus _Calyptocephalus_.
The HYOID APPARATUS of the Anura is complicated. It is originally composed
of the hyoidean and four branchial arches, with one median, copular piece.
The branchial arches form in the early life of the tadpole the elaborate
framework of the filtering apparatus mentioned on p. 44. During
metamorphosis the whole filter disappears, owing to resorption of the
greater part of the branchial arches; only their median portions remain,
and fuse with the enlarged copular piece and the hyoidean arches into a
broad shield-shaped cartilage (_corpus linguae_), whence several lateral
processes sprout out, the posterior pair of which are generally called
thyrohyals or thyroid horns. The true hyoid horns give up their larval
lean-to articulation with the quadrate, become greatly elongated, and gain
a new attachment on the otic region of the cranium. The transformation of
the whole apparatus has been studied minutely by Ridewood, in _Pelodytes
punctatus_.[13]
SKIN
The epidermis of the young larvae of Amphibia is furnished with cilia,
which later on are suppressed by the development of a thin hyaline layer or
cuticula, but clusters of such cilia remain, at least during the larval
life and during the periodical aquatic life of the adult, in the epidermal
sense-organs. In the frog, currents are set up by the ciliary action at an
earlier stage, and are maintained to a later stage than in the newt. In the
latter the tail loses its ciliation, whereas in the frog it remains active
almost up to the time of the metamorphosis. In tadpoles of 3-10 mm. nearly
the whole surface is ciliated (Assheton).[14] The cilia work from head to
tail, causing the little animal, when perfectly quiet, to move forwards
slowly in the water. Beneath the cuticula, in the Perennibranchiata and the
larvae of the other Urodela, lies a somewhat thicker layer of vertically
striated cells, the so-called pseudo-cuticula, which disappears with the
transformation of the upper layers of the Malpighian cells into the stratum
corneum. The latter is very thin, consists of one or two layers of
flattened cells, and is shed periodically by all {32}Amphibia in one piece.
In the Urodela it generally breaks loose around the mouth, and the animal
slips out of the delicate, transparent, colourless "shirt," which during
this process of ecdysis or moulting becomes inverted. In the Anura it
mostly breaks along the middle line of the back, the creature struggles out
of it, pokes it into its mouth, and swallows it. Urodela also eat this
skin. As a rule the first ecdysis takes place towards the end of the
metamorphosis, preparatory to terrestrial life. So long as the animal grows
rapidly, the skin has to be shed frequently, since this corneous layer is
practically dead and unyielding. Adult terrestrial Urodela do not seem to
moult often, mostly only when they take to the water in the breeding
season. Anura, on the other hand, moult often on land, at least every few
months. The surface of the new skin is then quite moist and slimy, but it
soon dries and hardens.
The Malpighian stratum consists of several layers, thickest in the
Perennibranchiata; in them it contains mucous cells throughout life, in
others such slime-cells are restricted to larval life. Later, regular
slime-glands are developed, which open on the surface. They are very
numerous, and more evenly distributed, over most parts of the body, than
the specific or poison-glands, which are restricted to certain parts, often
forming large clusters, especially on the sides of the body. They reach
their greatest development in the "parotoid glands" of the Anura. Both
kinds of glands are furnished with smooth muscle-fibres, which are said to
arise from the basal membrane underlying and forming part of the Malpighian
layer; these muscle-cells extend later downwards into the corium. For the
action of the poison, see p. 37.
The stratum corneum is mostly thin, but on many parts of the body,
especially in Anura, the epidermal cells proliferate and form hard spikes
or other rugosities, generally stained dark brown. With these may be
grouped the nuptial excrescences so frequent in the Anura, especially on
the rudiment of the thumb, and on the under surface of the joints of the
fingers and toes. In many Anura, less frequently in the Urodela, the tips
of the fingers and toes are encased in thicker horny sheaths, producing
claws or nails. They are best developed among newts in _Onychodactylus_,
among the Anura in _Xenopus_ and _Hymenochirus_. The horny covering of the
metatarsal tubercles reaches its greatest size in {33}the digging spur or
spade of _Pelobates_. In most of these cases the cutis is elevated into
more or less wart-like papillae, covered, of course, by the proliferated
and cornified epidermis. In the female of _Rana temporaria_ nearly the
whole surface of the body becomes covered with rosy papillae during the
breeding season. Similar nuptial excrescences are common, and are most
noteworthy in the male of the Indian _Rana liebigi_.
The epidermis also contains sense-organs. They attain their highest
development in the larvae; later on they undergo a retrogressive change.
Each of these sense-organs is a little cup-shaped papilla, visible to the
naked eye. It is composed of elongated cells which form a mantle around
some central cells, each of which ends in a stiff cilium perforating a
thin, hyaline membrane which lines the bottom of the cup, and is perhaps
the representation of the cuticula. These ciliated cells are connected with
sensory fibres, the nerve entering at the bottom of the whole organ. The
cilia are in direct contact with the water, but the outer rim of the whole
apparatus is protected by a short tube of hyaline cuticula-like secretion.
These sense-organs are, in the larvae, scattered over the head, especially
near the mouth and around the eyes, whence they extend backwards on to the
tail, mostly in three pairs of longitudinal rows, one near the vertebral
column, the others lateral. They are supplied by the lateral branch of the
vagus nerve. They disappear during the metamorphosis, at least in the
Anura, with the exception of _Xenopus_, in which they form conspicuous
white objects. The white colour is caused by the tubes becoming choked with
the débris of cells or coagulating mucous matter, so that it is doubtful if
these organs, which moreover have sunk deeper into the skin, are still
functional. In the terrestrial Urodela these organs undergo a periodical
process of retrogression and rejuvenescence. During the life on land they
shrink and withdraw from the surface, and their nerves likewise diminish,
but in the breeding season, when the newts take again to aquatic life, they
revive, are rebuilt and become prominent on the surface. They are an
inheritance from the fishes, in which such lateral line organs are
universally present.
The cutis of most Amphibia is very rich in lymph-spaces, which, especially
in the Anura, assume enormous proportions, since the so-called subcutaneous
connective tissue forms {34}comparatively few vertical septa by which the
upper and denser layers, the corium proper, are connected with the
underlying muscles. The spaces are filled with lymph, and into some of them
the abnormally expanded vocal sacs extend, notably in _Paludicola_,
_Leptodactylus_, and other Cystignathidae, and in _Rhinoderma_.
The cutis frequently forms papillae and prominent folds, sometimes regular
longitudinal keels on the sides of the back; but dermal, more or less
calcified or ossified scales are restricted to the Stegocephali and to the
Apoda, _q.v._, pp. 79, 87. We conclude that the Urodela and Anura have
entirely lost these organs. Dermal ossifications, besides those which now
form an integral part of the skeleton, like many of the cranial
membrane-bones, are rare, and are restricted to the Anura. They are least
infrequent on the head, where the skin is more or less involved in the
ossification of the underlying membrane-bones, for instance in _Triprion_,
_Calyptocephalus_, _Hemiphractus_ and _Pelobates_. The thick ossifications
in the skin of the back of several species of _Ceratophrys_ are very
exceptional. In _Brachycephalus ephippium_ these dermal bones enter into
connection with the vertebrae; small plates fuse with the dorsal processes
of the first to third vertebrae, while one large and thick plate fuses with
the rest of the dorsal vertebrae. Simple calcareous deposits in the cutis
are less uncommon, for instance, in old specimens of _Bufo vulgaris_. We
are scarcely justified in looking upon these various calcifications and
even ossifications as reminiscences of Stegocephalous conditions.
The skin contains PIGMENT. This is either diffuse or granular. Diffuse
pigment, mostly dark brown or yellow, occurs frequently in the epidermis,
even in the stratum corneum. The granular pigment is stored up in cells,
the chromatophores, which send out amœboid processes, and are restricted to
the cutis, mostly to its upper stratum, where they make their first
appearance. Contraction of the chromatophores withdraws the pigment from
the surface, expansion distributes it more or less equally. The usual
colours of the pigment are black, brown, yellow, and red. Green and blue
are merely subjective colours, due to interference. A peculiar kind of
colouring matter is the white pigment, which probably consists of guanine,
and is likewise deposited within cells; cf. the description of the white
spots in the skin of _Hyla coerulea_.
{35}Most Amphibia are capable of changing colour, the Urodela, however, far
less than the Anura, some of which exhibit an extraordinary range and
adaptability in their changes.
The mechanism by which the change of colour is produced in frogs has been
recently studied by Biedermann.[15] If we examine the green skin of the
common Tree-frog, _Hyla arborea_, under a low power and direct light, we
see a mosaic of green, polygonal areas, separated by dark lines and
interrupted by the openings of the skin-glands. Seen from below the skin
appears black. Under a stronger power the black layer is seen to be
composed of anastomosing and ramified black pigment-cells. Where the light
shines through, the skin appears yellow. The epidermis itself is quite
colourless. The mosaic layer is composed of polygonal interference-cells,
each of which consists of a basal half which is granular and colourless,
while the upper half is made up of yellow drops. Sometimes the tree-frog
appears blackish, and if then the black pigment-cells are induced to
contract, for instance, by warming the frog, it appears silver-grey; in
this case the pigment in the yellow drops is no longer diffuse, but is
concentrated into a round lump lodged between the interstices of the
granular portions; the black pigment-cells are likewise balled together.
These black chromatophores send out numerous fine branches, which
occasionally stretch between and round the polygonal cells. When each of
these is quite surrounded and covered by the black processes, the frog
appears black. On the other hand, when the black pigment-cells withdraw
their processes, shrink up, and, so to speak, retire, then the light which
passes through the yellow drops is, by interference, broken into green.
Stoppage of the circulation of the blood in the skin causes the black
chromatophores to contract. Carbon dioxide paralyses them and causes them
to dilate. This is direct influence without the action of nerves. But
stimulation of the central nerve-centres makes the skin turn pale. Low
temperature causes expansion, high temperature contraction, of the
chromatophores. Hence hibernating frogs are much darker than they are in
the summer. Frogs kept in dry moss, or such as have escaped into the room
and dry up, turn pale, regardless of light or darkness, probably owing to a
central, reflex, nerve-stimulus.
Tree-frogs turn green as the result of the contact with leaves. {36}Dark
frogs will turn green when put into an absolutely dark vessel in which
there are leaves. This is reflex action, and blinded specimens do the same.
The principal centres of the nerves which control the chromatophores, lie
in the corpora bigemina and in the optic thalami of the brain. When these
centres are destroyed, the frog no longer changes colour when put upon
leaves, but if a nerve, for instance the sciatic, be stimulated, the
corresponding portion of the body, in this case the leg, turns green. Rough
surfaces cause a sensation which makes the frog turn dark. _Rana_ seems to
depend chiefly upon temperature and the amount of moisture in the air, so
far as its changes of colour are concerned. Biedermann concludes that the
"chromatic function of frogs in general depends chiefly upon the sensory
impressions received by the skin, while that of fishes depends upon the
eye."
All this sounds very well, but the observations and experiments are such as
are usual in physiological laboratories, and the frogs, when observed in
their native haunts, or even when kept under proper conditions, do not
always behave as the physiologist thinks they should. There is no doubt
that in many cases the changes of colour are not voluntary, but reflex
actions. It is quite conceivable that the sensation of sitting on a rough
surface starts a whole train of processes: roughness means bark, bark is
brown, change into brown; but one and the same tree-frog does not always
assume the colour of the bark when it rests, or even sleeps upon, such a
piece. He will, if it suits him, remain grass-green upon a yellow stone, or
on a white window-frame. I purposely describe such conditions, changes,
coincidences, and discrepancies in various species, notably in _Hyla
arborea_, _H. coerulea_, _Rana temporaria_, _Bufo viridis_, to show that in
many cases the creature knows what it is about, and that the eye plays a
very important part in the decision of what colour is to be produced. The
sensory impression received through the skin of the belly is the same, no
matter if the board be painted white, black, or green, and how does it then
come to pass that the frog adjusts its colour to a nicety to the general
hue or tone of its surroundings?
Boulenger[16] has given us a summary of the action of the POISON of
Amphibia:
{37}It is well known to all who have handled freshly-caught newts, and
certain toads, especially _Bombinator_, that their secretion acts as a
sternutatory, and causes irritation of the nose and eyes, the effects
produced on us by _Bombinator_ being comparable to the early stages of a
cold in the head. Many collectors of Batrachians have learned, to their
discomfiture, how the introduction of examples of certain species into the
bag containing the sport of their excursion may cause the death of the
other prisoners; for although the poison has no effect on the skin of
individuals of the same species, different species, however closely allied,
may poison each other by mere contact. But when inoculated the poison acts
even on the same individual.
Miss Ormerod, to personally test the effect, pressed part of the back and
tail of a live Crested Newt between the teeth. "The first effect was a
bitter astringent feeling in the mouth, with irritation of the upper part
of the throat, numbing of the teeth more immediately holding the animal,
and in about a minute from the first touch of the newt a strong flow of
saliva. This was accompanied by much foam and violent spasmodic action,
approaching convulsions, but entirely confined to the mouth itself. The
experiment was immediately followed by headache lasting for some hours,
general discomfort of the system, and half an hour after by slight
shivering fits."
Numerous experiments have shown that the poison of toads, salamanders, and
newts is capable, when injected, of killing mammals, birds, reptiles, and
even fishes, provided, of course, that the dose be proportionate to the
size of the animal. Small birds and lizards succumb as a rule in a few
minutes; guinea-pigs, rabbits, and dogs in less than an hour.
This poison of Amphibia is not septic, but acts upon the heart and the
central nervous system. That of the common toad has been compared, in its
effects, to that of _Digitalis_ and _Erythrophlaeum_. Some authorities hold
that the poison is an acid, others regard it as an alkaloid.
Phisalix[17] has come to the conclusion that toads and salamanders are
possessed of two kinds of glands, different both anatomically and
physiologically. These are, first the mucous glands, spread over the
greater part of the body, with an alkaloid secretion, which acts as a
narcotic; secondly, specific glands, as {38}the parotoids and larger dorsal
glands, the secretion of which is acid, and acts as a convulsive.
The Indians of Colombia are said to employ the secretion of _Dendrobates
tinctorius_ for poisoning their arrows. The poison is obtained by exposing
the frog to a fire, and after being scraped off the back is sufficient for
poisoning fifty arrows. It acts on the central nervous system, and is used
especially for shooting monkeys. Concerning the use of this poison for
"dyeing" parrots, see p. 272.
The milky secretion of toads protects them against many enemies, although
not always against the grass-snake. A dog which has once been induced to
bite a toad, suffers so severely that it will not easily repeat the
experiment. The handling of tree-frogs also irritates both nose and eyes.
The hind limbs of the Water-frog, _Rana esculenta_, have a very bitter,
acrid taste. In short, most, if not all, Amphibia are more or less
poisonous, and it is significant that many of the most poisonous, e.g.
_Salamandra maculosa_, _Bombinator_, _Dendrobates_, exhibit that very
conspicuous combination of yellow or orange upon a dark ground, which is so
widespread a sign of poison. Other instances of such warning colours,
protective in a defensive sense, are the Wasps and _Heloderma_, the only
poisonous lizard.
NERVES
SPINAL NERVES.–Each spinal nerve issues originally immediately behind the
neural arch of the vertebral segment to which it belongs. This
intra-vertebral position is ultimately modified into a more inter-vertebral
one, owing to the predominant share of the neural arches, basidorsalia, in
the composition of the whole vertebra. Consequently the nerves issue behind
their corresponding vertebra.
The first spinal nerve, or N. suboccipitalis, is exceptional in several
respects. It develops a dorsal and a ventral root like a typical spinal
nerve, but the dorsal root soon degenerates in all Amphibia, while in the
Phaneroglossal Anura the whole nerve disappears. The first spinal nerve
reduced to its ventral half persists therefore only in the Apoda, Urodela,
and the Aglossal Anura. It issues originally between the occiput and the
atlas, but in the adult it is partly imbedded in the anterior portion of
the atlas. Its own vertebra is lost, having probably been added to the
cranium.
{39}In the Urodela the first spinal nerve either remains separate, or it
joins the second spinal, forming with it and with a branch from the third
nerve the cervical plexus, which supplies the muscles of the cervical
region. The third, fourth, and fifth nerves, and sometimes also the sixth,
form the brachial plexus.
In the Aglossal Anura N. spinalis I. mostly sends a fine thread to the
second spinal nerve, the rest supplies chiefly the M. levator scapulae, in
_Pipa_ the abdominal muscles also. In all the other Anura this N. spinalis
I. is lost; occasional vestiges have been reported in _Bufo vulgaris_ and
_Rana catesbiana_, and remnants of it may possibly be found in Pelobatidae
and Discoglossidae. The first actually persisting nerve of the
Phaneroglossa is consequently N. spinalis II.
The brachial plexus is composed as follows:–_Pipa_, N. spinalis II. and
III.; _Xenopus_ and Phaneroglossa, N. spinalis III. and IV., with a small
branch from the second; the next following three nerves, numbers V., VI.,
and VII., behave like ordinary trunk nerves.
The pelvic plexus of the Phaneroglossa is formed in _Rana_ by the VIII. +
IX. + X. + XIth nerves, the tenth issuing between the sacral vertebra and
the coccyx. In _Bufo_ and _Hyla_ the plexus is composed of five nerves, the
seventh spinal sending a branch to it. Occasionally the twelfth nerve
contributes a small branch to the posterior portion of the plexus. This and
the eleventh nerve leave the coccyx by separate holes, thereby indicating
its composition. The rest of the spinal cord gives off no more recognisable
nerves, owing to its reduction during the later stages of metamorphosis;
its terminal filament passes out of the posterior end of the coccygeal
canal.
Concerning the CRANIAL NERVES it is necessary to draw attention to one
point only. The last nerve which leaves the cranium of the Amphibia is the
vagus or tenth cranial nerve. There is consequently no eleventh, and no
twelfth or hypoglossal, pair of cranial nerves. Their homologues would be
the first and second spinal nerves, but the whole tongue of the Amphibia,
with its muscles, is supplied by the glossopharyngeal, or ninth cranial
pair, and is morphologically not homologous with the tongue of the Amniota.
{40}RESPIRATORY ORGANS
A very important and characteristic feature of the Amphibia is the
development of two sets of respiratory organs: Gills and Lungs. It is as
well to give definitions of these organs. _Lungs_ are hollow evaginations
from the ventral wall of the pharynx, and their thin, vascularised walls
enable the blood to exchange, by osmosis, carbon dioxide for oxygen from
the air which enters the lungs by the mouth or the nostrils, and the
windpipe. The latter is unpaired, the lungs themselves are paired. _Gills_
are highly vascularised, more or less ramified excrescences, covered by a
thin epithelium of ecto- or endo-dermal origin, which permits of the
exchange of carbon dioxide for oxygen from the air which is suspended in
the surrounding water. It is obvious that this definition applies to all
sorts of well-vascularised organs whose thin surface comes into contact
with the water. Various recesses of the pharyngeal cavity, the dorsal and
ventral folds of the tail-fin, nay, even any part of the skin of the body
can, and does occasionally, assume additional respiratory functions. The
proper definition of gills, in Vertebrates, requires, therefore, the
restriction that they must be developed upon and carried by visceral
arches.
The general statement that the Amphibia breathe by lungs, and, at least
during some stage of their life, also by gills, requires various
restrictions. As a rule the majority of Amphibia first develop gills, later
on also lungs, whereupon, during the metamorphosis, the gills are gradually
suppressed, so that the perfect animal breathes by lungs only (see p. 61).
But a number of Urodela retain their gills throughout life, although the
lungs are also functional. These are the Perennibranchiata, not a natural
group, but a heterogenous assembly, Proteidae and Sirenidae. Some species
of _Amblystoma_ remain individually Perennibranchiate (cf. Axolotl,
p. 112). On the other hand, in some Anura the gills are almost or entirely
suppressed, or restricted to the embryonic period only. Lastly, a
considerable number of Salamandridae have lost their lungs; they breathe by
gills until their metamorphosis, but have in the adult state to resort to
respiration by the skin (cf. p. 46).
The general plan of the development of the branchial respiratory apparatus
is as follows:–The six visceral arches, {41}namely, the mandibular, the
hyoidean, and the four branchial arches, correspond, long before they are
cartilaginous, with four main arterial arches of the truncus arteriosus.
The first, the arteria hyo-mandibularis, belongs to the hyoidean and
mandibular segments, the second to the first branchial, the third to the
second branchial, while the fourth soon splits in two for the third and
fourth or last branchial arch. On the dorsal side these branchial arterial
arches combine to form the radix of the dorsal aorta. These arches,
especially the three branchials, appear in newts, less clearly in frogs, as
transverse ridges on the sides of the future neck. Between the arches the
pharynx gradually bulges out in the shape of five lateral gill-pouches; the
first between the mandibular and the hyoidean arch, the second between the
hyoidean and the first branchial arch, etc. These pouches soon break
through to the outside and become gill-clefts, except the first pouch in
Urodela. _Before_ the breaking through of the clefts there appears upon the
outside of the middle of the rim of each arch a little knob, which soon
ramifies and forms an external gill. The knob owes its origin to the
development of a blood-vessel which buds from the arterial arch, ramifies
and breaks up into capillaries, and returns a little further dorsalwards
into the arch. A secondary loop to the outside of the primary arterial arch
is thus formed; and whilst this outer loop sprouts out further, driving
before it the likewise proliferating skin, and thus producing the gill, the
middle portion of the primary arch remains in the Urodela as a short cut,
but in the Anura it partly obliterates, and henceforth acts as the internal
_efferent_ vessel of the gill. When, during metamorphosis, the gills
disappear, their intrinsic _afferent_ and _efferent_ vessels vanish
likewise, and the short cut completes the circuit. In order to do this they
have, in the Anura, to form new connections with the trunks of the afferent
vessels.
The arterial arches themselves are modified as follows:–The first pair
become the carotids, the second form the right and left aortic arches,
while the third and fourth unite and are transformed into the pulmonary
arteries and "ductus Botalli," the last arterial arch having previously
sent a branch into the developing lungs. In the Anura the third arch
obliterates.
The gills and clefts present various modifications. The Urodela possess
three pairs of gills, one each upon the dorsal {42}half of the three
branchial arches, just near the upper corners of the clefts; and the skin
of the body is continued upon the stem of each gill, pigmented like the
rest of the surface of the body. Such a gill is more or less like a blade,
standing vertically, and is composed of a stem of connective tissue, thick
at the base, and, as a rule, carrying two series of fine lamellae, which,
however, do not form two opposite series, but hang downwards, being, so to
speak, folded down, so that the upper surface of the stem is bare, and
carries the lamellae on its under side. In the Axolotl some of these
lamellae are further subdivided. In _Necturus_ they are enormously
increased in numbers, but are rather short, and they stand no longer in two
rows, but are crowded into one. Those of _Proteus_ form two rows of
dendritic filaments; those of _Siren_ are likewise much ramified.
The larvae of the Urodela have four clefts. In the adult _Siren_ these are
reduced to three, the first, namely, that between the hyoid and the first
branchial arch, being closed up. In _Necturus_, _Proteus_, and
_Typhlomolge_ the clefts are further reduced to two, owing to the closing
up of the first and last, only those between the first, second, and third
arches remaining. _Amphiuma_, and usually _Cryptobranchus alleghaniensis_,
possess only one pair of clefts, while in _C. japonicus_ and in the
Salamandridae all the clefts are abolished.
The gills of the Urodela are always uncovered, although a short operculum
is formed from the posterior margin of the hyoidean arch; the halves of
this fold meet below the throat, and persist in various terrestrial and
aquatic species as the "gular fold." It reaches its greatest size just
before metamorphosis, but scarcely ever produces a proper outer
gill-chamber, and it does not cover the gills owing to their rather
pronounced dorsal position. It is perhaps best developed in _Typhlomolge_,
and even there its dorsal portion is continued upon the first of the three
broad vertical and short-fringed blades which form the gills.
A description of the gills of the Apoda will be found in the systematic
part.
In the Anura the gills are complicated, owing to the development of the
so-called internal gills. First appear, exactly in the same way as in the
Urodela, the external gills, one upon each of the first three branchial
arches. In the larva of _Rana esculenta_, 5 mm. in length, a little
protuberance appears upon the first, {43}and then upon the second arch. In
the 6 mm. larva the first gill shows four knobs, the second two, the third
one knob. They are always delicate and thin, although sometimes pigmented,
long, and much-ramified structures. The first pair is always the largest;
well developed and persisting a long time in _Rana temporaria_; smaller in
_R. esculenta_ and _Bufo vulgaris_; very short, scarcely forked, in _B.
viridis_ and _Hyla arborea_. They are relatively largest in _Alytes_, while
still in the egg. Numerous descriptions of these gills will be found in the
systematic part.
Great changes take place about the time when the fourth or last branchial
arch and the pulmonary arteries are developed. This occurs in _R.
esculenta_ when the larva is about 9 mm. long. The sprouting of the gills
extends gradually downwards along the arches upon their ventral halves, and
these new gill-filaments or loops transform themselves into numerous
dendritic bundles, resting in several thickset rows upon the hinder margin
of the first to the third arch, one row only on the fourth arch, which
carries no external gill. These "internal gills" look like red bolsters or
thick and short-tasselled bunches. Whilst they are developing the dorsal,
older gills become arrested in their growth and disappear, and at the same
time a right and left opercular fold grows out from the head and covers
these new gills, shutting them up in an outer branchial chamber, just like
that of Teleostei and other Tectobranch fishes. This is the reason why
these new gills have been called internal, and the mistaken notion has
sprung up that they are comparable with the true internal gills of fishes.
In reality Amphibia have only external gills. They are always covered by
ectoderm, are restricted to the outside of the branchial arches, and are
developed before the formation of the clefts. These gills are in many cases
directly continuous with the more dorsally and more superficially placed
earlier external gills; but although nearly every one who has studied their
development has observed this agreement, the old error still prevails. They
are morphologically as little internal as the true internal gills of
Elasmobranch embryos are external gills, because these have become so
elongated that they protrude out of the gill-clefts.
The fact that the Amphibia possess only external gills throws important
light upon their phylogeny. Not only do the Apoda, Urodela, and Anura agree
much more with each other than {44}would be the case if the Anura possessed
both internal and external gills, but the Amphibia reveal themselves also
in this point as connected with the Crossopterygii and the Dipnoi, some of
which fishes also possess external gills. It is of course quite possible
that the Amphibia have developed these organs independently, but we
understand now that the latter are accessory, and not the primitive
respiratory organs; they are developed in adaptation to embryonic
conditions and to prolonged larval, occasionally perennibranchiate, aquatic
life (cf. the chapter on Neoteny, p. 63).
There is no valid reason for supposing that the Stegocephali had true
internal gills. We know their branchial skeleton, and we can discern even
gill-rakers on the arches. Such gill-rakers occur also, although but feebly
developed, in Urodela. The whole branchial framework of the Urodela and
Apoda undergoes simple reductions during metamorphosis (see p. 86), but in
the Anura these arches are in early tadpole life transformed into a most
complicated basket-work which acts as a straining apparatus or filter, to
prevent any particle of food or other foreign matter from finding its way
into the delicate gills, the current of water passing from the mouth
through the filter, past the gills and out of the clefts. During
metamorphosis this whole elaborate apparatus is again transformed, almost
beyond recognition, into the hyoidean apparatus for the support of the
generally very movable and much-specialised tongue. The fact that the hyoid
apparatus of the Aglossa, especially that of _Xenopus_, is constructed upon
the same lines, is a strong indication that these creatures have arrived at
their tongueless condition through the loss of this organ, and this is
intelligible in correlation with their absolutely aquatic life.
The opercular folds assume great dimensions in all tadpoles. They cover the
whole gill-region, thereby producing on either side an outer gill-chamber.
The posterior margins of the folds gradually become continuous with the
rest of the surface of the body. Each gill-chamber opens at first by one
lateral canal, usually called the spiracle. This condition prevails in the
tadpoles of the Aglossa. In the Discoglossidae the two canals gradually
converge and combine into one median opening on the middle of the belly. In
all the other Anura the right opening becomes closed, or rather its canal
passes over to and joins that of the {45}left side, both opening by one
short tube laterally on the left side, at a variable distance between the
eye and the vent. Hence the elegant terms of Amphi-, Medio-, and
Laevo-gyrinidae (γυρῖνος being the Greek for tadpole).
The external gills lead to a further consideration. _Protopterus_ possesses
a vestigial external gill on the shoulder-girdle. _Lepidosiren_ has them on
the gill-arches, resembling piscine internal gills, and _Polypterus_ has a
large biserially fringed external gill (in some cases not disappearing
until the fish is adult), which starts from the mandibular arch, at the
level of the spiracle or first visceral cleft, and overlaps the operculum
externally. The axis of this peculiar organ is possibly based upon the
homologues of the spiracular cartilages, which themselves are the
branchiostegal rays of the dorsal half of the quadrato-mandibular arch. The
branchiostegal rays of the hyoidean arch, at least their material, have
given rise to the elaborate opercular apparatus; and, in conformity
herewith, the hyomandibular itself is not known to carry a gill. Quite
possibly the large external gill of _Polypterus_ is not serially homologous
with other external gills–it may not be a true gill at all, it has perhaps
quite a different function–but it seems to throw light upon a mysterious
pair of organs which are common in larval and young Urodela, in the larval
Aglossa and in the Apoda. These are the "balancers."
In _Triton taeniatus_, before hatching, there appears a little protuberance
behind and below the eye; it rests upon the angle of the mandibular arch,
and is separated from the first transverse, externally visible ridge of the
first branchial arch by the beginnings of the hyoidean arch. A few days
later the arteria hyomandibularis sends a vessel into this knob, forms a
vascular coil, and leaves it as a vein which, instead of returning into the
arterial arch, passes into the veins of the body. Its epithelium is not
covered with flat, but with cubical cells; and sensory cells have not been
found in it. These organs attain some size, and are shaped like rods, with
thickened ends; they are movable, and are used by the larvae as
"balancers," keeping the head from sinking into the slime at the bottom.
But they may have other functions besides, and it is not unlikely that they
develop into sensory organs like feelers. They occur in many Salamandridae,
and are not reduced until, or even after, the metamorphosis, and during
this time they shift their place with relation to the eye and the mouth.
{46}The same kind of organs occur in _Amblystoma_.[18] They appear,
previous to the breaking open of the gill-clefts, as protrusions of
epiblast, long before any of the external gills on the branchial arches.
When the clefts have broken open, the quadrate sends out laterally a tiny
crescent-shaped process a little above the jaw-joint, and this process
extends to the base of the balancer, but not into it, and a bundle of
muscle-cells grows into the balancer. It is easy to recognise the same
organ in the extremely long thread-like structures of the larva of
_Xenopus_. In the Apoda they are likewise present, but are retained
permanently as highly specialised, probably tentacular organs (cf. p. 86,
Apoda).
One of the most unexpected features is the SUPPRESSION OF THE LUNGS in
various kinds of Salamandridae. The lungs are either reduced to useless
vestiges or they are quite absent. This occurs in aquatic and terrestrial,
American and European forms, and it is noteworthy that the reduction of the
lungs does not apply to all the species of the various genera, nor is it
restricted to one sub-family.
The following list is due to the researches of H. H. Wilder,[19] L.
Camerano,[20] E. Lönnberg,[21] and G. S. Hopkins[22]:–All the
Desmognathinae and Plethodontinae; Amblystomatinae, _Amblystoma opacum_;
Salamandrinae, _Salamandrina perspicillata_. In _Triton_ and other
Salamandrinae the length of the lungs varies; in some they extend more, in
others less, than half way down the distance between head and pelvis.
Hopkins remarks: "Two questions are naturally suggested by this apparently
aberrant condition of the respiratory organs. First, what structures or
organs have taken on the function of the lungs and branchiae; and secondly,
is there any modification in the form or structure of the heart which in
any way may be correlated with the above-mentioned peculiarities of the
lungless forms?" Wilder concluded that respiration was probably carried on
by the skin, and perhaps, to some extent, by the mucosa of the intestine.
Camerano thinks that, at least in the European forms, respiration is
effected by the bucco-pharyngeal cavity, and that the skin affords no
efficient aid. The left auricle in the lungless forms is much {47}smaller
in comparison than the right, and there is no pulmonary vein. The auricular
septum has a large aperture, the communication between the auricles being
larger than even in _Necturus_ (which breathes essentially by gills). The
sinus venosus, instead of opening into the right auricle only, opens more
freely into the left than into the right, and the latter communicates more
directly with the ventricle than the left, instead of about equally. In
short, the heart of these creatures appears almost bilocular, instead of
being trilocular, at least functionally.
The lungs of the Urodela are always simple, extremely thin-walled bags.
They are highly developed in the Anura, the walls being modified into
numerous air-cells, whereby the respiratory surface is considerably
increased. The lungs are filled with air by the pumping motion of the
throat while the mouth is closed, the nostrils being provided with muscular
valves. A muscular apparatus assists the filling of the lungs in the
Anura.[23]
[Illustration: FIG. 6.–Internal view of the mouth of A, _Rana esculenta_,
B, _Bufo calamita_ (cf. Fig. 52, p. 269). _Ch_, Choana, or inner nasal
opening; _E_, opening of the Eustachian tube; _S_, slit leading into the
vocal sac; _T_, tongue; _Vo_, patches of teeth on the vomers.]
Most, if not all, Anura and some Urodela have a VOICE produced by the
larynx, which, especially in the Anura, is provided with a complicated
cartilaginous and muscular apparatus and with vocal cords. The voice of the
Urodela is at the best a feeble squeak. The females of the Anura are either
mute or they produce a mere grunt, but that of many males is very loud,
and, moreover, in many species it is intensified by _vocal sacs_ which act
as resonators. These sacs are diverticula of the lining of the
mouth-cavity, and bulge out the outer skin and the muscles, chiefly the
mylo-hyoid, of the throat. The nostrils and the mouth are firmly closed
during the croaking. "The sacs are called internal when they are covered by
the unmodified gular integument, however much this may be distended;
external when their membrane projects through slits at {48}the sides of the
throat, as in _Rana esculenta_ (Fig. 52, p. 269), or when the skin is
thinned and converted into a bladder-like pouch, as in _Hyla arborea_."[24]
These sacs exhibit many modifications. They may be unpaired and median, and
open by two slits into the mouth, on either side below the tongue; in
_Bufo_ one of the slits or openings, either the right or the left, is
obliterated. They may be paired and symmetrical, and open one on each side
of the head, below and near the posterior angle of the jaws. These
modifications differ in closely allied species. They reach their greatest
complication in _Rhinoderma_ and in some of the Cystignathidae by extending
far back beneath the skin into the wide lymphatic spaces. In _Rhinoderma_
they are put to the unique use of nurseries for the young (see p. 228).
_Leptodactylus typhonius_ has a very distinct pair of outer vocal sacs and
a well-marked unpaired sac which extends into the belly and communicates
with each outer sac. Several species of _Paludicola_, e.g. _P.
fuscomaculata_ and _P. signifera_, have a similar arrangement, in addition
to an unpaired gular sac which can be inflated independently of the rest
(see Fig. 45, p. 220).
URINO-GENITAL ORGANS
The kidneys and the male generative glands are still intimately connected
with each other. The general plan is as follows:–
The kidneys consist of a large number of glomeruli, produced by the coiled
segmental tubes, each of which is composed of a nephrostome or funnel
opening into the body-cavity, a Malpighian body and an efferent canal. The
latter combine to form the segmental duct which opens into the cloaca. The
testes, composed of a large number of sperm-producing glands, are drained
by transverse canals which combine into a longitudinal canal, and this
again sends off numerous efferent canals which open into the efferent
canals of the kidney, so that the segmental duct (Leydig's duct of many
authors) conveys both sperma and urine.
{49}[Illustration: FIG. 7.–Diagrammatic representation of modifications of
the urino-genital ducts. 1, 2, Male and female Newt; 3, a tubule of the
kidney; 4, male _Rana_; 5, male _Bufo_; 6, male _Bombinator_; 7, male
_Discoglossus_; 8, male _Alytes_. _a_, Artery entering, and producing a
coil in, the Malpighian body, _M_; _B_, Bidder's organ; _ef.s.c_, efferent
segmental canal; _F.B_, fat-body; _gl_, glomerulus; _K_, kidney; _l.c.c_,
longitudinal collecting canal; _M_, Malpighian body; _Md_, Müllerian duct;
_N_, nephrostome; _O_, ovary; _Ov_, oviduct; _s.d_, segmental duct; _T_,
testis; _Ur_, ureter; _V.d_, vas deferens; _V.s_, vesicula seminalis.]
{50}In the female the network of transverse and longitudinal canals, which
originally connect the generative glands with the kidney's efferent canals,
is deduced in so far as the connection is interrupted and the vestiges of
the transverse canals are no longer functional. The eggs fall into the
body-cavity and are caught up by the ostium or inner abdominal opening of a
special duct, the oviduct (Müllerian duct of many authors). Vestiges, more
or less complete, of these oviducts persist in the males of most Amphibia.
This general scheme presents some modifications in the various groups of
Amphibia.
The Apoda retain the most primitive conditions. The kidneys are still long
and narrow, and the glomeruli are, at least in the anterior part of the
organ, still strictly segmental, agreeing in number and position, each with
a vertebral segment; later, the number of the glomeruli is greatly
increased, and the former agreement becomes quite disturbed. The generative
glands still retain their segmental arrangement, but they are restricted to
a much shorter region than the kidneys. In the male Apoda a considerable
portion of the cloaca can be everted by special muscles, and acts as an
intromittent organ. Both sexes possess a ventral urinary bladder.
In the Urodela both kidneys and testes are much concentrated, the testes
especially have lost all outward appearance of segmentation, and their
efferent canals, connecting them with the longitudinal collecting canal,
are much reduced in numbers. The greater portion of the kidneys, at least
their anterior half, has all the appearance of a degenerating organ and is
on the way to losing its urinary function, although it still possesses
Malpighian bodies and complete ducts; the main function of the latter is
now the conveyance of the sperma. In the Perennibranchiata, and in some
others, e.g. _Spelerpes variegatus_, the longitudinal collecting canal,
between testis and kidney, is sometimes suppressed, a very simple, but
pseudo-primitive arrangement. A urinary bladder is present. The cloaca is
not eversible.
In most Anura, e.g. _Rana_ and _Bufo_ (Fig. 7; 4, 5), the same scheme is
adhered to. The efferent canals of the testis form a network, with a
longitudinal canal, and open into the efferent canals of the kidney, in the
substance of which they are more or less deeply imbedded. The ducts which
lead out of the kidney to compose Leydig's duct, are frequently dilated, or
the latter duct is much elongated, convoluted or varicated, and this whole
portion is enclosed in a sheath of connective tissue, giving an
{51}appearance as if the single duct itself were dilated in the greater
part of its length; hence the occasional name of vesicula seminalis. Such
means of storing the sperma enable the latter to be ejected suddenly in
great quantities.
In _Bombinator_ (6) some of the most anterior seminal canals do not
perforate the kidney, but run over it superficially and open directly into
a branch of Leydig's duct. This branch, no doubt equivalent to a number of
segmental canals which have lost their uriniferous function, is curved
round the upper end of the permanent kidney, while its forward
continuation, ending blindly, is the remnant of its former headward
extension. This arrangement of _Bombinator_ is carried further in
_Discoglossus_ (7). The testis conveys its sperma through a wide duct
directly into Leydig's canal, without interfering with the kidney, and all
the testicular efferent network is lost. The anterior end of Leydig's duct
still extends headwards; its middle portion acts solely as a vas deferens,
while the lower portion still behaves like a typical segmental duct,
conveying both sperma and urine. Lastly, in _Alytes_ (8) the functional
division of the old segmental duct has been carried to an extreme. The
kidney is drained by one canal only, now a true ureter, and this is of
course produced by a consolidation of the multiple exclusively uriniferous
canals of the lower half of the kidney. The whole of the segmental duct is
now in the service of the testis, and near its junction with the ureter it
forms a large diverticulum or true vesicula seminalis.
Remnants of oviducts, or Müllerian ducts, are common in the male Anura;
they are best developed in _Bufo_, much reduced, and individually absent,
in _Rana_. In _Bombinator_ each duct is restricted to its upper or
abdominal portion, and is attached to the vestigial headward extension of
Leydig's duct. Lastly in _Discoglossus_ and in _Alytes_ all traces of
oviducts seem to have vanished, at least in the adult males.
It is interesting to note that in the arrangement of the urino-genital
ducts the Discoglossidae are the most advanced of all Amphibia, instead of
showing the most primitive conditions. This is rather unexpected, but is
paralleled by the epichordal type of the vertebral column.
The oviducts of the Apoda and Urodela remain more or less straight; in the
viviparous species they form uterus-like dilatations. In the Anura they
become greatly elongated during the {52}breeding season and form many
convolutions. As a rule each oviduct opens separately into the cloaca, but
in _Hyla_ they have one unpaired opening, while in _Bufo_ and _Alytes_ the
lower parts of both oviducts are themselves confluent.
All Amphibia possess FAT-BODIES. They consist of richly vascularised
lymphatic tissue, the meshes of which are filled with lymph-cells, globules
of fat and oil. In the Apoda these bodies lie laterally to the generative
glands, and along the posterior half of the kidneys. In the Urodela they
accompany the anterior half of the kidney. In the Anura they are lobate,
and are placed upon the anterior end of the testes or ovaries. Their exact
function is still doubtful, but it is intimately connected with that of the
generative glands. The old notion, that they are simply stores of fat for
the nourishment of the animal during hibernation, is quite untenable. The
fat-bodies do not decrease during this period, on the contrary they attain
their fullest size in the spring at the time of the rapidly awaking
activity of the reproductive organs, and they enable considerable
quantities of sperma and of eggs to be produced and ripened without
detriment to, or utter exhaustion of, the animals, which often spawn before
they have had time or opportunity to feed. After the spawning season the
fat-bodies have dwindled down to inconspicuous dimensions.
Lastly, there is in some Anura, hitherto observed in _Bufo_ only, a
mysterious organ, intercalated between the fat-body and the testis or
ovary. This is "Bidder's organ" and it seems to be a rudimentary ovary, or
rather that upper, anterior portion of the whole organ which undergoes
retrogressive metamorphosis. It disappears in old female toads, but in the
males it sometimes assumes a size equal to, or surpassing that of the
testes. The males are in this respect hermaphrodite, and cases are known in
which parts of the generative glands have developed testes and egg-bearing
ovaries.
The SPERMATOZOA of the Apoda and Urodela have an undulating membrane along
the tail, while the head-end is either pointed or truncated. Those of
_Spelerpes fuscus_ and of _Ichthyophis glutinosa_ measure about 0.7 mm. in
total length, those of the other Urodela being much smaller. A peculiarity
of the Urodela is that their spermatozoa are massed together in or upon
spermatophores, an arrangement which undoubtedly facilitates the internal
{53}fecundation of the female without actual copulation. The female takes
up such a deposited spermatophore with the cloacal lips, squeezes the
sperma out of the capsule which remains behind, and either conveys the
former into a special receptaculum seminis, _e.g._ in _Salamandra atra_ and
in _Triton_, or the spermatozoa wriggle their way, thanks to the undulating
tail, directly up the oviducts to the ova.
The spermatophores are composed of a colourless, soft, gelatinous mass,
which is probably produced by the cloacal gland. The shell of jelly is in
fact a cast of the cloacal cavity, reproducing all its ridges, furrows and
folds, while a toad-stool-shaped papilla of the cloaca makes the inside
lumen of the cast, _e.g._ in _Triton_. Those of _Salamandra maculosa_ are
much simpler, consisting, in conformity with the absence of a cloacal
papilla, merely of a cone with a globular mass of sperma on the top. Those
of _Amblystoma_ are similar.
The spermatozoa of the Anura show considerable differences in the various
genera, of which, however, only the European forms have been properly
examined. The "head" is wound like a corkscrew in _Discoglossus_,
_Pelobates_, and _Pelodytes_; spindle-shaped, more or less curved, in _Rana
temporaria_ and _R. agilis_, _Hyla_, _Bufo_ and _Bombinator_, in the latter
with an irregular membrane on one side; cylindrical in _Rana esculenta_ and
_R. arvalis_. The tail is mostly long and filiform, but in _Bufo vulgaris_
and _Discoglossus_ it is provided with an undulating membrane. Their size
is generally very small, only about 0.1 mm., excepting those of
_Discoglossus_ which reach the astonishing length of 3 mm. These
differences in shape, especially that of the head, explain why species of
the same genus, e.g. _Rana temporaria_ and _R. arvalis_, cannot fertilise
each other.
[Illustration: FIG. 8.–A bell-shaped spermatophore of _Triton alpestris_. ×
3. (After Zeller.)[25]]
The EGGS differ much in size, colour, and numbers. They are holoblastic,
with unequal cleavage, but those species which possess an unusual amount of
food-yolk, for instance _Rhacophorus schlegeli_ and the Apoda, approach the
meroblastic type of segmentation. As a rule, the greater the amount of
yolk, the smaller is the number of eggs produced. But the number which is
laid {54}during one season is not only difficult to calculate, but it
varies individually, old females laying more than young specimens.
Moreover, some kinds, _e.g._ the Discoglossidae, spawn several times in one
year. _Alytes_, _Rhinoderma_, _Hylodes_, _Rhacophorus_, _Pipa_, in fact
those kinds which are remarkable for special nursing habits, lay only a few
dozen eggs at a time. _Hyla arborea_ produces up to 1000, _Rana temporaria_
about 3000, _Bufo vulgaris_ averages 5000, _Bufo viridis_ and _Rana
esculenta_ up to 10,000 and more. T. H. Morgan[26] has observed a _Bufo
lentiginosus_ which laid 28,000 eggs within ten hours! The number of eggs
produced by the Apoda and Urodela is comparatively moderate, in the average
a few dozen, _Amblystoma_ alone laying about 1000.
The eggs possess a gelatinous mantle of variable thickness and consistency.
In _Amphiuma_ they are strung together like the beads of a rosary, and the
envelope hardens into a kind of shell. Many Newts and some Anura fasten
their eggs singly on to plants and other objects in the water, with or
without threads of stiffening mucus. In many Anura, _e.g._ Bufonidae, they
pass out as closely-set strings of beads, one string out of each oviduct;
in others, _e.g._ Ranidae, they are disconnected, and form large, lumpy
masses, especially when the gelatinous mantle swells up in the water. The
use of this mantle seems to be chiefly the protection of the growing
embryo, which in many species, when hatched out of the egg proper, drops
into and remains for some time in the softened jelly. Possibly the latter
affords some nutriment to the early larva.
Concerning the mode of FECUNDATION it is to be remarked that copulation
proper takes place only in the Apoda. For the Urodela Boulenger[27] has
given the following summary. In no case does actual copulation take place.
The male deposits the spermatophores which it is the office of the female
to secure:–
I. No amplexus, but a lengthy courtship in the water; the male is more
brilliantly coloured than the female, and ornamented with dorsal and
caudal crests, or other appendages: _Triton_, cf. also systematic part.
II. Amplexus takes place; there are no marked sexual differences in
colour and no ornamental dermal appendages.
A. Amplexus of short duration, partly on land, but deposition of the
sperma in the water. No accessory sexual characters: Terrestrial
Salamanders, namely _Salamandra_, _Chioglossa_, _Salamandrina_.
_Spelerpes_ breeds in damp caves without water.
{55}B. Amplexus of lengthy duration and in the water.
_a._ The male, distinguished by a greater development of the
fore-limbs, which are armed with temporary excrescences, clasps the
female in the axillary region with the fore-limbs: _Triton waltli_.
_b._ The male, distinguished by a greater development of the
hind-limbs and a prehensile tail, clasps the female in the lumbar and
caudal regions: The _Euproctus_-group of newts: _Triton asper_, _T.
rusconii_, and _T. montanus_.
The act of fecundation of most of the other kinds of Urodela, notably
_Cryptobranchus_, _Amphiuma_, _Proteus_, has not yet been observed.
Embracing of the two sexes is the universal rule with the Anura, the male
creeping on to the back of the female and clasping her firmly with the arms
and hands either in the inguinal region, higher up, or under the armpits.
See the numerous statements in the systematic part. This often extremely
forcible, pressing embrace seems to be necessary, although the females can
deposit the eggs without the help of the male, but in such cases the
expulsion takes place at irregular intervals instead of at one time. When
the eggs appear at last, and this happens in many species many hours, or
even some days, after the beginning of the embrace, the male voids the
contents of its seminal vesicles over them. Fertilisation is consequently
external, with the possible exception of _Pipa_, _q.v._ p. 152.
DEPOSITION OF THE EGGS AND NURSING HABITS.–The majority of the Amphibia are
oviparous, but some Apoda and Urodela are viviparous. It is unnecessary to
call the latter condition ovo-viviparous, since this is really a
distinction without a difference.
Viviparous forms:–amongst Urodela; _Salamandra maculosa_, the young burst
the egg-membrane in the act of being born, and are provided with long
gills; _S. atra_, the young undergo their whole development and
metamorphosis within the uterus (see p. 119); _Spelerpes fuscus_, the young
are likewise born in the perfect condition: amongst Apoda; _Typhlonectes
compressicauda_ and _Dermophis thomensis_.
The oviparous Apoda, at least _Ichthyophis_ and _Hypogeophis_, and a few of
the Urodela, as _Desmognathus_ and _Amphiuma_, take care of their eggs by
coiling themselves around them in a hole underground.
Nursing habits are very common amongst the Anura. {56}Boulenger[28] has
summarised the various conditions concerning the deposition and care that
is taken of the eggs, in the following list, in which more recent
discoveries have been interpolated.
I. The ovum is small, and the larva leaves it in a comparatively early
embryonic condition.
A. The eggs are laid in the water:–
_a._ Without further care or preparations: probably the majority of
Anura; all European forms, except _Alytes_.
_b._ The eggs are laid in a specially walled-in part of the pond:
_Hyla faber_.
B. The eggs are deposited out of the water:–
_a._ In holes, or under grass, near the banks of pools. The larvae
are liberated and washed into the water by the next heavy rain:
_Leptodactylus ocellatus_, _L. mystacinus_, _Paludicola gracilis_,
_Pseudophryne australis_ and _P. bibroni_.
_b._ On leaves above the water, the larvae dropping down when leaving
the egg: _Chiromantis rufescens_, _Phyllomedusa iheringi_, _Ph.
hypochondrialis_.
II. The yolk is very large and the young undergoes the whole or part of
the metamorphosis within the egg; at any rate the larva does not assume
an independent existence until after the loss of the gills.
A. The eggs are deposited in damp situations, or on leaves. The young
escape as:–
_a._ Tadpoles: _Arthroleptis seychellensis_, _Rhacophorus schlegeli_,
_Rh. maculatus_.
_b._ Perfect, air-breathing frogs: _Rana opisthodon_, _Hylodes
martinicensis_, _Hyla nebulosa_.
B. The eggs are carried by a parent.
_a._ By the male:–
α. Round the legs; the young leaves the egg in the tadpole stage:
_Alytes_.
β. In the enlarged vocal sacs; the young leave in the perfect
state: _Rhinoderma_.
_b._ By the female:–
α. Attached to the belly: _Rhacophorus reticulatus_.
β. Attached to the back; the young complete their metamorphosis
within the egg: _Pipa_.
γ. In a dorsal pouch which the young leave as tadpoles: _Nototrema
marsupiatum_;–or in the perfect state: _Nototrema testudineum_, _N.
cornutum_, _N. oviferum_, _N. fissipes_, and _Hyla goeldii_.
THE DEVELOPMENT AND METAMORPHOSIS of many species have been described in
the systematic part. The following is a short general account of some of
the more important features. Metamorphosis in the Apoda and Urodela is
restricted chiefly to the reduction of the gills, the closing of the
clefts, and the loss of the {57}gill-chamber and the finny margins of the
tail; but the change from the tadpole to the final Anurous animal implies
an almost entire reorganisation.
[Illustration: FIG. 9.–Four stages of the development of the adhesive
apparatus (_A_) of _Bufo vulgaris_; _M_, Mouth; _Sp.T._ spiracular tube. In
3 the gills are almost completely hidden by the united right and left
opercular folds. The small outlined figures indicate the shape and natural
size of the tadpoles. (After Thiele.)]
In the earliest condition the embryo consists of a large head and body,
while the tail is still absent. Behind the beginnings of the future mouth
appears a transverse crescentic fold, with the convexity looking backwards,
which develops into the paired or unpaired _adhesive apparatus_. This
consists of large complex glands, developed in the Malpighian layer,
originally covered by the cuticula, which soon disappears, whereupon the
sticky secretion enables the larva to attach itself to the gelatinous
mantle of the egg, later on to weeds or other objects in the water. The
name of suckers, often applied to this apparatus, conveys a wrong idea,
there being neither muscles nor any suctorial function. The shape of this
organ undergoes many changes during the early life of the individual, and
differs much in the various genera, affording thereby diagnostic
characters.[29] At first a crescent, it divides into a right and a left
oval or disc, which either remain asunder and behind the mouth (_Rana_,
_Bufo_), or they move forwards to the corners of the mouth (_Hyla_) or
further back, and unite again more or less completely, as in _Discoglossus_
and _Bombinator_. It is mostly of short duration, and disappears by the
time that the larva, by the proper development of the gills and the tail
and the functional mouth, changes into the tadpole. But in a few species
these discs transform themselves into an elaborate ventral disc. Such an
organ persists throughout the greater part of the tadpole-stage in certain
Oriental species of _Rana_, all of which, when adult, possess fully webbed
toes and {58}strongly dilated discs on the fingers and toes, e.g. _Rana
whiteheadi_, _R. natatrix_, and _R. cavitympanum_ of Borneo, _R. jerboa_ of
Java (this larva was originally described and figured as that of
_Rhacophorus reinwardti_), and _R. afghana_ of the Himalayan system. These
tadpoles, at least those of _R. jerboa_, are further remarkable for having
the "spiracular" opening very far back on the left side, nearer to the base
of the tail than to the snout, so as to be well out of the way when the
creature has attached itself by the adhesive disc.
[Illustration: FIG. 10.–1, Front view of the mouth of a tadpole of _Rana
temporaria_, showing the transverse rows of tiny horny teeth; 2, three
successive horny teeth, much magnified. (After Gutzeit.)]
The mouth of the tadpoles of Anura is furnished with horny armaments,
substitutes for teeth. Their development and that of the mouth in general
has been well described by Gutzeit.[30] In the young larvae of _Rana
temporaria_, one or two days after hatching, a shallow groove appears above
the conspicuous pair of adhesive organs. The groove becomes rhombic in
outline, and when the mouth has been formed in its centre, the jaws appear
in the median corners of the rhombus. The epidermis then rises like a
circular wall around the jaws, and divides into an upper and lower lip;
furrows appear on them, and between these various papillae and comb-like
transverse plates of teeth. The papillae are possibly tactile organs, but
although nerves enter them, nerve-endings of a sensory nature have not yet
been discovered. On the fourth day the jaws become black, by the tenth day
horny teeth have appeared upon all the plates of the mouth-armature, and on
the seventeenth day the mouth-apparatus has reached the configuration
typical of the tadpole, which is now about 14 mm. long. The number of horny
teeth in _R. temporaria_ amounts to about 640. These teeth are not
cuticular products, but cornified cells; they are very small, and consist
each of one horny cell, which is shaped like a nightcap, the apex of which
is curved back and serrated. The little teeth are shed continuously,
{59}the renewal taking place by successive cells growing into the bases of
the older series. The shape and size differ much in the various genera and
species. The comb-like plates, composed of those teeth which surround the
lips, seem to be used chiefly for the fixing or hooking of the food, while
those which compose the horny beak proper, the armature of the jaws, are
used like the radulae of snails. These beaks are likewise composed of a
great number of individual teeth, closely packed together in several rows,
but the teeth themselves are simple and not serrated.
In _Hyla arborea_ there are in all about 560 teeth. The development of the
mouth does not begin before the eleventh day; the horny teeth break
through, and the jaws get black edges, on the eighteenth. In _Pelobates
fuscus_ the number of horny teeth is increased to about 1100. In
_Borborocoetes taeniatus_ the horny teeth form series of five bells, which
fit into each other like the joints of a rattlesnake's tail.
One of the most extraordinary kinds of tadpoles is that of _Megalophrys
montana_.[31] Mr. Annandale (Skeat Expedition) found it at Bukit Besar,
Malay Peninsula, from 2000 to 3000 feet above the level of the sea. The
tadpoles (Fig. 11) were found in the beginning of the month of May 1899 in
sandy streams and in pools of rain-water; they floated in a vertical
position, the peculiar membranous funnel-shaped expansion of the lips
acting as surface-floats. The inside of the funnel is beset with radiating
series of little horny teeth, and the whole apparatus is possibly used for
scraping the under-surface of the leaves of water-plants in search of food.
Total length of the tadpoles 1 inch.[32]
The gills, the formation of the operculum, and the modifications of the
branchial arterial arches have been described fully on p. 43; those of the
hyo-branchial skeleton on p. 31. Fusion of the opercular fold with the skin
of the neck, across the branchial region, causes the head to become
confluent with the trunk (cf. Fig. 9, 3, p. 57). The body becomes oval,
more or less globular, and the alimentary canal is greatly elongated and
stowed away in the shape of a neat, very regular spiral, shining through
{60}the ventral wall of the body; the anus opens at the end of a somewhat
protruding tube, either in the median line, just in front of the ventral
fin (Discoglossidae, _Pelobates_, _Bufo_), or it assumes an asymmetrical
position by turning to the right side (_Hyla_, _Rana_).
[Illustration: FIG. 11.–Tadpoles of _Megalophrys montana_ from Bukit Besar,
Malay Peninsula. × 3.]
Although both pairs of limbs begin to bud simultaneously, or the fore-limbs
even earlier, the hind-limbs are hurried on, and appear first, long before
the fore-limbs. The latter lie ready beneath the skin of the gill-chamber,
and the right always breaks through the skin, while the left does the same
in the Mediogyrinidae, while in the Laevogyrinidae it is generally pushed
through the left-sided spiracular opening, immediately behind the outer
gills. According to Barfurth the right limb appears, in about 80 per cent.
of _Rana esculenta_, from two to eight hours before the left.
{61}Meanwhile the lungs are being developed, and the tadpole occasionally
rises to the surface to breathe air. The gills, which, as has been
explained elsewhere, are less ancestral than they are larval organs,
degenerate, and all the organs are modified for the coming terrestrial
life. The fins of the tail are absorbed, the horny armature of the mouth
and lips is shed in pieces and makes room for the true teeth, the eyes
receive lids, and the whole cranium, especially the apparatus of the jaws,
undergoes the final modifications–widening and lengthening of the mouth,
arresting of the mento-Meckelian cartilages, elongation of the Meckelian
cartilages or lower jaw proper, shifting backwards of the suspensorium, and
lengthening of its orbital process to form the pterygo-palatine bridge.
The tadpole ceases to feed, the whole intestinal canal is voided of its
contents, and by "histolysis" is thoroughly rebuilt, becoming wider and
shrinking to about one-sixth of its original length,–undoing thereby the
spiral–preparatory for the coarser food, which consists of insects, worms,
and other strictly animal, living matter. Hitherto the tadpoles have lived
on "mud," confervae, Diatoms, rotting vegetable and animal matter. The anal
tube collapses, becomes ultimately absorbed, and a new vent is formed at
and below the root of the tail.
Barfurth[33] has made interesting observations and experiments with regard
to the absorption of the tail and other organs which disappear during the
metamorphosis. This is retarded by low temperature; it is accelerated by
rest and freedom from mechanical disturbances, as, for instance, concussion
of the water. Hunger shortens or hurries on the last stages of
metamorphosis, the absorption of the tail taking place in four instead of
five days. Amputation of the tail has no retarding influence; it is
followed at once by regeneration, although the tadpole may be on the verge
of reducing the tail. Whilst hungering the whole organism draws upon its
available store of material, naturally first upon those parts which sooner
or later are to become superfluous. This applies eminently to the tail,
which represents a considerable amount of "edible" matter, and also to that
portion of the skin which still covers the fore-limbs. The elements of the
cutis are resorbed, thereby thinning the skin; and consequently the limbs
break through earlier in fasting than in well-fed {62}specimens. Nature
herself seems to apply hunger as an accelerator. Mlle. von Chauvin found
that the larvae of Urodela normally fast during the transformation, and
according to Barfurth the larvae of _Rana temporaria_ eat less after their
hind-limbs are fully developed. This is, however, also preparatory for the
reorganisation of the gut, which has to be more or less empty during the
shortening process.
The loss of the tail is not due to a sudden dropping off of this organ–a
crude but by no means uncommon belief–but is brought about by a very
gradual process of resorbtion. When the fore-limbs begin to break through
the skin, the tip of the tail shrinks and becomes black, owing to an
increase, or rather concentration, of the pigment cells. The reduction
proceeds from the tip forwards until on about the fifth day there remains
only a short, conical, black stump. From the beginning of this process of
reduction the tail is scarcely used for locomotion, the tadpole rowing with
its legs, or it crawls and hops about, although the tail may still be 20
mm. long. The cells of the epidermis atrophy, shrink, and peel off, while
those of the cutis, blood-vessels, nerves, muscles, and chorda dorsalis
become disintegrated, often undergoing fatty degeneration. The leucocytes
eat up the débris and other dissolved tissue, and carry it away through the
lymphatic vessels, to be used as new building material in the rest of the
animal.
Barfurth asks very properly, Why do these tissues degenerate and die?
Because the vasomotor nerve-fibres cease to regulate the circulation. And
why does this trophic influence of the central nervous system stop? Because
the function of the tail becomes superfluous through the appearance of the
fore-limbs. The tail is doomed, and degenerates like any other organ
without a function. The whole process is, of course, a recapitulation of
ancestral, phylogenetic evolution.
{63}CHAPTER III
NEOTENY–REGENERATION–TEMPERATURE–GEOGRAPHICAL DISTRIBUTION
NEOTENY.–It has long been known that the larvae of the Spotted Salamander
occasionally attain the size of 80 mm. or about 3 inches, whilst the
majority undergo metamorphosis when they are only 40 mm. long. Again,
larvae of _Triton_ have been found, in the months of April and May, 80 to
90 mm. long, still with functional gills, but with the sexual organs fully
developed. De Filippi[34] found in one locality in Lombardy, besides a few
normal fully metamorphosed specimens of only 30 mm. in length, more than
forty specimens, which, although they had attained full size, about 55 mm.,
and were sexually mature, still retained their gills. According to him such
gill-breathing, otherwise mature specimens, occur constantly in a small
lake in the Val Formazzo, on the Italian slope of the Alps, in the province
of Ossola. Later Duméril[35] astonished the world by his account of the
metamorphosis of the Mexican gill-breathing Axolotl into an entirely
lung-breathing and terrestrial creature, hitherto called _Amblystoma_, and
supposed to be not only a different species, but to belong to a different
family from the Axolotl, which was known as _Siredon axolotl_ s.
_pisciforme_, and naturally classed with the Perennibranchiata.
This discovery led to a series of observations and experiments, chiefly
conducted by Marie von Chauvin, instigated thereto by Koelliker and by
Camerano.[36] It was then found that many, if not most of the European
Amphibia, both Urodela and Anura, {64}occasionally postpone their
metamorphosis, and also that such Urodela sometimes become adult for all
practical purposes, but retain their gills.
This retardation, the retention of larval characters beyond the normal
period, was called _Neotenie_ by Kollmann[37] (νέος, young; τείνω, extend,
stretch). He distinguished further between:–I. Partial Neoteny, namely,
simple retardation of the metamorphosis beyond the normal period, for
instance, the wintering of tadpoles of _Pelobates fuscus_, _Bombinator
pachypus_, _Pelodytes punctatus_, _Alytes obstetricans_, _Hyla arborea_,
_Rana esculenta_, _R. temporaria_, _Bufo vulgaris_, and _B. viridis_: II.
Total Neoteny, where the animal retains its gills, but becomes sexually
mature; hitherto observed in Urodela only, e.g. _Triton vulgaris_, _T.
alpestris_, _T. cristatus_, _T. boscai_, _T. waltli_ and _Amblystoma_.
Intermediate stages between these two categories are not uncommon.
A satisfactory explanation of the meaning of neoteny is beset with
difficulties. Some authorities look upon the phenomenon simply as the
result of adaptation to the surroundings, which make it advantageous for
the creature to retain its larval features. Others think that the
surroundings somehow or other retard or prevent the assumption of the adult
characters. Undoubtedly there are many cases in which larvae have been
reared in water-holes with steep walls, so that they could not change from
aquatic to terrestrial life, and it stands to reason that abnormally forced
and prolonged use of the gills and of the tail may stimulate these organs
into further growth at the expense of the limbs and other organs which are
intended for terrestrial life. But not unfrequently typical neotenic and
overgrown specimens occur side by side with others which have completed
their metamorphosis, and the same is true of larvae of newts which were
reared, for experimental purposes, under exactly the same conditions–for
instance, in a high-walled glass vessel.
Weismann tried to explain neoteny as cases of reversion to atavistic
ancestral conditions, but this idea is based upon an assumption which is
probably wrong. His idea necessitates the supposition that all the Amphibia
were originally gill-breathing, aquatic, and limbless animals, and that
every feature seen in a larva must necessarily indicate an ancestral
phylogenetic stage. It is, on the contrary, much more probable that {65}the
external gills of the Urodela have been developed in adaptation to their
embryonic and larval, essentially aquatic, life. Consequently the
possession of such gills would be a secondary, and not, strictly speaking,
an atavistic feature. Normal loss of these gills, exclusively pulmonary
respiration, and preponderating terrestrial life characterise the final
adult Amphibian. These cases of neoteny are therefore instances of more or
less complete retardation, or of the retention, of partially larval
conditions.
The whole problem is, however, by no means simple. _Salamandra atra_ has
become viviparous, and the whole metamorphosis takes place within the
uterus; in fact, the young have an embryonic, but no larval period, if by
the latter we understand the free swimming and still imperfect stage.
Similarly, various Anura–for instance, _Hylodes martinicensis_–pass rapidly
through their metamorphosis, and have suppressed the stage of free swimming
tadpoles. On the other hand, in many newts, the duration of the larval
period is much prolonged, and moreover is very subject to individual
variation. In the Axolotl this larval period is continued until and after
sexual maturity is reached. The extreme condition would then be represented
by the Perennibranchiate genera. It may seem reasonable to look upon these
as the youngest members of the Urodela, and the loss of the maxillae in the
Sirenidae and Proteidae supports this idea. But it so happens that the
majority of the most neotenic genera are more primitive in the composition
of the skull and the vertebral column than the typically terrestrial and
rapidly metamorphosing genera. Witness the amphicoelous vertebrae, the
completeness of the pterygoids, the separate nature of the palatine bones,
and the separate splenials, as mentioned in detail in the description of
their skull.
We have therefore to conclude, first, that the various Perennibranchiate
genera do not form a natural group, but are a heterogeneous assembly;
secondly, that they have become Perennibranchiate at a phylogenetically old
stage–in fact, that they are the oldest, and not the newest, members of the
present Urodela. At the same time, it would be erroneous to suppose that
the first Urodela were aquatic creatures, provided with a finny tail, with
small, ill-developed lungs, and with epidermal sense organs. All these
features are, on the contrary, directly correlated with aquatic life, and
are larval acquisitions, not ancestral {66}reminiscences. It would be
equally wrong to allude to the absence of lungs in many newts as a piscine
and therefore ancestral feature. The development of the typical
pentadactyloid limb, the connexion of the pelvic girdle with the vertebral
column, the development of the lungs, and absolute suppression of internal
gills point without doubt to terrestrial creatures. What then, may we ask,
were the first Amphibia like? and how about the external gills? They were
undoubtedly akin to the less specialised Lepospondylous Stegocephali, in
particular the gill-less Microsauri, and the various stages may perhaps be
reconstructed as follows:–
(1) Terrestrial, with two pairs of pentadactyloid limbs; breathing by lungs
only; with a fully developed apparatus of five pairs of gill-arches, which
during the embryonic life perhaps still carried internal gills; with or
without several pairs of gill-clefts. Reduction of the dermal armour and of
the cutaneous scutes had taken place.
(2) Additional respiratory organs were developed by the embryo, in the
shape of external gills; these were at first restricted to embryonic life
(as in the existing Apoda), but were gradually used also during the aquatic
life of the larva. These external gills, together with the lungs, have
superseded the internal gills, of which there are now no traces either in
Urodela or in Anura.
(3_a_) Some Urodeles, retaking to aquatic life, retained and further
enlarged the external gills into more or less permanent organs (cf. also
_Siren_, p. 136).
(3_b_) The majority of Urodela hurried through the larval, aquatic stage,
and some–e.g. _Salamandra atra_–became absolutely terrestrial. The
possession of unusually long external gills by this species and by the
Apoda indicate that these organs are essentially embryonic, not larval,
features.
REGENERATION.–Most Amphibia possess the faculty of regenerating mutilated
or lost limbs. This takes place the more certainly and quickly the younger
the animal. The amputation necessary to study these phenomena need not be
experimental. Axolotls and other Urodelous larvae frequently maim each
other fearfully, by biting off the gills or one or more limbs. The gills do
not even require amputation. If the larvae are kept in stagnant water the
gills often shrivel up or slough off and grow again. {67}The same applies
to the larvae of viviparous species, e.g. _Salamandra atra_, which, when
cut out of the uterus and put into water, soon cast off their long, tender
gills and produce a stronger set. In an Axolotl,[38] two years old, a hand
was cut off. After four weeks there was a conical stump; after the sixth
week this stump had two points; in the eleventh week three or four fingers
were discernible, and a week later the complete hand. Frequently these
creatures reproduce five instead of the normal four fingers. But the more
proximal the cut, the more liable is the new limb to reproduce
supernumerary fingers, or even extra hands and feet. Complete regeneration
of the limb, cut off in the middle of the humerus, took place within five
months.
_Triton taeniatus_, adult, reproduces cut fingers within five or six weeks,
and if the hand be cut above the carpus, new finger-stumps appear in about
one month. Götte has observed that an adult _Proteus_ did not completely
reproduce its whole leg until after eighteen months; and, according to
Spallanzani, more than one year elapses before the limb, bones, and
cartilages of _Triton_ regain their normal strength.
The Anura are likewise capable of regenerating their limbs, the more
readily the younger the specimens. For instance, in a tadpole of _Rana
temporaria_, in which the fore-limbs were still hidden, the hind-limb, cut
at the middle of the thigh, reproduced nineteen days later a knee, followed
by a short two-toed stump. Ultimately the whole limb became completed. The
tail of tadpoles regenerates very quickly and completely, even if it be cut
off shortly before the final metamorphosis, when the tail would in any case
be reduced. Metamorphosed Anura have almost entirely lost this faculty, but
not absolutely. I myself have kept two specimens of _Rana temporaria_,
which, when already adult, had each lost a hand at the wrist. First there
was only the clean-cut stump with a scar, but within a year this changed
into a four-cornered stump, and two of the protuberances developed a little
further, reaching a length of about 4 mm. These specimens lived for four
years without further changes.
TEMPERATURE.–Amphibia, like Fishes and Reptiles, are, as a rule, classed as
cold-blooded animals, in opposition to the warm-blooded Birds and Mammals.
This distinction is one of degree only. The terms poikilothermous and
homothermous (ποίκιλος, {68}variable; ὅμος, equable) are based upon a
sounder principle, but are likewise liable to exceptions. Those creatures
which, like Birds and Mammals, possess a specific temperature of their own
under normal conditions, that of hibernation being excepted, are
homothermous. Cold-blooded creatures have no specific temperature; they
more or less assume that of their surroundings. Frogs and newts, for
instance, when living in the water, naturally assume its temperature, which
is, of course, many degrees lower in a cold spring than in a shallow pond
warmed by the sun on a hot summer's day. The same applies to the changes
from day to night. Dark-coloured tortoises basking in the sun are sometimes
so hot that they are disagreeable to touch, since they possess but little
mechanism for regulating their heat. The same individual cools down during
a chilly night by perhaps 40° C. Anura are, however, very susceptible to
heat; most of them die when their temperature rises to about 40° C. Under
such conditions they die quickly when in the water, but in the air their
moist skin counteracts the heat, lowering it by evaporation; otherwise it
would be impossible for a tree-frog to sit in the glaring sun in a
temperature of 120° F. Toads and others with drier skins seek the shade,
hide under stones, or bury themselves in the coolest spots available, and
many Amphibia and Reptiles aestivate in a torpid condition during the dry
and hot season. Many of them can endure a surprising amount of cold, and
during hibernation their temperature may sink to freezing-point. This power
of endurance does not apply to all alike; tropical species can stand less
than those which live in temperate and cold regions. In spite of many
assertions to the contrary, it may safely be stated that none of our
European frogs, toads, and newts survive being frozen hard. They may be
cooled down to nearly -1° C., and they may be partially frozen into the
ice. Circulation of the blood is suspended in such cooled-down frogs; their
limbs may become so hard that they break like a piece of wood, but the
citadel of life, the heart, must not sink much below freezing-point, and
must itself not be frozen, if the animal is to have a chance of recovering.
The protoplasm resists a long time, and so long as some of it is left
unfrozen the rest will recover. Hibernating frogs are lost if they are
reached by prolonged frost during exceptionally severe winters. Every frog
will be killed in an artificial pond with a clean concrete bottom, {69}but
if there is sufficient mud, with decaying vegetable matter, the creatures
survive, simply because they are not absolutely frozen. A severe winter not
infrequently kills off all the younger creatures, while the older and more
experienced hide themselves more carefully and live to propagate the race.
GEOGRAPHICAL DISTRIBUTION.
There is a very ably written chapter on the geographical distribution of
the Amphibia by Boulenger in the _Catalogue of Batrachia Gradientia_, pp.
104-118. He came to the important conclusion that the geographical
distribution of the Amphibia agrees in general with that of the freshwater
fishes. Günther's division into a Northern, Equatorial, and Southern zone
is modified only in so far as the last two are combined into one, "Tasmania
and Patagonia not differing in any point regarding their Frog Fauna from
Australia and South America respectively."
Boulenger recognises–
I. The Northern zone–(1) Palaearctic, (2) North American, region.
II. The Equatorial Southern zone.
_A._ Firmisternia division = Cyprinoid division of Günther.
1. Indian region.
2. African region.
_B._ Arcifera division = Acyprinoid division of Günther.
1. Tropical American region.
2. Australian region.
In the chapter on geographical distribution in Bronn's _Thierreich, Vögel,
Systematischer Theil_, p. 296 (1893), and in my _Classification of
Vertebrata_ (1898), due attention had been paid to the Amphibia as well as
to the other classes of Vertebrata. It will be seen in the following pages
that my arrangement is well applicable to the Amphibia so far as
fundamental principles are concerned.
It cannot be sufficiently emphasised that any attempt to form the various
faunas of the different classes of animals into one scheme must necessarily
be a _petitio principii_. The time-honoured six zoo-geographical regions
established by Sclater and Wallace represent fairly well the main
continental divisions: North America, South America, Africa, Australia, and
the large northern continental mass of the Old World, with India as a
tropical appendix. There is no correlation and no subordination {70}in this
scheme. Huxley's division (1868) into NOTOGAEA and ARCTOGAEA (see p. 74) is
of fundamental importance. The next improvement was the combination of the
Palaearctic and Nearctic "regions" into one, an advance originally due to
Professor Newton, carried out by Heilprin (1887) as the Holarctic region. I
have, in 1893, substituted for it the more appropriate term _Periarctic_,
meaning the whole mass of land which lies around the indifferent Arctic
zone. The want of further co-ordination and subordination required the
combination of the African and Oriental or Indian countries into a
_Palaeotropical region_ (1893); the Ethiopian or African and the Indian or
Oriental regions of Sclater and Wallace thereby assuming their proper
subordinate rank of subregions.
The two primary divisions NOTOGAEA and ARCTOGAEA are fundamental. The four
secondary divisions, namely the _Australian_ and _Neotropical_,
_Periarctic_ and _Palaeotropical regions_, also stand the test of
application to the various classes and main groups of Vertebrata; but
naturally, under the present configuration of the world, the Palaeotropical
region is nothing but the Southern continuation of the Eastern half of the
Periarctic mass of land. This is especially obvious so far as India is
concerned. There is, however, that broad belt of desert, sand, and
salt-steppes, which extends from North-West Africa to Manchuria, and this
belt is one of the most important physical features of the Old World. It is
complicated by the system of mountain-chains which, broadly speaking,
centre at the Pamirs, and radiate westwards through the Caucasus and Alps
into Spain, eastwards through the Himalayas into China, and north-eastwards
to Kamtschatka; interrupted by Bering's Sea, it is continued as the
backbone of both Americas to Patagonia.
The tertiary divisions, the subregions, have no real existence. They depend
upon the class, or even order, of animals, which we happen to study. The
faunistic distribution of the Urodela is not that of the Anura, and both
follow separate lines of dispersal, different from those of the various
orders of Reptiles, Birds, and Mammals. This must be so. There is no doubt
that the distribution of land and water was totally different in the Coal
Age from what it is now. The face of the globe at the Jurassic Age can
scarcely be compared with the aspect which the world has assumed in the
Miocene period.
This leads to another consideration, often neglected. We {71}know that the
various classes, orders, families, etc., of animals have appeared
successively upon the stage. A group which arose in the Coal Age followed
lines of dispersal different from one which was not evolved until Jurassic
times, and post-cretaceous creatures could not avail themselves of what
assisted their ancestors, and _vice versâ_. The Amphibia are bound
absolutely to the land and to fresh water; transportation across salt water
is not excluded, but must be accidental, and is not a case of regular
"spreading." Speaking generally, the older a group, the more likely is it
to be widely distributed. If it appears scattered, this may be due to
extinction in intermediate countries or to submergence of former
land-connexions.
There is great danger of arguing in a circle. It is one of the most
difficult tasks to decide in cases of great resemblance of groups of
animals between their being due to direct affinity or to heterogeneous
convergence, or parallel development. It is the morphologist who is
ultimately responsible for the establishment of faunistic regions, not the
systematist, least of all he who accepts an elaborate classification, and
then mechanically, mathematically, by lists of genera and species, maps out
the world. Let us take an example. The Neotropical region and Madagascar,
but not Africa, are supposed to be faunistically related to each other. In
both namely occur _Boa_ and _Corallus_ amongst snakes, Dendrobatinae
amongst Ranidae, and of the Insectivora _Solenodon_ in Cuba, _Centetes_ in
Madagascar. More cases can no doubt be found which would strengthen this
resemblance, perhaps in support of the startling view that Madagascar and
South America have received part of their fauna from the famous Antarctica.
But the value of the Insectivores has been disposed of by their recognition
as an extremely ancient group, or as a case of convergence, and the two
genera are no longer put into the same family as Centetidae. The
Dendrobatinae (_Mantella_ in Madagascar, the others in South America) are
decidedly not a natural group, but an instance of very recent convergence
(cf. p. 272). About the members of the ancient Boidae we do not feel quite
so sure.
It is therefore advisable to eliminate for zoogeographical purposes groups
about which there can be any reasonable doubt, otherwise we may argue that
certain genera must constitute a very old family, because they are now
restricted to widely {72}separated countries, or on the strength of their
distribution we may conclude that the genera in question cannot be related
to each other, and do not belong to the same sub-family or family as the
case may be. Such groups are the Engystomatinae and the genus _Spelerpes_;
amongst reptiles the Eublepharidae, Helodermatidae, Anelytropidae,
Ilysiidae, Amblycephalidae.
It is customary to represent the various regions and sub-regions as if they
had boundaries as fixed as political frontiers. Such limitations are quite
arbitrary, and what is of more importance, they differ in reality according
to the class or order of animals with which we happen to deal. Moreover,
there has been, and is probably still going on, an exchange or overlapping
of faunas. Such debatable grounds are Central America and the highlands of
North-western South America. The famous Wallace's line, between Borneo and
Celebes, Java and Lombok, is absolutely inapplicable to the Anura. From
their point of view the Austro-Malayan countries, Papuasia and Polynesia do
not form a sub-region of the Australian, but rather of the Palaeotropical
region. Concerning the Urodela, the division into Palae- and Ne-arctic
sub-regions is unjustifiable since Eastern Asia has emphatically American
affinities (cf. also p. 96). The Sahara and the rest of Northern Africa are
intimately connected with Arabia, Persia, Afghanistan, and Northern India,
just as equatorial Africa and Madagascar possess strong faunistic
relationship with Southern India and the Malay islands.
_Limiting factors of distribution._–Common salt is poison to the Amphibia;
even a solution of 1 per cent prevents the development of their larvae.
Consequently seas, salt lakes, and plains encrusted with saline deposits
act as most efficient boundaries to normal "spreading." But undoubtedly
many individuals have made long and successful voyages across the seas on
floating trees. Solutions of lime are likewise detrimental to many species,
and it is a general fact that limestone-terrain is poor in Amphibian life,
unless, of course, sufficient accumulation of humus counteracts or prevents
the calcareous impregnation of the springs and pools in meadows.
_Salamandra maculosa_ is, for instance, absent in Central Germany on the
Muschelkalk, but it occurs in abundance in neighbouring districts of red
sandstone or granite; nor can the larvae be reared successfully in very
"hard" water. On the other hand, _Proteus_ lives in the {73}subterranean
waters of Carniola, where the whole country is nothing but limestone.
Cold is another powerful limiting factor. The absolute northern limit of
Amphibian life coincides rather closely with the somewhat erratic line of
0° Centigrade of annual mean temperature, a little to the north of which
line the ground remains permanently frozen below the surface. The
surface-crust, which thaws during the summer, engenders an abundance of
insects as food-supply, but its freezing down to the icy bottom makes
hibernation impossible. There are, of course, some exceptions, for instance
the occurrence of Urodela in the Schilka river and in the district of Lake
Baikal.
Ranges of mountains are far less effective barriers than is generally
supposed. In many cases the fauna is the same on either slope, and they act
rather as equalising or dispersing factors, especially when they extend
from north to south. Witness the Andes, owing to which Ecuador and Peru
bear a great resemblance to the Central American fauna, and differ from the
tropical parts of South America. The existence of an _Amblystoma_ in Siam
is another instance.
The more specialised a family the more intimately is it connected with the
physical features of the country. Typically arboreal frogs are dependent on
the presence of trees. Some have undoubtedly spread into treeless countries
and have changed into prairie-frogs, e.g. _Acris_. They come out, so to
speak, as something different at the other end, and it is unlikely that
these modified descendants redevelop exactly the same features as their
ancestors before the migration. Baldwin Spencer[39] met with only six
species of frogs in Central Australia, _Limnodynastes_, _Chiroleptes_,
_Heleioporus_, and _Hyla_. They are in the main identical with certain
forms found in the dry inland parts of New South Wales and Queensland. They
are to be regarded as immigrants from the latter regions, which have been
able in the majority of cases to adapt themselves to unfavourable climatic
conditions by means of a marked development of the burrowing habit, to
which in certain cases has been added a capacity for absorbing and holding
water.
{74}FAUNISTIC DIVISIONS OF THE AMPHIBIA.
NOTOGÆA.–SOUTH WORLD.
* indicates Amphibia which are peculiar to the respective regions or
sub-regions.
Characterised by the Cystignathidae* and by the predominance of Arcifera,
which form nearly 90 per cent of the Anurous population.
I. AUSTRALIAN REGION.–Absence of Apoda and Urodela. All the Anura are
arciferous, with the exception of one species of _Rana_ in the Cape York
peninsula. The fauna of the Australian continent and of Tasmania consists
chiefly of Cystignathidae and Hylidae (_Hyla_ and _Hylella_) and several
small genera of Bufonidae (_Pseudophryne_,* _Notaden_,* and
_Myobatrachus_*).
It is customary, and from the study of other Vertebrata quite justifiable,
to divide the Australian region into several sub-regions, but the Amphibia
lend no support to this. The only Amphibian in the Sandwich Islands is a
_Bufo_, closely related to North American species. The only Amphibian in
New Zealand is _Liopelma_,* one of the Discoglossidae which are otherwise
confined to Europe, North-east Asia, and North-west America, and, to judge
from their low organisation, had formerly a much wider distribution. New
Caledonia possesses no Amphibia. The Fiji Islands are inhabited by one or
two species of _Cornufer_, a genus of Ranidae. The same genus is typical of
the Austro-Malayan and Papuasian islands, the fauna of which consists of
_Rana_ and _Cornufer_, _Ceratobatrachus_, several genera of Engystomatinae,
Hylidae, and Pelobatidae.
II. NEOTROPICAL REGION.–Characterised by Apoda, Aglossa (_Pipa_), abundance
of Cystignathidae (Hemiphractinae,* Cystignathinae, and
Dendrophryniscinae*), Hylidae (Hylinae and Amphignathodontinae*), numerous
Bufonidae and Engystomatinae; Dendrobatinae*; the Raninae are represented
by a few peculiar genera, mostly restricted to the Andesian province; the
genus _Rana_ occurs there in a few species only.
Absence of Discoglossidae, Pelobatidae and Dyscophinae.
Several species of Urodela, of the genus _Spelerpes_, extend from Central
America into the Andesian province, one occurs in Hayti, and _Plethodon
platense_ in Argentina.
This region is by far the richest in the number of families, {75}genera and
species; the total number of the latter being, according to Boulenger,
about four-ninths of the known species. The region comprises South America,
Central America, and the West Indian islands. Central America is naturally
debatable ground; one species of _Hylodes_ and one _Engystoma_, besides
about twenty Hylidae, extend into North America proper, while possibly the
Raninae have entered the Neotropical region from the north. _Bufo_ is too
cosmopolitan to assist our conclusions. The occurrence of four species of
_Hylella_ in South America, one in Australia, and one in New Guinea
indicate that this is not a natural genus.
From the point of the Amphibia the whole region can be divided into two
sub-regions only: (1) The West Indian islands with Central America and the
north-western Andesian province; (2) the rest of South America.
ARCTOGAEA.–NORTH WORLD.
Characterised by the absence of Cystignathidae.
I. PERIARCTIC REGION.–Characterised by the Urodela, these being almost
peculiar to the region (cf. p. 96). Absence of Apoda. Presence of
Discoglossidae, Pelobatidae, Bufonidae, Raninae. Few Hylinae occur.
The whole region can be subdivided into three sub-regions.
1. Western Palaearctic.–Prevalence of Salamandrinae (_Salamandra_,*
_Chioglossa_,* _Salamandrina_,* _Triton_); Proteidae (_Proteus anguinus_*);
_Spelerpes fuscus_.*–_Discoglossus_, _Bombinator_, _Alytes_,* _Bufo_, _Hyla
arborea_, _Pelobates_,* _Pelodytes_,* _Rana_.
2. Eastern Palaearctic.–Amphiumidae (_Cryptobranchus_); Salamandrinae
(_Triton_, _Pachytriton_,* _Tylototriton_*); Amblystomatinae.–_Bombinator_,
_Bufo_, _Hyla arborea_, _Rana_, _Rhacophorus_.
3. Nearctic.–Amphiumidae (_Cryptobranchus_, _Amphiuma_*); Proteidae
(_Typhlomolge_,* _Necturus_*); Sirenidae*; Amblystomatinae; most
Plethodontinae; Desmognathinae.*–Discoglossidae, Pelobatidae
(_Scaphiopus_*); _Bufo_; Hylidae (_Hyla_, _Acris_, _Chorophilus_); _Rana_.
II. PALAEOTROPICAL REGION.–Characterised by the presence of Apoda and by
the great prevalence of Firmisternal Anura, which amount to nearly 90 per
cent of the total population. {76}Absence of Urodela (except _Amblystoma
persimile_*), of Cystignathidae, and practically of the Hylidae, only two
of which occur in the Himalayan district. But this great chain of mountains
should not be included within the region, while the outlying spurs in Upper
Burma (with _Amblystoma_) are debatable ground. The subdivision of this
widely extended region is beset with difficulties, chiefly on account of
Madagascar and Papuasia. The fauna of Madagascar is very remarkable. All
its Amphibia are Firmisternal, a mixture of African and Indian forms. The
island agrees with Africa, in opposition to the Oriental countries, in no
special point; all the Raninae, except _Megalixalus_, _Rappia_, and two
rather common species of _Rana_, belong to different genera. Madagascar
differs from Africa by the absence of Apoda, of Aglossa, and Bufonidae. On
the other hand, it agrees with India or with the Malay islands, in
opposition to Africa, by the possession of Dyscophinae, of the Ranine genus
_Rhacophorus_, and the Engystomatine genus _Calophrynus_.
Africa and India agree with each other, and differ from Madagascar by the
possession of Apoda, the genera _Bufo_ and _Nectophryne_, and by the close
resemblance of several genera of Raninae.
India, the Malay islands, and Papuasia with Melanesia possess Pelobatidae
(_Leptobrachium_,* _Batrachopsis_,* _Asterophrys_*), and thereby differ
considerably from Africa and Madagascar. _Batrachylodes_* of the Solomon
Islands has unmistakable affinities with _Phrynoderma_* of Karen, between
Burma and Siam; _Oreobatrachus_* of Borneo much resembles
_Phrynobatrachus_* of West Africa; and _Cornufer_, typical of the Malay and
Melanesian islands, occurs also in West Africa. All these Raninae indicate
that the Austro-Malayan and Melanesian islands belong to the Palaeotropical
region. _Ceratobatrachus_,* type of a sub-family, is peculiar to Melanesia.
There are consequently several possible modes of subdivision, all with a
different result, according to the group of Amphibia, which we may select
as of leading importance, _e.g._ Apoda or Pelobatidae, or Dyscophinae and
_Rhacophorus_. The Engystomatinae and Raninae are to be eliminated, since
they occur in all the countries in question. We have either to leave the
whole region undivided–and it is a significant fact that the {77}Indian
countries possess not one sub-family of their own–or we must break it up
into four provinces, not sub-regions:–
1. Ethiopian, or continental African, with Aglossa and Apoda, no
Pelobatidae, no Dyscophinae, few Bufonidae, and many Raninae.
2. Indian and Malayan, with Apoda, no Aglossa, but with Pelobatidae,
Dyscophinae, many Bufonidae and Raninae, amongst which _Rhacophorus_.
3. Malagasy, without either Apoda or Aglossa; with Firmisternal Anura
only, chiefly Dyscophinae, and _Rhacophorus_ and other Raninae.
4. Papuasian, without Apoda, Aglossa, Dyscophinae, and Bufonidae, but
with Pelobatidae and Ranidae.
DISTRIBUTION OF FAMILIES AND SUB-FAMILIES OF THE AMPHIBIA.
Aus. = Australian.
N-t. = Neotropical.
N-a. = Ne-arctic.
Pal-arct. = Palae-arctic.
Eth. = Ethiopian.
Mal. = Malagasy.
Ind. = Indian.
Pap. = Papuasian.
N.Z. = New Zealand.
+––––––––––––––––––––+––––+––––+––––+––––+––––+––––+––––+––––+––––+––––+
| |Aus.|N–t.|N–a.|Pal–arct.|Eth.|Mal.|Ind.|Pap.|N.Z.|
| | | | +––––+––––+ | | | | |
| | | | | W. | E. | | | | | |
+––––––––––––––––––––+––––+––––+––––+––––+––––+––––+––––+––––+––––+––––+
|Amphiumidae | | | + | | + | | | | | |
|Salamandridae | | + | + | + | + | | | 1 | | |
|Proteidae | | | + | + | | | | | | |
|Sirenidae | | | + | | | | | | | |
|Apoda | | + | | | | + | | + | | |
|Aglossa | | + | | | | + | | | | |
|Discoglossidae | | | | + | + | | | | | + |
|Pelobatidae | | | + | + | | | | + | + | |
|Bufonidae | + | + | + | + | + | + | | + | + | |
|Hylinae | + | + | + | 1 | 1 | | | | | |
|Amphignathodontinae | | + | | | | | | | | |
|Hemiphractinae | | + | | | | | | | | |
|Cystignathinae | + | + | 1 | | | | | | | |
|Dendrophryniscinae | | + | | | | | | | | |
|Genyophryninae | | | | | | | | | | |
|Engystomatinae | | + | 1 | | | | + | + | + | |
|Dyscophinae | | | | | | + | + | + | | |
|Dendrobatinae | | + | | | | | × | | | |
|Raninae | | + | + | + | + | + | + | + | + | |
|Ceratobatrachinae | | | | | | | | | + | |
+––––––––––––––––––––+––––+––––+––––+––––+––––+––––+––––+––––+––––+––––+
1 signifies the occurrence of only one species of an elsewhere numerous
group.
× _Mantella_, cf. p. 71 and p. 272.
{78}CHAPTER IV
STEGOCEPHALI OR LABYRINTHODONTS–LISSAMPHIBIA–APODA
_SUB-CLASS I. STEGOCEPHALI OR PHRACTAMPHIBIA_
_With a considerable amount of dermal armour, especially on the head._
The earliest known terrestrial four-footed creatures occur in the
Carboniferous strata of Europe and North America. They and their immediate
allies, which extend through the Permian into the Upper Trias, are now
comprised under the name of STEGOCEPHALI, so called because the whole of
the dorsal side of the cranium is covered, or roofed over, by dermal bones
(στέγος, roof; κεφαλή, head). That these creatures, of which naturally only
the skeletal parts are known, were not fishes, is shown by the typically
pentadactyloid limbs; but to recognise them as Amphibia, and as distinct
from Reptiles, is difficult, especially if the incipient Reptilia, which
have sprung from some members of this Stegocephalous stock, are taken into
account. However, they possess either two occipital condyles, or none, and
their vertebrae are either pseudocentrous or notocentrous, but not
gastrocentrous. Moreover, the whole skeletal organisation is still so
ideally generalised, that it is easy to derive directly from it the
arrangement prevailing in the Apoda and Urodela.
The vertebral column always comprises a well-developed, sometimes a very
long tail. The vertebrae exhibit three types, two of which are
fundamentally distinct, while the third is a further development of the
second.
1. _Lepospondylous and pseudocentrous._–The vertebra consists of a thin
shell of bone surrounding the chorda dorsalis, and is composed of two pairs
of arcualia, which meet each other, {79}forming a suture, along the lateral
side of the vertebra, both partaking in the formation of a transverse
process which carries the rib.
2_a_. _Temnospondylous._–The vertebra is composed of three pairs of units,
which remain in a separate, unfused state. Two of them are dorsal arcualia,
one of which tends to form the centrum of the vertebra, which then carries
the neural arch.
2_b_. _Stereospondylous._–The three component units fuse by co-ossification
into a solid, amphicoelous vertebra.
The ribs are one- or two-headed, rather strong, but short, rarely reaching
half-way round the body. They occur on all the vertebrae of the trunk and
on most of those of the tail. One pair of ribs connects one vertebra, the
sacral, with the pelvis, of which the ilium and ischium are generally
ossified, rarely also a portion of the pubic region.
The shoulder-girdle is very primitive, greatly resembling that of the
Crossopterygian fishes. It consists of the following bones:–a median,
rhombic, or T-shaped interclavicle, a pair of clavicles, of cleithra, of
coracoids, and of scapulae. The limbs show the typical pentadactyle plan,
but even in these earliest Tetrapoda the hand possesses only four fingers,
with 2, 2, 3, 2 phalanges respectively. The foot has five toes, with 2, 3,
4, 4, 3, or 2, 2, 3, 4, 3 phalanges.
Many Stegocephali were possessed of a dermal armour, covering either the
whole body or only the under parts. Hence the term Phractamphibia (φρακτός,
armoured). The armour consists of a great number of small cutaneous scales,
partly calcified, or perhaps ossified, and arranged in many more or less
transverse rows. We can only surmise that these scales were covered by
corresponding epidermal sheaths. The skull is ideally complete in the
number of separate bones which appear on its surface. Besides the outer
nares and the orbits there is always an unpaired, small, interparietal
foramen. The whole temporal region is completely roofed over. The following
bones are present:–nasals, frontals, parietals, supra- and
latero-occipitals; lacrymals (unless fused with the jugals?), prefrontals,
postfrontals, postorbitals, squamosals, and epi-(or opisth-)otics;
premaxillaries, maxillaries, jugals, quadrato-jugals, and supra-temporals;
quadrates, pterygoids, palatines, vomers, and an unpaired parasphenoid.–The
lower jaw is composed of a pair of dentaries, {80}articulars, angulars, and
splenials. The dentaries and apparently sometimes the splenials, the
palatines, maxillae, and vomers carry teeth. The eyes possess a ring of
sclerotic bones.
ORDER I. STEGOCEPHALI LEPOSPONDYLI.
Vertebrae pseudocentrous.
SUB-ORDER 1. BRANCHIOSAURI.–The young had several pairs of gill-arches,
which, to judge from their size and from the fact that they are beset with
numerous nodules, denticles, or irregular little processes like
gill-rakers–seem to have been exposed to the surface and to have carried
gills. In the adult the arches and gills seem to be absent.
[Illustration: FIG. 12.–A, Dorsal and B, ventral views of the cranium of
_Branchiosaurus salamandroides_, × about 4. (After Fritsch.) C, Posterior
view of the cranium of _Trematosaurus_, × about ½. (After Fraas.) _Br_,
Branchial arches; _C_, condyle; _Ep_, epiotic; _F_, frontal; _J_, jugal;
_L.O_, lateral occipital; _M_, maxillary; _N_, nasal; _No_, nostril; _Pa_,
parietal; _Pl_, palatine; _Pm_, premaxillary; _P.o_, postorbital; _Pr.f_,
prefrontal; _Ps_, parasphenoid; _Pt_, pterygoid; _Ptf_, postfrontal; _Q_,
quadrate; _Qj_, quadrato-jugal; _S.o_, supraoccipital; _Sq_, squamosal;
_St_, supratemporal; _V_, vomer.]
One of the commonest genera is _Branchiosaurus_, including _Protriton_. _B.
salamandroides_ of the Lower Red Sandstone of Europe is known in every
stage, from larvae of 16 mm. to the full grown animal of 64 mm. in length.
The whole body was {81}covered with little cutaneous scales. _Pelosaurus_
and perhaps _Melanerpeton_ are allied genera.
The following genera are small newt-like creatures of the Carboniferous age
of Europe and North America. In _Keraterpeton_ of Bohemia, Ireland, and
Ohio, the dermal scales were restricted to the under parts; and the ribs
were rather long, reaching half way round the body. Gills have not been
observed. _K. crassum_, a European species, reached more than one foot in
length, two-thirds of which fall to the tail. The ventral side is covered
with a most elaborate armour, which consists of about eighty chevron-shaped
rows of little scale-shaped nodules. The epiotic bones end in strange
processes, carrying a pair of spikes, giving the skull a "horned"
appearance, hence the generic name. _Urocordylus_ is an allied genus.
SUB-ORDER 2. AISTOPODES.–Body snake-like and without any limbs, hence the
name ἄιστος, unseen; ribs long, and reaching half way round the body; from
Carboniferous strata in Ireland and Bohemia, with allied, or perhaps
identical forms in Ohio. _Dolichosoma longissimum_ possessed more than 150
vertebrae, and was about a yard long. The epiotics end in obtuse
projections, recalling those of _Keraterpeton_. These marvellous creatures
had strange appendages, extending from behind the sides of the head, which
were possibly the supports of external gills; since the upper end of one of
the visceral arches, probably the hyoidean arch, is attached to the
labyrinthic region, and from this arch starts a bony rod which carries long
skeletal filaments. The body seems to have been naked.
_Ophiderpeton_ had a compound ventral shield, while the skin of the back
contained granular scutes. Although the Aistopodes have, not without
reason, been looked upon as greatly resembling the Coeciliae or Apoda in
organisation, especially in that of the vertebral column, the total absence
of any other fossils which might bridge over the enormous gulf between the
Coal Age and recent times, makes the attempt to derive the Apoda from these
creatures very hazardous.
ORDER II. STEGOCEPHALI TEMNOSPONDYLI.
Mostly with rather long ribs and with chiefly ventral armour.
{82}_Chelydosaurus_ from the Lower Red Sandstone of Bohemia was 3 feet
long, and possessed a beautiful, complicated, ventral armour, consisting of
about sixty chevron-shaped rows, about three times as numerous as the
vertebrae in the corresponding region. _Sphenosaurus_ from the same strata
and localities must have been 2 yards long. The trunk-vertebrae of both
these genera were composed of four pairs of arcualia. _Trimerorhachis_ from
the Permian of Texas is very imperfectly known, but its trunk-vertebrae, as
the name implies, consist of three pairs of separate arcualia, one of
which, the interdorsal pair, tends to form a kind of centrum.
_Dissorophus multicinctus_, also from the Permian of Texas, has been
described by Cope[40] as a "Batrachian Armadillo," and considered allied to
_Trimerorhachis_. Ten vertebrae are known, of an aggregate length of 93
mm.; the length of the creature was perhaps one yard. The neural spines are
elevated, and the apex of each extends in an arch on each side to the ribs.
These spinous branches touch each other, forming a carapace. Above, and
corresponding to each of them, is a similar dermal and osseous element,
which extends from side to side without interruption in the median line,
forming a dermal layer of transverse bands which correspond to the skeletal
carapace beneath it. This creature remotely approaches the genus
_Zatachys_, Cope, where a dermosteous scute is co-ossified with the apex of
the neural spine. The systematic position of this genus is at least
doubtful.
_Archegosaurus decheni_ from the Lower Red of Germany, known by many
well-preserved specimens, reached a length of 4 or 5 feet. The trunk
vertebrae are tri-partite, those of the tail quadri-partite, like those of
the trunk of _Chelydosaurus_. Young specimens show traces of gill-arches.
The thoroughly terrestrial walking limbs have four fingers and four toes;
the arrangement of the tarsalia, most of which are ossified, lend support
to the view that the morphological axis went through femur, fibula,
intermedium, the centralia, the second distal tarsale, and the second toe.
The dentine and enamel of the teeth are much folded, and this feature,
which applies to most members of this Order, to a lesser degree also to
others, has caused them to be comprised under the name of LABYRINTHODONTA.
The upper {83}surface of the head shows very characteristically arranged
grooves, which probably contained slime-canals and possibly sensory organs.
_Actinodon_ and _Euchirosaurus_ are closely allied forms, chiefly from the
Lower Red Sandstone of France; _Gondwanosaurus_ occurs in the Permian of
India.
ORDER III. STEGOCEPHALI STEREOSPONDYLI.
These are the most highly developed members of the typical Labyrinthodonta,
characterised by their much-folded teeth, and by their solid, bi-concave
vertebrae. _Loxomma_ occurs in the Upper Carboniferous of England and in
the Lower Red of Bohemia: _Trematosaurus_, _Capitosaurus_, and _Metopias_
from the New Red or Lower Trias to the Keuper of Germany. _Mastodonsaurus_
from the Trias of England and Germany is the most gigantic Amphibian known,
with a skull of nearly 1 yard in length.
_Labyrinthodon_ from the Keuper of Warwickshire is one of the latest
members of the group. Labyrinthodont creatures have also been described
from the Trias of South Africa, _e.g._ _Rhytidosteus_; those from North
America are insufficiently preserved.
Many of these and allied genera have left their footprints in slabs of
Sandstone, both Lower and New Red, in Europe, Africa, and America. But
although their spoors are common enough, only a few can with certainty be
referred to Stegocephali, _e.g._ _Saurichnites salamandroides_ of the Lower
Red of Germany. The spoors of _Chirotherium_, common in the New Red of
Germany and England, for instance in Cheshire, belong to unknown owners;
both the large hind feet (which measure nearly half a foot in length) and
the much smaller fore feet, had five digits, the first of which stood off
like a thumb. Five-fingered Stegocephali are unknown.
There is an almost complete absence of fossil Amphibia from the Upper Trias
to the Oligocene. The Stegocephali as such seem to have died out with the
Trias. The recent Amphibia, of course, must have had ancestors in the
Mesozoic age. There is one little skeleton, from the Wealden of Belgium,
which belonged to a newt-like creature, called _Hylaeobatrachus croyi_.
Scarce fragments, described as _Megalotriton_, are known from the Oligocene
of France, and _Triton_ itself seems to be indicated by {84}remnants in the
Lower Miocene of France and Germany. But fairly complete specimens of large
creatures, much resembling _Cryptobranchus_, have been found in the Upper
Miocene of Oeningen, Canton Solothurn, Switzerland. The first known
specimen, now at Haarlem, indicating a total length of 3 feet or more, was
described and figured in the year 1726 by Scheuchzer, in a learned
dissertation entitled "_Homo diluvii testis_."
Betrübtes Beingerüst von einem alten Sünder
Erweiche Herz und Sinn der neuen Bosheitskinder.
Which may be rendered as follows:–
Oh, sad remains of bone, frame of poor Man of sin
Soften the heart and mind of sinful recent kin.
This was the motto attached to the illustration, and it remained a warning
to mankind until Cuvier declared the skeleton to be that of some large
newt. Tschudi named it _Andrias scheuchzeri_, but it is scarcely
generically distinct from _Cryptobranchus_, being almost intermediate
between _C. alleghaniensis_ and _C. japonicus_, see p. 97.
_SUB-CLASS II. LISSAMPHIBIA._
_Amphibia without dermal armour._
ORDER I. APODA OR LIMBLESS AMPHIBIA.
The Amphibia Apoda, Coeciliae or Gymnophiona, are a small group of
worm-shaped, burrowing creatures, restricted to the Neotropical and
Palaeotropical regions, excluding Madagascar. They have no limbs and no
girdles. The tail is extremely short; the vertebrae are pseudo-centrous,
and most of them carry rather long ribs, none of which, however, meet to
form a sternum. The whole snake-like body is covered with a smooth and
slimy skin which forms numerous transverse folds or rings.
The most remarkable feature of the SKULL is its solid compactness, which
stands in direct correlation with the burrowing habits of these creatures.
The whole dorsal surface of the cranium is practically roofed in by bone,
so that, in this respect, it greatly resembles that of the Stegocephali;
but this resemblance is produced chiefly by a broadening of those bones
which exist also in the other Lissamphibia, while supratemporals and
supra-occipitals are absent.
{85}[Illustration: FIG. 13.–Skull of _Ichthyophis glutinosa_. × 3. (After
Sarasin.) A, Lateral, B, ventral, C, dorsal view. _A_, Posterior process of
the os articulare; _Ca_, carotid foramen; _Ch_, choana or posterior nasal
opening; _F_, frontal; _J_, jugal; _Lo_, lateral occipital; _Mx_,
maxillary; _N_, nasal; _No_, nostril; _O_, orbit; _P_, parietal; _Pa_,
palatine; _Pm_, premaxillary; _Pof_, postfrontal; _Prf_, prefrontal; _Pt_,
pterygoid; _Q_, quadrate; _S_, squamosal; _St_, stapes; _T_, tentacular
groove; _Vo_, vomer; _X_, exit of vagus nerve.]
There is, however, a pair of bones which represent either the postorbitals
or the postfrontals, perhaps both, of the Stegocephali. The quadrato-jugal
arch is enormously developed, and by reaching the parietal, frontal, and
postorbito-frontal bones (which latter occur only in _Ichthyophis_ and
_Uraeotyphlus_) and the maxilla, extends over the whole of the
orbito-temporal fossa. The squamosal is completely fused with the
quadrato-jugal. The stapes has the typical stirrup-shape, is even
perforated by an artery, and articulates distally with the shaft of the
quadrate (as in the snakes). The maxilla is very large and broad. Owing to
its broad junction with the quadrato-jugal arch, the prefrontal and
frontal, the orbital fossa is reduced to a very small hole, or the maxilla
completely covers the eye. Somewhere between the latter and the nares the
maxilla is perforated by the tentacular groove. The periotic bones are
represented by the prootics and epiotics; they fuse with the lateral
occipitals and with the parasphenoid. The whole {86}orbito-ethmoidal region
of the primordial skull is also turned into one mass of bone.
The angular element of the lower jaw forms a thick and large process which
projects upwards and backwards from the mandibular joint. The former
possession of a splenial bone is indicated by the occurrence of a second
series of teeth in the mandibles of _Ichthyophis_ and _Uraeotyphlus_. Other
genera have vestiges of this second row, or it may be completely lost.
The hyoid and branchial apparatus is more primitive than in any other
recent Amphibia. In the larva the hyoid and the first and second branchial
arches are connected with each other by a median copular piece. The third
branchial arches are free from the rest, but are fused in the middle line,
the fourth are loosely attached to the previous pair. In the adult both
fuse into one transverse, curved bar, and the second pair of branchials
lose their connexion with the basal longitudinal piece and likewise form a
transverse bar.
The vertebrae are built upon the pseudocentrous type, are amphicoelous, and
the chorda is intravertebrally destroyed by cartilage, as in the majority
of the Urodela. The number of vertebrae is great, amounting in some species
to between 200 and 300, of which a few belong to the tail. The first
vertebra is devoid of an odontoid process. The ribs are proximally
bifurcated as in the Urodela.
The eyes are practically useless, being either more or less concealed under
the skin, or they are covered by the maxillary bones. All Coecilians
possess a peculiar tentacular sensory apparatus, which consists of a
conical flap-shaped or globular soft tentacle, which is lodged in a special
groove or canal of the maxilla, between the eye and the nose, whence it is
frequently protruded while the animal is crawling about. These tentacles in
the young _Siphonops_ lie, according to the Sarasins, quite close to the
eyes, but are later transferred nearer to the nose. The organ consists of a
peculiarly rolled up and pointed fold which arises from the bottom of the
sac or pit, where it receives a nerve. It is protruded by becoming turgid
with blood, and is retracted by a strong muscle. Into the lumen of the sac
are poured secretions from the large orbital (Harderian) gland, to keep the
apparatus clean. Hence arose the mistaken {87}notion of its being a
poison-organ. The whole structure is possibly an offshoot of the
naso-lacrymal duct.
The skin is most remarkable. In the ripe embryo the epidermis passes
smoothly over the surface. Beneath follow two layers of soft cutaneous
connective tissue, bound together by transverse or vertical lamellae, so
that ring-shaped compartments are formed, and in these are embedded
slime-glands. In the adult each compartment is modified into an anterior
glandular belt and a posterior space, from the bottom of which grow several
scales. The number of cutaneous rings agrees originally with that of the
vertebrae; but later, and especially in the hinder portion of the trunk,
each ring breaks up into two or more secondary segments, and these no
longer agree with those of the skeleton. Each scale is beset with numerous
smaller scales which consist of hardened cell-secretions infiltrated with
calcareous matter. The whole scale is consequently an entirely mesodermal
product of the deeper layers of the cutis. The usual statement that the
skin forms imbricating lamellae, on the inner side of which appear the
scales, is wrong. The "lamellae" can be lifted up only after the general
epidermal sheath has been broken artificially in the constrictions between
the rings. No scales exist in the Indian genus _Gegenophis_ and in the
American _Siphonops_, _Typhlonectes_, and _Chthonerpeton_, a secondary loss
which does not indicate relationship. The scales develop late in embryonic
life, and they are reasonably looked upon as inheritances from the
Stegocephali. The glands either produce slime, whose function seems to be
the keeping clean of the surface of the body, or they are squirt-glands.
The latter kind are also numerous and are filled with a fluid which is
squeezed out by muscular contraction, and seems to be poisonous, as it
causes sneezing to those who handle or dissect fresh specimens.
The Coecilians live in moist ground and lead a burrowing life. Their
developmental history has only recently been studied, and in but a few
species, see _Ichthyophis_, p. 91, and _Hypogeophis_, p. 92. The female is
fertilised internally, copulation taking place by means of eversion of the
cloacal walls in the shape of a tube. The spermatozoa possess an undulating
membrane; the eggs undergo meroblastic division and the embryos have three
pairs of long external gills. Some are viviparous.
The snake-like, limbless shape of the body (Fig. 15) is, as in {88}snakes,
correlated with an asymmetrical development of the lungs; the left is
reduced, while the right is drawn out into a long cylindrical sac. The
liver is likewise very long, and partly constricted into a great number of
lobes. Owing to the great reduction of the ribs progression is effected in
an almost earthworm-like fashion by the peristaltic motion of the skin,
assisted by its numerous ring-shaped constrictions.
The systematic position of the Coeciliae has been, and is still, a
controversial matter. The Sarasins took up Cope's suggestion, that their
nearest allies are the Urodela, especially _Amphiuma_, and they went so far
as to look upon _Amphiuma_ as a neotenic form of the "Coecilioidea," which
they divided into Amphiumidae and Coeciliidae; the Coecilioidea and
Salamandroidea forming the two sub-orders of the Urodela. They based this
startling conclusion chiefly upon remarkable resemblances between
_Amphiuma_ and _Ichthyophis_, namely, (1) the mode of laying the eggs on
land and coiling themselves around them; (2) the existence of remnants of a
tentacular apparatus in _Amphiuma_; (3) Cope's statement that _Amphiuma_
alone among the Urodela possesses an ethmoid like the Coeciliae. This
latter point is, however, erroneous; it has since been shown by Davison[41]
that _Amphiuma_ possesses no ethmoid bone, but that, instead of it,
descending plates of the frontals join below the premaxilla and function as
a nasal septum, with a canal for the olfactory nerves.
We look upon the Apoda with more reason as creatures which of all the
Lissamphibia have retained most Stegocephalous characters and at the same
time form a highly specialised group equivalent to the Urodela and the
Anura. The following are Stegocephalous inheritances peculiar to the Apoda
in opposition to the other recent Amphibia: retention of cutaneous scales
with calcareous incrustations, greatly resembling the scales of the
Carboniferous Microsauri; occasional retention of post-frontal and lateral
nasal or lacrymal bones, and of a second row of teeth in the mandible. To
these may be added the presence of epiotic bones, and the primitive
character of the branchial arches. The loss of all these characters would
turn the present Apoda into limbless Urodela, but this assumption does not
justify their inclusion in this Order. The possible homology of the
tentacular apparatus has been discussed elsewhere, p. 45.
{89}Fossil Apoda are not known; their subterranean life does not favour
preservation.
[Illustration: FIG. 14.–Map showing the distribution of the Coeciliae or
Amphibia Apoda.]
Only family, COECILIIDAE. About forty species are known. These have been
placed in seventeen genera, mostly on comparatively slight grounds, and
several of these genera are probably unnatural, the distinctive characters
having undoubtedly been developed independently in various countries. We
have to remember that the recent species are the remainder of a formerly
much more numerous group; it is also likely that more will be discovered in
the tropical forests of South America and Sumatra.
Boulenger[42] has distinguished them as follows:–
I. Cycloid scales embedded in the skin.
_A_. Eyes distinct, or concealed under the skin.
_a_. Two series of teeth in the lower jaw.
α. Quadrato-jugal (squamosal) and parietal bones in contact.
Tentacle between eye and nostril.
_Ichthyophis_, 2 species, India and Malay islands, p. 90.
" below and behind nostril.
_Hypogeophis_, 3 species, East Africa and Seychelles, p. 92.
" below and in front of eye.
_Dermophis_, 5 species, America and Africa, p. 93.
" below the nostril. _Coecilia_, 6 species, America.
β. Quadrato-jugal separated from parietal.
Tentacle close to the eye. _Rhinatrema_, 2 species, America.
" below and behind nostril.
_Geotrypetes_, 1 species, West Africa.
" below nostril.
_Uraeotyphlus_, 3 species, West Africa and India.
_b_. One series of teeth in the lower jaw.
Tentacle in front of the eye.
_Cryptopsophis_, 1 species, Seychelles.
_B_. Eyes below the cranial bones. Quadrato-jugal in contact with{90}
parietal.
Tentacle near the nostril.
_Gymnophis_, 4 species, South America.
_Herpele_, 2 species, Panama and Gaboon.
II. Without scales.
_A_. Eyes distinct, or concealed under the skin.
_a_. Two series of teeth in the lower jaw.
α. Quadrato-jugal in contact with parietal.
Tentacle behind nostril; end of body laterally compressed.
_Typhlonectes_, 3 species, America, p. 93.
β. Quadrato-jugal separated from parietal.
Tentacle between eye and nostril.
_Chthonerpeton_, 2 species, America.
_b_. One series of teeth.
α. Quadrato-jugal and parietal in contact; tentacle in front of
the eye.
_Siphonops_, 4 species, America.
β. Quadrato-jugal separated from parietal.
_Bdellophis_, 1 species, East Africa.
_B_. Eyes below the cranial bones.
_a_. Two series of teeth. Quadrato-jugal and parietal in contact;
tentacle behind and below nostril.
_Gegenophis_, 1 species, India.
_b_. One series of teeth. Quadrato-jugal separated from parietal.
_Scolecomorphus_, 1 species, East Africa.
_Boulengerula_, 1 species, East Africa.
_Ichthyophis glutinosa_ extends from the slopes of the Himalayas to Ceylon,
the Malay islands, and into Siam. A second species, _I. monochrous_, occurs
in Malabar, Malacca, Borneo, and Java. _I. glutinosa_ reaches about one
foot in length, with a greatest thickness of a little more than half an
inch. The general colour is dark brown or bluish black, with a yellow band
along each side of the body.
This species has been studied extensively by the Sarasins.[43] It breeds in
Ceylon after the spring monsoon. The ovarian egg is oval, measuring 9 by 6
mm. The yolk is yellow; the blastoderm lies towards one of the poles. The
strong vitelline membrane becomes surrounded in the oviduct by a dense
albuminous membrane, which forms twisted chalazae, just like those of
birds' eggs, and by these two cords the eggs are strung together. Around
all this lies another mantle of albumen. The female digs a hole close to
the surface in moist ground near {91}running water, and there lays about
two dozen eggs. The egg-strings become glued together, entangled into a
bunch, and the female coils herself round the bunch and remains in that
position, probably to protect the eggs against other burrowing creatures,
as blind snakes (_Typhlops_ and _Rhinophis_) and certain limbless lizards,
with which the ground literally swarms. During this kind of incubation the
eggs assume a round shape, and grow to twice their original size, and the
mature embryo weighs four times as much as the newly laid egg.
[Illustration: FIG. 15.–_Ichthyophis glutinosa_ × 1. (After P. and F.
Sarasin.) 1, A nearly ripe embryo, with gills, tail-fin, and still with a
considerable amount of yolk; 2, female guarding her eggs, coiled up in a
hole underground; 3, a bunch of newly laid eggs; 4, a single egg, enlarged,
schematised to show the twisted albuminous strings or chalazae within the
outer membrane, which surrounds the white of the egg.]
The external gills are delicately fringed and red, and they move up and
down in the fluid of the egg. The body of the embryo is at first white, but
becomes pigmented with dark grey. A strong line of lateral sense-organs is
formed, and a ring of them lies around the eye and others on other parts of
the head. The short tail develops a fin. Of the three pairs of gills the
third is the shortest, and is generally turned dorsalwards. In embryos of 4
cm. in length the longest gill measures as much as 2 cm. Yolk is still
present in embryos which have reached the surprising length of 7 cm. Then
the gills begin to shrink a little, and at this time one pair of
gill-clefts breaks through at the base of the third external gill.
When the larvae are hatched the gills are lost. The young larva takes to
the water in a gill-less state, and moves about like an eel. At the bottom
of the gill-hole on each side two arches are visible, and there are at this
stage neither inner nor {92}outer gills. The larvae frequently come up to
the surface to breathe. The eyes are large and clearly visible, but the
tentacles are still undeveloped. The epidermal sense-organs are numerous,
and appear as white spots in the grey skin; about fifty extend from the
gill-opening to the tip of the tail.
_Ichthyophis_ seems to live a long time in the larval state. At last the
gill-clefts close, the tail-fin disappears, and the tentacles come to the
surface. The whole skin assumes a totally new structure, and the fish-like
larva turns into a burrowing, subterranean creature so terrestrial that it
gets drowned when made to remain in the water.
_Hypogeophis._–According to A. Brauer[44] three species of Coecilians are
found in the Seychelles: _Cryptopsophis multiplicatus_, which is rare,
_Hypogeophis rostratus_ and _H. alternans_. They live in moist ground, near
the coast in swamps, higher up in humus, under rotten trees and rocks, down
to the depth of one foot. In the island of Silhouette, Brauer found them in
brooks, at least during the dry season, from May to September. The natives
call them "vers de terre." They seem to propagate during the greater part
of the year, provided there is sufficient moisture. The female coils round
the eggs, which vary from half a dozen to thirty in number, those of _H.
rostratus_ measuring 7-8 mm., those of _H. alternans_ only 4-5 mm.
The embryos undergo their whole development in the egg. Four pairs of
gill-clefts break through, the first between the hyoid and the first
branchial arch, the fourth between the third and fourth branchial arches.
There appears also a spiracular cleft between the quadrate and the hyoid
arch; this cleft is, however, only developed dorsally, and persists for a
shorter time. The external gills appear at the same time as the clefts,
upon the first three branchial arches; the third gill is the latest, and
remains in a vestigial condition covered up by the two others. The gills,
of which the second is the longest, are not (as stated by the Sarasins)
direct prolongations of the gill-arches, but they begin as button-like
growths upon the arches. They begin to disappear with the absorption of the
yolk, getting actually smaller. In embryos of 6 cm. they are 6 mm. long,
while in embryos of 6.5 cm. they are reduced to 4.5 mm. in length. The
{93}first to disappear is the third gill, of course by being resorbed; and
the clefts are closed before the creature leaves the egg. _Hypogeophis_ not
leading an aquatic larval life possesses no tail-fin in the embryonic
state, the gill-holes are closed, and the epidermal sensory organs
disappear long before the time of hatching.
Vestiges of gills appear also on the hyoid and on the mandibular arch, but
on the latter they are of very short duration. Those of the hyoid gradually
fuse with the first of the branchial gills, and these also concentrate with
their bases so that they ultimately seem to spring from one common stem.
Brauer remarks that the distinction between internal and external gills
seems to be one of degree only; the hyoidean and mandibular gills namely
start from the hinder margin of the arches, just like the internal gills of
_Torpedo_ according to Ziegler, while the other gills start from the sides
of the branchial arches. He also found a pair of little swellings behind
the last gill-cleft, and an unpaired swelling (corresponding with a double
one in _Ichthyophis_) in front of the vent. Not unreasonably he sees in
these swellings the last, very transitional vestiges of the paired limbs.
_Typhlonectes compressicauda_ of Guiana and Venezuela is one of the largest
Coecilians, reaching a length of 18 inches, with a body-diameter of ¾ inch.
The general colour, as in most of these creatures, is olive brown to black.
A sort of adhesive disc surrounding the vent occurs in this genus. Peters,
who described this species, found in one female six embryos of
comparatively enormous size, one of them being 157 mm. (more than 6 inches)
long, and 12 mm. thick, and devoid of a tail-fin. Instead of lateral
gill-openings there is a "bag" on each side 55 mm. long, upon which is
distributed a blood-vessel. The Sarasins have examined the same specimen:
The gills are not a bag, but consist of two flat, unbroken membranes which
are closely connected with each other. In fact the outer gills of all
Amphibia may be said to begin in the shape of small bags, whence sprout
secondarily the gill-fringes; but in _Typhlonectes_ they form these flaps
instead of growing into the usual three gills. The embryos have no
epidermal sense-organs, but plenty of skin-glands. Probably when born they
take at once to terrestrial life, the flaps are possibly shed at birth, and
there remains a little cicatrix.
_Dermophis thomensis_ of West Africa (its other relations live in East
Africa, South and Central America) is also viviparous.
{94}CHAPTER V
LISSAMPHIBIA (_CONTINUED_)–URODELA
ORDER II. URODELA OR TAILED AMPHIBIA.
The recent tailed Amphibia, Salamanders and Newts in the wider sense, have
been grouped into four families which can be conveniently diagnosed by the
following characters:–
Both the upper and lower jaws are furnished with teeth. Fore- and
hind-limbs are always present.
Maxillary bones present.
Eyes free and devoid of lids .......... AMPHIUMIDAE, p. 97.
Eyes with movable lids[45] .......... SALAMANDRIDAE, p. 102.
Maxillary bones absent.
Eyes without lids. Perennibranchiate .......... PROTEIDAE, p. 132.
Both jaws are toothless. The hind-limbs, the maxillary bones and eyelids
are absent. Perennibranchiate .......... SIRENIDAE, p. 136.
These four families are closely allied to each other, especially the
Amphiumidae and the Salamandridae.
The geographical distribution of the Urodela is essentially Periarctic,
except that about one dozen species each of _Amblystoma_ and of _Spelerpes_
extend southwards into Central America, and in the case of the latter genus
even into the Andesian parts of South America. _Plethodon platense_
inhabits Argentina.
The Urodela afford good reasons for dividing the Periarctic region into
three co-ordinate sub-regions, namely, Nearctic, Eastern and Western
Palaearctic. The difference between the European and the Eastern Asiatic
fauna is well marked; the two are–at least with our present
knowledge–separated by a wide stretch of country very poor in Urodele
forms; while, lastly {95}there are not a few resemblances between this
Eastern Asiatic and the American fauna. The Urodela thus lend no support to
the usual division of the Periarctic into a Palaearctic and a Nearctic
sub-region. Nor is it possible to divide the Palaearctic into a Eurasian
and a Mediterranean province. We have in this case to distinguish between
an American, an Asiatic, and a European fauna. The Asiatic or Eastern
Palaearctic sub-region assumes the central position, at least from a merely
geographical point of view. It would be unjustifiable to assume a spreading
from this centre into Europe, and, on the other hand, into America. The
centre existed more probably in the Arctic circle, now devoid of Urodela.
[Illustration: FIG. 16.–Map showing the distribution of the Urodela.
"Ichthyodea" = Amphiumidae + Proteidae + Sirenidae.]
So far as mere numbers of species are concerned the huge Asiatic or Eastern
Palaearctic region is the poorest, but it is also the least explored, and
China will probably yield a good many new forms. We know at present only 15
species, nearly all from the eastern half. These 15 species represent no
less than 11 genera, 8 of which (= 73 per cent) are peculiar to the
sub-region. Next comes the Western Palaearctic or European sub-region with
about 21 recent species of 5 genera, 4 of which are peculiar. America is by
far the richest, with no less than 66 species (36 eastern, about 16
western, and the rest Central American, etc.), belonging to 19 genera, 17
of which (= 90 per cent) are peculiar to the New World. But this richness
in species is due mainly to the abundance of the two genera _Amblystoma_
and _Spelerpes_, just as Europe is characterised by its many Tritons.
One of the most striking features of the Asiatic sub-region is {96}its
difference from the European. They have very little in common.
_Pachytriton_, _Tylototriton_, and two species of _Triton_ (_T.
pyrrhogaster_ and _T. sinensis_) are the only Salamandrinae, while all the
rest are Lechriodont (see p. 102), like the American Urodela, excepting the
two American Tritons, _T. torosus_ and _T. viridescens_.
GEOGRAPHICAL DISTRIBUTION OF THE URODELA
+–––––––––––––––+–––––––––––––––––+––––––––––––––––––+––––––––––––––––––+
| | Western | Eastern | American. |
| | Palaearctic. | Palaearctic. | |
+–––––––––––––––+–––––––––––––––––+––––––––––––––––––+––––––––––––––––––+
| Sirenidae | ... | | 1 Siren |
| | ... | | 1 Pseudobranchus |
| | | | |
| Proteidae | 1 Proteus | | 1 Necturus |
| | | | |
| Amphiumidae | (1 _Andrias_, | ... | 1 Amphiuma |
| | Miocene) | 1 Cryptobranchus | 1 Cryptobranchus |
| | | | |
| Salamandridae | Desmognathinae |
| | –––––––––––––– |
| | ... | | 1 Thorius |
| | ... | | 1 Haptoglossa |
| | ... | | 3 Desmognathus |
| | ... | | 1 Typhlotriton |
| | | | |
| | Pleithodontinae |
| | ––––––––––––––– |
| | 1 Spelerpes | | 21 Spelerpes |
| | ... | | 2 Manculus |
| | ... | | 7 Plethodon |
| | ... | | 3 Batrachoseps |
| | ... | | 1 Typhlomolge |
| | ... | | 2 Autodax |
| | | | |
| | Amblystomatinae |
| | ––––––––––––––– |
| | | 1 Amblystoma | 16 Amblystoma |
| | | ... | 1 Dicamptodon |
| | | 1 Batrachyperus | |
| | | 1 Ranidens | |
| | | 1 Geomolge | |
| | | 1 Onychodactylus | |
| | | 2 Salamandrella | |
| | | 3 Hynobius | |
| | | | |
| | Salamandrinae |
| | ––––––––––––– |
| | ... | 1 Pachytriton | |
| | ... | 1 Tylototriton | |
| | 14 Triton | 2 Triton | 2 Triton |
| | 1 Salamandrina | | |
| | 1 Chioglossa | | |
| | 3 Salamandra | | |
| +–––––––––––––––––+––––––––––––––––––+––––––––––––––––––+
| | 21 species, | 15 species, | 66 species, |
| | 6 genera | 11 genera | 18 genera |
+–––––––––––––––+–––––––––––––––––+––––––––––––––––––+––––––––––––––––––+
The occurrence of an _Amblystoma_, _A. persimile_, in the mountains of Siam
and Burmah, is most suggestive, and others will in all probability be
found. It must also be borne in {97}mind that the differences between the
genera of Amblystomatinae are in reality very slight; and the same applies
to the sub-families themselves. The presence or absence of teeth on the
parasphenoid, the possession of amphi- or opistho-coelous vertebrae, do not
mean much, and certainly do not forbid the notion that all the recent
Urodela are the offspring of one common generalised stock which inhabited
the northern portion of the globe. Nothing is gained by hiding the solitary
European species of the essentially American genus _Spelerpes_ under the
name of _Geotriton_. It is a _Spelerpes_ in all characteristic points.
Speaking broadly, each of the three principal sub-families of Salamandridae
is characteristic of a sub-region; the Salamandrinae of the Western
Palaearctic, the Plethodontinae of the American, while the Amblystomatinae
are chiefly Asiatic, at least so far as diversity of genera is concerned.
FAM. 1. AMPHIUMIDAE.–Without gills in the perfect state. The gill-clefts
are in a vanishing stage, being either reduced to one pair of small holes
or being altogether absent. The maxillary bones are present. Teeth occur in
both jaws; those of the vomers form transverse rows. The vertebrae are
amphicoelous. The fore-limbs and hind-limbs are present, but small. The
small eyes are devoid of lids.
This family is now represented by two genera, with only three species,
found in the United States and in Eastern Asia.
_Cryptobranchus._–The limbs are functional, with four fingers and five
toes. The outer digits and the sides of the limbs are bordered with folds
of skin. The head and body are stout and depressed; the tail is short,
laterally compressed, and provided with a fin. The skin is very glandular
and slimy, and forms a thick, irregularly-shaped fold along the side of the
body.
_C. (Menopoma) alleghaniensis._–The gill-clefts are normally reduced to one
pair, individually to the left cleft, the right closing up. There are,
however, four branchial arches and vessels. The general colour is brown or
grey above, sometimes with darker patches, lighter below. The "Hellbender"
reaches a length of nearly 18 inches (about 46 cm.), is entirely aquatic,
and is apparently restricted to the rivers and streams of the mountainous
districts of the Eastern United States. It is very voracious, living on
worms and on fish, being much disliked by the fishermen, as it takes the
angler's bait, and destroys great quantities of the valuable food-fish
_Coregonus albus_. Although rather common and easily kept, its larvae still
remain unknown.
{98}[Illustration: FIG. 17.–_Cryptobranchus japonicus._ Japanese Giant
Salamander. × ⅙.]
{99}_C. japonicus_ s. _maximus_.–The Giant Salamander of Japan differs from
its American relation in one essential point only, namely, by the absence
of gill-openings and of the modifications of the branchial apparatus
connected therewith. It has but three branchial vessels, and the skeletal
arches are reduced to two. It lives in Japan and in China, from 600 to 4500
feet above the level of the sea, in small streams of mountain-meadows. It
feeds upon fishes, Amphibia, worms, and insects. It is easily fished with
the hook and is eaten by the Japanese.
The first living specimen was brought to Europe in 1829 by Th. von Siebold,
its discoverer. It grew within a few years from 1 foot to 3 feet in length,
and died in 1881, at least fifty-two years old. Another specimen lived in
the Hamburg aquarium for fourteen years, during which time it is said to
have grown 36 cm. (more than 14 inches), having attained a length of nearly
4½ feet, or 134 cm. The largest specimen known measures 159 cm = 5 feet 3
inches.
The life-history of this species is still imperfectly known. Japanese
picture-books contain drawings of the adult and of larvae, the latter
showing three pairs of fringed external gills. Young specimens of 16 cm.
length have already lost the gills, but still retain a cleft on either side
of the neck, in the shape of a horizontal slit, and this is soon after
closed up by the skin.
The best account has recently been given by Sasaki.[46] According to him
the Giant Salamander leads a solitary life, concealed in dark places, under
rocks in swift-flowing, thickly shaded small brooks of clear and cold
water.
The animal may be easily captured with a fish-hook, baited with a fish,
frog, or several earth-worms, and tied to a string a few feet in length.
This is thrust by the aid of a small bamboo-stick into the salamander's
retreat. The string is not tied to the stick, but the point of the loaded
hook is forced into one end of it, far enough to keep it in place while
this end of the rod is pushed under the rock. When the bait has been thus
brought near the salamander, any bite will be instantly felt through the
{100}rod. The latter is then withdrawn as quietly as possible, the hook and
bait being left. As soon as a jerk of the string is noticed, a pull is
made, which generally ends in the capture of the unfortunate animal. If the
first pull should fail, the bait is replaced as before, and a second
opportunity is offered, which the unwary creature accepts as readily as the
first. The fisherman, having obtained one bite, is sure of ultimate
success, as the salamander does not learn by experience to refuse the
proffered morsel. When captured, it emits a peculiar slimy secretion,
having an odour much like that of the leaves of the Japan pepper
(_Xanthoxylon peperitum_). This secretion hardens into a gelatinous mass
after a short exposure to the air.
Temminck and Schlegel state that the act of inspiration is ordinarily
performed once every 6-10 minutes. This is true for specimens kept in tubs;
but Sasaki is inclined to think that they perform this act less frequently
in their native brooks. The eyes are so small that they are obviously of
little importance; the salamanders capture their prey not by pursuing, but
by waiting for its near approach, whereupon they seize it with their teeth
by a swift lateral movement of the head. The eggs are said to be laid in
August and September, and they form a string resembling a rosary. Each egg
floats in a clear fluid, inclosed in a bead-shaped gelatinous envelope, and
this is connected with the next by means of a comparatively small string.
The egg measures about 6 mm. by 4 mm., and is yellow everywhere except at
the upper pole, where it is whitish. All attempts to make _Cryptobranchus_
breed in captivity have failed hitherto, owing no doubt to the difficulty
of obtaining the cool temperature of its mountain streams. Sasaki's
smallest specimens measured 19 to 20 cm. These had three pairs of very
short branchial processes, from 3 to 5 mm. in length, attached just inside
the branchial orifice. Each process was somewhat flattened and tapering,
most of them still with branchlets. In another specimen, 20.5 cm. in
length, the gills had almost wholly disappeared, but the branchial slits
were still visible. One of 24.5 cm. length showed no trace of gills, and
the branchial orifice was completely closed, but still marked by a light
streak.
{101}[Illustration: FIG. 18.–_Amphiuma means._ × ⅕.]
_Amphiuma means_ s. _tridactyla_.–The limbs are very much reduced, and end
in two or three little fingers or toes. Just in front of the fore-limbs
lies the pair of small gill-clefts, each guarded by two flaps of the skin.
There are four branchial arches. The general colour of this eel-shaped
creature is black, lighter below. The head is covered with numerous pores,
arranged in several rows, which unite in the region of the neck, so that
only two rows extend along the sides of the body. It reaches a length of
three feet, and lives in swamps or muddy waters, for instance in the
ditches of rice-fields, burrowing occasionally in the mud, feeding on
crayfishes, molluscs, small fishes, etc. It is confined to the
south-eastern States of North America, from Carolina to Mississippi.
According to Davison,[47] copulation takes place in May. The rather
hard-shelled eggs are deposited in the following August or September, and
are connected by a twisted cord. The female lies about them in a coil. The
embryos, which are hatched in the month of November or December, have
well-developed external gills. By the following February they have
{102}reached a length of from 68 to 90 mm. (about 3 inches), living in damp
localities under rocks or rooted stumps, and have already lost their gills.
The legs are said to be relatively longer than they are in the adult.
FAM. 2. SALAMANDRIDAE (Salamanders and Newts).–Without gills in the perfect
state. Maxillaries are present. Both jaws are furnished with teeth. The
eyes are protected by movable lids, except in _Typhlotriton_. Fore- and
hind-limbs present, although sometimes very much reduced.
To this family belong by far the greater number of tailed Amphibia. They
have been, for the sake of convenience, grouped into four sub-families, the
determining characters of which are all internal and of comparatively
slight importance. Little better is the division into _Mecodonta_, with the
teeth of the palate in two longitudinal rows diverging behind and inserted
upon the inner margins of the two palatine processes, which are much
prolonged posteriorly, and _Lechriodonta_, in which the series of palatal
teeth are restricted to the posterior portion of the vomers and form either
transverse or posteriorly converging rows.
I. Series of palatal teeth transverse, restricted to the posterior
portion of the vomers. Parasphenoid beset with dentigerous plates.
Vertebrae opisthocoelous: _Desmognathinae_, p. 102.
" amphicoelous: _Plethodontinae_, p. 103.
II. Series of palatal teeth transverse or posteriorly converging,
restricted to the posterior portion of the vomers. Parasphenoid
toothless. Vertebrae amphicoelous: _Amblystomatinae_, p. 109.
III. Series of palatal teeth in two longitudinal series, diverging
behind, inserted on the inner margin of the long palatine processes.
Parasphenoid toothless. Vertebrae amphicoelous: _Salamandrinae_, p. 115.
SUB-FAM. 1. DESMOGNATHINAE.–Comprising only three genera, with five
species, in North America. Five toes.
_Desmognathus._–The tongue is attached along the median line, free behind,
oval in shape. Three species in the eastern half of the United States. _D.
fuscus_ is one of the lungless Urodela, for which condition see p. 46. The
skin is nearly smooth; parotoids prominent, gular fold strongly marked.
General colour above, brown suffused with pink and grey, sometimes with a
dark lateral band; under parts mottled brown. The vomerine teeth are
frequently absent. Total length, about 4 to 5 inches. They live, carefully
concealed in the daytime, under {103}stones in or on the edge of the banks
of little mountain streams. The eggs are laid in two long strings, and are
wrapped round the body of the female like a rosary, the female having
resorted to a hollow in the mud, below a stone or other suitable place. The
outer envelope of each egg tapers out into a short stalk, and the several
stalks all converge, or are glued together into one common knot, "much like
a bunch of toy balloons held in the hand of a street vendor." The egg is
said to be meroblastic. The larvae seem to remain in the egg until they are
nearly adult, and they emerge at midsummer, with the gills already much
reduced. The complete metamorphosis takes place in the autumn of the same
year. These little newts can, according to Wilder,[48] be collected all the
year round, in Massachusetts from March to December, except during the time
of deep snow. They are nocturnal and are easily kept.
[Illustration: FIG. 19.–_Desmognathus fuscus_; female with eggs in a hole
underground. × 1. (After Wilder.)]
_Thorius pennatulus_, from Orizaba, Mexico, the only species, is noteworthy
for its extremely large nostrils, and for the tongue, which is supported by
a central pedicle, free all round, and ending in a thick knob, which can
probably be protruded. The limbs are weak, and the digits are also much
reduced. Total length, under 2 inches, or 50 mm.
_Typhlotriton spelaeus_, of the Rock House Cave in Missouri, is blind, the
eyes becoming concealed by the skin during metamorphosis, when the gills
are lost.
SUB-FAM. 2. PLETHODONTINAE.–The five genera of this almost entirely
American sub-family (only one species of which, _Spelerpes fuscus_, occurs
in Europe) can be distinguished as follows:–
I. The tongue is attached by its central pedicle only, is free all round,
ends in a soft knob and can be shot out to a considerable distance.
With 5 toes: _Spelerpes_, p. 104.
With 4 toes: _Manculus_, p. 106.
{104}II. The tongue is attached along the middle line and cannot be
protruded out of the mouth.
Jaws with numerous small teeth.
With 5 toes: _Plethodon_, p. 106.
With 4 toes: _Batrachoseps_.
Maxillary and mandibular teeth few in number but very large.
With 5 toes: _Autodax_, p. 107.
_Spelerpes._–Except in a few species the limbs are well developed and
possess 4 fingers and 5 toes, which are either free or webbed. But in the
Colombian _S. parvipes_, still more in _S. lineolus_ of Orizaba and _S.
uniformis_ of Costa Rica the limbs and digits are reduced to mere vestiges,
and are practically without function, the body, with the extremely long
tail, having assumed a wormlike shape. The young of many, if not all,
species have a pair of short balancers below each nostril; in the adult
these organs are reduced to little swellings or lost completely. Several
species are lungless, see p. 46.
The geographical distribution of this genus, of which some twenty species
are known, is very remarkable. The majority live in Mexico and in the
United States, a few are found in Colombia and Northern Peru (_S.
altamazonicus_ and _Plethodon platense_ being the only Urodeles hitherto
recorded from south of the equator), one in Hayti (_S. infuscatus_), two
(_S. subpalmatus_ and _S. uniformis_) in Costa Rica, and _S. fuscus_ in
Europe.
_S. bilineatus_ is a little newt under 4 inches in length–60-95 mm.–found
in the Atlantic States. It is brownish-yellow above, with a black lateral
line extending from the eye to nearly the end of the tail. The under parts
are bright yellow. It lives on land, in damp places, concealed during the
daytime under stones or old trees, whence it emerges after a rain or in the
dusk of evening.
According to H. H. Wilder,[49] "the eggs are deposited in May and June in a
single layer upon the lower side of submerged stones, each batch containing
30 to 50 eggs. The stones which are suitable for this purpose must be in
the form of an arch, allowing the water to flow beneath. They are generally
in the more rapidly flowing portions of the brook, but the depth of water
must be such that the eggs are at all times entirely submerged. They are
attached to the stone by gelatinous threads, proceeding from the outer
envelope, and although they are generally contiguous, they {105}are each
attached separately." The eggs are holoblastic. The larvae hatch early and
continue for a long time in the larval state, probably two or three years.
_S. porphyriticus_ s. _salmoneus._–Yellowish-brown or purplish-grey above
with tiny darker dots and markings. The sides of the body are
salmon-coloured, with a tinge of yellow. The under parts are whitish,
turning into salmon-pink on the tail. This beautiful newt reaches about 6
inches in length and has a very moist, slimy skin, which, combined with the
lively motions of the creature, make it as slippery as an eel. It is found
in the Alleghany range, from New York to Alabama.
Specimens which I am keeping prefer the wettest part of the cage, where
they lie concealed in the moss and mud, leaving their hiding-places at
night in search of insects. One of them escaped into the greenhouse and was
discovered after nine months, having established its permanent home in a
cleft between mossy stones: when the sweepings of a butterfly-net are
emptied near its hiding-place it peeps out and with a flash of its long,
forked, white-coloured tongue it secures its prey. Occasionally it goes
into a tank, when it swims with rapid, undulating motions, the limbs being
laid back and remaining inactive; it sometimes rises to the surface to emit
and to take in air, but, although mostly resting half in the water, upon a
rotten stump, it often lies for hours at the bottom without stirring. When
kept in dry surroundings, the skin soon dries and wrinkles, and the animals
show every sign of suffocation and general discomfort. The respiration of
this lungless species by means of rapid movements of the throat is very
limited, most of the necessary oxidisation of the blood being effected
through the skin.
_S. fuscus._–This, the only European species, is thoroughly terrestrial. It
is found in the mountains bordering the Gulf of Genoa, and in Sardinia. Its
total length remains under four inches. The smooth, very delicate and
easily broken skin is brown above, light below, and speckled with lighter
and darker markings. Below each nostril is a slight swelling, the remnant
of the cirri or balancers common to the young of many species. It lives in
shady surroundings, under stones, in old trees and in limestone-caves,
glued to the walls with spread-out toes, belly and tail, quietly waiting
for insects and spiders which it catches by flashing out the long tongue.
{106}According to J. Berg,[50] it keeps well in cool, moist and
well-ventilated places. It lives on flies, small beetles, and maggots; ants
are also taken at once, probably owing to their lively movements, but a few
minutes later the newts roll about in spasms and soon die. Towards the end
of March one of Berg's specimens gave birth to four young, which were 36
mm., or nearly 1½ inches long, and differed from the adult only by their
exceptionally large nostrils, thereby resembling the Mexican _Thorius_. The
little ones shot out their tongues about 10 mm., feeding on Aphides.
[Illustration: FIG. 20.–_Spelerpes fuscus_, showing the position and shape
of the partly and fully protruded tongue. The figure on the right side
shows the tongue and the skeleton of the hyoid apparatus. _B_, the
threadlike, elongated, first branchial arch; _H_, hyoid, in reality
attached by its outer end to the vicinity of the quadrate; _T_, tongue.
About × 2. (After Berg and Wiedersheim.)]
_Manculus._–The two species of this genus live in Carolina and Florida. _M.
quadridigitatus_ is a very slender, graceful little animal, about 3 inches
in length, the long and thin tail being considerably larger than the rest
of the body. Yellowish, minutely speckled with brown above and on the
sides, greyish-white below. Life entirely terrestrial.
_Plethodon._–About seven species in North America. This genus has given its
name to that of the subfamily, which might with more reason be called
Spelerpinae.
_P. glutinosus_ is slaty or bluish-black, with small whitish specks,
especially on the sides of the trunk, where they are large and often
confluent. The skin is smooth and shiny. Total length about 5 inches, half
of which belong to the tail. Holbrook considered this as one of the
commonest of the North American newts, and mostly widely distributed, from
Ohio to the Gulf of Mexico. It usually lives concealed under stones, but
prefers fallen trees, probably on account of the insects upon which it
{107}preys. When taken in the hand it gives off a great quantity of slime.
_P. erythronotus_ extends into Canada and is much smaller. Brown or grey
above, mostly with a broad, reddish-brown band over the head, back, and
tail. The under parts are white, with grey and brown specks.
_Autodax_ s. _Anaides_.–The large tongue is attached along the median line.
The jaws are furnished with few, but surprisingly large, knife-shaped
teeth, about ten in the upper and fewer in the lower jaw. The small teeth
of the vomers form a chevron-shaped series behind the choanae, those of the
parasphenoid stand in one elongated patch. The tail is round; number of
toes, five. Three species in Western North America, from California to
Oregon.
_A. lugubris._–The eyes are very large and prominent. The upper jaw shows a
peculiar recess on either side for the reception of the large lower teeth.
The skin is smooth, devoid of parotoid glands, but has a strong gular fold.
The upper parts are dark brown or lead-coloured, with whitish dots on the
sides; under parts white. Total length some 6 inches, about half of which
belongs to the tail. The fingers and toes are very rich in subcutaneous
venous sinuses.
The habits of these creatures are in many respects peculiar. Van
Denburgh[51] says of _A. iecanus_ "that it usually moves quite slowly,
moving one foot at a time, but is capable of motion surprisingly rapid for
a salamander. When moving rapidly, it aids the action of its legs by a
sinuous movement of its whole body and tail. The latter is prehensile.
Several individuals, when held with their heads down, coiled their tails
around my finger, and, when the original hold was released, sustained
themselves for some time by this means alone. One even raised itself high
enough to secure a foothold. This animal's tail is also of use in another
way. When caught, it will often remain motionless, but if touched, will
either run a short distance with great speed, or quickly raising its tail
and striking it forcibly against the surface on which it rests, and
accompanying this with a quick motion of its hind-limbs, will jump from
four to six inches, rising as high as two or three."
Ritter and Miller[52] have made extensive observations on the life-history
of _A. lugubris_. When wishing to pass from the hand to {108}the table, the
creature will frequently execute a well co-ordinated spring and alight on
its feet some distance away, instead of falling over the edge in the
typical salamander-fashion. This species is nocturnal and entirely
terrestrial, and seems to be indifferent even to proximity to water. Rotten
stumps and logs are the habitations preferred, and wherever these occur in
the region about San Francisco Bay, even though at the places remotest from
water, specimens are sure to be found.
The eggs are laid in a hollow under ground, and the female seems to remain
curled around them until they are hatched, which takes place in two or
three weeks. The specimen observed by Ritter and Miller laid 19 eggs. Each
was contained in a gelatinous capsule 6 mm. in diameter, and was firmly
anchored to a clump of earth by a narrow peduncle about 8 mm. long. The
embryos developed very large gills, each being composed of three broad
membranous lobes, the latter being thin and delicate, much expanded, highly
vascular and widely confluent at their bases, so that the gills of each
side really form one three-lobed mass. Their dorsal surfaces are applied to
the inner surface of the egg-capsule. The amount of food-yolk is
considerable. The whole larval life is passed through within the egg.
Before the young is hatched the gills wither and cease to be functional,
and the gill-slits close up. The tail is round, and shows no indication of
a fin at any time during the larval period. Newly hatched individuals
appeared much distressed when put into water, and were quite unable to
swim. They immediately sank to the bottom and remained there until they
were removed. The integumentary sense-organs, so well developed in the
aquatic larvae of Urodeles, are entirely wanting. When hatched the young
creature is about 32 mm. long; its general colour is blackish-grey, finely
sprinkled with bluish-silver. During the second year this garb is changed
to the dusky brown of the adult, and the fine silver speckling is replaced
by much larger and less numerous yellow spots.
Although one of the most terrestrial of Urodeles, this species is lungless,
but the skin remains delicately smooth and moist throughout life. According
to the observers quoted, the pharynx plays an important part in
respiration. From 120 to 180 or even more vibrations are made by the throat
in a minute, and in some cases these movements are grouped into series of
about {109}20 to 25 extremely rapid vibrations, with periods between each
two series.
SUBFAM. 3. AMBLYSTOMATINAE.–Composed of seven closely allied genera, the
distinguishing characters of which are the grouping of the palatal teeth
and the number of the toes, which varies between 4 and 5. The geographical
range of the subfamily extends over the whole of North America and Mexico
and over the whole of Northern Asia, from Kamtchatka and Japan westwards to
the Ural, and southwards into China. The occurrence of one species,
_Amblystoma persimile_, in the mountains of Siam, makes it highly probable
that other species and genera exist in the hitherto unexplored intervening
countries.
Boulenger gives the following synopsis:–
I. The series of palatal teeth converge backwards, forming a V-shaped
figure.
With 5 toes: _Hynobius_, 3 species in Japan.
With 4 toes: _Salamandrella_, 2 species Lake Baikal, Ussuri and Schilka
rivers, and Kamtchatka, p. 109.
II. The series of palatal teeth form an uninterrupted, doubly arched
V-shaped figure.
The 4 fingers and 5 toes are furnished with black, horny claws:
_Onychodactylus japonicus_.
III. The series of palatal teeth form two arches, convex forwards,
separated by a wide interspace.
The two series are short, confined to the space between the choanae.
With 5 toes: _Ranidens sibiricus_, Eastern Siberia and N.E. China.
With 4 toes: _Batrachyperus sinensis_, Moupin in China.
The series are long and converge backwards, 5 toes: _Dicamptodon
ensatus_, California.
IV. The palatal teeth are arranged in a nearly straight, transverse line,
or they form an angle which points slightly forwards; they are not
separated by a wide median space. With 5 toes: _Amblystoma_. Some 16
species in North and Central America, one in Siam, p. 110.
_Salamandrella keyserlingi._–The mode of propagation of this newt-like
species has been observed by Shitkow near Jekaterinburg in the Ural
mountains. The eggs were laid at the end of April and were deposited in
bags, which were attached to a plant, with one end about an inch below the
surface of the water. The bag measured 15 cm. in length and 2 cm. in width
and contained 50 to 60 eggs. The larvae were hatched in 14 days in a sunny
aquarium; in another with a northern {110}aspect the hatching took 23 days.
The larvae were 10 mm. long, and remarkable for the length (1 mm.) of their
balancers.
_Amblystoma opacum._–The general shape is very much like that of the
European Spotted Salamander. The head is short and broad, the snout is
rounded. The eyes are very prominent, with a black pupil and a dark-grey
iris. The neck has a well-marked gular fold. The tail is thick and almost
round. The hind-limbs are considerably larger than the fore-limbs. The
general colour of the shiny, moist skin is a purplish-black with light
grey, transverse, partly confluent bars, giving the creature a pretty
appearance; the under parts are paler, bluish-grey. Total length between 3
and 4 inches, or 9 cm.
This beautiful species inhabits many of the United States east of the Rocky
Mountains, from New Jersey to Florida and Texas. In the perfect state it is
thoroughly terrestrial and easily kept. My specimens prefer the holes of
rotten and moist, moss-covered stumps, or holes beneath stones, which they
leave, at night only, in search of earthworms and insects.
_A. talpoideum_ is closely allied, somewhat stouter and almost uniform
brownish-back. According to Holbrook, "it chooses light soil in which it
will bury itself in a few seconds like a mole, and there continue its
course concealed from view; but its track can often be followed by the
elevation produced on the surface of the soil, similar to that seen in
fields infested by moles."
[Illustration: FIG. 21.–Egg-sac of _Salamandrella schrenki_. × ½. (After
Shitkow.)]
_A. punctatum_ is bluish-black, with a row of roundish yellow spots on each
side of the body and tail and upon the limbs.
E. A. Andrews[53] has made observations upon the breeding of this species.
Near Baltimore the eggs are very abundant in March and even in February, in
small pools in the woods, but the adults are then rarely seen. Even when
small pools, but 4 feet wide and 9 inches deep, were thoroughly raked out
{111}before and after the eggs appeared, no adults were found, so that it
is to be inferred that the laying takes place in the night and that the
adults leave the water every day to conceal themselves under stones. One
female was found moving away from a bunch of eggs early in the morning.
This specimen was kept isolated, and laid many eggs, and as these developed
into normal larvae, the existence of internal fertilisation was proved.
Previously to the laying of the eggs white spermatophores were found in the
small pools, on the dead twigs and leaves covering the bottom.
_A. jeffersonianum._–This very slender and slippery species, reaching a
length of 6 inches, is remarkable for its long fingers and toes, and its
rather compressed tail. The general colour is brown above, dirty whitish
below, generally with numerous, small, light blue and pale brown spots on
the sides of the neck, body, limbs, and tail. There are several
colour-varieties, one of them with white specks. It is a very active and
surprisingly good climber, easily escaping out of high-walled bell-glasses,
hiding in the daytime in dark and moist localities. Its range extends from
Indiana and Virginia to Quebec.
_A. persimile._–This species is remarkable on account of its geographical
distribution. It is the only non-American species, inhabiting the higher
mountains of Siam and Upper Burmah. There is no doubt about its belonging
to the genus _Amblystoma_, although it had originally been described as a
_Plethodon_. It closely resembles _A. jeffersonianum_ in most of its
characters, notably in the arrangement of the palatal teeth, general
proportions, slender toes, and even in the presence of whitish spots, which
are scattered over the sides of its blackish, smooth skin.
_A. tigrinum._–This, the commonest species, is conspicuous for its large,
depressed head, which is as broad as it is long, its width being enhanced
by the unusually large parotoid glands. The mouth is very wide. The large,
prominent eyes are golden, and reticulated with brown. The gular fold is
strong. The limbs are stout, the fingers and toes short. The trunk is
strongly constricted by twelve intercostal grooves. The tail, which is as
long as the rest of the body, is somewhat compressed laterally, but bears
no trace of a fin. The general colour is more or less dark brown or bluish
black, marked with numerous yellow spots and large blotches; the under
surface inclines to {112}grey. The length of the adult male is about half a
foot; the females, as usual being larger, sometimes reach the length of 9
inches. The range is from New York to California and to Central Mexico.
The larva of this species is the famous Axolotl. It is provided with three
pairs of delicate and much-branched external gills, a flat, long tail with
a broad ventral and dorsal fin, the latter extending along the back almost
to the neck. The limbs, although comparatively slender, are fully
developed, and the head is much more pointed than it is in the perfect
form. The larvae usually reach 8 or 9 inches in length; exceptional
specimens have been recorded of one foot in length, and have been described
as _Triton ingens_.
[Illustration: FIG. 22.–Axolotls or larvae of _Amblystoma tigrinum_. × ½.]
These larvae were found by the Spanish conquerors to occur in great numbers
in the lakes near Mexico City, and were called Axolotl by the natives, a
word signifying "play in the water." They were, and are still, eaten,
either roasted or boiled, with vinegar or cayenne pepper.
For many years these creatures were looked upon as a species of the
Perennibranchiata, under the generic name of _Siredon_ (_S. axolotl_, _s.
pisciformis_, _s. mexicanus_, etc.), although Cuvier suspected that they
were but the larvae of an otherwise unknown terrestrial Urodele. The
mystery was not cleared up until the year 1865, when some Axolotls which
had been kept for a year in the Jardin des Plantes at Paris, suddenly began
{113}to pair, and laid eggs which within six months developed into
full-sized Axolotls. This certainly looked as if these creatures were not
larvae, but a true Perennibranchiate species. But to the general surprise
several of these young Axolotls gradually lost their gills, the clefts
closed up, the fins of the back and tail disappeared, the head became
broader, the creatures left the water permanently, and in fact turned into
the already well-known terrestrial _Amblystoma tigrinum_. The other
brothers and sisters of the same brood remained aquatic Axolotls, which
thereby revealed themselves after all as the larval and not as the perfect
stage of this remarkable species.
At the suggestion of Kölliker and Weismann, Frl. Marie von Chauvin[54]
undertook, at the University of Freiburg, long and carefully conducted
experiments, showing (1) that little Axolotls can comparatively easily be
caused to develop further into the perfect _Amblystoma_ if they are induced
to breathe air more frequently than usual; shallow vessels, perhaps also
insufficiently aerated water, will produce the desired result; (2) that the
commencing metamorphosis can again be checked, the shrinking gills then
undergoing fresh development; (3) that they can be forced to remain
Axolotls; (4) that the cutting off of the gills has no influence upon their
possible metamorphosis, the gills being easily and quickly renewed. The
same lady found also that _Amblystoma_, the perfect form, lives in the
water during the pairing time and behaves in the same way as the Axolotls.
The latest observations have been made by Metzdorff.[55] Axolotls, at least
those which are kept in captivity in Europe, are ready for propagation
several times in the year, either in the spring, from April to June, or in
December. The male deposits spermatophores, which in the following night
are taken up by the female into the cloaca. On the following day,
preferably in the afternoon, she grasps a suitable leaf, for instance that
of _Vallisneria_, with the hind-limbs, and presses it against the vent. The
eggs are expelled by strong wriggling movements of the body, and are formed
into three or four packets of six to ten eggs each, so that about thirty
eggs are laid at one sitting. {114}Then she takes a rest before proceeding
again; the whole process, in which the male takes no further interest,
lasting about two days. The most suitable temperature is one of 18-20° C.,
or about 68° F. The water must be well aerated. Sterile eggs turn white on
the second day. The little larvae are hatched in about a fortnight. Eggs
which are kept in a higher temperature, from 22-24° C., develop more
quickly, but the resulting young are smaller; they show already on the
fifth day head, tail, and the beginning of the gills. According to
Bedriaga, they live at first upon Infusoria and _Daphnia_; when they are
20-25 mm. long they eat _Tubifex rivulorum_; later on they take scraped
meat and are liable, when hungry, to nibble off each other's gills, but
these are easily reproduced. When 20-25 cm. long, at the age of about six
months, they are able to breed. The chief point of interest is the fact
that this species of _Amblystoma_ frequently remains throughout life in the
larval state, except that it develops generative organs. The natural causes
of this retention are not completely known. According to Shufeldt, who
observed them under natural conditions near Fort Wingate in New Mexico,
plenty of food, the drying up of the swamps, and the increasing temperature
of the diminishing water, hurries on the metamorphosis, while deeper water
retards it. Weismann[56] suggested that the specimens in the Mexican lakes
which remained Axolotls were prevented from becoming perfect Amblystomas on
account of these lakes, after the disappearance of the surrounding forests,
having receded from their former boundaries, which are now covered with a
saline, uninhabitable crust. This may be an explanation, although Axolotls
do not live in brackish water. But Weismann went farther, and with his
well-known dialectic powers has succeeded in spreading the belief not only
that the Axolotl is a case of reversion to an ancestral stage, but that the
present _Amblystoma_, instead of being the progressive, perfect form, is
likewise a case of reversion. A reversion from a reversion! The whole line
of evolution would then be as follows: _Amblystoma_; its young, owing to
adverse circumstances, revert to the stage of the Perennibranchiate
ancestors of all Urodela; if some of these Axolotls lose their gills and
fins, they revert thereby into the original _Amblystoma_. {115}Surely a
roundabout way of explaining a curious but after all rather simple process
of Neoteny; cf. p. 63.
Observations on the metamorphosis of _Siredon lichenoides_ into _Amblystoma
mavortium_ have been made by Marsh, who also gives figures of the larval
and adult forms.[57]
SUB-FAM. 4. SALAMANDRINAE.–The six genera of this subfamily fall into two
natural groups: I, True Salamanders, with the palatal teeth arranged in a
pair of S-shaped figures, and without a fronto-squamosal arch. II, Tritons,
with the palatal teeth in the shape of a Λ, _i.e._ the right and left
series meet at an angle; the fronto-squamosal arch is present, either bony,
or at least ligamentous. _Triton cristatus_ is, however, exceptional, in
that the two palatal series often do not meet and that the arch is absent.
The number of fingers is universally four, that of the toes is five except
in _Salamandrina_, which has only four.
The geographical distribution of the sub-family, entirely Periarctic, may
be said to be the reverse of that of the Amblystomatinae. Of the
twenty-five species namely, only two are American, four are Eastern
Asiatic, and of the remaining nineteen, two are Algerian, while the rest
live in Europe or in Asia Minor. It is in fact an essentially Palaearctic
group.
The six genera can be distinguished as follows:–
I. The palatal teeth are arranged in two S-shaped curves. True
Salamanders.
Tongue short and thick. _Salamandra_, p. 115.
Tongue long and projectile. _Chioglossa_, p. 121.
II. The palatal teeth are arranged in a Λ shape. True Tritons.
With only four toes. _Salamandrina_, p. 122.
With five toes.
Pterygoids separated from the maxillary and quadrate bones: _Triton_,
p. 122.
Pterygoids touching the maxillae and quadrates. Himalo-Chinese:
_Tylototriton_, p. 132.
Pterygoids united broadly with the maxillae. Chinese: _Pachytriton_,
p. 132.
_Salamandra._–Without fronto-squamosal arch. Five toes. Tail round. Three
species in Europe and Western Asia.
_S. maculosa._–The Spotted or Fire Salamander. General habit stout. Usual
length about 5 to 6 inches; the females are mostly larger than the males;
specimens of more than 8 inches in {116}length are giants. Head as broad as
it is long, snout rounded. Limbs and digits stout and short. The skin is
smooth, shiny and full of pores, with a strong gular fold. The parotoid
glands are large and covered with large pores. A series of distinct
swellings, or cutaneous glands, each with a distinct opening, extends along
either side of the back, and a shorter series along the flanks. The general
colour of the Spotted or Fire-salamander is black, with irregular, large
yellow patches on the back and limbs. These markings vary extremely, so
much so that scarcely two specimens, collected at random, are alike. In
some the yellow patches form two more or less regular bands, in others they
are partly confluent; again the yellow may be preponderant on the back or
much restricted. Occasionally the chrome-yellow is replaced by orange. The
under surface is as a rule bluish grey-black. This combination of shiny
yellow and black is a good instance of warning colours. The creature is
poisonous, cf. p. 38. When left in peace, or handled gently, it is
perfectly harmless, but when treated with violence, or submitted to severe
pain, a milky white fluid exudes from the glands and is, under violent
contractions of the muscular skin and body, sometimes squirted out in fine
jets to the distance of a foot. Burning pain and subsequent inflammation
result if this poison gets into the eye. The same applies to the mucous
lining of the mouth and throat. A few drops of this poison introduced into
the blood or into the stomach of a small animal are sufficient to cause its
death. Cold-blooded animals are as susceptible as warm-blooded creatures.
I once put two American bull-frogs into the same outdoor enclosure with a
large number of salamanders. Next morning the huge frogs were found dead,
each having swallowed a salamander, which they were not acquainted with and
had taken without suspicion.
The Fire-salamander has a wide range, namely the whole of Central,
Southern, and Western Europe with the exception of the British Isles. It
extends southwards into Corsica and Algeria, eastwards through Asia Minor
into Syria. Where it does occur it is rather common, provided the terrain
is mountainous or hilly and covered with vegetation. There it lives under
moss or rotten leaves, in the roots of old trees, in the cracks and clefts
of the ground, of rocks or of ruins of buildings; {117}in default of
anything better under heaps of stones, or in the holes dug by mice or
moles. One chief necessity for its happiness is moisture.
The salamander does not occur everywhere, but is rather local. On certain
kinds of limestone it is rare or absent; granitic terrain and red sandstone
seem to suit it best, for instance the Hartz Mountains, Thuringia, and
Heidelberg are favourite localities. But even there we may spend days and
weeks and never come across a single specimen. We may turn stones, rake up
the moss and leaves, pry into cracks, and we unearth perhaps a few
sorry-looking, listless, dull and dry, half-emaciated creatures. The same
place after a thunderstorm will be literally swarming with sleek, lively
salamanders, in search of earthworms and all kinds of insects, especially
at dusk or during the night. They disappear in the autumn, in October, to
hibernate in the ground, out of the reach of frost, and they reappear again
in April. Later on they congregate at little springs, always at running
water, to reach which they have often to make long migrations. This is the
only time when these thoroughly terrestrial creatures approach water, in
which they easily get drowned.
Although this species is so common its mode of reproduction has been
satisfactorily discovered only quite recently. There are some puzzling
facts which it took a long time to observe correctly and to interpret. The
larvae are born in April, May, or June, while there are no eggs in the
oviducts, but in July these are full of fertilised eggs before copulation
takes place. This seems contradictory. The explanation is as follows. In
July there is an amplexus of the sexes, short, and often on land–a sort of
preliminary exciting performance. Both sexes then descend into the water,
but generally remain on land with the fore part of the body. The male
deposits a spermatophore and the female takes part of this into its cloaca.
In the case of a virgin female the eggs are fertilised in the oviduct and
ripen until the autumn, but the larvae nearly ready for birth remain within
the uterus until the following May, _i.e._ about ten months. The mother
then crawls half into the water, mostly at night, and gives birth to from a
few to fifty young, fifteen being perhaps the average. The young are
surrounded by the egg-membrane, which either bursts before or shortly after
expulsion. This species is consequently viviparous in the proper sense. If
she produces a few young only, say from {118}two to five, these are much
larger and stronger than those of a large litter. Occasionally a few addled
or only partly developed eggs are also expelled.
In the case of old females which have produced offspring before, the whole
process is more complicated. The sperma, taken up in July, remains in the
receptaculum of the cloaca until the May or June following, _i.e._ until
the previous larvae have passed out of the uterus and are born. Then the
spermatozoa ascend to the upper ends of the oviducts, where they meet and
fertilise the new eggs. After these have descended into and filled the
uterus, and are already developing into embryos, copulation takes place
again in July, preparatory for next year's eggs.
The new-born salamanders have three pairs of long external gills, a long
tail furnished with a broad dorsal and ventral fin, and four limbs,
although these are small. The total length is about 25 mm. or 1 inch. The
general colour is blackish with a pretty metallic golden and greenish
lustre. The little creatures are very active, and at once eat living or
dead animal matter. In captivity they are liable to nibble each other's
gills and tails. During the first six or eight weeks they assume a row of
dark spots on the sides; these spots enlarge, and the whole skin becomes
darker. Yellow spots appear next, first above the eyes and on the thighs,
later upon the back; the ground-colour at the same time becomes black,
until at the beginning of the fourth month they look like the parents.
The metamorphosis is very gradual. The tail-fin diminishes first, but the
gills grow until shortly before the little creatures leave the water.
Darkness, cold, and insufficient food retard the metamorphosis, sometimes
until October. It is easy to rear them artificially provided they are well
fed, kept in a light place, and in clean, well aerated water. If prevented
from leaving the latter, for instance when kept in a glass vessel with
vertical walls, or if hindered by a piece of gauze from rising to the
surface and taking in air, they can be kept as larvae well into the winter.
Very young, perfect little salamanders, of from 1 to 2 inches in length,
are excessively rare; even specimens of 3 inches are far from common. They
probably spend the first two or three years of their life in careful
seclusion.
A few adults can be easily kept for many years in shady {119}places
provided with moss, rotten stumps and stones, to afford them suitable moist
and cool hiding-places, and they readily take earthworms, larvae of
beetles, snails, woodlice, etc. But any attempt to keep them in large
numbers ends in failure. They congregate together in clumps, all making for
the same cavity or recess, as if that were the only one in existence (very
likely they are right in so far as that place is probably the best), and
they get rapidly enlarging sores, chiefly on the elbows and knees. These
are soon infested with fungoid growths, and this disease spreads like an
epidemic and soon carries them off.
_S. atra._–The Alpine Salamander differs from the Spotted Salamander by its
uniform black colour and smaller size, which averages between 7 and 5
inches. It is restricted to the Alps of Europe, from Savoy to Carinthia, at
from 2000 to as much as 9000 feet elevation, living with predilection near
waterfalls, the spray of which keeps the neighbourhood moist, or in mossy
walls, in the shade of forests near brooks, or under flat stones on
northern slopes. The most interesting feature of this species is that it
produces only two young at a time. These are nourished at the expense of
the partially developed eggs in the uterus, and they undergo their whole
metamorphosis before they are born. By far the best and most complete
account of this mode of propagation has been given by G. Schwalbe.[58] The
length of the ripe embryos is about 45 mm.; they lie mostly bent up, with
their heads and tails turned towards the head of the mother. The gills are
beautiful, delicate red organs, the first pair being generally directed
forwards and ventralwards, the second upwards, the third backwards; they
are longest when the creature is about 32 mm. long, while there is still
much yolk present. At this stage the gills are so long as to envelop nearly
the whole embryo. There is rarely a second embryo in the same uterus, and
an extra foetus is generally smaller, frequently a monstrosity not fit to
live; it is probable that it is not used as food, but that it is expelled
at parturition. The embryo passes through three stages, (1) still enclosed
within its follicle and living on its own yolk, (2) free within the
vitelline mass which is the product of the other eggs, (3) there is no more
vitelline mass, but the embryo is possessed of gills 10-12 mm. in length,
and is still growing. During the {120}second stage the yolk is directly
swallowed by the mouth. The walls of the maternal uterus are rather red.
The exchange of nutritive fluid takes place through the long external
gills, which thereby function in the same way as the chorionic villi of the
Mammalian egg. Each gill contains a ventral artery and a dorsal vein, each
of which looks like the midrib of a pinnate leaf; there is also a fine
nerve and a weak bundle of striped muscular fibres. Each gill-filament
receives a capillary artery which extends to the epithelium of the tip,
where it turns into a capillary vein. The epithelium of these filaments,
which are full of blood, is ciliated, the resulting current being directed
from the base towards the tip. In older larvae this ciliation becomes
restricted to the tips. The body of the gills is furnished with flat
epithelium, these non-ciliated portions alone are closely appressed to the
uterine wall, and it is here that the exchange of gas takes place between
mother and larva. The nutrition takes place through the gills, as they are
bathed by the yolk-mass.
Schwalbe also explains the whole question of the reduction of the number of
embryos. He says rightly that in _S. maculosa_, which gives birth to many
young, there are in the oviduct many eggs which have only partly developed
into embryos, and these, perhaps from want of room and nourishment,
degenerate into the irregularly shaped whitish-yellow bodies which are
occasionally found packed in between the developing embryos. Consequently
all those eggs had been fertilised near the ovaries. _S. atra_ exhibits a
further stage in so far as most of the eggs, fertilised above in the
oviduct, degenerate, and only two or three become fully developed. These
few embryos live on the degenerating eggs, which together produce the
vitelline material spoken of above. The two full-grown and metamorphosed
embryos, each measuring about 50 mm. in length, are equivalent to the
numerous new-born larvae of _S. maculosa_, especially if the smaller size
of the adult Alpine Salamander is taken into consideration.
Mlle. von Chauvin[59] has experimented with the unborn larvae of this
Salamander. She cut out 23 larvae and put them into water. One of them,
already 43 mm. long, took earthworms on the next day, and the beautiful
long, red gills became pale and shrunk, and on the third day were cast off
close to the {121}body. New gills sprouted out on the same day, first in
the shape of three tiny knobs on either side. After three weeks they had
become round globes, which gradually sprouted out into several branches,
far shorter and more clumsy than the original gills. During the whole time
the larva was lying quietly at the bottom, in the darkest corner, but
showed a good appetite. The fin of the tail disappeared and was supplanted
by a stronger one. In the sixth week the skin was shed in flakes, and this
process took fifteen days. This larva lived in the water for fourteen weeks
and grew to 6 cm. in length! When the new gills gradually shrank, the
compressed and finny tail assumed a round shape, the skin became darker and
shinier, and after the larva had again shed its skin, there appeared the
dark rugose skin of the typical _S. atra_. The gills were reduced to
useless appendages–not cast off–and the creature crawled out of the water.
A fortnight later the gill-clefts were closed. A second larva behaved
similarly, first casting off the feathery gills, substituting a new and
stronger set, which, however, fourteen days after excision from the uterus,
shrank again, and on the nineteenth day the gill-clefts were closed. The
lady also observed that nearly ripe larvae, when cut out, rushed about in
the water and ate, just like the new-born larvae of the Spotted Salamander.
A third species, _S. caucasica_, is found in the Caucasus. It rather
resembles the Spotted Salamander in coloration, but has a larger tail and
lacks the lateral warts. The male is remarkable for the possession of a
soft permanent knob or hook at the top of the root of the tail. This pommel
possibly prevents the slipping off during the amorous amplexus, provided
the sexes then entwine like certain Tritons.
_Chioglossa lusitanica._–The only species of this genus is restricted to
the north-western third of the Iberian peninsula. This graceful,
slenderly-proportioned and beautiful Salamander is apparently very rare and
local, having hitherto been found at a few places, namely, near Coimbra,
Oporto and Coruña. It lives under moss, and runs and climbs with an agility
surprising in a Urodele. The tongue is long, ending in a fork, and is
supported by a median pedicle so that the tip can be quickly protruded to
the distance of more than an inch. The whole length of the animal is about
5 to 6 inches, two-thirds of which belong to {122}the long tail, which is
compressed at the end. The skin is smooth and shiny, with a gular fold and
large parotoids. The general colour is a rich dark brown, with a pair of
broad reddish-golden bands along the back and tail, the bands being
separated by an almost black vertebral line.
The few specimens which I have been lucky enough to observe made little
holes or passages in the moist moss of their cage, peeping out with their
heads in wait for little insects, which they caught with flash-like
quickness. They seem to be crepuscular.
_Salamandrina perspicillata._–This genus, represented by one species, a
native of Liguria and Northern Italy, possibly extending into Dalmatia, is
the only Salamander which has but four toes. The skin is not shiny and
smooth, but is finely granular and dry, forms no gular fold, and is devoid
of parotoid glands. The tail is more than half the length of the animal,
which measures from 3 to 4 inches. The general colour is black-brown with a
broad V-shaped orange-yellow mark extending from eye to eye over the
occiput. A faint irregular yellowish line extends along the middle of the
back and tail. The throat is black, with a diffused white patch in the
middle; the belly is white, with black dots; the anal region, the inner
sides of the legs and the under side of the tail are carmine-red.
This slender and pretty Salamander is diurnal, and feigns death when
discovered. Only the female goes into the water, in March, to glue the eggs
on to submerged rocks or water-plants. The young finish their metamorphosis
by the month of June, and reach full size during the winter, the climate of
their home being sufficiently genial to make hibernation scarcely
necessary.
_Triton_ s. _Molge_.–The tail is strongly compressed and frequently has a
permanent fin. The fronto-squamosal arch is variable, it being either bony
as in the South European, Eastern and American species, or reduced to a
ligament, or lastly absent as in _T. cristatus_. The males of all the
English Newts, of _T. vittatus_ and of _T. marmoratus_, develop a high
cutaneous crest on the back and tail during the breeding season, and this
crest acts not only as a swimming organ and ornament, but also as a sensory
organ.
The whole genus comprises some eighteen species, twelve of which are
European, although some of these extend into Western {123}Asia; _T.
pyrrhogaster_ and _T. sinensis_ are found in N.E. China, the former also in
Japan; _T. poireti_ and _T. hagenmuelleri_ live in Algeria, and only two,
_T. torosus_ and _T. viridescens_, are North American. Some of the species
have a limited range; thus _T. montanus_ is confined to Corsica, _T.
rusconii_ to Sardinia, _T. boscai_ to the north-west of the Iberian
peninsula and _T. asper_ to the Pyrenees.
Newts all prefer moisture without heat. During the pairing season they take
to the water, mostly to stagnant pools, which sometimes implies long
migrations. During this period, which is in some cases rather prolonged,
they become thoroughly aquatic and undergo some important changes. The
tail-fins are much enlarged; in the males of some species a high cutaneous
fold grows out on the back, devoid of muscles, but rich in sense-organs.
The whole skin, instead of being dry, possesses numerous mucous glands and,
what is of more importance, specialised sensory apparatuses which are
arranged chiefly along the lateral lines of the body and part of the tail.
After the breeding season Newts become terrestrial, hiding in cracks,
trees, or in the sandy soil. Some species aestivate during the hot and dry
season. They hibernate either in the ground, or occasionally in ponds. _T.
vulgaris_ is difficult to keep in the water beyond the pairing season,
while this is easily done with _T. alpestris_ and _T. cristatus_; _T.
waltli_ can live in the water for years. The food consists of all kinds of
insects, centipedes, worms, snails, etc., which are searched for chiefly at
night. It is astonishing to see a little Triton getting hold of and
gradually swallowing a wriggling earthworm almost as thick and as long as
itself. When two newts seize the same worm, as these voracious and jealous
creatures often do, each gets hold of one end, and swallowing as much as it
can, twists and rolls round in a direction opposite to that of its rival,
until the worm breaks, or until the jaws of the two newts meet and the
stronger of the two draws it out of the weaker one and swallows the whole
worm. They do not drink, but soak themselves in the water.
The skin is shed periodically, and rather often by the rapidly growing
young; by the adult, during the life in the water, rarely during the
sojourn on dry land. The skin breaks round the mouth; assisted by the
fingers and by contortions of the {124}body, it is then slipped backwards
over the trunk and tail, whereupon the newt seizes the skin with the mouth,
draws the shirt off entirely, and–swallows it. Such freshly shed skins are
very delicate and pretty objects when suspended in water or some preserving
fluid. The shed skin, consisting only of the outermost layer of the
epidermis, is entire, but turned inside out, with fingers and toes
complete, the only holes being those for the mouth, eyes, and vent.
None of the Tritons are viviparous. The eggs, which are glued singly or in
small numbers on to stones or water-plants, are hatched in about a
fortnight, sooner or later according to the species and the prevailing
temperature. The larvae are always provided with three pairs of branched
external gills; the fore-limbs appear much earlier than the hind-limbs.
Most, perhaps all, larvae develop two pairs of thread-like protuberances on
the sides of the upper jaw, by means of which they attach or anchor
themselves on to water-plants shortly after they are hatched. Thus moored
they remain motionless in a slanting position, now and then wriggling their
tails and shifting their place, or sinking to the bottom. The metamorphosis
is finished during the first summer, and the little newts, often partially
transparent, leave the water to hide under stones. Not unfrequently the
metamorphosis is retarded and not finished by the autumn. The larvae of _T.
cristatus_, especially when reared in ponds with abrupt or overhanging
banks, so that they cannot leave the water, retain considerable remnants of
the gills, still more frequently the clefts, although breathing chiefly by
the lungs. Such individuals reach a length of 3 inches, and are larvae so
far as the finny tail and the gills are concerned. They hibernate in this
condition, and in exceptional cases reach sexual maturity;–at least the
females, which develop ripe eggs; the males are not known to produce
spermatozoa.
Much has been written on the amorous games of newts, but it is only
recently that the mode of fecundation has been actually observed. Gasco[60]
placed the newts in glass vessels suspended from the ceiling of his
laboratory. The antics of the enamoured male around the female, rubbing the
latter with its head, or lashing it gently with the tail, and playing
around it in its often beautiful nuptial dress, are meant to excite the
{125}female. The male then at intervals emits spermatophores, which sink to
the bottom, and the female takes them up into its cloaca. For further
information see p. 54.
_Triton cristatus._–The Crested Newt has a slightly tubercular skin with
distinct pores on the head, on the parotoid region and on a line along the
side of the trunk. There is a strong gular fold. The general colour above
is dark or black-brown with an olive tinge, interspersed with darker spots;
the sides of the body bear irregular white spots. The under parts are
yellow, almost always with large black spots. The iris is golden
yellow.–The nuptial dress of the male is very striking. A high, serrated
crest occurs on the head and body; the upper surface of the head is marbled
with black and white; the under parts are orange-yellow with black spots,
and the sides of the tail are adorned with a bluish-white band.–The female,
always devoid of a crest, generally exhibits a yellow line along the middle
of the back.–The average length of fully adult specimens is about 5-6
inches or 13-15 cm.; the females are as usual larger than the males; 144
and 162 mm. for an English male and female respectively are exceptional
records.
[Illustration: FIG. 23.–_Triton cristatus._ 1, Female; 2, male in nuptial
dress. × ⅔.]
Propagation takes place in April. The newly hatched larvae are
yellowish-green, with two black dorsal bands, and with a whitish edge to
the tail-fin. By the middle of July they are about 5 cm. long, and the
white-margined tail now ends in a {126}thread 1 cm. in length. The general
colour above is light olive-brown, dotted with black; the flanks and belly
have a golden shimmer.
The Crested Newt has a wide distribution, extending from England and
Scotland through Central Europe into Transcaucasia; the northern limits are
Scotland and Southern Sweden. Although found in Greece and Lombardy, it
does not occur in the Iberian peninsula nor in the South of France, where
it is represented by the next following species.
_Triton marmoratus._–The Marbled Newt is of the same size as the Crested
Newt. Its ground colour is grass-green above, brown below, with numerous
large and small irregularly shaped marbling patches, spots and dots of
black. The crest of the neck and trunk is entire, not serrated, adorned
with dark vertical bands, and separated from the high dorsal fin of the
tail by a deep indenture or gap. The female has an orange line, slightly
sunk in, instead of the crest. This newt is confined to France and the
Iberian peninsula. In the North of Portugal and in Galicia it is frequently
seen in little streams and ponds during the months of March and April. The
rest of the year it spends on land. In France occur hybrids of this species
and _T. cristatus_. They have been described as _T. blasii_.
_T. alpestris._–The Alpine Newt is easily distinguished by the rich orange
colour of its under parts, which are unspotted, excepting a few dark specks
across the throat, below the gular fold. Specimens with many ventro-lateral
black spots are exceedingly rare. All the upper parts are dark, but vary
individually. The prettiest specimens are dark purplish grey, with black
marblings; others incline more towards brown ground-tones, the blackish
markings then appearing more prominent. The sides are often stippled with
tiny whitish dots. The iris is golden yellow.–The nuptial male has a low,
not serrated crest, which extends uninterruptedly from the nape into the
dorsal fin of the tail. The crest is pale yellow, with black vertical bands
and spots. The ground-colour of the upper parts inclines to blue,
especially on the sides. The lower fin of the tail assumes an irregular
band of bluish-white confluent patches.
This newt is rather small, females rarely exceeding 100 mm. or 4 inches in
length. Its home is chiefly the hilly and mountainous parts of Central
Europe, from Holland to Lombardy, {127}Austria-Hungary, and Greece.
Although it ascends the Alps to between 6000 and 7000 feet, it is also
found in the Netherlands, but not in the North German plain.
_T. vulgaris_ (s. _taeniatus_, s. _punctatus_).–The Common or Spotted Newt
usually reaches 3 inches (7-8 cm.) in length. Boulenger's record-specimen
measured 104 mm. It is characterised by the yellow, partly orange under
surface, which is always spotted with black. The upper parts are
olive-green or brown, inclining to white on the flanks; the black spots of
the back, sides, and especially of the tail, are arranged in more or less
distinct lines, giving a somewhat banded appearance to some females.–The
breeding dress of the male shows a non-serrated, but "festooned" high and
very wavy crest, which extends from the neck without interruption into the
likewise wavy tail-fin. The tail is adorned with a lateral, glittering blue
stripe, interrupted by vertical dark spots. The larvae are marked by a
series of yellow dots, which extend over the lateral line and the tail,
which latter temporarily possesses a terminal filament like that of the
larvae of _T. cristatus_.
The distribution of the Spotted Newt is the same as that of _T. cristatus_,
namely Europe with the exception of the Iberian Peninsula, and Western
Asia.
_T. palmatus_ s. _helveticus_.–This is the smallest of all the European
newts, rarely reaching more than 3 inches in length. It is distinguished by
several specific characters. The tail ends in a thread which is in some
males 10 mm. in length, but is only just indicated in the female. The
breeding male develops a cutaneous fold along each side of the back, and a
low, entire, vertebral crest; the toes are fully webbed. The under parts
are pale yellow, inclining to orange towards the middle of the belly, and
with a few blackish dots. The lower caudal crest has its edge blue in the
male, orange in the female. The general colour of the smooth skin is
olive-brown above, with numerous dark spots, which are arranged in more
longitudinal streaks on the head.
The Webbed Newt is a native of Western middle Europe, ranging from Great
Britain and Northern Spain to Switzerland and Western Germany.
Closely allied to the last species are _T. boscai_ of Spain and Portugal,
_T. italicus_, _T. montadoni_ of Moldavia, and the {128}beautiful _T.
vittatus_ of Asia Minor. From China and Japan are known _T. pyrrhogaster_
and _T. sinensis_.
The North American species are _T. torosus_ and _T. viridescens_. The
former, of Western North America, is one of the largest newts, reaching a
length of more than six inches. The head is much depressed and broad, and
has very prominent parotoid and other glands. The limbs are strong,
especially in the male. The skin of the upper parts is very granular,
uniform dark brown, without a crest. The tail, which is larger than the
head and body, is strongly compressed, with a low dorsal and ventral fin.
The under parts and the lower edge of the tail are uniform yellow or orange
red. The iris is green. A specimen in my keeping spends most of its time in
the cracks of rotten stumps or on the top of moss in the darkest shade. It
lives on earthworms but despises insects. Like most of the other newts it
becomes lively at dusk.
[Illustration: FIG. 24.–_Triton viridescens._ 1, Egg just after deposition,
with the outer membrane opened, × 6; 2, a spermatophore just discharged
showing its gelatinous base with a projecting spike which bears a tuft of
spermatozoa, × 2. (After Jordan.)]
_T. viridescens_ is common throughout the Northern and Eastern parts of the
United States. Large females are about 11 cm. long, the males 1 cm. less.
The general colour above is brown, with a tinge of green; on each side of
the trunk, with a row of bright vermilion spots; the under parts are
orange, studded with small black dots. Half-grown specimens are brownish
red, with the same lateral red spots as the adult. According to Jordan,[61]
this voracious species lives chiefly on the larvae of insects, on small
molluscs such as _Cyclas_ and _Planorbis_, on earthworms and on small
Crustacea. It is eminently aquatic in the adult stage. The eggs are laid
from April to June, the period lasting for one individual four to six
weeks, or even longer. One female laid 108 eggs in all from 20th April to
30th May. After having selected a suitable plant, for instance an
_Anacharis_ or a bunch of _Fontinalis_ leaflets, she bestrides the plant
and gathers in the surrounding shoots with her hind-limbs, {129}pressing
the leaves closely around the cloaca. She next turns on her side, or
occasionally on her back; with fore-limbs outstretched and rigid, with
hind-limbs and leaves completely hiding the cloaca, she remains perfectly
motionless for six to eight minutes. Then she slowly leaves the "nest,"
which now holds an egg well protected by a tangle of shoots glued together
by the gelatinous secretion poured out of the cloaca. Jordan concludes,
from the fact that he never found spermatozoa in the oviducts, that the
eggs are fertilised just before they are expelled, when passing the
receptaculum seminis.
The metamorphosed young pass their life on land under stones and logs as
the so-called red variety, which is merely a stage in the life-history of
the species. It seems to take them several years to reach maturity, and to
become again typically aquatic. Young, red individuals which I have myself
kept, have behaved for more than a year like the young of other newts,
spending their time under moss and bark without going into the water.
The change from the red-spotted stage has been exhaustively studied by
Gage.[62] He remarks that this species is very common near Ithaca, in an
upland forest and along the head-waters of the Susquehannah. The
transformation takes place either in the autumn or in the spring, either
while the newt is still on land, or after entering the water.
Of two which were kept in a jar with moist wood, one was especially
brilliant, but within two weeks it assumed, in the middle of September, the
characteristic coloration of the viridescent form. The two specimens were
in the jar until the following July, when they were placed where they could
enter the water. This they did with great readiness, and they remained
submerged for a considerable time at first. The time under water increased
in length, until within two or three days the pharyngeal respiration under
water was fully established. On the other hand, viridescent specimens never
reassume the red garb when kept out of the water.
Red specimens entering the water in the spring, changed into the greenish
form within a few weeks, and established the pharyngeal respiration, losing
the ciliated oral epithelium. Branchiate larvae and the adult aquatic forms
have non-ciliated {130}epithelium, and the cilia are re-established when a
green specimen is forced again to live on land. Ciliation always exists in
the red stage, and in the green stage before the newt has taken to the
water. The cilia sweep towards the stomach.
The three following South European species belong to the _Euproctus_ group,
so called on account of the mostly conical, backward directed, and vividly
coloured vent.
_T. asper_ s. _pyrenaeus_.–The Pyrenean newt has hitherto been found only
in the Pyrenees, for instance in Lac Bleu and Lac d'Oncet, which latter
lies about 7000 feet above the level of the sea. According to Bedriaga,[63]
it prefers lakes which are supplied during the whole summer with water from
glaciers. It is very sluggish, only moving to breathe and when in search of
food, which consists of worms and insects. The general colour is greenish
brown, dark above; the under side of the head and body are bright orange
red in the female, yellow in the male; dark spots separate this bright
colour from the flanks. The tail has a narrow ventral stripe of bright red
and yellow. The cloaca of the female is bright red, that of the male dull
grey. The total length amounts to about 4 inches or 10 cm.
The pairing time is the end of June, or later in cold seasons. The male
gets hold of the female by forming a noose with its tail round her; it lies
underneath, the cloacae being pressed together so that the spermatozoa can
be taken in directly. The larvae have large yellow-green spots on the back
and sides, and a bright red ventral tail-fin; when metamorphosed the
greenish spots become more confluent on the back, producing a broad spinal
band. Larvae which live in deep water are dark, while those in sunny places
are light-coloured and spotted with yellow.
_T. montanus_ in Corsica and _T. rusconii_ in Sardinia are allied forms,
but the males are distinguished by a spur-like process or dilatation at the
end of the fibula.
_T. waltli_, the Iberian Newt, is olive-brown above, yellowish with
blackish markings below. The tail has a yellow or orange ventral line.
There is no crest. A remarkable peculiarity of this species (which it
shares only with _Tylototriton andersoni_ of the Loo-Choo Islands) is its
ribs, which are very long, sharply pointed, and frequently perforate the
skin. Before {131}perforation the point of the rib lies in a lymphatic
space. This surprising feature has by many authorities been considered as
abnormal or pathological. Certainly young, and even many adult, individuals
are found in which the skin is not perforated, but when these are handled
the wriggling motions of this strong newt force the points of the ribs
through the skin, and they remain sticking out to the extent of several
millimetres. The wounds heal up, the skin forming a neatly finished-off
hole through which the spike projects, not as a formidable, but as a
sufficiently awkward, protective weapon.
[Illustration: FIG. 25.–_Triton waltli._ Spanish Newt, adult and larvae. ×
⅔.]
Large females reach a length of 10 inches. The larvae metamorphose, as a
rule, when they are between 2 and 3 inches long, but those which have been
bred in tanks often reach double this length. These newts are frequent
inhabitants of the rain-water cisterns common in the South of Portugal and
Spain, into which they tumble without ever being able to get out again.
This species spends most of its time in the water, {132}preferring ponds,
among the vegetation of which they can be watched lying motionless, with
their limbs hanging down and with the head close to the surface; but they
are lively during the night. When their ponds dry up they leave them,
crawling into the most unexpected places, to aestivate under rocks, or even
in the walls of old buildings, where they are found by accident only. The
range extends from Central Spain and Portugal into Morocco.
_Tylototriton verrucosus_ lives in the Eastern Himalayas and in the
mountains of Yunnan. The skin is tubercular, with large parotoids; above
uniform black-brown, pale below; the tail has a ventral yellow or orange
line. Total length about 6 inches. _T. andersoni_ of the Loo-Choo Islands
is remarkable for the pointed ribs which perforate the skin.
_Pachytriton brevipes_, discovered in Kiansi, Southern China, has a smooth
skin, olive-brown above, with many black dots; the under parts are
yellowish, dotted with black. Total length about 7 inches.
FAM. 3. PROTEIDAE.–The three pairs of fringed external gills persist
throughout life. Both fore- and hind-limbs are present. The eyes are devoid
of lids. The maxillaries are absent. Teeth are present on the
premaxillaries, on the vomers, and on the mandible. The vertebrae are
amphicoelous.
This family consists of only three genera, with one species in each.
_Necturus maculatus_ s. _Menobranchus lateralis_.–The eyes are functional,
being covered by the thin transparent skin. The limbs, although short, are
well developed, and have four fingers and four toes. The whole animal,
which reaches the length of one foot, is quite smooth and slimy, brown with
irregular dark, blackish spots and patches, which frequently form a dark
lateral band extending from the mouth to the tail. The latter, which
measures about one-third of the whole length, is strongly compressed,
carries a thick dorsal and ventral fin, and is rounded off at the end. The
skin of the throat forms a strongly-marked transverse fold. The thick
stalks of the gills are brown, while the numerous and delicate fringes are
dark red in life; beneath and behind them are two gill-clefts. _N.
maculatus_ is found in the eastern half of the United States, chiefly the
eastern part of the basin of the Mississippi and the Canadian lakes.
{133}These creatures are rather dull; they remain mostly at the bottom of
the water, more or less concealed in the weeds or between rocks during the
daytime. Mine, which are kept in a roomy, light-coloured tank, lie
motionless, with their gills spread out transversely. Every now and then
the gills contract suddenly and become pale, whereupon they are filled
again with blood. Very rarely they rise to the surface, but tiny
air-bubbles are let out more frequently, especially when the animals are
disturbed. Then the gills collapse, are laid flat against the neck, and the
creature darts about with quick, eel-like motions. At night they leave
their hiding-places, swim about or creep along the ground with slow,
undulating movements, the limbs being scarcely used, in search of food,
which in their wild state consists of rather large Crustacea, small fishes,
worms, insects and frogs. They are most voracious, and absolutely
indifferent to cold. The spawning takes place in the months of April and
May.
_Proteus anguinus._–The fore- and hind-limbs are fully developed, but
possess only three fingers and two toes. The eyes are completely hidden
beneath the opaque skin. This peculiar creature is restricted to the
subterranean waters of Carniola, Carinthia, and Dalmatia. The vast caves of
Adelsberg not far from Trieste are especially celebrated for the occurrence
of the "Olm," the German name of this animal. The river Poik, a moderate
mountain-stream, but a large, fierce torrent during the rainy season,
disappears into the limestone-hills, and rushes through enormous
stalactite-grottoes, most of which have been only partially explored, until
several miles farther on it reappears on the surface. There, deep down
below the surface, in absolute darkness, in an almost constant temperature
of about 50° F. is the home of _Proteus_.
Their total length is scarcely one foot. The whole body is white,
occasionally suffused with a slight fleshy, rosy tinge, while the three
pairs of gill-bunches are carmine-red. They are easily kept in captivity,
and live for many years, provided three conditions are strictly adhered to,
viz. fresh and clean water, an equable low temperature of about 50° F. =
10° C. and darkness. The question of food is not so very important, since
specimens are known to have existed for years, although they refused to
take any nourishment. How far darkness is an {134}absolute necessity is not
known. Anyhow, the white skin is almost as susceptible to light as is a
photographic plate. If light is not absolutely excluded the white skin
becomes in time cloudy, with grey patches, and if kept exposed to stronger
light, the whole animal turns ultimately jet-black. Mr. Bles has succeeded
in producing several totally black specimens, having kept them for several
months in a white basin under ordinary conditions of light. No experiments
have yet been made to find out if the black pigment deposited is lost again
in darkness. Those which are kept in a tank in an absolutely dark cellar of
the Cambridge Museum, with permanent water-supply, are doing very well.
When approached with a candle they become restless or remain partly hidden
in all sorts of seemingly most uncomfortable attitudes, squeezed in between
the sharp-edged tiles and drain-pipes with which their lodgings are
furnished. But the introduction of a wriggling worm, a little crustacean or
other live bait draws them from their hiding-places, and, guided by the
motions of the prey in the water, possibly also by the sense of smell, they
snap it up and devour it.
[Illustration: FIG. 26.–_Proteus anguinus._ × ⅔. Front view of the mouth in
the left upper corner.]
If the water is not sufficiently well aerated, they rise to the surface,
emit a bubble of air, and take a new supply into their lungs. As a rule
they remain motionless under water, but the gills contract spasmodically
and become paler, whereupon they fill again with blood and darken; the
contrast between the pure white body and the carmine-red feathery gills is
very beautiful.
Until recently the mode of propagation was quite unknown. Several
_Proteus_, kept by E. Zeller, laid, in the middle of April, {135}a number
of eggs which were then fastened singly on to the under side of projecting
stones in the water. The pale yellow yolk measured 4 mm. in diameter and
was surrounded by a cover of 1 mm. in thickness, besides an outer
gelatinous mantle, so that the whole egg measured about 11 mm. The larvae
were hatched after 90 days; they were 22 mm. long, and already much like
the adult, except that the fin was not restricted to the tail, but extended
over the last quarter of the trunk, and that their eyes were still visible.
The fore-limbs were already typical in shape, but the hind-limbs were still
toe-less little stumps.[64]
_Typhlomolge rathbuni._–It is of the greatest interest that a subterranean
Perennibranchiate newt, in many respects closely resembling _Proteus_, has
recently been discovered in Texas. There can be no doubt that similar
conditions of life have produced these two forms from _Necturus_- and
_Spelerpes_-like ancestors,[65] one in Europe, the other in North America,
absolutely independently of each other. The limbs of _Typhlomolge_ are long
and very slender, the four fingers and five toes are thin, free and
pointed. The head is large, the mouth square. The eyes are completely
hidden and the whole animal is colourless and white. The tail is furnished
with a dorsal and a ventral fin. The very deep gular fold is nothing but
the pair of united but large opercular flaps. The three pairs of gills are
remarkable for their blade-like stalks, while the gill-lamellae proper are
short and restricted to the tapering ends. Total length about 75 mm., of
which the head measures 15, the tail 32 mm.
This peculiar creature inhabits subterranean caves in Texas, to judge from
the fact that all the specimens hitherto known have come up with the water
of an artesian well 188 feet deep, near San Marcos. According to
Blackford,[66] "the legs are used for locomotion and the animals creep
along the bottom of the aquarium with a peculiar movement, swinging the
legs in irregular circles at each step. They climb easily over the rocks
piled in the aquarium, and hide in the crevices between them. All efforts
to induce them to eat have been futile, as has also been the case with
blind cave-fish in captivity, and they are {136}either capable of long
fasts or live on infusoria in the water." It seems more reasonable to
suppose that these newts live upon Crustacea, four kinds of which, all new
to science, also came up with the water.
FAM. 4. SIRENIDAE.–The three pairs of fringed external gills persist
throughout life. The body is eel-like. Hind-limbs are altogether absent,
while the fore-limbs are short and have three or four fingers. The
maxillary bones are absent. With the exception of small teeth on the vomer
the mouth is toothless, but the jaws are furnished with horny sheaths. The
eyes are devoid of lids, but shine through the skin.
[Illustration: FIG. 27.–_Siren lacertina._ × ½.]
The Sirenidae are the most degraded members of the Urodela and are
represented by two closely-allied genera, each with one species, in the
south-eastern parts of the United States. Their most interesting feature,
which bears upon the question of neoteny, is their retrograde metamorphosis
as described by Cope.[67] The gills atrophy in the young and are
subsequently redeveloped. Cope therefrom concludes rightly that the
ultimate or persistent gills of _Siren_ are signs of maturity and not a
larval character. In young specimens of _Siren_ of 5 to 6 inches in length
the gills are functionless; in one of 3 inches they were found to be
entirely vestigial and "subepidermal," _i.e._ covered by a common dermal
investment. Unfortunately really young larvae are still unknown. Old Sirens
can live without gills, as has been shown by aquarium-specimens. In the
adult _Pseudobranchus_ all the gills are normally covered up by an
investment of the skin so as to be quite without function and movability.
_Siren lacertina_, the "mud-eel," is distinguished by the {137}possession
of three pairs of gill-clefts and by its four fingers. It reaches a length
of 70 cm., or about 2½ feet, of which about one-third is taken up by the
tail, which is strongly compressed and finned. The skin is smooth, mostly
blackish, lighter below, sometimes with whitish specks all over the body.
This creature is frequently found in ditches and ponds, where it burrows in
the mud. When swimming the limbs are folded back. They are said sometimes
to leave the water and to crawl about on the moist ground.
_Pseudobranchus striatus_ has only one pair of gill-clefts and only three
fingers. The slightly granular skin is dusky brown above, with a broad
yellow band on either side and with a paler, narrower stripe below. Total
length about 7 inches.
{138}CHAPTER VI
LISSAMPHIBIA (_CONTINUED_)–ANURA
ORDER III. ANURA OR TAILLESS AMPHIBIA.
The recent tailless Amphibia, or Frogs and Toads in the widest sense,
contain such a great number of species (about 900), with such a diversity
of characters, that it is necessary, if only for the sake of mere
convenience, to group them into a considerable number of families and
sub-families. The characters available for this purpose are few.
1. The possession of a tongue characterises the PHANEROGLOSSA, the
absence of a tongue the AGLOSSA.
2. The character of the shoulder-girdle.–Overlapping of the two halves of
the shoulder-girdle on the ventral side characterises the ARCIFERA, while
in the FIRMISTERNIA the two ventral halves meet in the middle line and
form a firm, median bar. See, for details, p. 24.
3. The shape of the transverse processes or diapophyses of the sacral
vertebra which carries the iliac or hip-bones. These processes are either
_dilated_ or _cylindrical_.
4. The presence or absence of teeth in the upper and lower jaws. This is
indicated by a formula in which 0 means absence of teeth; max. means
presence of teeth in the upper jaw; mand. means presence of teeth in the
lower jaw.
5. The terminal joints or phalanges of the fingers and toes are sometimes
_claw-shaped_. See p. 26.
6. The shape of the centra of the vertebrae.–_Opisthocoelous_, if the
posterior end is cup-shaped or concave, _procoelous_ if the anterior end
is concave and the posterior is convex. See p. 19.
By means of these characters we can arrange the Anura in the following
key:–
I. Aglossa. Sacral diapophyses dilated. } AGLOSSA, p. 143. {139}
Vertebrae opisthocoelous, with ribs. }
II. Phaneroglossa.
_A_. Arcifera.
_a_. Sacral diapophyses dilated.
α. Terminal phalanges not claw-shaped.
Opisthocoelous, with ribs,
max./0 } DISCOGLOSSIDAE, p. 152.
Procoelous, without ribs, 0/0 } BUFONIDAE, p. 166.
Precocious, or opisthocoelous,}
without ribs, max./0 } PELOBATIDAE, p. 160.
β. Terminal phalanges claw-shaped–HYLIDAE
{ max./mand. _Amphignathodontinae_,
{ p. 188.
{ max./0 _Hylinae_, p. 189.
_b_. Sacral diapophyses cylindrical–CYSTIGNATHIDAE
{ max./mand. _Hemiphractinae_,
{ p. 210.
{ max./0 _Cystignathinae_, p. 211.
{ 0/0 _Dendrophryniscinae_, p. 227.
_B_. Firmisternia.
_a_. Sacral diapophyses dilated–ENGYSTOMATIDAE
{ max./0 _Dyscophinae_, p. 235.
{ 0/mand. _Genyophryninae_, p. 236.
{ 0/0 _Engystomatinae_, p. 225.
_b_. Sacral diapophyses cylindrical–RANIDAE
{ max./mand. _Ceratobatrachinae_,
{ p. 237.
{ max./0 _Raninae_, p. 238.
{ 0/0 _Dendrobatinae_, p. 272.
Concerning the evolution of the classification of the Anura, it is
interesting to follow the changes of the value attached to the various
anatomical characters by systematists. At first the presence or absence of
teeth and of adhesive discs on the fingers and toes were considered to be
of prime importance for the division of the Phaneroglossa.
Duméril et Bibron, 1841. "Erpétologie générale."
I. PHRYNAGLOSSES = Aglossa of Wagler: _Pipa_ and _Xenopus_.
II. PHANÉROGLOSSES. 1. With teeth. _a_. Without discs: Raniformes.
_b_. With discs: Hylaeformes.
2. Toothless. Bufoniformes.
Stannius, 1856 (see p. 8), separated the Engystomatidae as "Systomata," and
used the presence or absence of the "manubrium sterni" (omosternum) as a
character of distinction between his Bufoninae and Raninae.
{140}Günther, 1858, "Catalogue of the Batrachia Salientia." No progress was
made by his scheme, which relied upon the tongue and digits.
Aglossa with _Myobatrachus_.
Opisthoglossa. _a_. Oxydactyla. _b_. Platydactyla.
Proteroglossa: Rhinophrynidae.
Cope, 1864. "On the limits and relations of the Raniformes."[68] He
introduces the shoulder-girdle and the sacral diapophyses, and drops the
discs as too adaptive and misleading. He distinguishes between RANIFORMES
and ARCIFERI.
Cope, 1865. "Sketch of the primary groups of the Batrachia Salientia."[69]
Aglossa.
Bufoniformia (Bufonidae).
Arcifera (Discoglossidae, Scaphiopodidae, and Hylidae).
Raniformia.
In 1867 Cope separates the genus _Hemisus_ as Gastrechmia on account of its
peculiar pectoral arch.[70]
In 1875, "Check-list of North American Batrachia and Reptilia," Cope
elaborates his system:
Class Batrachia. Order Anura.
1. Raniformia.
2. Firmisternia. [Dendrobatinae and Engystomatidae.]
3. Gastrechmia: _Hemisus_.
4. Bufoniformia. [Bufonidae.]
5. Aglossa. _Pipa._
6. Odontaglossa. _Xenopus._
7. Arcifera. [Cystignathidae, Hylidae, Pelobatidae and Discoglossidae.]
Cope consequently considered the characters of the pectoral arch as
equivalent to those of the dentition.
Boulenger, 1882, "Catalogue of the Batrachia Gradientia s. Ecaudata,"
recognises that the pectoral arch is of greater systematic value than the
dentition. The latter is used, together with the shape of the sacral
diapophyses, for the separation into families.
I. Phaneroglossa. _A_. Firmisternia. { 1. Ranidae.
{ 2. Dendrobatidae.
{ 3. Engystomatidae.
{ 4. Dyscophidae.
_B_. Arcifera. { 5. Cystignathidae.
{ 6. Dendrophryniscidae.
{ 7. Bufonidae.
{ 8. Hylidae.
{ 9. Pelobatidae.
{ 10. Discoglossidae.
{ 11. Hemiphractidae.
{ 12. Amphignathodontidae.
II. Aglossa. { 13. Dactylethridae.
{ 14. Pipidae.
{141}This emendation of the Arcifera and Firmisternia was accepted by Cope
in his synopsis of the families of Vertebrata (_Amer. Natural._ xxiii.,
1890), except that he still retained his suborder Gastrechmia.
Since the publication of Boulenger's great work a number of forms have been
discovered which, from the characters of their dentition, have necessitated
the establishment of certain new families, namely, Ceratobatrachidae and
Genyophrynidae; and Boulenger was the first to recognise that the taxonomic
value of the mere presence or absence of teeth in the jaws had been
overestimated. I therefore propose using it as a character distinctive of
the sub-families only, thereby reducing the number of families, relying
first (leaving the Aglossa aside) upon the firmisternal or arciferous
condition of the pectoral arch, secondly upon the dilated or cylindrical
shape of the sacral diapophyses, thirdly upon the dentition. Blindly
consistent application of these principles would reduce the Phaneroglossa
to four families only, namely Ranidae, Engystomatidae, Cystignathidae and a
fourth family comprising all the Arcifera with dilated sacral diapophyses.
This would obviously be wrong. We have therefore to resort to other
additional characters or rather peculiarities. The opisthocoelous character
of the vertebrae and the possession of distinct ribs, together with the
disc-shaped tongue, separate the Discoglossidae and justify their retention
as a family. The Hylidae are marked off by the claw-shaped terminal
phalanges, but the remaining forms, comprising the Bufonidae and
Pelobatidae, cannot be separated except by their dentition, and I plead
guilty of inconsistency in retaining them as separate families.
After all, our classification may not represent the natural system, and it
may be nothing but a convenient key.
When we have eliminated the characters of the vertebrae, the dentition, the
claw-shaped phalanges and the adhesive discs, it may well be asked what
characters remain. The firmisternal is a further, higher modification of
the older, more primitive arciferous condition. The difference between the
dilated and cylindrical shape of the sacral diapophyses is in not a few
cases very slight, and there are various, most suggestive exceptions. The
presence or absence, size and shape of the omosternum and metasternum are
of very limited taxonomic value, not always applicable to all {142}the
members of the same family. The fact is, that the Anura are a very recent
and a most adaptive, plastic group. The earliest known fossils are scarcely
older than the Middle Eocene.
Almost every one of the greater families has produced terrestrial,
arboreal, aquatic, and burrowing forms. Their habits have modified, and are
still shaping their various organs, first of course those by which the
animals come first and most directly into contact with their surroundings
(_e.g._ adhesive discs, dentition, general shape of the body, length of
limbs, wartiness of the skin, tympanic disc). These are the so-called
adaptive characters, sometimes decried as merely physiological; as if
habits, use, and requirements did not likewise influence and ultimately
model every other organ (_e.g._ tympanic cavity, Eustachian tubes,
vertebrae, ribs, coccyx, pectoral arch, etc.). There are true Toads,
Bufonidae, which are as smooth, wartless, slender-bodied and long-legged as
the most typical of "Frogs"; true Ranidae, like _Rhacophorus_, which by
their green colour, large adhesive discs and arboreal habits may well put
many of the Hylidæ to shame. _Ceratohyla_ has developed the claw-shaped
terminal phalanges which are otherwise typical of, and peculiar to, the
Hylidae, but this genus reveals itself by various details as a close
relation of the other Hemiphractinae; and these fall in with the
Cystignathidae on the strength of their cylindrical, not dilated, sacral
diapophyses.
In sketching the phylogenetic tree of the families of the Anura we have to
proceed with great caution.
There is not much doubt about the Aglossa. They have retained some of the
most primitive characters, but have by now been so much modified and
specialised that they are to be looked upon as an early side-branch.
Among the Phaneroglossa the Discoglossidae are with certainty the oldest,
but are now scarce in genera and species, and much specialised. The
Pelobatidae connect them with the Bufonidae. The Cystignathidae form a
rather ill-defined assembly which points downwards to the Pelobatidae,
upwards to the Hylidae. There is no divergence of opinion about the Ranidae
being the highest of all the Anura, and amongst them the Raninae the most
typical, the Dendrobatinae the most specialised. If we assume that
moderately dilated sacral diapophyses represent a more primitive stage than
cylindrical processes, we shall {143}naturally look to the Engystomatidae
as the connecting link between the Ranidae and the Arcifera, through
Bufonoid creatures still with teeth in both jaws. If, on the other hand, we
take the dilatation to be a further development from more or less
cylindrical processes, then the Ranidae can be considered as having sprung
from Cystignathoid creatures, which have consolidated their pectoral arch
into the firmisternal condition; and in this case the Firmisternia would
not be a natural group, the Engystomatidae pointing, to the Bufonoid stock.
This would, to a great extent, mean a reversion to Cope's idea.
SUB-ORDER 1. AGLOSSA.–The two diagnostic peculiarities of the few members
of this group are: first, the absence of a tongue; secondly, the union of
the Eustachian tubes into one median pharyngeal opening in the posterior
portion of the palate.
[Illustration: FIG. 28.–Map showing distribution of Aglossa. _Hymenochirus_
to be added in Equatorial Africa.]
The pharyngeal opening and the tubes themselves are wide, the tympanic
cavities are present, but the tympanic discs are not distinct from the rest
of the skin. The fronto-parietal bones are fused into one mass, a rare
feature in the Anura. The nasals are large. _Pipa_ and _Hymenochirus_ have
no teeth, _Xenopus_ has teeth on the upper jaw. The vertebrae are
opisthocoelous and typically epichordal in their development; the second,
third, and fourth carry long ribs, which in old specimens fuse with the
supporting diapophyses. The sacral diapophyses are enormously dilated, and
the sacrum is fused with the os coccygeum. The serial number of the sacral
vertebrae exhibits a most interesting gradation. In _Xenopus_ the ilium is
carried by the diapophyses of the 9th, in _Pipa_ the 9th and 8th, in
_Hymenochirus_ the 7th and 6th. In these cases the two diapophyses of each
side are fused together into a single broad blade, and their original
duplicity is indicated only by the {144}holes for the spinal nerves.
_Hymenochirus_ has consequently only 5 presacral vertebrae, the vertebral
column being shortened to the greatest extent known amongst Vertebrata. For
further information see p. 22. The ilia are much broadened vertically, and
are firmly attached to the sacrum. The shoulder-girdle is sometimes
described as of the arciferous type, but this is quite unjustifiable. The
epicoracoid cartilages do not overlap each other, but meet, and partly fuse
in the middle line. The three genera exhibit some differences. In _Pipa_
and _Hymenochirus_ the bony portions of the coracoids are much expanded
dorsally, and there is a considerable amount of epicoracoid cartilage, that
of the precoracoid bars extending backwards as a broad-based and blunt
omosternum. _Xenopus_ is devoid of an omosternum, and the configuration of
the whole apparatus is more slender. The metasternum of _Xenopus_ and
_Hymenochirus_ broadens out laterally. _Hymenochirus_ greatly resembles
_Breviceps_, a genus of Engystomatinae, in the relative position and size
of the various parts of the shoulder-girdle and sternum.
The tibio-fibula of _Hymenochirus_ has a wing-like expansion of thin bone
on each side, forming a deep groove on the outer aspect. The astragalus and
calcaneum are united by a similar bony expansion with wing-like
projections.
The lungs are remarkable for the prominent development of trabecular
projections and niches, so that their free lumen is much restricted; they
have thereby reached a much higher stage than in any other Amphibia or even
many Autosauri. The persistence of an arteria sacralis s. caudalis, a
vessel absolutely absent in the adult _Rana_, is a primitive feature, and
the same applies to the presence of a true first spinal or suboccipital
nerve.
The skin of the back and belly is supplied by two great branches from the
arteria anonyma, one arising proximally, the other distally from the
subclavian; herewith is correlated the almost complete absence of the
arteria cutanea magna, which as a branch of the ductus pulmo-cutaneus plays
such a prominent rôle in the other Anura. Only in _Pipa_, but not in
_Xenopus_, is the great cutaneous vein represented by a very small branch.
Both these genera possess a much more complicated "diaphragm" than the
other Anura, chiefly owing to a special muscle which arises {145}from the
anterior end of the ilia and spreads out fan-like to the oesophagus and to
the bases of the lungs.[71] This diaphragmatic arrangement is correlated
with the great development of the lungs, and is not a primitive but an
advanced feature. It is reasonable to suppose that this has caused the
reduction of the usual arteria pulmo-cutanea, and that the other two
cutaneous arteries have been developed secondarily. The Aglossa are
generally considered as the lowest Anura, and only Cope looked upon _Pipa_
and _Xenopus_ as two convergent terminal branches. Beddard came to the
conclusion that both are closely related to each other, chiefly on account
of their peculiar diaphragmatic arrangement. The whole question has entered
upon a new stage since the recent discovery of _Hymenochirus_, which is in
many ways intermediate between the two other genera. Moreover, the
mid-Tertiary _Palaeobatrachus_ of Europe is undoubtedly related to them,
and we conclude now that all these four genera belong to one group with a
distribution formerly much wider than Africa and part of South America. But
this does not necessarily mean that the Aglossa are in all respects the
most primitive group of living Anura. On the contrary, they possess few
decidedly primitive characters, namely, the long typical ribs, the presence
of the first spinal nerve, the unimportant persistence of the arteria
sacralis, and lastly, the possession in the tadpoles of a right and left
opercular "spiracle." The absence of the tongue cannot possibly be an
archaic feature, considering its universal presence in all the other
Amphibia, including the Apoda, and the suggestive circumstance that this
organ is least developed in the entirely aquatic members of the Urodela. In
fact, thoroughly aquatic creatures, which seize and swallow their prey
under water, require no elaborate tongue; and since we know that the Anura
must owe their typical formation to terrestrial life, it follows that those
which have again taken to the water and are tongueless, have lost this
organ. As I have shown elsewhere,[72] the epichordal development of the
vertebrae is likewise a secondary feature, far from primitive; and the
tendency of the shortening of the vertebral column, which has reached its
extreme in _Hymenochirus_, points to the same conclusion. The apparatus of
the shoulder-girdle and sternum is in the last transitional stage from the
former arciferous to the typically consolidated firmisternal {146}type. In
fact there is little left which is primitive, but much that is very
specialised and highly developed in the Aglossa, mostly in adaptation to
their absolutely aquatic life, to which they must however have taken very
early. They are in a position somewhat analogous to the Ratitae among
Birds, which are likewise an old group, although many of their most
striking features have been acquired secondarily.
_Xenopus_ s. _Dactylethra_. The upper jaw is furnished with teeth. The ilia
are attached to the ninth vertebra. The pupil is round. The terminal
phalanges are pointed. The fingers are free, the toes broadly webbed, and
the first three are covered with sharply pointed, horny, black-brown nails,
a feature which is alluded to by the alternative generic names. A cutaneous
tentacle projects from below the eye and naturally invites comparison with
the tentacle of the Apoda and of Urodela. The skin is smooth, rich in
mucous glands, besides certain tube-like apparatuses, possibly sensory,
which are scattered over the body, especially on the head, and form a
conspicuous series of white dots along the dorso-lateral line, from the eye
to the vent. The general colour of the upper parts is olive brown, mottled
darker, while the under parts are whitish. The female has three cutaneous
flaps closing the vent. The male develops black nuptial brushes along the
inner side of the fingers. There are several species, all African
(Ethiopian).
_X. laevis_, ranging from the Cape to Abyssinia, is distinguished by the
absence of a metatarsal spur. The tentacle is very short. Size about 3
inches. _X. muelleri_ of Zanzibar and Benguella, is smaller. The tentacle
is conspicuous, as long as the diameter of the eye. The inner metatarsal
tubercle carries a sharp claw. _X. calcaratus_ of tropical West Africa is
only 2 inches long, and has strong metatarsal claws, short tentacles and
very minute eyes.
The habits and oviposition of the "Clawed Toad" have been described by
Leslie.[73] The Boers call it "Plathander," _i.e._ flat hand. Entirely
aquatic, it rests floating in the water, with the nostrils exposed, and
leaves the water only if it has to change the locality on account of
drought or scarcity of food. The pairing takes place, at least at Port
Elizabeth, in the early spring, _i.e._ in the month of August. The only
sound which is emitted is heard during this time, a very slight and dull
tick-tick, audible at only a few feet distance. The male grasps the female
by the loins; the eggs are extruded singly, measuring only 1.5 mm. in
diameter, but swell to double that size. They are attached singly to stones
or water-plants.
{147}[Illustration: FIG. 29.–_Xenopus laevis._ Clawed Toad, adult and
larvae, × ⅔.]
{148}Latterly these creatures have frequently been brought over to England.
They stand confinement very well, even in a little aquarium with sufficient
water-weeds to keep the water fresh; and they do not require special heat.
They greedily snap up worms, strips of liver, or meat, and poke the food in
with their hands. A few kept by Boulenger in a glass jar have lived for the
last eleven years in the ordinary temperature of a room in London.
Curiously enough they are often in amorous embrace, regardless of the
season, but they have never shown any signs of spawning.
Some of those in the Zoological Gardens in London laid eggs on Saturday the
27th of May, and on the morning of the following Monday the larvae were
already hatched. They have been described by Beddard.[74] The larvae are
provided with an unpaired circular, ventral sucker. The tentacles begin to
sprout out on the sixth day after hatching, at first not in connexion with
the cranial cartilage, but soon a cartilaginous rod runs into the tentacle
from the ethmoid "just above the joint with the under jaw.". Boulenger has
most reasonably compared these organs with the "balancers" of _Triton_ and
_Amitystoma_ (cf. p. 46 for the possible homologies of the balancers). The
tentacles soon reach a great length and give the tadpole a curious
appearance. In tadpoles of _X. calcaratus_, 65 mm. long, the tentacles are
30 mm. long, and are inserted just at the angle of the mouth. By the time
that these tadpoles show their fore-limbs, the feelers are reduced to 4 mm.
in length, and their relative position has been shifted to a little above
the angle of the gape, and whilst the latter gradually extends further and
further back, the feelers come to lie, or rather remain, below and a little
in front of the eyes.
The tadpoles have no traces of horny teeth. External gills project as low
conical or lamellar processes from the first three branchial arches, but
so-called internal gills are not developed.
Amongst a number of Clawed Toads imported in the spring one female became
swollen with eggs, but as they did not show signs of wanting to breed, a
pair was put into the tropical tank {149}in the Cambridge Botanic Gardens,
a transfer which had the desired effect. Eggs were laid, and more during
the following nights; they hatched out within thirty hours. The whole brood
was lost, before any of them were older than a few days, since they were
attacked, beyond the possibility of a cure, by a _Saprolegnia_ or some
similar pest.
_Hymenochirus_, represented by one species, _H. boettgeri_, has been
discovered in the Ituri, German East Africa, and in the French Congo, and
has no doubt a much wider distribution. It is scarcely 1½ inch long, and is
easily recognised by the toothless mouth, the half-webbed fingers (hence
the generic name), the incompletely webbed toes, the third of which is
longer than the fourth, and the absence of sensory muciferous canals in the
skin. The three inner toes are, as in _Xenopus_, furnished with small black
claws. The skin is rough, beset with small granular tubercles. The general
colour above and below is olive-brown. The vent is, as in _Xenopus_,
produced into a spout or semi-canal, but is devoid of dorsal flaps of skin.
_Pipa._–This Neotropical member of the Aglossa is quite toothless, but the
jaws of the adult have horny substitutes. The only species is _P.
americana_, the famous Surinam Toad, chiefly known from the Guianas, but
undoubtedly extending much further, having recently been reported from the
neighbourhood of Pará.
The general shape of this creature is very peculiar. The head is much
depressed and triangular; the eyes are very small; the skin forms several
short, irregularly-shaped flaps and tentacles on the upper lips and in
front of the eye, and at the angle of the mouth. The tympanum is invisible.
The pupil is round. The fingers are very slender and free, ending in
star-shaped tips; the toes are broadly webbed. The whole skin is covered
with small tubercles and is dark brown above, while the under parts of the
very flat and depressed body are whitish, sometimes with a dark brown
stripe along the middle line. In the female the skin of the back forms
growths for the reception of the eggs, and in these the young undergo their
whole metamorphosis.
{150}[Illustration: FIG. 30.–_Pipa americana._ Surinam Toad. × ⅔.]
{151}The most characteristic feature of the skin,[75] which has exactly the
same structure in both sexes, is the papillae, which are spread over the
whole surface, except on the webs of the toes, on the cornea and on the
star-shaped points of the fingers. Each papilla carries a little horny
spike, and a poison-gland frequently opens near its base. Larger
poison-glands exist on the dorsal and ventral side in four rows, and
smaller glands open upon the sides of the body, but there are no parotoid
complexes. Slime-glands occur all over the surface. The epidermis consists
of the usual layers, namely the Malpighian, the stratum corneum, and the
part which is shed periodically. The latter is completely horny, appearing
to be structureless like a cuticle, but it is in reality composed of
polygonal cells with flattened nuclei; each little spike is one modified
horny cell. The whole outermost layer contains black-brown pigment. The
upper portion of the cutis is devoid of pigment, then follows a layer of
clusters of ramified dark pigment-cells, and lastly the rest of the cutis.
Each of the four fingers ends in a four-armed star, the tips of which again
carry four or five sensory papillae. The cartilage of the terminal
phalanges is correspondingly star-shaped.
According to Klinckowstroem these toads, which are entirely aquatic, are
easily collected at the end of the long dry period, when they are all
confined to the half-dried-up pools. But they do not spawn there. This
happens after the rains have inundated the forest, and then it is very
difficult to get the females with eggs on their backs. Each of the eggs,
when once they have been glued on to the back, sinks into an invagination
of the skin. The initial stages are probably the same as those caused by
the eggs on the belly of _Rhacophorus reticulatus_ (see p. 248). Later,
each egg is quite concealed in a cavity with a lid. These cavities are
simply pouches of the skin, and are not formed by enlarged glands as has
been suggested by some anatomists. Each cavity consists of the epidermal
pouch and the lid. How the latter is produced is not known. According to
the authors quoted above, the lid looks like a shiny or sticky layer which
has hardened into horn-like consistency. It lies exactly like a lid upon
the rim of the pouch itself, and is certainly not in structural or organic
continuity with the epidermis. Most probably it is produced by the remnant
of the egg-shell itself, which, after the larva is hatched, is cast up to
and remains on the top of the cup.
{152}Bartlett[76] has described the spawning of specimens in the Zoological
Gardens in London.
"About the 28th of April 1896 the males became very lively, and were
constantly heard uttering their most remarkable metallic, ticking
call-notes. On examination we then observed two of the males clasping
tightly round the lower part of the bodies of the females, the hind parts
of the males extending beyond those of the females. On the following
morning the keeper arrived in time to witness the mode in which the eggs
were deposited. The oviduct of the female protruded from her body more than
an inch in length, and the bladder-like protrusion being retroverted,
passed under the belly of the male on to her own back. The male appeared to
press tightly upon this protruded bag and to squeeze it from side to side,
apparently pressing the eggs forward one by one on to the back of the
female. By this movement the eggs were spread with nearly uniform
smoothness over the whole surface of the back of the female to which they
became firmly adherent. On the operation being completed, the males left
their places on the females, and the enlarged and projected oviduct
gradually disappeared from one of the females. In the other specimen, the
oviduct appears not to have discharged the whole of the eggs."
Boulenger, who examined this second specimen, which died, confirmed this
egg-bound condition. He remarks further: "The ovipositor formed by the
cloaca (not by the prolapsed uterus), was still protruding and much
inflamed. It may be deduced from the observation made by the keeper, that
fecundation must take place before the extrusion of the eggs, and it is
probable that the ovipositor serves in the first instance to collect the
spermatozoa which would penetrate into the oviducts, the eggs being laid in
the impregnated condition, as in tailed Batrachians."
SUB-ORDER 2. PHANEROGLOSSA–FAM. 1. DISCOGLOSSIDAE.–The tongue has the shape
of a round disc, adherent by nearly the whole of its base, and it cannot be
protruded. The vertebrae are opisthocoelous, and in the aquatic genera are
of the most exaggerated epichordal type; the diapophyses of the second to
the fourth vertebrae carry short, free ribs, and those of the sacral
vertebra are dilated. The metasternum behind is forked. The {153}upper jaw
and the vomers are provided with teeth. The males have no vocal sac. The
tadpoles are distinguished by having the opercular spiracle placed in the
middle of the thoracic region (see general anatomical part, p. 44).
The few members of this family have a peculiar distribution. _Liopelma_ is
confined to New Zealand, where it is the solitary representative of the
Amphibia. _Ascaphus_ is found in North America. The other genera,
_Discoglossus_, _Bombinator_, and _Alytes_, are typical of the Palaearctic
sub-region, and are, with the exception of _Bombinator_, confined to the
Western Provinces (cf. Map, Fig. 32, on p. 161).
_Discoglossus._–The tympanum is frequently more or less concealed by the
skin. The pupil is round or triangular. The omosternum is small. The
vertebrae are of the epichordal type.
_D. pictus_, the only species, has a smooth and shiny skin, provided with
numerous small mucous glands. The palms of the hands are provided with
three tubercles, of which the innermost is the largest, and is carried by
the vestige of the thumb. The coloration of this species is very variable.
The ground-colour of the upper parts is a rich olive brown with darker,
light-edged patches, which are either separate or confluent in various
ways, forming broad, longitudinal bands, or a few larger asymmetrical
patches, separated in some individuals by a broad and conspicuous light
brown or yellowish vertebral stripe. An irregular reddish band frequently
extends from the eyes backwards along the sides. The under parts are mostly
yellowish white. This variability is purely individual, the most
differently marked and variously coloured specimens being found in the same
locality and even amongst the members of one and the same brood. The male
develops various nuptial excrescences, consisting of minute, dark, horny
spines, notably on the inner palmar pad, on the inner side of the first and
second finger, on the chin and throat, and smaller and more scattered
spicules on the belly and legs.
This pretty and extremely active little creature, which measures between 2
and 3 inches in length, is confined to the south-western corner of the
Palaearctic sub-region, being found in Algiers and Morocco, Sicily,
Sardinia, Corsica, and the southern and western parts of the Iberian
Peninsula. Curiously {154}enough it is absent in the Balearic Isles. Rather
aquatic in its habits, frequenting pools and streams, it is also often
found on land.
The male has a feeble voice, which sounds like "ha-a, ha-a-a," or
"wa-wa-wa," uttered in rapid succession. The pairing season lasts a long
time, in Algeria from January to October, but a much shorter time in the
north of Portugal, where it extends over the spring and summer months.
Boulenger has made extensive observations on many specimens kept in
captivity. The embrace, which never lasts long, is lumbar. The eggs are
small, 1 to 1.5 mm. in diameter, dark brown above and greyish below, each
surrounded by a gelatinous capsule of 3-7 mm. in diameter. The eggs are
laid singly, and a set amounts to from 300 to 1000, the whole mass sinking
to the bottom of the pool. Each female lays several times during the
season. The eggs are developed very rapidly, the larvae escaping sometimes
after thirty-six hours, but usually from the second to the fourth day. The
external gills are lost on the seventh day, when the tadpoles are 11 mm.
long; the hind-limbs appear on the tenth, and after four weeks the tadpoles
reach their greatest length, namely from 25-30 mm. The fore-limbs appear on
the thirtieth day, and a few days later the most precocious specimens leave
the water and hop about. Others, however, of the same brood took from two
to three months in metamorphosing.
This species lives on insects and worms, and can swallow its prey under
water.
_Bombinator._–The tympanum is absent and the Eustachian tubes are very
minute. The pupil is triangular. The omosternum is absent. The vertebrae
are absolutely epichordal. The fingers are free, the toes are webbed. The
upper parts are uniformly dark, and are covered with small porous warts.
The general shape of the head and body is depressed or flattened downwards.
The habits are eminently aquatic. This genus consists of three species, two
of which are European, the third Chinese.
_B. igneus._–The under parts are conspicuously coloured bluish black with
large irregular red or orange-red patches; the upper parts are more or less
dark grey or olive black. The iris is golden, speckled with brown. The male
has a pair of internal vocal sacs by which the throat can be inflated;
nuptial excrescences are developed on the inner side of the fore-arm and
the {155}first two fingers. Total length from 1½ to 2 inches, the males
being generally smaller than the females. This "Fire-bellied toad," the
"Unke" of the Germans, is essentially a native of lakes, ponds, and other
standing waters of the plains.
It ranges through the whole of North Germany, Bohemia, and Hungary into
Russia, eastwards as far as the Volga. The latter river, the Danube, and
the Weser form, roughly speaking, its boundaries; northwards it extends
into Denmark and the southern extremity of Sweden.
[Illustration: FIG. 31.–_Bombinator igneus._ × 1. Fire-bellied Toad. Two of
them in "warning" attitude.]
_B. pachypus._–The under parts are yellow instead of red. The male is
devoid of vocal sacs, but has nuptial excrescences on the under surface of
most of the toes, in addition to those on the fore-arm and fingers. The
"Yellow-bellied Toad" is the representative of the red-bellied species in
Southern and Western Europe, preferring, although not exclusively, the
hilly and mountainous districts. It ranges from France and Belgium through
South-Western Germany, continental Italy, and the whole of Austria and
Turkey in Europe. Where both species meet, for instance in the hilly
districts between the Weser and the Rhine, in Thuringia and in Austria, the
predilection of the yellow-bellied {156}species for the hills, and that of
the other for the plains, is well marked.
While _B. igneus_ prefers standing waters with plenty of vegetation, _B.
pachypus_ is often found in the smallest occasional puddles produced by
recent rain, for instance in the ruts of roads. Both species have otherwise
much in common. They are essentially aquatic. They hang in the water, with
their legs extended, nose and eyes just above the surface, and bask or lie
in wait for passing insects, the fire-bellied kind preferring to conceal
itself in the vegetation of the margins of ponds. During the pairing
season, in Germany in the month of May, they are very lively and perform
peculiar concerts, one male beginning with a slowly repeated note like
"hoonk, hoonk," or "ooh, ooh," in which all the other males soon join, so
that, when there are many, an almost continuous music is produced. This
sound is not at all loud, a little mournful and very deceptive. It appears
to be a long way off, certainly at the other end of the pond, until by
careful watching you see the little creature almost at your very feet. But
on the slightest disturbance the performance ceases, they dive below and
hide at the bottom. The yellow-bellied kind, when surprised in a shallow
puddle, skims over the mud, disturbs it, and allows it to settle upon its
flat body, so that nothing but the little glittering eyes will betray its
concealment. When these toads are surprised on land, or roughly touched,
they assume a most peculiar attitude, as shown in Fig. 31. The head is
partly thrown back, the limbs are turned upwards with their under surfaces
outwards, and the whole body is curved up so that as much as possible of
the bright yellow or red markings of the under parts is exposed to view.
The creature remains in this strained position until all danger seems
passed. In reality this is an exhibition of warning colours, to show the
enemy what a dangerous animal he would have to deal with. The secretion of
the skin is very poisonous, and the fire-toads are thereby well protected.
I know of no creature which will eat or even harm them. I have kept numbers
in a large vivarium, together with various snakes, water-tortoises, and
crocodiles, but for years the little fire-bellies remained unmolested,
although they shared a pond in which no other frog or newt could live
without being eaten. Hungry water-tortoises stalk them under water, touch
the intended prey with the nose in order to {157}get the right scent, and
then they withdraw from the _Bombinator_, which has remained motionless,
well knowing that quick movements, or a show of escape, would most likely
induce the tortoise to a hasty snap, with consequences to be regretted by
both.
After they have been handled frequently, they do not readily perform, but
simply lie still, or hop away. Miss Durham experienced considerable
difficulty in inducing her tame specimens to assume and to keep up the
correct warning attitude. The statement that they "turn over on the back"
is a fable, graphically fixed in various illustrated works.
It has been said that these two species are diurnal and thoroughly aquatic.
They are certainly active in the daytime, sing in full sunshine, and spend
most of their time in the water, but they display much more liveliness
towards the evening and during the night, especially when there is a moon.
My fire-toads live by no means always in the water, but conceal themselves
in the daytime under stones, while they are regularly all astir at night in
search of worms and all kinds of small insects.
The spawning takes place several times during the spring and summer. The
amplexus is lumbar, and the eggs are extruded singly. They sink to the
bottom, or are attached to water-plants. The oviposition takes a long time,
perhaps the whole night, and several dozen eggs, not hundreds as in the
allied genera, make a set. The egg, with its swollen gelatinous capsule, is
large for so small a creature, namely 7-8 mm. in diameter. The embryos
escape after a week, and the tadpoles reach two inches in total length.
Those of _B. igneus_ have a triangular mouth, but in _B. pachypus_ this is
elliptical, as in _Alytes_ and _Discoglossus_. Metamorphosis is completed
in the same autumn; the little toad is then about 15 mm. long, and differs
from the adult by the absence of the conspicuous coloration of the under
parts. In reasonable conformity herewith it does not take up the warning
attitude. The colour appears gradually during the second year, but full
growth is generally not reached until the third year. They do not hibernate
in the water, but hide on land out of the reach of frost.
_Alytes._–The tympanum is distinct, the pupil vertical, the omosternum is
absent. The only two species live in South-Western Europe. The male
attaches the eggs to its hind limbs, and nurses them until they are
hatched.
{158}_A. obstetricans_, the "Midwife-toad," has the general appearance of a
smooth toad. The upper parts are rather smooth, sometimes almost shiny, in
spite of the numerous more or less prominent warts, of which those of the
lateral lines, and those above the ear, are generally most marked. The
colour of the upper parts varies a great deal according to the prevalence
of greenish and reddish spots upon the grey or brown ground-colour. The red
is sometimes, especially in the breeding males, rather conspicuous on the
parotoid region and on the upper sides of the body. The under parts are
whitish grey. The iris is pale golden, with black veins. The male has no
vocal sac, and is as a rule smaller than the female, the latter reaching a
length of two inches.
This species occurs in the whole of the Iberian Peninsula and in France,
extending into Switzerland and beyond the Rhine valley into Thuringia.
Altitude above the sea does not seem to have any influence upon its range,
which reaches from sea-level to the tops of subalpine mountains. I have
found great quantities of its tadpoles in Portugal on the Serra d'Estrella,
nearly 6000 feet high, and they are recorded from 6500 feet in the
Pyrenees. They seem to be ubiquitous in Spain and Portugal, not that they
are often found or seen, but they are heard everywhere; besides, tadpoles
are sure to be in the clear cold lakes on the tops of the mountain-ranges,
in the dirty puddles caused by the village fountains, and in the sun-heated
swampy ditches on the roadside with scarcely enough water to hold the
wriggling mass. Wherever there is water within easy reach, on the lonely
mountains, in fertile valleys, in the gardens of the busy towns, you hear
during the whole night, from March to August, the double call-note of the
male, sounding like a little bell; but to see the performer is quite a
different matter. He sits in front of his hole, dug out by himself or
appropriated from a mouse, in a crack of the bottom of a wall, under
stones, or in a similar place into which he withdraws for the day.
The pairing and the peculiar mode of taking care of the eggs by the male,
which habit has given it the specific name _obstetricans_, the midwife,
have been most carefully observed by A. de l'Isle du Dréneuf, near Nantes.
A condensed account has been given by Boulenger. Several males collect
around a female on land, not in the water, and the successful one grasps
{159}her round the waist. For nearly half an hour the male lubricates the
cloacal region of the female by more than one thousand strokes of his toes,
whereupon the female extends the hind-limbs, forming with the bent
hind-limbs of the male a receptacle for the eggs, which are then expelled
with a sudden noise. The eggs are yellow and large, up to 5 mm. in
diameter, and are fastened together in two rosary-like strings, several
dozen making one set. During the expulsion of the eggs the male shifts its
body forwards, clasps his fore-limbs round the female's head, and
fecundates the eggs. After a rest he pushes first one hind-limb and then
the other through the convoluted mass of eggs, which then have the
appearance of being wound round the hind-limbs in a figure of 8. Then the
sexes separate and the male withdraws with its precious load into its hole,
which it, however, leaves during the following nights, in search of food,
taking this opportunity to moisten the eggs in the dew, occasionally even
immersing them in the water. After at least three weeks, when the larvae
are nearly ready, he betakes himself to the nearest water, and the larvae
burst the thereby softened gelatinous cover of the eggs. Not infrequently
the same male ventures upon a second pairing, and adds another load to the
one which already hampers its movements. The eggs being large, owing to the
great amount of yellow food-yolk, the embryos are enabled to be hatched in
a more advanced stage than in most other Anura. The larva develops only one
pair of external gills within the egg. These appear first in the shape of
oval bags upon the third branchial arch, which sprout out secondary
branches, soon in their turn to be resorbed and replaced by the so-called
internal gills before hatching.
Fischer-Sigwart[77] gives the following account of the growth of this
species. The male took to the water, with its load of twenty to thirty
eggs, on the 6th of June. The larvae escaped out at once, 16-17 mm. long,
the body measuring 5 mm. On the 14th they had reached 32 mm. in length,
whereupon they grew very slowly, although they were well fed, in a
temperature of about 50° F. This same brood did not metamorphose until May
of the next year. The growth took place as follows:–The hind-limbs appeared
on the 8th of September, when the tadpoles were 50 mm. long; by the middle
of the next May they {160}had reached their greatest length, 76 mm., the
hind-limbs being 18 mm. long, whilst the fore-legs were just indicated. On
the 21st of May the hind-limbs were 27 mm. long, and the whole creature was
practically metamorphosed, except for the tail. The latter was resorbed on
the 13th of July, and the little toads, 25 mm. in length, were actually
smaller, certainly far less bulky and heavy, than the tadpoles, which had
required one year and a quarter for their metamorphosis.
The early broods probably finish their development by the autumn of the
same year, but those which are born later, in July and August, certainly
hibernate in the water. I have found very small tadpoles, scarcely 15 mm.
long, on the Cantabrian mountains as late as the end of September, and
rather large ones in the spring at the time of first pairing; the fact that
this takes place during the whole summer explains the occurrence of
tadpoles in all stages of development almost the whole year round.
_A. cisternasi_ has only two palmar tubercles, the middle or third one of
_A. obstetricans_ being absent; the outer finger is short and thick.
Instead of a very long and wide fronto-parietal fontanelle, the
fronto-parietal bones diverge only in front so that there are two
fontanelles, a small one in the parietal and a large triangular one in the
frontal region. The limbs are relatively shorter and stouter in conformity
with the habits of this species, which prefers to burrow in sandy
localities. Otherwise it leads the same kind of life as _A. obstetricans_,
and the male carries the eggs. It has hitherto been found in Central Spain
and in the middle provinces of Portugal.
_Liopelma_ is intermediate between _Alytes_ and _Bombinator_, agreeing with
the latter, in conformity with its essentially aquatic life, in the absence
of a tympanum, while the Eustachian tubes are entirely suppressed. The
tongue is disc-shaped, but is slightly free behind. The pupil is
triangular. The male is devoid of a vocal sac. _L. hochstetteri_ is the
sole representative of the Amphibia in New Zealand, where it is apparently
rare. The upper parts are covered with smooth tubercles, and are dark brown
with blackish spots; the under parts are whitish. Total length only 1½
inch.
FAM. 2. PELOBATIDAE.–The upper jaw and, as a rule, the vomers are provided
with teeth. The tongue is oval, slightly {161}nicked, and free behind, so
that it can be thrown out, except in _Asterophrys turpicola_ of New Guinea,
which has a large but entirely adherent tongue. The vertebrae are
procoelous, except in _Asterophrys_ and the Malay genus _Megalophrys_,
where they are opisthocoelous. The sacral diapophyses are strongly dilated.
The omosternum is small and cartilaginous. The metasternum has a bony
style, and ends in a cartilaginous, rounded or heart-shaped disc, but in
_Scaphiopus_ it forms an entirely cartilaginous plate. The tympanic disc is
mostly hidden or indistinct, and is quite absent in _Pelobates_. The
Eustachian tubes are very small in _Pelobates_, and exceedingly minute in
_Scaphiopus stagnalis_ of New Mexico. The pupil is vertical. This family
contains seven genera with about twenty species, with a rather scattered
distribution.
[Illustration: FIG. 32.–Map showing distribution of Cystignathidae,
Discoglossidae, and Pelobatidae.]
_A._ Toes extensively webbed, sacrum and coccyx confluent.
_a._ Metasternum a cartilaginous plate. America ..........
_Scaphiopus_, p. 164.
_b._ Metasternum with a bony style. Europe .......... _Pelobates_,
p. 162.
_B._ Toes nearly free. Metasternum with a bony style.
_a._ Vertebrae procoelous.
α. Sacral vertebra articulating by one condyle with the coccyx.
Europe .......... _Pelodytes_, p. 165.
New Guinea .......... _Batrachopsis_.
β. Sacral vertebra with two condyles.
India and Malaya .......... _Leptobrachium_, p. 166.
_b._ Vertebrae opisthocoelous.
Ceylon and Malayan Islands .......... _Megalophrys_, p. 60 (Fig. 11).
New Guinea .......... _Asterophrys_.
{162}_Pelobates_ ("Spade-foot").–The tympanum is absent; the toes are
webbed. The inner tarsal tubercle is large, and is transformed into a
shovel which is covered with a hard, sharp-edged, horny sheath. The skin of
the upper surface of the head is partly co-ossified with the underlying
cranial bones, giving them a pitted appearance. The general shape is
toad-like.
_P. fuscus._–The smooth skin is brown above, with darker marblings, while
the under parts are whitish, but the coloration varies greatly, from pale
to dark brown or olive-grey with more or less prominent irregular dark,
sometimes confluent, patches. Some specimens are adorned with numerous red
spots. The tarsal spur is yellow or light brown. The iris is metallic red
or golden. The male has a long oval gland on the upper surface of the upper
arm, and although possessed of a voice, has no vocal sacs. The total length
of full-grown females is nearly 3 inches, that of males half an inch less.
The "Spade-footed Toad," which occurs throughout the whole of Central
Europe, extends from Belgium and the middle of France to North-Western
Persia, and from the southern end of Sweden to Northern Italy. It prefers
sandy localities, in order to dig its deep hole, in which it sits concealed
during the daytime. Owing to the looseness of the sand, the hole is filled
up so that no trace of its inhabitant is left. The digging is done by means
of the spades, and in suitable localities the animal soon vanishes, sinking
backwards out of sight. Except in the breeding season, or at night, it is
therefore found only accidentally. The sand-loving habits do not, however,
prevent it from enjoying moist localities. Several which I have kept for
years dig themselves into the wettest moss in preference to the drier parts
of their habitation. Being thoroughly nocturnal, they hunt after nightfall,
the food consisting of all sorts of insects and of worms. When captured
they utter a startling shrill cry, and their skin becomes covered with a
dermal secretion which smells like garlic, a peculiarity which has given
them in Germany the name of "Knoblauchskröte," "garlic-toad." Although they
become very tame, so that they no longer smell when handled, they can be
made ill-tempered by being pinched or otherwise teased, whereupon they take
up a defiant attitude, and with open mouth continue to cry for several
minutes. Some such scenes occur now and then, without {163}my interference,
with the specimens which share their abode with several species of
_Amblystoma_ and _Spelerpes_; there are heard now and then sudden loud
yells, like the squeak of a cat or the yapping of a little dog.
In the spring the Spade-footed Toads take to the water for about a week,
and the male's call-note is an ever-repeated clucking sound, which can also
be produced under water, with the mouth shut, the air being shifted
backwards and forwards through the larynx. The male grasps his mate below
the waist; the eggs are combined into one thick string, which is about 18
inches long, and is wound round and between the leaves and stalks of
water-plants. The eggs measure 2-2.5 mm., and are very numerous, a large
string containing several thousands. The larvae are hatched on the fifth or
sixth day in a very unripe condition. They are only 4 mm. long, quite
black, and still devoid of gills and tail. They attach themselves to the
empty gelatinous egg-membranes, which they possibly live upon. On the
following day the tail begins to grow; two days later fringed external
gills sprout out and serve for about ten days, when they in turn give way
to new, inner gills. The little tadpoles then leave their moorings and
become independent. The hind-limbs appear in the ninth week, the fore-limbs
in the twelfth. At the age of three months they begin to leave the water.
The most remarkable feature is the enormous size of the full-grown tadpole,
the body of which is as large as a pigeon's egg; the usual total length,
including the tail, amounts to about 4 inches or 100 mm., but occasionally
regular monsters are found. This was the case some thirty years ago, when
the Berlin Museum received a number of tadpoles, the largest of which
measured nearly 7 inches. They were found in the month of December near
Berlin, in a deep clay-pit with high, steep walls, so that the tadpoles
were prevented from leaving the water. Similarly hemmed-in broods probably
hibernate in the water under the ice, and such instances have been
recorded. Normally they metamorphose into the much smaller toad within the
same year.
_P. cultripes._–This is the Spade-foot of the whole of Spain and Portugal
and of the southern and western parts of France. It is similar in habits to
_P. fuscus_, from which it differs but slightly. The tarsal spur is black,
and there is a parieto-squamosal bridge which completely roofs over the
temporal fossa {164}and closes the orbit behind.–Boulenger has discovered
the rare, individual occurrence of minute teeth on the parasphenoid and on
the pterygoids of this species. These teeth are unquestionably the last
reminiscences of a condition almost entirely superseded in the recent
Anura.
_P. syriacus_ from Asia Minor and Syria agrees with _P. cultripes_ in the
cranial configuration, but has the yellow or brown spur of _P. fuscus_.
[Illustration: FIG. 33.–_Pelobates cultripes_, Spade-foot Toad, × 1, and
under surface of left foot.]
_Scaphiopus._–The Spade-foot of North America and Mexico differs slightly
from those of Europe, chiefly by the presence of a more or less hidden
tympanum and of a subgular vocal sac, and by the sternum, which forms an
entirely cartilaginous plate without a special style. The close
relationship of these two genera is further indicated by the occurrence of
peculiar large glandular complexes in some of the species, pectoral in _S.
solitarius_, tibial in _S. multiplicatus_ of Mexico. At the same time this
genus approaches _Pelodytes_.–About eight species are known, two of which
inhabit the United States, the others Mexico.
{165}_S. solitarius_ is the commonest species of the Southern States. It is
brown above, with darker patches; its total length is about 2 inches.
According to Holbrook it excavates small holes half a foot deep, in which
it resides, seizing upon such unwary insects as may enter its dwelling. It
never leaves the hole except in the evening or after long-continued rains.
It appears early in March, and soon pairs; as an instance of hardiness
Holbrook mentions that he has met it whilst there was still snow on the
ground. When teased they assume a humble attitude, bending the head
downwards with their eyes shut, as illustrated by Boulenger.[78]
_Pelodytes_ is, like the rest of the genera, devoid of the tarsal digging
spur. The tympanic disc is rather indistinct; the male has a subgular sac.
The general appearance of the slender body with long hind-limbs and toes is
frog-like. Two species only are known, one in South-Western Europe, the
other in the Caucasus.
_P. punctatus._–The "Mud-diver" has the upper parts covered with small
warts, and is about 1½ inch in length. Its coloration is variable, and
changes much. One day it may appear greenish brown, the next day pale grey;
in the daytime perhaps with many bright green spots, and in the evening
spotless and unicoloured. The under parts are mostly white, sometimes with
a fleshy tinge. The male has a voice like "kerr-kerr" or "creck-creck,"
uttered during the breeding season, which lasts from the end of February
until May, according to the temperature and the more Southern or Northern
locality. Occasionally they breed a second time in the summer or autumn.
The male develops nuptial excrescences, chiefly three rough patches on the
inner side of the fore-limbs or on the inner side of the first two fingers,
while the belly and thighs are covered with small granules. In the mode of
copulation, the laying of the small and numerous eggs, the hatching of the
larvae in a tail- and gill-less condition, this genus closely resembles
_Pelobates_; but the tadpoles never reach a colossal size, the usual length
being 2 inches, and even this is comparatively large for so small a
species. It inhabits the greater part of France, most of Portugal, and the
southern half of Spain, avoiding, however, the central plateaux and the
mountain-ranges. Its habits are essentially nocturnal, {166}living in the
immediate vicinity of the water, into which it hops with a long jump in
order to hide in the mud. Easily kept, it breeds regularly in captivity,
according to circumstances at almost any time of the year.
_P. caucasicus_ has been discovered in the Caucasus at an altitude of 7000
feet. The remaining genera of this family contain only a few species each,
and are restricted to South-Western Asia, the Malay and Papuan Islands. The
commonest is _Leptobrachium_, which ranges from the Himalayas to Borneo and
Java. Pupil vertical. Vomerine teeth sometimes absent. Tongue roundish,
very slightly nicked behind. Tympanum indistinct. Omosternum small,
cartilaginous. Male with internal vocal sacs. Tarsus with a roundish
tubercle. Some of the species, e.g. _L. carinense_ from the Karen Hills,
attain to a large size, namely, 6 inches; they seem to live on rats and
mice, and one specimen contained a young squirrel.
FAM. 3. BUFONIDAE (Toads).–The formula:–no teeth in the upper and lower
jaws, vertebrae procoelous and without ribs, sacral diapophyses dilated,–is
sufficiently diagnostic of this cosmopolitan family. The generally
entertained notion that toads have a rather thick-set, short-limbed, warty
appearance, does not apply to all the members of the family. The majority
are quite terrestrial, many are burrowing, the Javanese _Nectes_ is
aquatic, the Afro-Indian _Nectophryne_ is arboreal, while the Australian
_Myobatrachus_ and the Mexican _Rhinophrynus_ eat termites and are
correspondingly modified; lastly, _Bufo jerboa_ is a slender, long-legged
creature.
Teeth are almost entirely absent, except in _Notaden_, which has teeth on
the vomers. The omosternum is mostly absent, except in _Engystomops_ and in
some species of _Bufo_, while in _Notaden_ it is merely vestigial. The
metasternum shows more variety. The tympanum is usually distinct, but
varies even within the same genus, being hidden beneath the skin or being
entirely absent. The terminal phalanges are modified according to the
habits of the species, but they are never claw-shaped.
The Bufonidae are connected in various directions. The Neotropical
_Engystomops_ greatly resembles the likewise Neotropical Cystignathoid
_Paludicola_, and the Australian _Pseudophryne_ closely approaches the
Australian Cystignathoid _Crinia_. It is therefore all the more remarkable
that a similar approach, in another direction, namely, towards the
Firmisternal family of the {167}Engystomatidae, is indicated by the Mexican
_Rhinophrys_ and the Australian _Myobatrachus_. However, since there are no
true Engystomatidae in Australia, although several genera occur in
Papuasia, these cases may be instances of convergence without necessarily
implying relationship. An unmistakable line of connexion leads, according
to Boulenger, to the Pelobatidae, the link being the Himalayan
_Cophophryne_, with very strongly dilated sacral diapophyses, with a single
condylar articulation of the coccyx with the sacral vertebra (as in some
Indo-Malayan Pelobatidae), while this articulation is bicondylar in all the
other Bufonidae.
[Illustration: FIG. 34.–Map showing distribution of Bufonidae. The vertical
lines indicate the occurrence of Bufonidae, but not of _Bufo_.]
The whole family is divided into nine genera with more than a hundred
species, of which only about fifteen do not belong to the genus _Bufo_. The
distribution of the family is well-nigh cosmopolitan, with the remarkable
exception of Madagascar, Papuasia, and the small islands of the Pacific;
_Bufo_ has been wrongly said to inhabit the Sandwich Islands. The greatest
number of species, chiefly _Bufo_, occur in the Neotropical region, the
greatest number of genera in Central America, where _Bufo_ is rare, and in
Australia, where it is absent.
A. Pupils contracted to a horizontal slit. Typically arciferous.
_a._ Australian. Tympanum invisible. Fingers and toes not dilated.
1. With vomerine teeth. Both the omo- and meta-sternum are
rudimentary. East Australia: .......... _Notaden bennetti_.
2. Without vomerine teeth. Omosternum absent. Metasternum
cartilaginous: .......... _Pseudophryne_, p. 168.
{168}_b._ Not Australian.
1. Omosternum narrow and cartilaginous. Metasternum with a bony style
ending in a cartilaginous disc. Fingers and toes slightly swollen.
Neotropical: .......... _Engystomops_, p. 168.
2. Omosternum absent. Metasternum cartilaginous.
α. Fingers and toes webbed; terminal phalanges T-shaped and with
adhesive broadened tips. Africa and India: ..........
_Nectophryne_, p. 169.
β. Fingers free, toes webbed; terminal phalanges simple, not
dilated. Tympanum distinct. Java: .......... _Nectes_, p. 169.
3. Metasternum cartilaginous, sometimes ossified along the middle.
Fingers free; toes more or less webbed; tips simple or dilated into
very small discs: .......... _Bufo_, p. 169.
B. Pupil a vertical slit. The epicoracoid cartilages are narrow and
scarcely overlap. Omosternum absent except in _Cophophryne_. Vomerine
teeth absent. Sacral diapophyses strongly dilated. The terminal phalanges
are simple and the tips are pointed.
_a._ Australian. Tympanum distinct. The metasternum is calcified
along the middle: .......... _Myobatrachus_, p. 184.
_b._ Mexican. Tympanum absent. Metasternum rudimentary: ..........
_Rhinophrynus_, p. 185.
_c._ Himalayan. Tympanum absent. Metasternum with a slender bony style:
.......... _Cophophryne sikkimensis_.
_Engystomops_ is interesting because it closely resembles the Cystignathoid
genus _Paludicola_, and thereby seems to connect these two families. It
differs from _Paludicola_ chiefly by the absence of teeth, by the
moderately dilated sacral diapophyses and by the slightly swollen tips of
the fingers and toes, the end-phalanges of which are, in one species, _E.
petersi_, T- or anchor-shaped The tympanic disc is either distinct or
hidden. The males have a large subgular vocal sac. The generic name refers
to the small head with a prominent snout. Three species are known from
Central America and Ecuador.
_Pseudophryne_ appears to be another link with the Cystignathidae by its
resemblance to the Australian genus _Crinia_, from which it differs by the
absence of teeth and by the absence of an omosternum. The sacral
diapophyses are but moderately dilated. The males have a flat oval gland on
the hinder side of the thighs, and they are provided with a subgular vocal
sac. The 3 or 4 species of this genus which live in Australia, both East
and West, are not unlike _Bombinator_ in their general shape, short limbs
and coloration. The skin of _P. australis_ and _P. bibroni_ is covered with
small smooth warts and is blackish brown, while the under parts are
blackish with large yellow {169}patches. Total length little more than one
inch. Concerning the breeding habits, see p. 223.
_Nectophryne._–The sacral diapophyses are strongly dilated. _N. afra_,
without a tympanum, but with fully-webbed digits and several broad,
cushion-like or lamellar pads on the fingers and toes, inhabits the
Cameroons, _N. tuberculosa_ of Malabar, and _N. guentheri_ and _N. hosei_
of Borneo, have a visible tympanum and the fingers are webbed at the base
only. These slender and long-legged species are most probably arboreal, as
indicated by the broadened, but truncated, tips of their fingers and toes.
_N. hosei_ is about 4 inches long, _N. misera_ is a little creature of only
¾ inch in length. _Nectes_, hitherto known by one species, _N. subasper_ of
Java, is a swimmer and exceeds 6 inches in length. The tympanum is very
distinct; the small nostrils look upwards. The toes are long and webbed to
the tips; the hind-limbs are very long. The sacral diapophyses are strongly
dilated. The skin of the upper parts is very rugose, covered with round
warts, and dark brown; the under parts are granular and uniformly light
brown.
_Bufo._–The great number of species, more than 100, renders a strict
definition of this genus difficult. The tongue is pear-shaped, thicker in
front, entire, not cut out, but free behind, so that it can be projected.
The fingers are free, the toes more or less webbed although never
completely so. The terminal phalanges are obtuse and sometimes carry tiny
discs. The omosternum is absent or merely vestigial. The metasternum is a
rather large cartilaginous plate with a waist, which is sometimes
incompletely calcified. The sacral diapophyses are moderately dilated. The
tympanum is distinct or hidden. The skin of the upper parts is always rich
in specific poison-glands, a concentration of which forms in many species
very conspicuous, thickened parotoid glands. The surface of the skin may be
smooth, moist and slimy, or rough and warty, sometimes covered with tiny,
sharp, horny spikes and quite dry.
The genus is cosmopolitan, with the exception of the whole Australian
region and Madagascar, from which we may perhaps conclude that its original
centre was not in Notogaea, in spite of the diversity of species in the
Neotropical region, which now contains about half of all the species known.
Next to Central America the Indian region is richest in species of _Bufo_.
{170}_B. vulgaris._–The Common Toad of the Palaearctic region. The skin of
the upper parts is much wrinkled and beset with numerous round warts or
poison-glands, the openings of which can be seen with the naked eye,
especially on the large parotoid complexes. The outermost layer of the
epiderm, in fact all that portion which is periodically shed, is elevated
into numerous little cornified spines. The extent of their development
varies much; southern specimens, especially those from Portugal, being
perhaps the roughest. Others appear quite smooth to the touch, and this is
the case with many English specimens. The skin of the under parts is more
granular and devoid of specific glands. The general colour of the upper
parts is olive grey to dark brown, more or less mottled; the under parts
are whitish, often with a brown, yellow or reddish tinge.
The coloration of this species varies considerably and is moreover very
changeable. These changes depend chiefly upon the surroundings and the
locality, in which certain styles of coloration seem to be the fashion, not
necessarily to the absolute exclusion of others. Some specimens are of a
rich brown colour, with or without dark brown spots and patches, and these
are sometimes confluent, forming irregular, longitudinal bands. The
ground-colour of other individuals is olive grey, with or without darker
patches, and these paler tones prevail in toads which live on
light-coloured soil, for instance on chalk. I recently found one between
two dark-coloured slates, and this creature was so black that it gave the
impression of having soiled itself with coal-dust. One and the same
specimen will appear paler or darker according to its mood and the leading
tones of its immediate surroundings, but it cannot change its dominant
ground-colour. A third colour-variety occurs more frequently in the
mountainous districts of Southern Europe. I have obtained the most handsome
specimens in the Serra Gerez, in North Portugal. Their ground-colour is
pale brownish-yellow, with many large and small, rich brown patches, or if
the latter colour predominates, these patches and spots are separated from
each other by creamy seams, with the occasional effect of dark brown,
yellow-ringed eyes. Eastern Asiatic specimens often have a fine yellow
vertebral line and the under parts are inclined to be marked with dark
spots.
The iris is red or coppery, mottled with black. The male {171}has no vocal
sacs, and, besides being smaller than the female, is distinguished by
slight nuptial excrescences in the shape of little horny brushes on the
inside of the inner palmar tubercle and the three inner fingers. The full
size of this toad varies extremely. Taking the standard of everyday
experience in England and Central Europe, one would call any female beyond
3½ inches in length, and any male of more than 2½ inches, unusually large.
But occasionally they grow to a much larger size, especially in the
mountains of Southern Europe, provided there is a rich vegetation of
meadows and deciduous trees so as to insure a variety of plentiful food.
Although Fatio[79] mentions a toad 153 mm. = 6 inches long, and Boulenger
succeeded in getting a toad from Paris which measured 132 mm., _i.e._
almost 5¼ inches, one of my specimens from the Serra Gerez seems to hold
the record with a total length from snout to vent of 135 mm. or more than
5¼ inches. Jersey is also famous for its large toads, possibly on account
of the many large greenhouses. These large specimens do not constitute a
special race. The monsters among them are without exception females, often
but not always sterile, as I have often found large masses of eggs in them.
Food is the chief cause. At least I have observed that the more voracious
of some Spanish and Portuguese specimens, which were already 3½ inches
long, and therefore entitled to respect, continued to grow rather rapidly,
adding about half an inch within a year. Again, if the growth of a
promising toad is arrested for a season–not necessarily by starvation, but
by uncongenial surroundings, sameness, and unvaried nature of food–they
consolidate so to say, or settle down, and no amount of future good feeding
will turn them into exceptionally big specimens. There are no data to tell
how old such monsters really are. At least ten years are required by the
Southerners to reach four inches. The usual length of life attained by a
toad is likewise unknown. Boulenger kept one in a box provided with a sod,
a pan of water and plenty of varied food, but twelve years of close
captivity did not make any appreciable difference in its appearance.
{172}[Illustration: FIG. 35.–_Bufo vulgaris._ Portuguese specimen. × ⅔.]
A number of large Spanish and Portuguese specimens in my greenhouse were at
first very shy, and tried every possible means of escape or sullen hiding,
but gradually they condescended to take food when lifted on to the
slate-covered stage upon which their food was spread. After a few weeks
they had learned this so thoroughly that, towards the usual hour of
feeding, they climbed most laboriously on to the slates, lying in wait
between the flower-pots, and coming forward when we entered the house. The
rest of the day and night they spent on the ground, under stones or plants,
each in its individual lair. The biggest of all, and several others, became
so tame that they took food whilst sitting on the hand, and then they
looked up for more. The food must be alive and show movement. Mealworms,
snails, beetles and other small creatures are first carefully inspected
with bent-down head, and are sometimes followed for a few inches; then
comes an audible snap, a flash of the rosy tongue and the prey has
disappeared. Large earthworms are nipped up with the jaws and laboriously
poked in with the hands, the fingers being so placed as to clean the worm
of adherent soil and other impurities. Very large worms are shaken,
twisted, pressed against the ground and gulped down with convulsive
movements, but not unfrequently the tip-end remains for some minutes
sticking out of the tightly shut mouth. Several are taken at one sitting,
until the toad is gorged. One of the biggest took full-grown mice, which
{173}were not "fascinated by the fiery eyes" but were stalked into a corner
and then pounced upon immediately when they moved. The shells of snails can
for half a day be felt through the body; they then dissolve or are
disgorged. The dung, which is passed in large, long masses, is often full
of fine earthy matter, the contents of the earthworm's intestines, and
sometimes it contains the chitinous remains of certain beetles which are
supposed to be excessively rare. I know of no instance of slugs being
eaten.
The regular hunting-time begins with the evening and is continued
throughout bright nights, the toads crawling and hopping about. They are
expert climbers of rocks, and succeed in reaching apparently inaccessible
places by shoving themselves up between vertical walls, and taking
advantage of any roughnesses for foothold. Every few weeks they shed their
skins. Without any preliminary symptoms or loss of appetite or liveliness,
the body makes a few twisting motions, the back is now and then curved, and
the skin splits down the middle line. Owing to the more forcible
contortions of the body it slides down to the right and left of the back,
whereupon the toad gets hold of the peeling-off skin with fingers and toes,
scraping the head and sides, and conveys the thin, transparent, slightly
tinged skin into the mouth, slips out of it backwards and swallows it. The
new surface is then quite wet and shiny, but it soon dries and hardens.
Many toads, for instance the Common Toad and the Pantherine Toad, assume a
peculiar attitude when surprised. Instead of blowing themselves up by
filling their lungs with air, they raise themselves upon their four limbs
as high as possible, but turning the back towards the enemy in a slanting
position, either to the right or to the left side, apparently in order to
present as much surface as possible, in other words to look their biggest.
Some of my specimens hibernated regularly for a few months, burying
themselves completely in loose, dry soil, under leaves, or,–a favourite
place,–in a heap of cocoa-nut fibre. Others, and this applies also to
English specimens transferred from the garden into the greenhouse, are
lively all the year round, but even they withdraw for an occasional sleep
of a few weeks at any time of the year.
The whole family of large toads came to a sad end after four years, when
they were put into new temporary quarters, a {174}slate-bottomed terrarium.
Being kept during my absence in wringing wet moss, which became fouled by
their own excretions, they contracted a mysterious disease from which they
never recovered. They are rather averse to wet surroundings, and except
during the short pairing season they live in cool, shady places, preferably
with just a little dampness. Occasionally they take a soaking bath. One
specimen, living in the garden, repaired during the hot and dry summer
nights to a standpipe in the garden, enjoying the occasional drips of
water.
Considering the amount of snails and other noxious creatures destroyed by
them during their regular nocturnal hunts, toads are eminently useful
creatures. Nevertheless, they suffer much through the stupid superstition
of people who ought to know better. It is difficult to find a gentle,
absolutely harmless and useful creature that is more maligned than the
European toad. It brings ill-luck to the house, the "slimy toad" spits
venom, sucks the cows' udders and after that destroys their power of giving
milk; it poisons the milk in the cellar, and a certain builder's horse,
which was grazing in the grounds of the Cambridge Museums, and died there
from a large concrement obstructing its bowels, was solemnly declared to
have swallowed one of my toads. Silly superstitions, owing to faulty, or
rather entire want of, observation! The toad is not slimy, but dry; it is
often found in buildings, where it keeps down the woodlice; it cannot suck,
nor does it drink at all; it does not spit venom, but becomes covered with
milky white and very strong poison when in acute agony, for instance when
trodden upon; and unless the big skin-glands be forcibly squeezed, there
will be no squirting. Therefore, leave it alone, or put down food on its
evening beat, and it will soon come to know and to recognise its friends.
The Common Toad can exist without food for a long time, provided the
locality is cool and damp, but it wastes away almost to skin and bones. In
order to disprove the persistently cropping up fable and sensational
newspaper-accounts of toads having been discovered immured in buildings,
where they were supposed to have lived for many years, Frank Buckland put a
dozen specimens into separate holes bored in a block of porous limestone,
covered them up tightly with a glass plate and buried the block a yard deep
in the soil. A second dozen were treated similarly, but were put into a
block of dense sandstone. After a {175}year and two weeks all the toads
enclosed in the latter block were of course found dead and decomposed, but
most of those in the porous block were still alive, with their eyes open,
and did not succumb to starvation until eighteen months of confinement.
These poor creatures could of course not move about, and were practically
undergoing enforced continuous hibernation. Otherwise they would soon have
wasted away and have died within six months. Those which tumble into deep
and dry wells remain rather small, but generally manage to keep alive for
years on the spiders, woodlice, earwigs and other insects which likewise
tumble in.
Toads hibernate far from the water in dry holes or clefts, retiring in the
middle of October in Central Europe, and they do not reappear before March.
Soon after, and this depends naturally upon the season, they congregate in
ponds or pools, and the males, which far outnumber the females, for whom
they fight, make a peculiar little noise, something like the whining bleat
of a lamb, uttering this sound day and night. The male having, after much
wrestling with competitors, secured a female, which is often several times
bigger than himself, clasps her tightly, by pressing his fists into the
armpits, and the pair swim or crawl about in this position sometimes for a
week before the spawning takes place. The number of eggs laid at one
sitting is enormous, varying from 2000 to 7000. They are very small, only
1.5-2.0 mm. in diameter, and are expelled in two double rows or strings,
one coming out of each oviduct. These strings consist of a soft gelatinous
mass, in which the double rows of entirely black eggs are imbedded, and
they measure in the swollen condition about 6 mm. or ¼ inch in diameter,
and from 10 to 15 feet in length. The strings are wound round and between
water-plants by the parents, which move about during the laying and
fertilising process. According to the coldness or warmth of the season the
larvae are hatched in about a fortnight, and for the next few days they
hang on to the dissolving gelatinous mass of the egg-strings. They then
leave the slime and fasten themselves by means of their suckers to the
under side of grasses and water-plants or sticks, with their tails hanging
downwards, still in a rudimentary condition, but henceforth progressing
rapidly.
Fischer-Sigwart[80] found the time of development as follows:–The {176}eggs
were laid on the 6th of March; the larvae left the jelly on the 16th, being
4 mm. long. On the 2nd of April they measured 13 mm.; on the 25th, 20 mm.
On the 7th of May the hind-limbs appeared. On the 18th of May the tadpoles
had reached their greatest length, namely 24 mm., and this is a rather
small size for so large a species. The fore-limbs broke through on the
28th, and the metamorphosis was completed eighty-five days after the eggs
were laid, the creatures leaving the water on the 30th of May. The tadpoles
showed a preference for rotten pieces of _Agaricus_, which were floating in
the water. The little baby-toads are surprisingly small, scarcely 15 mm.
long, and live in the grass, under stones, in cracks of the ground, and hop
about in much better style than their heavier and more clumsy-looking
parents. Where many broods have been hatched they can be met with in
myriads, the ground literally swarming with them, and as they are naturally
stirred up by a sudden warm rain, perhaps after a drought, people will
occasionally state it as an observed and well-ascertained fact that "it has
rained toads."
What becomes of all these hopeful little creatures? Although it takes them
fully five years to reach maturity, one would expect that the whole country
would be swarming with toads; but since this is not the case, there being
not more toads now than there were before, it follows that their enormous
fecundity is only just sufficient to keep the race going. Adult toads seem
to have scarcely any enemies except the Grass Snake, which takes them in
default of anything better. But how about the reduction where there are no
snakes? We know nothing about epidemics which might carry them off, but
elderly toads are liable to a horrible disease produced by various kinds of
flies, notably by _Lucilia bufonivora_ and _Calliphora silvatica_, the
maggots of which somehow or other eat their way from the nostrils into the
brain and into the eyes. Those which reach the brain at first produce
effects similar to those of _Coenurus cerebralis_, the hydatid or
bladder-worm of sheep. The toad inclines its head towards one side, and
cannot crawl straight, but walks in a circle. By eating away the brain they
gradually destroy the host's life. But if none enter the brain, and a few
only find their way into the eye, they only impair or destroy its sight.
Such toads show signs of pain, poking at or stroking the affected eye,
which becomes {177}inflamed, and ultimately remains enlarged, with the iris
partially or entirely destroyed by the maggot, which does not develop
further, but dies in the eye-chamber, this being really an unsuitable place
for it. The eyesight is of course affected, and is mostly, but not in all
cases, lost. Such half-blind individuals–the disease affecting sometimes
one eye only–recover their health, and except for a little awkwardness,
behave like normal specimens. This applies to _Bufo vulgaris_ as well as to
_B. calamita_. Australian Anura are cursed with a fly of their own, called
_Batrachomyia_.[81]
_B. vulgaris_ inhabits almost the whole of the Palaearctic region;–the
whole of Europe, with the exception of Ireland, the Balearic Islands,
Sardinia and Corsica. Northwards it extends to Trondhjem, and thence along
a line drawn across Russia and Siberia to the Amoor. Its southern limit in
Asia is indicated by a line drawn from the Caucasus through the Himalayas
into China. In Asia Minor and in Persia it is absent. South of the
Mediterranean it occurs only in Morocco and Algeria.
_B. melanostictus_ is the common toad of the whole Indian region and of the
Malay Archipelago. The epidermis of the fingers and toes is thicker and
more cornified than usual, and is stained black brown, hence its specific
name. The male has a subgular vocal sac. In other respects the Indian
species much resembles the more spinous or rough-skinned and brown
varieties of the European species. According to S. S. Flower this toad is
very common in the Straits Settlements, hiding by day under stones or logs,
or in holes, coming out shortly before sunset, and remaining abroad till
dawn; it may be met with on the roads and in the grass, hopping or crawling
about in search of ants, bees, and similar food. It utters a rather feeble,
plaintive cry when handled for the first time. It can change its colour
from light yellowish to dark brown. The spawn, which resembles that of _B.
vulgaris_, may be seen in March and April in ponds, in long strings twined
about the water-weeds. The tadpoles are very like those of the common
English toad in form, size, colour, and structure of mouth. The largest
adult found in Penang measured 115 mm. (about 4 inches) from snout to vent.
{178}_B. lentiginosus_ s. _americanus_ is the common toad of North America,
from Mexico to the Great Bear Lake. It is worth noting that this species
resembles in its coloration the Eastern races of _B. vulgaris_, in so far
as they generally have a light vertebral line, and frequently dark spots on
the under surface. The upper parts are brown and olive, with darker spots,
two of which form a chevron behind the eyes. But the tympanum is large, and
the male has a subgular vocal sac; the inner metatarsal tubercle is very
large, and is used as a kind of digging spur. During the pairing time they
take to the pools in great numbers, uttering their music, which consists of
a prolonged trill, continued by different individuals, both day and night.
Holbrook knew an individual which was kept for a long time, and became
perfectly tame. During the summer months it retired to a corner of the room
into a habitation which it had prepared for itself in a small quantity of
earth placed there for its convenience. Towards the evening it wandered
about in search of food. Some water having been squeezed from a sponge upon
its head one hot day in July, it returned the next day to the spot, and
seemed well pleased with the repetition, nor did it fail during the extreme
heat of the summer to repair to it frequently in search of its shower-bath.
Several varieties of this widely distributed species, whose average length
is 2½ inches, have been described. The prettiest was called _B. quercinus_
by Holbrook–according to whom it is mostly found in sandy places covered
with a small species of oak–which springs up abundantly where pine-forests
have been destroyed. It is called the "oak-frog," as it spends most of its
time in concealment under fallen oak-leaves, or partially buried in the
sand.
_B. marinus_ s. _agua_ is the giant among toads, and is one of the
commonest species of the Neotropical region, ranging from the Antilles and
Mexico to Argentina. It frequently reaches a length of 6 inches, with a
width of 4 inches when squatting down in its favourite attitude. The upper
parts are rough, owing to the prominent warty glands, of which the parotoid
complex is enormous. The general colour above is dark brown, with sooty
dark patches; below whitish, often with blackish patches. This creature
appears at dusk, often in large numbers, especially during the rainy
season, hopping about, not crawling, with surprising {179}activity. The
voice of the male, strengthened by a subgular sac, is said to be a kind of
loud snoring bark. The pairing time begins, according to Hensel,[82] with
the winter rainy season, especially June, and lasts several months, until
October, but it is interrupted by the cold, which in the hills of
South-Eastern Brazil covers the ponds with ice. Then the tremulous bass
voice of the males is heard no longer; they have all withdrawn beneath
stones and trees in the neighbourhood of the water. The eggs are laid in
strings. The larvae are at first quite black and very small, and the young
baby-toads are only 1 cm. in length. They differ considerably from the
adult until they are more than 1 inch long; the upper parts are yellowish
brown, with darker ocellated patches, each with a light seam, most
conspicuous along the sides of the head and back. The under parts are grey,
finely stippled with yellow.
Budgett[83] remarks that _B. marinus_ feeds on all kinds of insects. "One
half-grown specimen sitting by a man's foot picked off fifty-two mosquitoes
in the space of one minute, picking them up with the tongue as they
settled. The call of this very common toad consists of three bell-like
notes; the middle one being the highest. The enormous parotoid glands are
discharged like squirts when the creature is roughly handled. When wet
weather comes on it hops out from its hiding-place to sit in a puddle, with
its head out."
In many species of _Bufo_ the crown of the head forms more or less
prominent ridges, especially strong in the region between the eyes; for
instance, in _B. melanostictus_ and _B. lentiginosus_. The skin overlying
these ridges is liable to be involved in the cranial ossification, and this
reaches its greatest extent in the two Cuban species _B. empusus_ and _B.
peltocephalus_. It is a curious coincidence, to say the least, that such
dermal ossifications should be best developed in Neotropical species, in
those very countries which amongst the Cystignathidae have produced the
abnormal genera _Triprion_, _Calyptocephalus_, and _Pternohyla_. The most
peculiar and odd-looking species is _Bufo ceratophrys_, a native of
Ecuador, which has the upper eyelid produced into a horn-like appendage,
the two sharply-pointed cones standing out transversely, reminding us of
several species of the Cystignathoid genus _Ceratophrys_; there is also a
series of four small pointed {180}appendages on each side of the body.
Protective concealment is possibly the reason of these queer outgrowths.
_B. viridis_ s. _variabilis_, the Green or Variable Toad, reaches a length
of about 3 inches, and is the prettiest toad of Europe. The skin is
distinctly smooth, the numerous porous, large and small warts being
flattened. Parotoid glands are well developed, and a similar pair of glands
sometimes occurs on the inner side of the calf, especially in Central
Asiatic and in Algerian specimens. The coloration is very variable and
changeable. The ground-colour of the upper parts is creamy, with large and
small, partly confluent and irregularly shaped spots and patches of green,
here and there interspersed with vermilion-red specks, especially along the
sides of the back. The under parts are whitish, sometimes spotted with
black. The iris is brass-coloured, greenish-yellow, with fine dark dots.
The male does not differ from the female in size, but has an internal
subgular vocal sac, a conspicuous callosity on the inner side of the first
finger, and nuptial brushes on the first three fingers and on the inner
palmar tubercle.
The changing of colour affects mainly the intensity of the green; the same
individual which now looks almost uniformly dull, almost grey, with dusky
olive patches, will, if put into grass and sprinkled with water, within a
few minutes appear in a tastefully combined garb of grass-green on a creamy
ground. Some Southern and Eastern specimens have a creamy stripe along the
vertebral line, thereby closely resembling _B. calamita_, from which,
however, they can always be distinguished by the little pads below the
joints of the toes; these pads being single in B. viridis, and double in
_B. calamita_ and in _B. vulgaris_.
The Green Toad spends most of the day in holes, although it is not averse
to daylight, and it roams about chiefly in the evening. It can jump well,
much better and oftener than the Brown Toad. The food consists strictly of
insects of all kinds, and most individuals prefer slow starvation to eating
an earthworm. Although continuing to live four or five years in captivity,
they do not readily become tame; they are indeed no longer wild, and when
handled they no longer emit their peculiar insipid smell, but on being
approached they still crouch deeply into the grass, or withdraw into their
holes, just as they did when recently caught. The voice is heard during the
pairing season, and sounds like the slow creaking of a door, or a
combination of a spinning top and {181}rattle. In Germany, during the
months of April and May, they take to the ponds, or, improvident like the
common frog, to a roadside ditch. The male sits upon the female and grasps
her below the arms, his hands on her breast, and in this position they
remain for days. The eggs are laid in two strings, twisted around
water-plants, and are very numerous. Héron-Royer has calculated them at
10,000 or more in one set. The embryos are hatched, like those of the
Common Toad, before the appearance of the external gills and of the tail.
In this imperfect condition they remain in the jelly of the egg-strings for
a few days, while their external gills sprout out like unbranched little
stumps, only to disappear again. In about eight weeks the tadpoles, which
reach a length little more than 1½ inch or 40 mm., have metamorphosed and
leave the water as baby-toads scarcely half an inch in length.
This species has a very wide range, namely, the whole of Middle Europe
excepting the British Isles, France and the Iberian Peninsula; the region
between the Elbe and Rhine being its western limit; southwards it extends
over all the Mediterranean islands and the north coast of Africa, eastwards
through the whole of Russia, Western and Central Asia, not entering India,
but spreading along the Himalayas into China. Stoliczka mentions its having
been found in the Himalayas at an altitude of 15,000 feet, the highest
record of any Amphibian, at least in such latitudes.
_B. calamita._–The Natterjack is practically the representative of the
Green Toad in Western Europe, but both species occur together in Denmark,
Southern Sweden, and nearly the whole of Germany. Its southern limit is
Gibraltar. In the British Isles it occurs in South-Western Ireland, in Co.
Kerry, and in England and Wales, being however local, and preferring sandy
localities, where it is found in considerable numbers. This predilection is
shown by its frequency on the sandy dunes of most of the islands off the
German and Dutch coast, where it may be seen running about in glaring
sunshine.
Besides in the coloration, it differs from _B. viridis_ in the following
points. The little subarticular pads of the toe-joints are paired, not
single, and the hind-limbs are decidedly shorter, so much so that this
species cannot hop. But it runs well, like a mouse, generally in jerks,
stopping every few seconds, and owing {182}to this habit it is called the
"running toad" by the field-labourers of Cambridgeshire. The skin is
smooth, but less so than in _B. viridis_, owing to the slightly more
prominent warts; the parotoids are small; a similar pair of glands lies on
the upper surface of the fore-arm and another on the calf. The tympanum is
rather indistinct. The ground-colour of the upper parts is light brownish
yellow, with a green tinge and scattered green spots; most specimens have a
narrow yellow stripe along the vertebral line and over the head. The under
parts are white, more or less speckled with black. The iris is greenish
yellow and speckled. The male, which is of the same size as the
female,–very large specimens reaching 3 inches in length,–has a large
subgular vocal sac, and develops nuptial brushes on the first three
fingers, but the first lacks the thickened pad of _B. viridis_.
The yellow vertebral line is sometimes absent in specimens from the south
of France and the Iberian Peninsula; and since these southerners are as a
rule more handsomely marked, the green being more pronounced and arranged
in larger patches, interspersed with red spots, they much resemble _B.
viridis_. Boulenger, who has paid especial attention to this vertebral
streak, which is a not uncommon design in various species of different
families, has made the interesting observation that the streak has never
been found in Danish and German specimens of _B. viridis_, where _B.
calamita_ occurs also, while it is not uncommon in _B. viridis_ of Italy,
South-Eastern Europe, Asia, and North Africa, where _B. calamita_ is not
found. Lastly, he remarks that in Eastern Asia, where neither _B. viridis_
nor _B. calamita_ with such a line occurs, the same character is assumed by
some specimens of _B. vulgaris_. The only conclusion we can draw from these
facts is, that for some unknown reason the streak is a desirable, but not
necessary, possession, but that it is not kept by two species in the same
country, _B. viridis_ dropping it entirely where the typically streaked
species, _B. calamita_, also occurs. The breeding season does not begin in
England and Middle Europe until the end of April, in cold springs not
before May, but it lasts for several months. The males, congregating in
pools in great numbers, make a loud noise, each individual uttering a
rattling note which lasts a few seconds, the repetition distending its
bluish throat into the shape of a {183}globe as large as its head. As the
note is taken up by all the other males, a continuous chorus is
established, which on warm and still nights can be heard nearly a mile off.
Single croaks are uttered at any time of the day. The embrace, the male
digging its fists into the armpits of the female, often takes place on
land, near the edge of the water, to which they resort in the night for
spawning. The egg-strings are slung around water-plants, unless the water
is a mere puddle, and are much shorter than those of _B. viridis_,
measuring only 5 to 6 feet, and containing altogether 3000 to 4000 eggs.
The larvae, when hatched, are very small, imperfect, and blackish; the
external gills last a very short time. The young tadpoles live on mud,
subsisting on diatoms and low Algae; they are the smallest tadpoles of all
the European kinds, scarcely reaching more than one inch in length, and
they metamorphose quickly, the baby-toads leaving the water and running
about in less than six weeks, when they are only 10 mm., scarcely
three-eighths of an inch, in length. By the end of their second summer they
are still only three-quarters of an inch long, and they do not reach
maturity until the fourth or fifth year, with a size of 1½ to 2 inches;
still smaller young males become mature several years before they are full
grown.
Natterjacks stand captivity well and become very tame. When discovered,
they first do their best to run away, instead of hiding or squatting down,
and when caught they become covered with a slightly foamy lather, the
exudation of their glands, which has a peculiar smell, reminding some
people of gunpowder, others of india-rubber. They are not very particular
as to food, all sorts of insects and earthworms being taken. Natterjacks
are great climbers and diggers. Many of mine have established themselves in
the peat with which the walls of the greenhouse are covered, where they
have dug out, or enlarged, holes in which they pass the daytime, just
peeping out with their bright eyes; others sit high up, always in dry
places, and bask. In the evening they descend, hunting about on the ground,
and occasionally they go into the water, whereupon they become quite
flaccid and soft. When taken up and held between two fingers, being
slightly pressed under the armpits, both sexes utter little jerky notes,
as–by the way–most toads and frogs do under similar conditions.
In Cambridgeshire they frequent certain clay-pits surrounded {184}by high
and steep walls of sand, the breeding places of large colonies of
sand-martins. During the months of May and June they are found in the
shallow water, running about on the mud, sometimes swimming, in which they
are not very proficient, and rarely diving. But they spend most of the time
on land. Early in October they climb up and enter the holes of the
sand-martins, or they dig large, deep burrows for hibernation, and the old
males are the first to disappear.
_B. mauritanica_ s. _pantherina_.–The "Pantherine Toad" is one of the few
African species, and is one of the prettiest of all toads. The skin is
almost smooth, although provided with porous glands. The parotoids are
large, but flat; large glandular complexes on the legs or arms are absent.
The tympanum is very distinct. The upper parts are adorned with a delicate
pattern of dark-edged, rich brown or olive patches upon a light,
buff-coloured ground; the under parts are uniform white; the male has a
subgular vocal sac. The total length is 3 to 4 inches. This beautiful
species is one of the gentlest, and it becomes tame enough to lap up food
whilst sitting on one's hand. It lives entirely upon insects, prefers shade
and dusky light, and utters a sound like "kooh-rr." It is a native of
North-Western Africa, Algiers, and Morocco. In the rest of Africa, from
Egypt to the Cape, Senegambia to Abyssinia, it is represented by _B.
regularis_. This species has often little spiny tubercles upon the warts,
and occasionally a light vertebral line; the colour of the upper parts
either closely resembles that of the previous species, or it is uniform
light brown, while the under parts are whitish, or variegated with brownish
patches. West African specimens are the smallest, only 2 inches long; those
of the Cape are the largest, reaching 5 to 6 inches.
The next two genera approach the Engystomatinae, and thereby lead from the
arciferous towards the firmisternal type. The epicoracoid cartilages are
narrow, and they scarcely overlap, so that by a further step in this
direction they could easily fuse into the firmisternal condition. Another
bond between these two genera and the Engystomatinae is their habits, they
being ant-eaters of an extremely stout appearance, with exclusively short
limbs and very small heads.
_Myobatrachus gouldi_, living in Australia, has a smooth skin, brown above,
lighter beneath, and is about 2 inches long.
{185}_Rhinophrynus dorsalis_ of Mexico is remarkable for its tongue, which
is elongated, subtriangular and free in front, so that it can be protruded
directly–not by reversion as in other toads–and can be used for licking up
the termites which seem to be its principal food. The body of this ugly
creature is almost egg-shaped, and the head is merged into this mass, only
the narrow truncated snout protruding. The limbs are very short and stout.
The toes are more than half webbed, and there is a large oval, shovel-like
metatarsal tubercle, covered with horn and used for digging. The general
colour is brown, with a yellow stripe along the spine and with irregular
spots and patches on the flanks and limbs. Total length 2 to 2½ inches.
[Illustration: FIG. 36.–Map showing distribution of Hylidae. The vertically
shaded countries are inhabited by _Hyla_ and by other genera of Hylidae;
the horizontally shaded countries only by _Hyla_.]
FAM. 4. HYLIDAE (Tree-frogs).–The upper jaw–in _Amphignathodon_ the lower
jaw also–and the vomers carry teeth; _Triprion_ and _Diaglena_ alone have
teeth on the parasphenoid also, and the latter genus is further
distinguished by possessing palatine teeth. The vertebrae are procoelous
and have no ribs; the sacral diapophyses are dilated. The omo- and
meta-sternum are cartilaginous, the latter forming a plate with scarcely
any basal or style-shaped constriction. The terminal phalanges are
invariably claw-shaped and swollen at the base, and carry a flattened,
roundish, adhesive cushion. The tympanic disc is variable in appearance,
being either free, or more or less hidden by the skin. The tongue is also
variable in its shape and in the extent to which it can be protruded.
{186}Most, if not all, Hylidae are climbers, and many lead an arboreal
life, but it does not follow that all the "Tree-frogs" are green.
Their distribution is very remarkable. To say that this family is
cosmopolitan with the exception of the African region, is literally true,
but very misleading. There are in all about 150 species, and of these 100
are Notogaean; one-half of the whole number, or 75, being Neotropical; 23
are Central American, 7 Antillean, and about 18 are found in North America.
One species, _Hyla arborea_, extends over nearly the whole Palaearctic
sub-region, and two closely allied forms occur in Northern India and
Southern China. Consequently, with this exception of three closely allied
species, the Hylidae are either American or Australian. We conclude that
their original home was Notogaea, and that they have spread northwards
through Central and into North America. The enormous moist and steamy
forests of South America naturally suggest themselves as a paradise for
tree-frogs, and it is in this country, especially in the Andesian and the
adjoining Central American sub-regions, that the greatest diversity of
generic and specific forms has been produced. It is all the more remarkable
that similar forest-regions, like those of Borneo and other Malay islands,
are absolutely devoid of Hylidae (while there are about a dozen species in
Papuasia), whose place has however been taken for all practical purposes by
correspondingly modified Ranidae, notably the genus _Rhacophorus_. Lastly,
the fact that tropical evergreen forests of Africa and Madagascar possess
no Hylidae, but are inhabited by several kinds of tree-climbing
_Rhacophorus_, points with certainty to the conclusion that the origin of
this large and flourishing family of Hylidae was not in Arctogaea.
The versatility and the wide distribution of the Hylidae has naturally
produced cases of convergent analogy, and the various species of one
"genus" may be in reality a heterogeneous assembly. Such an instance is
probably the genus _Hylella_, of which four species live in the Andesian
and Central American provinces, while the two others occur in New Guinea
and Australia.
The two North American genera _Chorophilus_ and _Acris_, and the Brazilian
_Thoropa_, connect the Hylidae with the Cystignathidae, in so far as their
finger-discs are very small, or even {187}absent, and their sacral
diapophyses are only slightly dilated. On the other hand, it has to be
emphasised that the possession of adhesive discs on the fingers and toes
does not necessarily constitute a member of the Hylidae. That requires _the
further combination of an arciferous sternum, with dilated sacral
diapophyses and teeth in the upper jaw_. Finger-discs are easily developed,
and still more easily lost. Those of the typical Hylidae are constructed as
follows. The terminal phalanx is elongated, claw-shaped, swollen at its
base. Between it and the penultimate phalanx lies an interphalangeal
cartilaginous disc which projects ventrally below the end-phalanx, thus
assisting the formation of the ventral pad, and the turning upwards of the
whole disc-like phalanx like the claw of a cat. This peculiar motion can be
well observed in Tree-frogs which are at rest upon a horizontal leaf, or,
better still, upon a rough stone, when the creatures take good care to
adjust their discs into a safe and easy position. The pad or disc itself is
furnished with unstriped, smooth muscular fibres, the contraction of which
produces one or more longitudinal furrows on the under side. When the disc
is in action or adhering, being flattened to a smooth surface, the
end-phalanx sinks into the cushion; when not in action, the cushion swells
and the phalanx appears as a slight dorsal ridge. The disc is rich in
lymph-spaces, and its surface contains mucilaginous glands.
Various suggestions have been made to explain the function of these discs.
Suction, adhesion, and glueing-on have been resorted to. Suction, through
production of a vacuum, is quite imaginary and does not exist. The question
has been thoroughly studied by Schuberg.[84] Adhesion is due to the
molecular attraction of two closely appressed bodies. The less air remains
between them the stronger it is. Consequently it can be increased by the
interference of a thin layer of fluid, which as everyday observation shows,
possesses both adhesion and cohesion. The more sticky the fluid, the more
effective it is, as shown experimentally by Schuberg, who moistened the
under surface of a glass plate, and pressed it against a little disc of
glass from which was suspended a weight. A disc of 16 square millimetres,
approximately equal to the aggregate surface of the 18 discs of a European
tree-frog of 4 grammes in weight, carried with water-adhesion {188}no less
than 14 grammes, with glycerine-solution 20 grammes,–more than sufficient
to suspend the frog. The sticky secretion of its glands greatly enhances
the adhesive power. Tree-frogs, when hopping on to a vertical plane of
clean glass, slide down a little, probably until the secretion stiffens, or
dries into greater consistency. After a few days I find the glass-walls of
their recently cleaned cage quite dirty, covered everywhere with their
finger-marks. On the other hand, wet leaves or moist glass-walls afford no
hold. The adhesion of these frogs is assisted in most cases by their soft
and moist bellies, just as a dead frog will stick to a pane of glass.
All Hylidae have a voice, often very loud, and enhanced by vocal sacs,
which are either internal, swelling out the throat, or external, paired or
unpaired.
The various Hylidae resort to all kinds of modes of rearing their broods.
Most of them lay many eggs, up to one thousand, in the water, not coherent
in strings but in clumps; others lay only a few, attach them to various
parts of the body, or, as in the genus _Nototrema_, the female receives
them in a dorsal pouch. These modifications will be described in connexion
with the different species.
SUB-FAM. 1. AMPHIGNATHODONTINAE.–_Both upper and lower jaw with teeth._
_Amphignathodon_, of which only one species is known, _A. guentheri_ of
Ecuador, agrees with _Nototrema_ in all important characters except that it
possesses teeth in the lower jaw in addition to those in the upper. There
are further differences, but they are of degree only. The sacral
diapophyses are more strongly dilated and the omosternum is absent. The
tympanum is distinct. The pupil is horizontal; the roundish tongue is
slightly free behind. The terminal phalanges are claw-shaped and carry
large discs. The female has a dorsal pouch opening backwards. The skin of
the head is involved in the ossification of the cranial bones. The skin of
the back is smooth, slightly tubercular, non-granular below. The middle of
the upper eyelid carries a small, pointed, cutaneous appendage, and even
this little character occurs also in some species of _Nototrema_, _e.g._ in
_N. longipes_ and in _N. cornutum_. The heel carries a triangular little
flap. The upper parts are olive in spirit-specimens, probably green in
life; the borders of the dorsal pouch {189}are black. The sides of the body
are adorned with a black, white-edged streak, the limbs are whitish, with
black cross-bars. The total length of the female type-specimen is 3 inches.
SUB-FAM. 2. HYLINAE.–_Lower jaw toothless._
The Hylinae are divided by Boulenger into 13 genera, which can be
recognised by the following key, without reference to their natural
affinities:–
_A._ The contracted pupil forms a horizontal slit.
_a._ Tips of the fingers and toes with large discs,
α. With vomerine teeth.
Female without a dorsal pouch .......... _Hyla_, p. 189.
Female with a dorsal pouch .......... _Nototrema_, p. 202.
β. Without vomerine teeth .......... _Hylella_, p. 203.
γ. With parasphenoid teeth and peculiar helmet-shaped head.
Yucatan .......... _Triprion_, p. 207.
Ecuador and Mexico .......... _Diaglena_, p. 207.
_b._ Tips with very small discs. Tongue free behind.
Tympanum distinct. North America and Peru .......... _Chorophilus_,
p. 208.
Tympanum indistinct. North America .......... _Acris gryllus_,
p. 207.
_c._ Tips simply swollen, not dilated into discs. Brazil ..........
_Thoropa miliaris_, p. 209.
_B._ The contracted pupil forms a vertical slit. Tropical America.
_a._ Tips with large discs.
α. Tongue extensively free behind.
Inner finger and toe opposable .......... _Phyllomedusa_, p. 203.
Inner finger and toe not opposable .......... _Agalychnis_, p. 206.
β. Tongue scarcely free behind. Ecuador .......... _Nyctimantis
rugiceps_, p. 206.
_b._ Tips without discs. Without parasphenoid teeth, but head peculiar
in shape. Mexico .......... _Pternohyla fodiens_, p. 207.
_C._ Pupil rhomboid. Without parasphenoid teeth. Large discs. Head
helmet-shaped. Brazil .......... _Corythomantis greeningi_, p. 207.
_Hyla._–The pupil is horizontal. The tympanum is distinct or hidden. The
tongue is entire or slightly nicked in its hinder margin, which is more or
less free behind. The fingers and toes are provided with typical adhesive
discs.
This is the largest genus of all Amphibia, containing about 150 species,
and its distribution coincides with that of the whole family. Many of the
species are very closely allied to each {190}other, differing only in small
points, for instance in the extent of the webs to the fingers and toes, the
configuration of the vomerine teeth, the size and appearance of the
tympanic disc, and the relative length of the hind-limbs. In some of the
West Indian, and in one Brazilian species, _H. nigromaculata_, the upper
surface of the head is rough, owing to the cutis being involved in the
cranial ossification. Bony or perhaps only calcareous deposits in other
parts of the skin are rare, but are notably developed in _H. dasynotus_ of
Brazil, in which they extend from the head to the sacrum, rendering the
skin immovable.
Many are capable of changing colour to a great extent, and it is a popular
error to suppose that all tree-frogs are green, although this colour is
perhaps the most common in the arboreal kinds.
[Illustration: FIG. 37.–_Hyla arborea_, var. _meridionalis_. South European
Tree-frog, × 1.]
_H. arborea._–The tongue is rather round, slightly nicked behind, and can
be protruded but little. The tympanum is distinct, but small. The upper
parts are grass-green, quite smooth and shiny owing to the skin being
covered with a film of moisture; the under parts are yellowish-white and
granular, flesh-coloured or rosy on the thighs. Total length of large
females 2 inches. This, the Tree-frog of Europe, has an enormous range,
namely, from Morocco, France, and the south of Sweden, across the whole of
Europe and Asia Minor to Japan and Southern China.
{191}Several varieties have been described: the _typical_ or _European
form_ is ornamented with a narrow black stripe, which, beginning at the
nose, extends backwards along the side of the body to the groin, where it
generally forms a hook turned upwards. This black colour forms the ventral
boundary of the green, and is itself narrowly seamed with white on its
upper border.
In the south of France, the Iberian Peninsula, Morocco, and the Canary
Islands the black lateral stripe is often absent; this is the var.
_meridionalis_. In Spain and Portugal both forms are found in the same
localities.
In the Asiatic, chiefly in the eastern specimens, the lateral stripes tend
to break up into irregular spots, vanishing altogether towards the groins;
this var. _savignyi_ s. _japonica_ occurs also on most of the Mediterranean
islands.
_H. arborea_ can change colour to a great extent, mostly in adaptation to
its immediate surroundings, but ill health and moulting may also influence
it. The change is slow. The usual colour is green, brightest on bright,
sunny hot days, dull when the sky is overcast, or when it is windy and
showery. Day and night have no influence upon the colour-changes. The hue
of the green agrees mostly with that of the foliage on which the frog
happens to take its rest, for instance a field of Indian corn, birch-trees,
or oak-trees. I once received a consignment from Saxony. When the box with
moss was unpacked, they were of the dullest greenish-grey; they were put
into a wired-off corner of the yard and were given the freshly cut branches
of a lime-tree to sit upon. On the following morning I at first looked for
most of the frogs in vain. The leaves had withered and all those frogs
which sat upon the dark brown branches had put on a light brown garb,
mottled with darker patches.
Another specimen, one of several which were at liberty in a greenhouse,
took to resting on the frame of the window-pane, in a corner where putty,
glass, and discoloured white paint met; in the morning it was always of a
mottled leaden colour, but during the nocturnal hunting it was green. In
the winter, the window-corner being of course cold, the frog remained
stationary for several months, but kept the leaden grey colour, until one
day in the early spring it was mottled with green, and soon after it joined
its green mates.
Liebe observed a half grown tree-frog which he kept in Gera {192}during the
winter in a glass with water-cress. While the temperature was near freezing
the frog sat in the water, very lethargic, breathing perhaps once every
quarter of an hour. Its colour was light green. When the water-cress was
cut and removed, the frog darkened and became at last quite a discoloured
grey. When the water-cress was put back, the creature reassumed the light
yellowish-green colour, remaining in its lethargic condition until it
became lively in the spring sunshine.
The European tree-frog spends most of its time in the summer, after the
pairing is over, in trees, often in the very crowns; but the neighbourhood
of even a small patch of Indian corn has still greater attractions. There
are all sorts of green insects to be caught, there are fair chances of
coming across the common Cabbage White, a butterfly which the tree-frog
loves, and last not least the large luscious leaves afford a firm foothold,
and the axillae between stalk and broad-based leaves are just the places
for the frog to slip into, where nobody can find it. During the day they
mostly sit still, on the keen look-out for passing insects, which, when
they settle within reach, are jumped at; otherwise they have first to be
stalked. The jump is quite fearless, regardless of the height above ground;
there is the leaf upon which the prey sits, and even if this leaf be
missed, there are others, and one of them is sure to be struck by some of
the discs of either fingers or toes. If the fall is broken by the toes, and
the new leaf or branch is very elastic and bends down, then there are some
frantic antics to be gone through until the frog has settled itself again.
Then the large blue-bottle, or the butterfly, is devoured at leisure, wings
and all being poked in with the assistance of the little hands. But the
real hunting-time is the night.
During a shower the frog shifts its position to the under side of the leaf,
or into a less slippery position, and during continuous wet it descends
into the grass, or it takes to the water. Its greatest enemy is the Grass
Snake, which prefers it to anything else, not minding the poisonous
secretion of the skin, which is sharp enough to produce sneezing or even
temporary blindness when incautiously brought into the human eye.
The male has an internal vocal sac, which, when inflated, bulges out the
whole throat into a globe, much larger than the head. The voice is a sharp
and rapidly-repeated note, something {193}like "epp-epp-epp," or "creck,
creck, creck," with more or less of an _a_ sound. It is uttered at any time
of the day, more frequently at dusk, and of course chiefly during the
pairing season. This tree-frog suffers from the reputation of being a good
weather-prophet, and it is for this reason often kept in confinement, the
orthodox abode being a muslin-covered glass jar, with a hole to put flies
through, water and plants at the bottom, and a little ladder to sit upon.
The prophesying is of the usual popular unreliable nature, although the
little creature, provided it is a male, often sounds its voice on the
approach of a shower, or when there is a thunderstorm in the air. During
continuous fine weather it sits on the top of the ladder, or is glued on
near the rim of the glass, while on wet and dull days it is less active,
and may keep nearer the ground or in the water. There is a German rhyme
which well expresses the prophet's reliability by its ambiguity:–
Wenn die Laubfrösche knarren,
Magst du auf Regen harren.
When the tree-frogs croak, you may wait for rain. Sometimes it does come
true.
Tree-frogs are not very intelligent, although they have a keen sense of
locality; but they are nice pets, being easily kept, and have a pretty
appearance. There is a record of one which lived for twenty-two years in
confinement.
The pairing begins soon after the frogs reappear from their hibernation in
the ground; in Germany in the month of May. The congregating males make a
great noise and take to the water before the females, which join them when
ready to spawn. The male grasps his mate near the shoulders, and the pair
swim about together, sometimes for days, until the eggs are expelled. These
are laid in small clumps of 800 to 1000, which soon swell up and remain at
the bottom of the pond. The larvae are hatched in ten days; two days later
the adhesive sucker below the throat appears, and after another two days a
pair of thread-like external gills are developed. The tadpoles, which reach
a length of 2 inches, owing to the long tail, which is nearly three times
as long as the body, metamorphose in about twelve weeks, and the baby
tree-frogs, scarcely half an inch in length, hide in the grass for the next
two years, until they are about half grown, not reaching maturity until the
fourth year.
{194}Since many pairs congregate in the same pool, and each produces up to
one thousand eggs, most of which are hatched, the neighbouring meadows
sometimes literally swarm with tiny tree-frogs. Nevertheless the adults are
comparatively rare and are very local.
_H. carolinensis_ s. _lateralis_ of the South-Eastern States of North
America greatly resembles _H. arborea_ in general appearance, size, and
habits. But the head is more pointed, and the vivid green of the upper
parts is separated from the yellowish white under surface by a conspicuous,
pure white line, giving the little creature a very smart and neat
appearance. According to Holbrook, it ascends trees, but most commonly lies
upon broad-leaved water-plants, like _Nymphaea_, and in fields of Indian
corn. Motionless during the daytime, they emerge in the morning and evening
from their hiding-places, and become very brisk and noisy, often repeating
their single note, which is not unlike that of a small bell. When one
begins, hundreds take it up from all parts of the corn-field.
Among other tree-frogs of the South-Eastern States may be mentioned _H.
squirella_, 1½ inch in length, which is very changeable in colour,
generally olive above with darker spots and bars on the limbs, and with a
white upper lip. It lives in trees, sheltering in the bark. _H. femoralis_
of the same size, without the white lip, lives high up in the trees of the
dense forests of Georgia and Carolina.
_H. versicolor_ is one of the most delicately coloured species of Eastern
North America, extending northwards into Canada. It is about 2 inches long.
Its colour passes within a short time from dark brown or olive grey to pale
delicate grey, almost white, occasionally retaining a few large darker
patches on the back, and delicate cross-bars on the limbs. A small portion
of the sides and the posterior part of the belly are bright yellow. The
skin is granular, owing to the presence of small warts which produce an
acrid secretion. It is said to be found in trees, or about old stone fences
overgrown with lichens, the colour of which it resembles to perfection. It
becomes very noisy towards the evening, in cloudy weather or before rain,
the voice consisting of a liquid note, terminating abruptly, like
"l-l-l-l-luk." My own captives fully bear out this statement of Holbrook's.
Settled motionless during the day upon a piece of bark in a shady
{195}corner, but occasionally uttering the quaint and rather faint note,
they become very lively in the evening, catching insects by long jumps, or
investigating the hollows of decaying mossy stumps. Their general colour is
then spotless, almost silvery grey. In the day-time they are sometimes
suffused with delicate green.
The propagation has been studied by Miss M. H. Hinckley.[85] They pair in
shallow pools, in Massachusetts, in May. On the 10th of that month eggs
were attached singly, and in groups, on the grasses resting upon the
surface of the water; first drab-coloured, they became lighter in a few
hours. Some larvae escaped from the gelatinous envelopes on the following
day, the others on the third day; they clung to the grasses by means of
their prominent suckers. The head and body were cream-coloured, with olive
dots, and averaged ¼ inch in length. Gills appeared on the fourth day, to
disappear again during the four following days, first those of the right,
then those of the left, side; the suckers became less conspicuous, and the
general colour turned into deep olive-green, with fine golden dots on the
upper and lower surfaces. The eyes were of a brilliant flame-colour. On the
eleventh day the suckers or "holders" had disappeared, and the hind-limbs
were indicated by small white buds. By June 5th, _i.e._ the twenty-seventh
day, the toes developed the terminal discs; the mottling of gold had given
way to a uniform olive or pea-green. Movements of the future arms beneath
the skin appeared on the 28th of June, at the age of seven weeks. The arms,
mostly the right one first, were thrust out on the 2nd of July; the fins of
the tail were absorbed rapidly, and towards the end of the seventh week the
nearly transformed creatures began to leave the water. The young frogs
changed colour rapidly, in adaptation to their surroundings, but the four
specimens which survived were never all found to be of the same colour
during the next three months. They first lived upon Aphides, later upon
flies, and they were alert nocturnally. About the beginning of October they
left the fronds of their fernery and nestled away in the damp earth, which
they left only when the temperature rose above 60° F.
_H. vasta_ of Hayti is the giant of the tree-frogs, reaching a length of 5
inches. In order to support its great weight the {196}adhesive discs of the
fingers and toes are of a surprising size, about as large as a threepenny
piece. The skin is covered with small warts, and forms a peculiar fold on
the hinder surface of the fore-arm and on the tarsus, and small flaps near
the vent. The colour is grey above, blackish on the head, with a brown band
between the eyes; the under parts are flesh-coloured, the throat with black
spots.
_H. maxima_, of the forests of British Guiana, is scarcely less gigantic,
and is distinguished by a projecting rudiment of the pollex, while the
adhesive discs are smaller than the tympanum. The skin forms folds on the
arms and tarsus, like those of _H. vasta_, in addition to a triangular flap
at the heel. The general colour is reddish-brown above, sometimes with a
dark vertebral line, the under parts are whitish and covered with large
granules; the throat of the male, which has an inner vocal sac, is brown.
_H. faber_ of Brazil is closely allied to the last species, but the skin of
its upper parts is quite smooth. There is a small tarsal fold, and one
extending from the upper eyelid to the shoulder. It is light brown above,
with darker marks which form a conspicuous vertebral line, transverse bars
on the hind-limbs, and a few irregular, scattered, vermicular or linear
marks on the head and body. The adult, when put into a strong light, will
rapidly turn pale; at night the longitudinal stripe on the back and the
bars on the hind-limbs become very distinct; the under parts are white, and
exhibit a beautiful orange tinge. This is the famous "_Ferreiro_" or
"smith." As will be seen from the following graphic account by Dr.
Goeldi[86] of Para, this species doubly deserves its name of _faber_, not
only in virtue of its voice, but also because of the marvellous
nest-building habits recently discovered.
"The _Ferreiro_ is common in the Province Rio de Janeiro, more frequently
still in the mountain regions of the Serra dos Orgãos than in the hot
lowland. Its voice is one of the most characteristic sounds to be heard in
tropical South America. Fancy the noise of a mallet, slowly and regularly
beaten upon a copper plate, and you will have a pretty good idea of the
concert, given generally by several individuals at the same time and with
slight variations in tone and intensity. When you approach the {197}spot
where the Tree-frog sits, the sound ceases. But keep quiet, and it will be
resumed after a few moments. You will discover the frog on a grass-stem, on
a leaf of a low branch, or in the mud. Seize it quickly, for it is a most
wonderful jumper, and it will utter a loud and shrill, most startling cry,
somewhat similar to that of a wounded cat."
The "Smith" makes very regular pools, in the shallow water of ponds, or
nurseries for the tadpoles surrounded by a circular wall of mud. Dr. Goeldi
has watched the building process during a moonlit night: "We soon saw a
mass of mud rising to the surface carried by a Tree-frog, of which no more
than the two hands emerged. Diving again, after a moment's time, the frog
brought up a second mass of mud, near the first. This was repeated many
times, the result being the gradual erection of a circular wall. From time
to time the builder's head and front part of body appeared suddenly with a
load of mud on some opposite point. But what astonished us in the highest
degree was the manner in which it used its hands for smoothing the inside
of the mud wall, as would a mason with his trowel. When the height of the
wall reached about 4 inches, the frog was obliged to get out of the water.
The parapet of the wall receives the same careful smoothing, but the
outside is neglected. The levelling of the bottom is obtained by the action
of the lower surface (belly and throat principally) together with that of
the hands."
The male takes no active share in the construction of the nest, but will
suddenly climb up the wall of his home, and then upon the back of his busy
mate. The building operation may take one or two nights, and is performed
in the most absolute silence; the croakers around are all males clamouring
for a mate.
The eggs are laid during one of the following nights, and are hatched some
four or five days later, the parents keeping hidden in the neighbourhood of
the nursery. Heavy rains may destroy the walls, and thus prematurely
release the tadpoles.
It is only owing to such keen observers and lovers of nature's fascinating
ways that the breeding habits of some Brazilian Hylidae have become known.
_H. nebulosa_ s. _luteola_ also living in Brazil, is yellow above, with
brown dots; the sides of the belly and thighs have {198}transverse bluish
bars, the under parts are whitish. Its size is under 2 inches. Goeldi has
often found it in the sheaths of decaying banana-leaves. It glues the lumps
of eggs on to the edges and to the inside of the withered leaves, where
even during the hot hours of the day sufficient coolness and moisture are
preserved. These lumps are enveloped in a frothy substance, in which the
nearly metamorphosed tadpoles can be watched wriggling. If these are put
into water, all will die in a few hours.
_H. polytaenia_ deposits its eggs in free lumpy masses on water-plants. It
is a small creature, little more than 1 inch in length, light olive above,
with numerous brown parallel longitudinal bands on the body and limbs. A
dark, white-edged band extends from the nose along the side of the body.
The heel has a short flap of skin. The male has an internal vocal sac.
_H. goeldii_ is a most interesting form, leading to the allied genus
_Nototrema_. Boulenger[87] has described a female which was captured by
Goeldi in January on the Serra dos Orgãos. It is about 1½ inch long. The
whole surface of the back is occupied by a layer of twenty-six pale yellow
eggs which are 4 mm. in diameter. The skin of the back is expanded into a
feebly reverted fold, which borders and supports the mass of eggs on the
sides, thus suggesting an incipient stage of a dorsal brood-pouch. Owing to
the great amount of yolk, the young are probably able to remain upon the
mother until they are nearly metamorphosed.
[Illustration: FIG. 38.–_Hyla goeldii._ × 1. Female with eggs in the
incipient dorsal brood-pouch.]
_H. coerulea_ s. _cyanea_ is one of the largest Australian green
tree-frogs, ranging from the South to the very North of Australia. The
discs are as large as the fully-exposed tympanum. There is no projecting
rudiment of the pollex, but a slight cutaneous fold borders the inner side
of the tarsus. The skin is smooth and shiny, always a little moist, and
studded with numerous rather large pores on the nape and shoulders; this
somewhat thickened region forms a prominent fold which begins behind the
eyes. The belly and the under parts of the thighs are granular as in most
Hylidae. The male has an internal vocal {199}sac; and during the breeding
season, which seems to occur during our autumn and winter, develops brown
rugosities on the inner side of the first finger. The tongue is round,
slightly notched behind and free enough to be protruded a little.
[Illustration: FIG. 39.–_Hyla coerulea._ Australian Tree-frog (from
photographs). Length of the large specimen 4.2 inches. The upper right
specimen with vocal sac inflated.]
The alternative specific names are most unfortunately chosen, as they apply
only to spirit-specimens. During life this tree-frog exhibits a
considerable amount of colour-changes. The normal colour is bright green
above, white below. A conspicuous feature of this species is the frequent
occurrence of white specks or spots, which are probably due to the
deposition of guanine, a peculiar white colouring matter. The spots appear
in any part of the green skin, and are quite irregular in their
distribution. Sometimes they remain for weeks in the same place, or they
disappear after a few days and others appear. They are in no way connected
with the shedding of the skin, nor do they indicate ill-health. _H.
coerulea_ lives well in confinement, and becomes tame enough to take food
from one's fingers, even when sitting upon the hand. Some of mine took to
living during the daytime in a small box, preferring a crowded condition in
companionship with {200}Natterjacks. Others squeeze themselves into the
most uncomfortable cracks, while others again prefer the broad leaves of
_Philodendron_. A favourite place for two or three at a time is the
funnel-shaped spaces formed by _Bromelia_-plants. Those specimens which are
hidden in the box or in the hollows of rotten stumps are, almost without
exception, dull, very dark brownish olive, while those on the Bromelias
assume exactly the sombre dull green of its leaves. Lastly, those which sit
in the light, exposed places, no matter if upon a leaf, on a white stone,
or upon a board, are emerald-green, especially beautiful on hot, sunny
days;–and they are not always averse to the full glare of the sun. When
squatting upon a flat surface, such as a broad leaf, they tuck the
fore-paws under the head like a cat, and with half open eyelids, the pupil
contracted to a tiny slit, so that the golden iris is exposed, they remain
motionless during the day. They take food when offered, but at night they
roam about, either hopping on the ground, or making enormous leaps from
leaf to leaf, sometimes deliberately stalking some choice insect, and
patiently climbing up a stem, hand over hand. At night their whole aspect
is changed. The colour is saturated green, the eyes are transformed into
round, projecting shiny black beads, and the head is erect. The ludicrously
dreamy, complacent look has given way to wide-awake alertness. They take
all kinds of living food. When they find an earthworm, they first look at
it, bending the head sharply down, lift themselves upon the fore-limbs and
then pounce upon it, nipping the prey with the jaws, and then poking it
down deliberately with the hands. Cockroaches are simply lapped up, and
disappear in the twinkle of an eye. Mealworms, wood-lice, butterflies and
moths, flies and spiders are taken. The stomach of a specimen in the
Dresden Museum, from the Aru Islands, contained some four or five young
freshwater Crustaceans of the genus _Sesarma_. They fortunately do not
molest smaller frogs of their own kind and of other species. Like many
Amphibia they like a change of diet, and ultimately refuse their food if it
is unvaried. To my surprise my largest specimen, which measures a little
more than 4 inches, takes snails, _Helix virgata_, half-a-dozen at a time,
and on the following day, not during the night, vomits the sucked-out
shells in a lump, like the pellets of birds of prey. During this rather
painful-looking procedure the whole tongue and about half an {201}inch of
the everted gullet are protruded out of the mouth, and are then slowly
withdrawn. After having roamed about all night, they return to their
respective resting-places, where each individual is sure to be found in
exactly the same spot, day after day. They do not mind being looked at, but
if taken up and put back they avoid that place for perhaps a week, taking
shelter somewhere else.
Both sexes have a voice, but that of the female is only a grunting noise,
while the male inflates its gular sac and sends forth a sharp cracking
sound, which can turn into a regular bellowing like the gruff barking of an
angry dog. They bellow at any time of the year, frequently on the approach
of a shower or during a thunderstorm. Certain noises will also induce them
to bark. The rattling produced by the syringing of the greenhouse, sawing
of wood, hammering, the raking of the gravel, or even the scraping of boots
on the gravel-path is liable to start one of the males, and the others are
sure to chime in.
According to Fletcher, _H. coerulea_ and _H. aurea_ lay their eggs in round
white frothy patches, which float in the water, chiefly during the months
of August and September; but when the spring months are very dry, the
pairing is delayed until the following January. Several other Australian
species of _Hyla_, e.g. _H. ewingi_, spawn at any time of the year if the
conditions are favourable. They attach their eggs to submerged blades of
grass or to twigs.
_H. aurea_ is one of the commonest and most beautiful species, occurring
throughout Australia and Tasmania, excepting of course in the large
deserts. It has the appearance and restlessness of a water-frog, is not
unlike _Rana esculenta_, and grows to about three inches in length. The
tympanum is very distinct, but rather small. The fingers are without a
pollex-rudiment, the tarsus has a fold along its inner edge. The adhesive
discs are decidedly small. The male has two internal vocal sacs, which
bulge out sideways. The skin is smooth and shiny. The under parts are
white; the upper parts are, speaking generally, a mixture of blue and
olive, with blue or brown spots, but spirit-specimens give no idea of the
beauty which this changeable species can assume. Sometimes the same
individual is saturated blue and green, with several longitudinal stripes
of burnished copper along the back; a few minutes later the stripes glitter
{202}like gold, and in other moods the whole upper surface is mottled blue,
green, and brown. My specimens often went into the water and did not climb.
The food is said to consist chiefly of other small frogs in preference to
insects.
_Nototrema_ differs from _Hyla_ in so far as the female has a pouch on the
back for the reception of the eggs. This bag is formed by an infolding of
the skin; it opens backwards in front of the vent, it has a sphincter and
is permanent, although it distends to larger dimensions when in use. An
initial stage of such a pouch is possessed by _Hyla goeldii_ (Fig. 38). The
pupil is horizontal, the tongue can be protruded but little; the tympanum
is free, and the adhesive discs of the fingers and toes are well developed.
These "marsupial frogs," of which about half-a-dozen species are known,
live chiefly in the tropical forest-region of South America, notably from
Peru to Venezuela.
_N. marsupiatum_ is green with darker blue-green spots, or with
longitudinal patches which are each surrounded by a whitish or yellow seam
of little dots. The limbs have cross-bars. Total length about 2½ to 3
inches. The eggs of this species are comparatively small and numerous. The
very small tadpoles have no external gills, and escape from the pouch to
finish their metamorphosis in the water.
_N. testudineum_, about 3 inches in length, is of a uniform lead-colour,
but is lighter beneath. The skin of the back is studded with stellate
calcareous deposits, a peculiarity which is alluded to in the specific
name.
_N. oviferum_ is brown above, with darker patches on the sides of the body
and with cross-bars on the limbs. The last two species and _N. fissipes_ of
Brazil, near Pernambuco, carry their young in the pouch until the
metamorphosis is completed. This long nursing-period necessitates a great
amount of food-yolk in the eggs, and this enlargement in turn implies a
considerable reduction in their number. The female's load consists of about
fifteen eggs only, but these are of a great size, namely one-eighth of the
length of the mother's body.
_N. pygmaeum_, in Venezuela, is a tiny creature. The female, just one inch
in length, carries only from four to seven eggs. It looks then "as if it
carried a sac filled with a few gigantic balls." This species is further
worthy of note on account of the opening of the brood-pouch, which is a
longitudinal slit, whence a kind {203}of thin and slightly elevated ridge
or fold of the skin extends on to the neck. The suggestion, that this seam
is burst open, in order to set the full-grown young free, instead of their
passing through the existing opening, is scarcely credible.
These Neotropical tree-frogs seem to be rare, and females with embryos are
of course still more uncommon, so that the best account of their structure
is still that given by Weinland[88] of _N. oviferum_. How the eggs get into
the pouch has not yet been observed, but it is most likely with the help of
the male, immediately after fertilisation. The pouch forms two blind sacs
which extend forwards over the sides of the back. The eggs are large, 1 cm.
in diameter, and the enclosed embryos, or rather tadpoles, had a length of
15 mm., with a large amount of yolk still contained in the spirally wound
intestine. The first two gill-arches carried each a double thread, which
expanded into a funnel-shaped membrane, not unlike the flower of a
_Convolvulus_, and furnished with a capillary network; the stalk contained
muscular fibres. These most peculiar structures are of course the much
modified external gills. Those of _N. testudineum_ and _N. cornutum_ are
likewise bell-shaped.
_Hylella_ differs from _Hyla_ chiefly by the absence of vomerine teeth, and
consists of about half-a-dozen small species, about one inch in length. The
fact that two species live in Queensland and New Guinea, while the others
are natives of tropical America, suggests that this genus is not a natural
but an artificial assembly, an instance of convergent evolution.
_Phyllomedusa_, composed of about one dozen species of tree-frogs, is
characterised by the vertically contracted pupil, large adhesive discs, and
the opposable nature of the inner finger and of the hallux, the last joints
of which are like thumbs. The sacral diapophyses are strongly dilated. The
range of the genus extends from tropical Central America to Buenos Aires.
Most of the species are about 2 inches in length, blue-green to violet
above, with white purple-edged patches on the sides of the body; the under
parts uniform white, or with purple or brown patches. The male has a
subgular vocal sac. Some have more or less distinct parotoid glands. _Ph.
dacnicolor_ of Mexico is uniform green above, whitish below, and attains a
size of more than 3 inches. In _Ph. bicolor_ of Brazil, the skin of the
upper {204}parts is studded with calcareous deposits, and the parotoids are
large. It is blue-green above, purplish white below, the sides of the body
and limbs with white purple-edged spots.
_Ph. hypochondrialis_ has been found breeding freely in the Paraguayan
Chaco by Budgett,[89] from whose account the following notes have been
extracted. This brilliantly coloured frog is green above, which colour may
become brown-grey or bluish at will; below, white and granular. The flanks
are scarlet, with black transverse bars, and the plantar surfaces are deep
purplish black. Total length about 1½ inch.
The "Wollunnkukk," as it is called by the Indians, from the call of both
male and female at pairing time, is extremely slow in its movements, and is
active only at night. At this time, if it is seen by the aid of a lantern
as it slowly climbs over the low bushes and grass, it is very conspicuous.
In the daytime, however, nothing is seen but the upper surface of the body
as it lies on the green leaf of a plant. It has a remarkable power of
changing its colour to harmonise with its surroundings, and can effect a
change from the brightest green to light chocolate in a few minutes. The
skin is also directly sensitive to light; for if the frog is exposed to the
sun while in a tuft of grass in such a way that shadows of blades of grass
fall across it, on removal it will be found that dark shadows of the
grasses remain on the skin, while the general colour has been raised to a
lighter shade. Its food consists largely of young locusts. The ovaries on
each side are divided into five distinct clusters. The rectum has a large
saccular diverticulum, which is very heavily pigmented.
In the breeding season–December to February–this beautiful frog collects in
considerable numbers in the neighbourhood of pools. During the night-time
they call incessantly to one another, and produce a sound as of a dozen men
breaking stones, well imitated by the native name.
The eggs are enclosed in batches in leaves near the margin of the water.
Budgett has been able to watch the whole process of oviposition and
fertilisation. He found, at 11 P.M., a female carrying a male upon her
back, wandering about in search of a suitable leaf. At last the female,
climbing up the stem of a plant near the water's edge, reached out and
caught hold of the {205}tip of an overhanging leaf, and climbed into it.
Both male and female held the edges of the leaf together, near the tip,
with their hind-legs, while the female poured her eggs into the funnel thus
formed, the male fertilising them as they passed. The jelly in which the
eggs were laid was of sufficient firmness to hold the edges of the leaf
together. Then moving up a little further, more eggs were laid in the same
manner, the edges of the leaf being fastened together by the hind-legs, and
so on up the leaf until it was full. As a rule, two briar-leaves were
filled in this way, each containing about 100 eggs. The time occupied in
filling one leaf was three-quarters of an hour.
Development proceeds rapidly. Within six days the embryo increases from the
2 mm. of the egg-diameter to 9 or 10 mm. When it leaves the leaf it is a
transparent glass-like tadpole, whose only conspicuous parts are the eyes.
These are very large and of a bright metallic green colour, so that when
swimming in the water all that is seen is a pair of jewel-like eyes. The
newly-hatched tadpole has also a bright metallic spot between the nostrils
somewhat in front of the pineal spot. This is the point which touches the
surface of the water when the tadpole is in its favourite position. Whether
it is a protective coloration, or some mechanical arrangement for holding
the surface, Budgett could not make out.
The egg contains a great amount of yolk; the rest of the jelly-like
contents of the egg becomes fluid, so that towards the end of embryonic
life the larva comes to lie quite freely within a membranous capsule. The
external gills appear on the third day, and reach their greatest size on
the fifth, when these bright red filamentous organs extend beyond the vent.
By the time the tadpoles are ready to be hatched these gills have quite
disappeared, there is a median spiracle, and the lungs are shining through
the transparent body-wall. Five weeks later, _i.e._ six weeks after the
eggs were laid, the tadpole is 8 cm. long, glossy green above, rosy and
silvery below, and the hind-limbs protrude. The young frog at the close of
its metamorphosis is two-thirds the length of the adult, and at this time
acquires the red flanks barred with black.
The first account of the breeding of _Phyllomedusa_ was given by v.
Ihering[90] concerning _Ph. iheringi_ of Southern Brazil.
{206}"_Phyllomedusa_ does not lay its eggs in the water, although the larva
develops in that element, but in the open air in masses 50 millim. long by
15-20 broad, between leaves hanging over the water. Willows are frequently
used for that purpose. The egg-mass contains rather large white ova,
wrapped up between two or three leaves in such a way as to be completely
enveloped save an inferior opening. My attempts at rearing the eggs failed
owing to the leaves drying up; but I am assured that the tailed larvae may
be seen wriggling in the gelatinous mass. As at a later period the latter
is found empty, we must infer that the larvae drop into the water below.
The eggs are found only on plants hanging over stagnant water."
[Illustration: FIG. 40.–A branch with eggs of _Phyllomedusa iheringi_, × 1,
enveloped in the leaves. (After v. Ihering.)]
"The adult animal is a stupid creature, and will let itself be taken
without attempting to escape. Their moderately loud voice resembles
somewhat the sound produced by running the finger nail over the teeth of a
comb. Only during the breeding season, in the month of January in Rio
Grande do Sul, do these frogs make their appearance; at other times not one
is to be seen, probably because they establish themselves high up in the
trees."
_Agalychnis_, with two species in Central America, is practically like
_Hyla_; but the pupil is vertical, and the tongue is extensively free
behind.
_Nyctimantis_ differs from either by its round tongue, which is not nicked
behind, and is almost completely adherent, much resembling that of the
Discoglossidae. The sacral diapophyses are but slightly dilated. The only
species, _N. rugiceps_, lives in Ecuador, and grows to nearly three inches
in length. The head is large and rough owing to the skin being involved in
the cranial ossification. It is further peculiar in its coloration, the
under parts being chestnut-brown instead of whitish. The upper parts are
olive-grey or brown.
The following four genera, each represented by one or two species
{207}only, much resemble each other in the curious shape of the head, which
forms a flat projecting snout, used probably for digging in rotten wood in
search of insects. There is a peculiar degradation in the extent of
dentition of the palatal region. _Diaglena_ and _Triprion_ are the only
Hylidae which possess a longitudinal row of parasphenoid teeth. _Diaglena
petasata_ of Mexico and _D. jordani_ of Ecuador have, moreover, a
transverse row of teeth on the palatine bones in addition to those on the
vomer.
_Triprion petasatus_ of Yucatan has parasphenoid and vomerine teeth. The
head is a bony casque, with strong superciliary ridges, the skin being
extensively ossified. The mouth forms a flat snout, owing to the long
projection of the upper over the lower jaw. The skin of the back is smooth
brown with darker spots; the under parts are uniform whitish. The male has
a subgular vocal sac. Like _Diaglena_ and _Corythomantis_ they possess
adhesive discs on the fingers and toes, and climb trees. The total length
of this curious creature is 2 inches.
_Corythomantis greeningi_ of Brazil has a similar head. The vomers alone
carry teeth, besides of course the maxillae. The pupil is rhomboid. The
tongue, as in the two previous genera, is roundish, scarcely free. General
colour above olive, with darker freckles; the sides are studded with
whitish tubercles; the under parts are whitish. The male is devoid of vocal
sacs. Total length 3 inches.
_Pternohyla fodiens_ of Mexico approaches the previous three genera by the
curious shape of the head and prominent upper jaw, although these features
are not so exaggerated. The dentition agrees with that of _Corythomantis_
and other normal tree-frogs. The fingers and toes are not provided with
discs, in conformity with the burrowing, not climbing, habits of this
creature. The next following three genera connect the Hylidae with the
Cystignathidae. The sacral vertebrae are but slightly dilated.
[Illustration: FIG. 41.–Head of _Corythomantis greeningi_. × 1. (After
Boulenger, _Cat. Batrach._)]
_Acris._–The adhesive discs are very small, the tympanum is indistinct. _A.
gryllus_, the only species, inhabits the greater part of Eastern and
Central North America, extending northwards into Canada. It attains a
length of 1½ inch. The coloration is very changeable, in adaptation to the
surroundings. As {208}a rule it is brown, with a more or less reddish or
grey ground-tone, ornamented with dark brown or blackish irregular,
longitudinal patches,one of which is bordered with light green,and there is
often a light vertebral streak. The legs are cross-barred, the under parts
are whitish brown and yellowish. The male has a subgular vocal sac, and its
most remarkable feature is the voice, which closely resembles the noise of
a cricket or of certain grasshoppers. Holbrook describes it as a merry
little frog, constantly chirping like a cricket, even in confinement. It
frequents the borders of pools, and is often found on the leaves of aquatic
plants, rarely on the branches of such low shrubs as overhang or dip into
the water. When disturbed it takes long jumps, and hides at the bottom of
the pond. Insects are secured by leaps. It can easily be domesticated, and
takes food readily from the hand. Sprinkling them with water never fails to
make them more lively and noisy. Appearing in April in great numbers, they
are said to vanish early in the autumn for hibernation. The tadpoles are
metamorphosed by the end of August.
_Chorophilus._–The fingers and toes are provided with very small adhesive
discs. The sacral diapophyses are very slightly dilated. About seven
species occur in North America, chiefly in the Southern States, one, _Ch.
cuzcanus_, in Peru. _Ch. ocularis_ is the smallest of the frog-kind known,
and lives in South Carolina, frequenting damp places, the vicinity of
stagnant pools, water-plants or low shrubs, for instance the "myrtle,"
_Myrica cerifera_. I once had two of these tiny creatures less than
three-quarters of an inch in length. They were very active, and took
surprisingly long leaps, jumping distances of 2 feet, but could not be kept
through the winter, although they took minute insects readily enough. The
head is narrow, long and pointed; the upper parts are of a rich
chestnut-brown with a bronzy gloss. The upper jaw is white; a black band
extends along the sides of the head and body. The under parts are yellowish
white.
_Ch. ornatus_ is another inhabitant of the South-Eastern States; its name
refers to the dark brown patches on the back and sides, bordered with
golden yellow, upon a reddish-brown ground-tone, while the under parts are
silvery white with fine grey spots. This frog, a little more than one inch
in length, lives on land in dry places, preferably in corn-fields, has no
voice, and, except during the pairing season, carefully avoids the water.
{209}_Thoropa._–The fingers and toes are free, the tips simply swollen and
not dilated into discs. Closely allied to _Chorophilus_. _Th. miliaris_, of
Brazil, the only species, has very long toes. The head is broad and flat.
The upper, nearly smooth surface of the body is flesh-coloured, with brown
marblings; the limbs are cross-barred; the under parts whitish, granular on
the belly. The male is devoid of vocal sacs. The total length may be 2
inches. Hensel has published the following notes of this species, under the
name of _Hylodes abbreviatus_. The tadpoles are quite flat, their bellies
forming a kind of sucking disc, so that these creatures, even before the
appearance of the hind-limbs, can quickly wriggle up vertical walls of
stones, provided these are covered with a little water. In correlation with
this habit, the root of the tail is not compressed laterally, but is as
broad as it is high, and the usual vertical fin is restricted to its distal
third. On the proximal portion of the tail the ventral fin is flattened and
broadened out so as to form almost the continuation of the peculiar
disc-like belly. The anal opening is not a projecting tube, but is a
flattened transverse slit.
FAM. 5. CYSTIGNATHIDAE.–This is one of the largest families, and also one
of the least satisfactory. Its numerous members, more than 150, exhibit
such a versatility in adaptation to circumstances (there are aquatic,
terrestrial, arboreal, and burrowing species), with a corresponding
development or loss of anatomical characters which we should like to rely
upon as taxonomic marks, that the numerous genera not only run into each
other, but also get entangled with those of other families. In fact the
whole family is ill defined. It can be characterised as follows:–The
shoulder-girdle is arciferous; the sacral diapophyses are cylindrical or
but slightly dilated; the metasternum has either a bony style or it forms a
cartilaginous plate; the terminal phalanges, although they sometimes carry
adhesive discs, are never claw-shaped.
The last statement is, of course, intended to separate the Cystignathidae
from the Hylidae, of which, however, the three genera _Thoropa_,
_Chorophilus_, and _Acris_ stand on debatable ground (cf. p. 186, Hylidae),
while, on the other hand, most of the Australian genera, notably
_Chiroleptes_, have unmistakably dilated sacral diapophyses. The difference
from the Pelobatidae can in this case be one of degree only.
{210}The Cystignathidae may be said to represent the Ranidae in Notogaea.
Some of them can be distinguished from the true, typical frogs solely by
the arciferous type of the shoulder-girdle and sternum. There is in both
families the same adaptive versatility, the same amplitude in the formation
of the fingertips, the occasional slight dilatation of the sacral
diapophyses, the same range in the configuration of the omo- and
meta-sternum. In fact, young Ranidae, before the firmisternal character is
assumed, are indistinguishable from Cystignathidae, and the latter would
turn into Ranidae if they could be induced to consolidate their sternal
apparatus.
The geographical distribution of the Cystignathidae is suggestive of their
being an old family, most of whose members have reached a high stage of
morphological development. The overwhelming majority inhabit the
Neotropical region, a few forms extending into tropical Central America and
into the Antilles; the rest, some twenty species only, are confined to the
Continent of Australia and to Tasmania.
The family name is rather a misnomer. It is taken from the genus
_Cystignathus_, which is, or rather was, characterised by the peculiarly
broadened lower jaw, hollowed out by the vocal sacs; but this generic name
had to give way to that of _Leptodactylus_, in obedience to the often
senseless rule of priority. The family is composed of three subfamilies.
SUB-FAM. 1. HEMIPHRACTINAE.–Teeth are carried by both jaws, the vomers and
the palatine bones; or by the palatines and parasphenoids in _Amphodus_.
The vertebrae are opisthocoelous, devoid of ribs, and the sacral
diapophyses are not dilated. The shoulder-girdle and sternum are strictly
arciferous. The omosternum is very much reduced; the metasternum forms a
cartilaginous plate. The tongue is slightly free behind. The tympanum is
distinct. Three genera, with eight species, all inhabitants of South
America.
_Hemiphractus._–The head is large; the upper surface of all the cranial
bones appears pitted, owing to most of the covering skin being involved in
the ossification. The temporal fossa is bridged over or roofed in by the
fronto-parietal and the squamosals, so that the orbit is completely
encircled by bone, as in _Pelobates cultripes_. The terminal phalanges are
simple and are not dilated into discs. The teeth of the lower jaw are
{211}very small and numerous. The tongue is round and very small. _H.
scutatus_, the only species, living in Ecuador and Colombia, is a frog-like
creature, with a large helmet-shaped head. Total length 2½ inches.
_Ceratohyla_ has the same kind of helmet-shaped head, and the orbit is
likewise enclosed by bone, but the terminal phalanges are claw-shaped and
carry regular adhesive discs. This genus, the five species of which live in
Ecuador, bears undoubted resemblances to the Hylidae. In _C. proboscidea_
the upper eyelid is produced into a little upright fold, as in
_Amphignathodon_ and some species of _Nototrema_ and _Ceratophrys_ among
Cystignathidae. The snout is produced into a long, compressed, bifid
appendage, and the heel carries a triangular flap. In _C. bubalus_ the
partly ossified helmet sends out a pair of diverging processes, formed by
the squamosals, extending backwards and sideways from the concave and
ridged interorbital spaces. The tip of the snout and the tips of the
divergent horns form an equilateral triangle, and the whole head bears a
striking resemblance to some of the fossil Reptiles from the Elgin
Sandstone, e.g. _Triceratops_. Total length 3 inches.
_Amphodus wucheri._–The only species of this genus has been found near
Bahia. It has teeth on the palatine bones and five series of small teeth on
the parasphenoid, but none on the vomers. The teeth of the mandible number
about eleven on each side and decrease in size towards the symphysis. The
tympanum is distinct; the heart-shaped tongue is free behind. The cranial
bones are only slightly pitted. The skin is smooth above, chocolate-brown,
spotted with yellow, and with a yellow band on the sides of the body
beginning with the upper eyelid and ending in a broad patch above the vent.
The under parts are yellowish white.
SUB-FAM. 2. CYSTIGNATHINAE.–The upper jaw alone is provided with teeth.
Vertebrae procoelous. The twenty-seven genera of this sub-family have been
arranged in the following key, merely for convenient determination.
I. American genera.
_A._ The metasternum forms a cartilaginous plate without a narrow
handle. The pupil contracts into a horizontal slit.
_a._ The terminal phalanges are bifurcated, Y-shaped, and provided
with large discs; the tympanum is distinct; the omosternum is absent
.......... _Centrolene geckoideum_, Ecuador.
{212}_b._ The terminal phalanges are T-shaped and carry discs. The
omosternum is cartilaginous.
α. Discs divided by a dorsal groove.
With vomerine teeth .......... _Elosia_, 3 species in Brazil.
Without " .......... _Syrrhopus_,[91] 9 species, South
America.
β. Discs undivided.
With vomerine teeth .......... _Hylodes_, p. 214.
Without " .......... _Hylopsis._
_c._ Terminal phalanges simple, pointed, or with very small discs.
First finger opposed to the others .......... _Pseudis_, p. 213.
_d._ Terminal phalanges simple, without discs.
α. Tympanum hidden. A large, flat gland on each side of the body
.......... _Cyclorhamphus fuliginosus_, Brazil.
β. Tympanum distinct. Head rough, entirely bony. ..........
_Calyptocephalus_, p. 215.
γ. Tympanum hidden or absent. Tongue roundish, not nicked, free
behind. Toes webbed. .......... _Telmatobius_, 6 species in Western
South America.
δ. Tongue heart-shaped, free. Toes webbed. ..........
_Ceratophrys_, p. 215.
ε. Tongue round, free behind. Toes webbed. With two tooth-like
projections in the lower jaw. .......... _Lepidobatrachus_, p. 218.
ζ. Tongue entire, or slightly nicked, free behind. Toes free.
.......... _Borborocoetes_, 11 species in Western South America.
η Tongue entirely adherent Tympanum distinct. .......... _Zachaenus
parvulus_, Brazil.
_B._ Metasternum with a bony style.
_a._ Pupil horizontal
α. Terminal phalanges T-shaped, with discs. Tympanum distinct.
.......... _Plectromantis_, 2 species in Western South America.
β. Terminal phalanges simple; tips not dilated into regular discs.
1. Tympanum distinct.
Sacral diapophyses slightly dilated. .......... _Edalorhina_, 3
species in Ecuador and Peru.
Sacral diapophyses not dilated. .......... _Leptodactylus_,
p. 218.
2. Tympanum indistinct or hidden, _Paludicola_, p. 220.
_b._ Pupil vertical. Terminal phalanges simple and not dilated.
Chili.
α. Tongue slightly nicked .......... _Limnomedusa macroglossa._
β. Tongue entire, but free behind. Digits very long. ..........
_Hylorhina silvatica._
II. Australian genera. The terminal phalanges are simple and not dilated.
The omosternum and metasternum are cartilaginous, the latter forming a
plate, semi-ossified only in _Heleioporus_.
{213}_A._ Pupil contracted into a horizontal slit.
_a._ Omosternum rudimentary. Vomerine teeth present.
α. Tympanum distinct .......... _Phanerotis fletcheri._
β. Tympanum hidden .......... _Cryptotis brevis._
_b._ Omosternum present. Vomerine teeth vestigial. ..........
_Crinia_, 4 species.
_c._ First finger opposed to the others .......... _Chiroleptes_,
p. 221.
_B._ Pupil contracted into a vertical slit.
_a._ Omosternum rudimentary. Vomerine teeth absent. ..........
_Hyperolia marmorata._
_b._ Omosternum fully developed. Vomerine teeth present.
α. Tympanum distinct. Toes webbed. .......... _Mixophyes
fasciolatus._
β. Tympanum hidden. Toes webbed. .......... _Heleioporus_, p. 222.
γ. Tympanum indistinct. Toes free or slightly webbed. ..........
_Limnodynastes_, p. 222.
_Pseudis_, widely distributed over South America, consists of four species
which have the appearance of long-legged frogs. The fingers, of which the
first is opposed to the others, are free; the long toes are fully webbed.
The tympanum is exposed.
_P. paradoxa_ is absolutely aquatic, floating in pools, and is extremely
shy. In life it is most beautifully coloured with bronze, bright green, and
black markings above; underneath it is shiny yellow, with brown spots on
the body and stripes on the thighs. Within a few minutes after death all
the brilliant colours of the smooth skin of the back turn into dull uniform
brown, with indistinct darker spots. Total length of the adult from 2 to 2½
inches. The specific name refers to the peculiar shape and monstrous size
of the larva or tadpole.
One of the larvae described and figured by Parker measures 10⅓ inches in
length, the head and body taking up 3⅓ inches. The spiracle lies on the
left side and the hind legs are ½ inch long, just breaking through the
skin. The vent is median. The huge tail is very thick and muscular, and is
furnished with a high, irregularly shaped dorsal and ventral fin, the whole
organ measuring 4 inches dorso-ventrally. Another larva, or rather tadpole,
in the national collection is older, and although still very large, namely,
7 inches long, has fully developed hind-limbs 3 inches long; the fore-limbs
are less than half that size, the left protrudes through the spiracle,
while the right has broken through the skin. The dorsal and ventral fins of
the tail have much shrunk; the whole organ, 5 inches long, is gradually
tapering to a point like the tail of ordinary tadpoles. By the time that
the {214}tadpole is nearly ready to leave the water, its whole bulk is
reduced to less than one-fifth that of the largest tadpole. It measures
from snout to vent only 1½ inch (in the 7-inch tadpole this distance is
fully 2 inches), and the tail, devoid of fins, is reduced to 2 inches in
length. Instead of the solitary left spiracle there are now two, one on the
ventral side and a little in front of the base of each arm, the border of
each hole being continued by a peculiar semilunar fold.
[Illustration: FIG. 42.–_Hylodes martinicensis._ 1, an egg with embryo
about seven days old; 2, another, twelve days old; 3, the young Frog just
hatched; all × ¾; 4, adult male × 1. (After Peters.)]
_Hylodes._–The numerous species, nearly fifty, of this tropical American
genus exhibit several anatomical differences. The tympanum is sometimes
indistinct or hidden, in which case the Eustachian tubes are generally very
narrow. The fingers are free, and carry discs, like the toes, which are
sometimes slightly webbed. The males have a subgular vocal sac, producing a
loud, or whistling, voice. The general appearance is that of land- and
tree-frogs; the size is small, mostly between 1 and 2 inches.
_H. martinicensis_ is about 1½ inch in length. The ground-colour is pale
yellow-grey, with a large brown patch on the nape, which colour is
continued over the back in the shape of more or less coherent or dissolved
patches. A dark brown stripe runs along the middle of the sides. The limbs
are barred with brown, the under parts are whitish. This species, known by
the vernacular name of "_coqui_" inhabits many of the West Indian islands,
_e.g._ Barbadoes, Martinique, Porto Rico, and Hayti. It has become famous,
as it was the first instance known of a frog which undergoes its whole
metamorphosis within the egg. The pairing takes place on land, in the
months of May and June, when the female lays about twenty eggs, which are
enveloped in a foamy mass and glued on to a broad leaf, or hidden in the
axillae of Iridaceous plants. The mother seems to remain in the
neighbourhood watching the eggs, which are {215}large, measuring 4-5 mm. in
diameter. Dr. Gundlach, a resident in Porto Rico, was one day, in the month
of May, attracted by sounds like those of a young bird, and found three
males and one female of this species sitting between two large leaves of an
orange-tree. He put them all into a glass vessel and soon saw a pair in
embrace. The female laid about twenty-five pale straw-coloured eggs. The
embryo develops neither gills nor gill-openings, but a large
well-vascularised tail, by means of which, being immersed in the watery
fluid contained within the egg, it seems to breathe. After twenty-one days
the tadpole, having used up all the available yolk and fluid, and most of
its own tail, bursts the egg-shell and hops away as a little frog of 5 mm.
in length, but still with a stumpy white tail, which is quite absorbed
within the same day.
This species has several times made its appearance in the tropical houses
of Kew Gardens. It seems to have bred and vanished again.[92]
_Calyptocephalus_ is remarkable for the dermal ossification of the cranium,
which has assumed the greatest possible extent. It affords a curious
parallelism to _Triprion_ and other Hylidae, which are likewise Central
American forms. Only two species are known; _C. gayi_ of Chili, and _C.
testudiniceps_ of Panama. They are large, thoroughly aquatic creatures, 5
to 6 inches in length, with huge heads. The tadpoles grow to an enormous
size. One specimen of _C. gayi_ in the National Collection is more than 6
inches in length, the tail taking up more than half of the total: the
spiracle lies on the left side, the vent on the right, and the hind-limbs
are still half enveloped in a kind of fold of the skin.
_Ceratophrys_ is a genus of some ten toad-like species, living in South
America, from Guiana to Argentina. The generic name alludes to the peculiar
modification of the eyelid, which in most species is developed into a
triangular, upright, but flexible appendage. The head, in conformity with
the huge mouth, is very large. The tympanum is rather indistinct, sometimes
quite hidden. Several of the species have a large dorsal shield, which is
produced by a thick ossification of the cutis, but is not fused with any of
the vertebral processes. The male has a vocal sac. _C. dorsata_ s. _boiei_
of equatorial Brazil is a monster toad, reaching {216}a length of 6 inches.
The upper eyelid is transformed into a triangular horn, whence a cutaneous
ridge extends all along the side of the back, meeting that of the other
side above the vent. There is no osseous shield on the back. The tympanum
is hidden. Ground-colours, orange or green, with sharply marked dark brown
or blackish patches.
_C. cornuta_, in Northern Brazil, lacks the dorsal shield, but has horned
eyelids and a visible tympanum. Its coloration renders it one of the most
beautiful toad-like creatures known. The ground-colours are green, black
and brown, with an orange-yellow stripe over the head and back. All these
colours are most pleasingly blended and arranged in marbled patches or
stripes radiating from various centres, as, for instance, from the eyes
towards the circumference of the mouth, the slit of which they pass, the
same line of the pattern being continued upon the lower jaw. The whole
surface makes the impression of a gay but exquisitely harmonious carpet.
The under parts are yellow, inclining to white towards the middle.
[Illustration: FIG. 43.–_Ceratophrys ornata._ Horned Toad. × ¾.]
_C. ornata_ has a dorsal shield. The tympanum is just visible, and the
eyelids form only low but sharp-edged projections. This is likewise a
beautiful toad, living chiefly in Uruguay, Northern Argentina, and
Paraguay, where it is universally known as the "escuerzo," one of the
Spanish words signifying a toad. Its size rarely surpasses 4½ inches. The
ground-colours are greenish and yellow, with large dark green patches on
the back, decreasing in size on the flanks.
{217}[Illustration: FIG. 44.–_Ceratophrys ornata._ (From _Nature_.)]
Each of these insular patches is surrounded by a narrow line of white and
yellow dots, interspersed here and there with lines of rusty brown or red.
The object of this elaborate carpet-like pattern is concealment. These
toads–and this applies to all the species,–bury themselves half in the
ground, preferably in the grass, where they are well-nigh invisible. If
there is not enough green vegetation, they throw, with their feet, little
lumps of earth upon their backs, the skin of which becomes at the same time
more crinkled and assumes duller tones. There the creature lies, perfectly
concealed, betrayed only by the metallic glittering eyes, waiting for some
unfortunate creature to pass into the trap represented by the enormous
mouth, which opens and shuts with lightning-rapidity and with an audible
snap. They seem to live chiefly on frogs, and sometimes they turn
cannibals. Two specimens were brought over to me from Buenos Aires by a
friend, in a well-closed basket with moist soil at the bottom, but only one
was visible on arrival. The other was inside the {218}larger one, and could
still be felt through the soft body. This same cannibal took large-sized
frogs greedily, one or two for a meal, swallowing them whole and then
sinking back into its lair, which it scarcely ever left, except for an
occasional soaking bath in its water-pan, especially before shedding its
skin. It lived for many months in the same enclosure with a pantherine
toad, _Bufo mauritanica_, of equal bulk, until one morning I found the
Moroccan half swallowed and almost lifeless in the mouth of the American,
whence it was rescued with difficulty. It came round after a few hours, but
never fully recovered, lingering on for weeks; the skin was changed to a
lead-colour so far as it had been swallowed and partly dissolved by the
gastric juices, and soon began to develop festering ulcers.
These "horned toads" make a squeaking noise when teazed, not at all loud or
strong in proportion to their size. Ill-tempered individuals jump at their
aggressor and can inflict rather painful nips. They hibernate during the
dry season in the ground.
_Lepidobatrachus._–Large teeth in the upper jaw, and two large tooth-like
projections in the lower jaw near the symphysis. Vomer toothless. Sacral
diapophyses not dilated. Tongue round, and free behind. Tympanum distinct.
Great development of the membrane-bones on the head, and a weaker
ossification in the skin of the back, recalling that in _Ceratophrys_. The
eyes are closely set together, and the nostrils take up the most elevated
portion of the head. Pupil horizontal. The two species of this genus were
discovered by Budgett[93] in the Paraguayan Chaco. _L. asper_ lives
continually in muddy pools, floating with just the eyes and nostrils above
the surface. If disturbed it slowly sinks to the bottom, leaving no ripple.
It feeds largely on _Bufo granulosus_. Total length from about 3 inches.
The skin of the upper parts is tubercular, tough, and of a dull leaden
colour; the tips of the toes are horny. _L. laevis_ is smooth and slimy,
"with the organs of the lateral line showing clearly upon it," a feature
elsewhere known to exist in _Xenopus_ and _Leptobrachium_ only.
_Leptodactylus_ = _Cystignathus_.–Some twenty species inhabit tropical
America, from Central Mexico to Buenos Aires. The fingers and toes are not
webbed and end mostly in points; only a few species, e.g. _L.
hylaeodactylus_, having small adhesive discs. {219}The legs are long and
the general appearance is very much like that of an ordinary frog.
One of the commonest and prettiest Brazilian species is _L. ocellatus_,
which is characterised by a number of longitudinal glandular folds on the
back and flanks. The colour of the upper parts is olive-brown, that of the
prominent folds is yellowish white, interspersed with black spots. The
under parts are yellowish white, with blackish marblings on the throat. The
males have a sharp black spur on the inner carpal edge and one on the
rudiment of the thumb. Total length about 4 inches.
According to Hensel[94] the spawning takes place in Rio Grande do Sul after
hibernation. The voice of the male is then very loud, resembling the sound
made by a carpenter chopping a beam. They repair to ponds and produce a
cup-shaped puddle, about 1 foot in width, by raising a wall of mud, which
separates the inner water from that of the pond. The tadpoles remain in
this nursery until the spring-rains demolish it and set the young ones
free. Drought causes the drying up of these water-pans and subsequent
destruction of the brood.
_L. mystacinus_ is another Brazilian species, about 2 inches in length. Its
specific name refers to the dark brown stripe which runs from the tip of
the mouth through the eye to the tympanum. This species is thoroughly
terrestrial, and never enters the water. It digs a cavity, the size of an
ordinary tea-cup, under stones or rotten trunks, always in the
neighbourhood of ponds and just so high above the water that the latter can
rise up to the nest in the rainy reason. The straw-coloured eggs are laid
in this cavity, and are enveloped in a foamy, sticky mass, like the
well-beaten white of an egg. The young tadpoles seem to live on this froth
until the rains set them free. When, however, the rains delay and a drought
kills the broods of other less circumspect species, these tadpoles, still
provided with gills and long tails, remain in their moist nest or withdraw
further beneath the rotten stumps, huddled together in large numbers until
the next rainy season.
Similar nursing habits have been recorded of _L. albilabris_, which
inhabits Mexico, Cuba, and several other West Indian islands. The same
applies to _L. typhonius_. Gundlach found eggs {220}of this "Sapo" in
Puerto Rico on the 4th of November; on the 25th the young showed the first
signs of hind-limbs, on the 3rd of December of fore-limbs, and on the 7th
of the same month they began to climb out of the water.
_Paludicola_ is a semi-aquatic genus with some eighteen species, ranging
from Mexico to Patagonia and across the Andes into Chili. Some of them have
a peculiar gland on the lumbar region, or large, flat warts on the back,
sometimes arranged in longitudinal folds. The toes are slightly webbed, or
free, according to the more or less pronounced aquatic habits.
[Illustration: FIG. 45.–_Paludicola fuscomaculata_, × 1, with vocal sacs
partly filled.]
_P. fuscomaculata_, an inhabitant of Southern Brazil, Paraguay, and
Uruguay, is a short-limbed frog, with spreading slender toes and a small
head. There are shovel-shaped, black, horny tubercles on the metatarsus.
The general colour is olive above, with darker markings and confluent
white-edged spots; the limbs are cross-barred; the lumbar glands are black,
with a white margin in front. The male has a vocal sac. Budgett[95] gives
the following account of its habits:–
The peculiar cry, which is so constantly heard in the neighbourhood of
shallow pools in the Paraguayan Chaco, and resembles that of a kitten, is
produced by the alternate inflation of throat and abdomen. When fully
inflated, the frog appears to be the size of a golf-ball, but, if startled,
instantaneously shrinks to one-fifth of that size, so that it seems to have
vanished. It has also the power of ventriloquising. The food consists
largely of water-beetles. In the spawning time it was found at night
floating on the surface of pools in the distended condition, and crying to
the females in a most mournful way. On coming to the surface it fills its
lungs with a few gasps, greatly distending the walls of the abdomen, and
then drives the air into the vocal sacs, causing them to become distended
as the body collapses, and giving rise to a kitten-like cry.
The eggs are chiefly laid in January, and are found embedded {221}in a
frothy mass floating upon the surface of the water. The eggs measure only 1
mm. and are without pigment, and with extremely little yolk. The larvae
become free-swimming within from eighteen to twenty-four hours after the
first segmentation. When ready for hatching they wriggle their way through
the froth to the water below, and hang into it from the floating froth.
_P. biligonigera_ s. _notata_, in Brazil, lacks the lumbar gland, the place
of which is marked by a black spot. The upper parts are olive, with darker
marblings and a dark lateral stripe. The male has a black throat and two
external vocal sacs. Hensel found the eggs, in Rio Grande do Sul, in
September, forming a frothy mass of the size of a fist, floating between
grass upon the water near the margin.
The following three genera may serve as Australian examples, especially
since we are indebted to Baldwin Spencer for interesting observations made
on their habits in Central Australia.[96]
_Chiroleptes_, of which six species are known, is easily recognised by the
first finger, which is opposed to the others. The sacral diapophyses are
slightly dilated. The general shape is that of a thick-headed, rather stout
land-frog or of a tree-frog. The tympanum is distinct, and the toes are
only half webbed, or even less, except in _Ch. platycephalus_, in which the
toes are entirely webbed and the tympanum is indistinct. This species is
about 2 inches long, uniformly olive-green above, with a few tubercles on
the otherwise smooth skin. Other species rather resemble the European
Natterjack in coloration.
Spencer's account is as follows:–"In Central Australia _Ch. platycephalus_
seems to prefer the hard clay pans rather than sandy creeks, as the
sand-beds of the latter are too loose for the formation of the burrow. We
came across the animal first when encamped by the side of a very shallow
clay pan, the floor of which was deeply cracked with the sun's heat. Around
the edge were withered shrubs of _Chenopodium nitrariaceum_, and it was at
the base of these that the black fellows looked for the burrow. In the
hard-baked clay were imprints made by the frog as it burrowed, and about a
foot underground we came across the animal, puffed out into a spherical
shape, and just filling up a cavity, the walls of which were moist but not
wet. The ground {222}was so hard that it had to be chipped away. When one
side of the burrow was opened, the frog remained perfectly still; its lower
eyelid was drawn up over the eye and was very opaque, giving rise to the
belief amongst the blacks that the animal is blind. In the sunlight, after
a short time, it opened its eyes.
"On squeezing the body, water was forced out of the cloaca; this was
accumulated principally in the urinary bladder. On cutting the body open it
was seen that there was a certain amount of water in the subcutaneous
spaces, but that the greater portion, which caused the great swelling-out
of the body, was contained in the body-cavity itself; and it was also
observed that the lungs were considerably distended and lengthened, their
apices lying right in the pelvic region. They contained air and not water,
but their outer faces were bathed with the water in the body-cavity." The
larvae and tadpoles probably develop with extreme rapidity, soon to
aestivate as very small frogs.
_Heleioporus_ has a calcified metasternal plate and slightly dilated sacral
vertebrae. The two species have a toad-like appearance, owing to their
stout bodies, short limbs and conspicuous parotoid glands. _H.
albopunctatus_ is mottled whitish red and brown above; it extends from
Western into Central Australia. _H. pictus_ is olive, with darker
marblings, and is distinguished by a light vertebral line. It is likewise
found in Central Australia, and it extends into Victoria and New South
Wales. Spencer found it in swarms after heavy rains, the specimens being
much swollen and distended with caterpillars and beetles. They looked as if
they were simply gorging themselves with food preparatory to returning
again to their long aestivating condition.
_Limnodynastes_ is one of the commonest genera in Australia. The six
species have the habits and appearance of stout frogs or smooth toads. _L.
dorsalis_ seems to range through the whole of Australia, from east to west,
and looks like the European _Pelobates_. The skin is smooth, but with an
elongated white gland extending from beneath the eye to the shoulder, and
another glandular complex on the thigh. The upper parts are mottled
olive-brown, often with a light vertebral line. The under parts are
whitish, with brown spots. The male has a vocal sac. One of the specimens
in the National Collection contained a half-grown _Heleioporus
albopunctatus_ in its stomach.
{223}Concerning the pairing and the other habits of the Anura of New South
Wales we have some valuable notes by J. J. Fletcher.[97] He observes that
Australian frogs spawn whenever they are ready, and when the very irregular
conditions of moisture will allow it, but that they are not all ready at
the same time, _i.e._ they have no fixed period of the year.
_Limnodynastes_, _Hyla aurea_, and _H. coerulea_ deposit their spawn in the
water, in more or less irregular floating patches, which look white and
frothy. The period extends from July to May, and is at its height in August
and September; but if there is a spring-drought vigorous spawning may be
looked for about the middle of January, when heavy showers are likely to
occur. _Crinia_ and several _Hyla_, e.g. _H. ewingi_, spawn at any time of
the year. The eggs form small submerged bunches, enclosed in a transparent
jelly, attached to the blades of grass or twigs of dead branches in the
water.
_Pseudophryne_, a genus closely resembling _Crinia_, but on account of the
absence of teeth in the lower jaw relegated to the Bufonidae, spawns during
the Australian summer and autumn. The numerous ova of _P. australis_ and
_P. bibroni_ are laid separately, not in the water, but under stones, or in
the débris of reed- and grass-tussocks, on the edge of a pool.
The larvae of _Pseudophryne_ and others have often to depend upon the next
following rain, sometimes waiting for months to be released from the eggs,
wherein they have so far developed. But the tadpoles, once hatched,
probably do not bury themselves; they either metamorphose or die.
The males of _Mixophyes_ and _Hyla_, grasp the females in the axillary
region; those of _Limnodynastes_, _Hyperolia_, _Crinia_, and _Pseudophryne_
throw their arms round the inguinal or lumbar region.
For some three months during the winter, commencing about May, the frogs,
like lizards and snakes, resort to shelter under logs and stones, beneath
which they are then to be met with in a more or less sleepy condition.
During the hot and very dry periods many bury themselves in the drying-up
mud, which becomes very hard, and does not release them until the next
rains. They croak during showery times of the year. There is no evidence
that any Australian species live in the high _Eucalyptus_-trees.
{224}_Hylopsis platycephalus_, of South America, is of importance as
forming a link with the Dendrophryniscinae, owing to the very small size of
the teeth in the upper jaw. There are no vomerine teeth. The fingers and
toes are webbed, and furnished with discs. The very small omosternum and
the metasternum are cartilaginous. The pupil is horizontal. Total length,
about or under 1½ inch.
SUB-FAM. 3. DENDROPHRYNISCINAE.–The two Neotropical genera of this
sub-family are characterised by the entire absence of teeth. The toothless
condition of the upper jaw is really the sole character which separates
them from the Cystignathinae, taken as a whole. The suppression of the
tympanum and of the Eustachian tubes in _Batrachophrynus_, and the fully
webbed toes of _B. macrostomus_ indicate complete adaptation to aquatic
life. The absence of the omosternum in _Dendrophryniscus_, the absence of
vomerine teeth, the dilated phalangeal tips, the entire and quite adherent
tongue, are all features which likewise occur in some of the
Cystignathinae, and therefore cannot be urged against their affinity.
Lastly, the recently discovered South American genus _Hylopsis_ is, as
pointed out by Werner,[98] an intermediate link, owing to the extremely
small, scarcely visible teeth in the upper jaw.
_Dendrophryniscus brevipollicatus_ has been found in the neighbourhood of
Rio Janeiro. The head is depressed and triangular. The tongue is entire,
but free behind. The tympanum is suppressed. The omosternum is absent; the
metasternum forms a long bony style. The sacral diapophyses are
cylindrical. The terminal phalanges are simple, but carry dilated tips. The
first finger is rudimentary. The skin is nearly smooth, reddish brown
above, whitish below; the limbs are cross-barred.
_Batrachophrynus_ inhabits the mountains of Peru. The head is much
depressed and small, with the eyes directed upwards, as is usual in
essentially aquatic species. The tongue is large, circular, and entirely
adherent. The tympanum and the Eustachian tubes are suppressed. The
omosternum is cartilaginous, and the metasternum forms a cartilaginous
plate. The sacral diapophyses are cylindrical. The terminal phalanges are
simple, and carry no discs. The four fingers are short; the toes are
webbed. The male has no vocal sac. _B. brachydactylus_ has a {225}smooth
skin, olive-brown above with darker spots. _B. macrostomus_, 2 inches in
length, is distinguished by its larger size, and by its completely webbed
toes.
FAM. 6. ENGYSTOMATIDAE (Narrow-mouthed Toads).–_Firmisternia with dilated
sacral diapophyses._
SUB-FAM. 1. ENGYSTOMATINAE.–_Without teeth in the upper jaw._–Although
there are only about 60 species known, these have been grouped into more
than two dozen genera, many of which are represented by one or two species
only. The range of this sub-family is peculiar, namely, Neotropical and
Palaeotropical. _Scaphiophryne_ and _Rhombophryne_ are peculiar to
Madagascar; _Calophrynus_ occurs in the same island and in the Indian
region; _Xenobatrachus_, _Sphenophryne_, _Liophryne_, _Mantophryne_,
_Callulops_ and _Xenorhina_ live in New Guinea. _Breviceps_, _Cacosternum_
and _Hemisus_ are confined to Africa, while of _Phrynomantis_ two species
live in Africa, and the third in the Malay island of Amboina. Such freaks
of distribution indicate either that many of these genera are not
established upon very valid characters, or that their respective species
are instances of convergent evolution, and do not form natural genetic
groups.
Many of the members of this sub-family live upon ants and termites, and it
is a well-known fact, not restricted to the Anura, that this kind of fare
has a peculiar, modifying influence upon the structure of the mouth, teeth,
tongue, limbs, and various other organs. In the present case the tongue is
not much affected; it is, with few exceptions, more or less oval, not
nicked, but free behind; in the Indian _Glyphoglossus_ and in
_Rhombophryne_ of Madagascar only is it modified into a rather long and
grooved, almost double, apparatus.
A very common feature is the small size of the mouth and the formation of a
snout, which projects beyond the upper rim of the mouth and beyond the
nostrils. Such a prominent and pointed snout is well developed in
_Rhinoderma_, _Phryniscus_, _Calophrynus_, _Stereocyclops_, _Hypopachus_
and _Engystoma_. The mouth is very narrow in _Cacopus_, _Glyphoglossus_,
_Breviceps_, _Rhombophryne_, and _Hemisus_, all creatures which seem to be
confirmed eaters of ants and termites. However, it must not be supposed
that the mouth of all the genera is narrow, although this character, rather
marked in _Engystoma_, is now embodied in the name of the family. A
peculiar development of the palatal region {226}is possibly correlated with
this food. The palate is mostly toothless, but its skin is frequently
raised into a transverse fold, between or behind the vomers, and into a
second fold in front of the oesophagus; these folds are sometimes rather
hard and serrated or denticulated. The palatine bones carry true teeth in
_Rhombophryne_, and sometimes in _Callula_; in _Xenobatrachus_ the teeth
are reduced to two large pairs. The tympanum is usually hidden.
The shape of the body is generally very stout. The limbs are short, notably
so in _Glyphoglossus_, _Breviceps_, _Rhombophryne_, _Hemisus_,
_Stereocyclops_ and _Cacopus_. Others, for instance most species of
_Microhyla_, _Phryniscus_, _Callula_, and _Sphenophryne_, are of a very
slender build; and their limbs, instead of being short and well adapted to
digging, are long and may even be provided with typical adhesive discs,
supported by T-shaped phalanges, especially in the two genera last named,
and in _Scaphiophryne_ and _Phrynomantis_. However, none of the forms
provided with discs are known to be arboreal.
Exceptional diversity is shown in the shoulder-girdle and sternum. The
omosternum occurs only in _Rhinoderma_ and _Hemisus_. The metasternum is a
cartilaginous plate, very large in _Cacopus_, distinctly small in
_Breviceps_, and almost absent in _Hemisus_. The precoracoids and clavicles
show all stages from a well-developed condition (_Breviceps_,
_Rhombophryne_, _Hemisus_, _Rhinoderma_, _Phryniscus_ and _Brachycephalus_)
to complete absence. The circumstance that these bars are very weak in
_Melanobatrachus_, _Calophrynus_, _Scaphiophryne_ and _Hypopachus_, i.e. in
Palæo- and Neo-tropical genera, indicates a widespread tendency towards
complete suppression, a feature independently aimed at both in America
(_Engystoma_) and in the Old World.
Until we know something about the habits of the members of this much
diversified sub-family, it is idle to connect the various modifications
with each other, and thus, by correlation, to find out their meaning. Those
forms which possess well-developed discs on their fingers and toes are said
not to be arboreal. What is the true meaning of the prominent snout which
is not restricted to the digging forms? Most of the good diggers have
well-developed precoracoid bars, and the coracoids are distinctly
strengthened, but in _Glyphoglossus_ and in _Cacopus_ the precoracoids are
entirely {227}absent, and this loss is compensated for by exceptionally
strong coracoids.
On the whole, those genera are to be considered as the most primitive which
have undergone the fewest losses. Those with a complete shoulder-girdle,
with an omo- and meta-sternum and with simple phalanges, are necessarily
the older forms. One step farther back in another direction, the possession
of teeth on the palate, and on the upper jaw, leads to those genera which
have been separated off as DYSCOPHINAE, while teeth in the lower jaw
constitute the GENYOPHRYNINAE. Lastly, the firmisternal type has
necessarily been evolved from the arciferous condition, and there the two
Bufonid genera _Myobatrachus_ and _Rhinophrynus_, the former Australian,
the latter Mexican, with their narrow and scarcely overlapping epicoracoid
cartilages, seem to form a connecting link, although their ant-eating
habits, with concomitant modifications in structure, may be nothing but
cases of convergent evolution.
Key to the genera:–
I. American. _A_. with omosternum .......... _Rhinoderma_, p. 228.
_B_. without omosternum.
_a_. Pupil horizontal. Precoracoids present.
Sacrals strongly dilated. .......... _Oreophrynella._
" moderately " .......... _Phryniseus_, p. 230.
" feebly " .......... _Brachycephalus_, p. 231.
_b_. Pupil vertical.
α. Precoracoids feeble. .......... _Hypopachus._
β. " absent. .......... _Engystoma_, p. 231.
_c_. Pupil round. Precoracoids present .......... _Stereocyclops_,
p. 231.
II. Palaeotropical. _a_. Pupil horizontal.
α. Precoracoids present.
With palatal teeth. Madagascar. .......... _Rhombophryne._
Palate with dermal papillae. Africa. .......... _Breviceps_,
p. 232.
With palatal dermal folds. Madagascar. ..........
_Scaphiophryne._
With serrated palatal folds. Madagascar and India. ..........
_Calophrynus._
Palate smooth. New Guinea. .......... _Sphenophryne_ and
_Liophryne_.
β. Precoracoids absent.
Malacca .......... _Phrynella_, p. 233.
New Guinea .......... _Mantophryne._
Africa .......... _Cacosternum._
{228}_b_. Pupil vertical.
α. Precoracoids present. India. .......... _Melanobatrachus._
Africa. _Hemisus_, p. 232.
β. Precoracoids absent.
Tongue oval. India. .......... _Cacopus._
Tongue elliptical. India. .......... _Microhyla._
Tongue divided by a longitudinal furrow. India. ..........
_Glyphoglossus_, p. 233.
Fingers and toes with discs. Africa and Amboina. ..........
_Phrynomantis._
New Guinea. .......... _Callulops._
_c_. Pupil round. Precoracoids absent. Tongue round. India.
_Callula_, p. 234.
Tongue long, oval, with a deep groove. New Guinea. ..........
_Xenorhina._
_Note._–_Xenobatrachus ophiodon_, New Guinea. Palatine bones, each with
two large curved teeth. Otherwise imperfectly known.
_Rhinoderma._–Omosternum and precoracoids present. Palate without teeth.
Tympanum indistinct. Terminal phalanges simple, and not dilated. Tongue
heart-shaped, and free behind. Pupil horizontal. Habitat, Chili.
_Rh. darwini_, the only species, was discovered by Darwin, during the
voyage of the _Beagle_. Its total length is only 3 cm., or little more than
one inch. The shape is grotesque, as the skin is prolonged, beyond the very
small triangular mouth, into a false nose, _i.e._ a nose-shaped projection,
while the nostrils remain at their original place. The skin is smooth
above, granular on the under parts, and forms a triangular flap or
spur-shaped appendage on the heel. A glandular fold extends along the sides
of the body. The general colour is brown above, black below, with large
white patches, the latter colour being sometimes predominant on the throat
and chest. The male has a pair of internal vocal sacs, and the use of these
as nurseries for the young has made this species famous.
Espada[99] has given an elaborate account of this species, which lives on
the ground in shady woods. Its voice sounds like a little bell, and before
taking its short jumps, it erects itself vertically upon the hind-limbs.
The gular sac of the male opens by two slits, one on each side of the
tongue. Generally this sac does not extend beyond the middle of the chest,
but during the breeding time the eggs are put into it, whereupon it becomes
greatly distended, so much so indeed that it reaches back as far as the
groins; {229}dorsalwards around the flanks, almost to the vertebral
diapophyses; ventrally and forwards it reaches the chin. The walls of the
sac are of the same structure as the buccal lining, of which they are in
fact continuations. They adhere, at intervals, to the cutis and to the
pectoral and abdominal muscles.
The effect of the distension of the sac upon neighbouring organs is
twofold. First, the viscera are pressed back within the abdomen; this
disturbance is temporary and does not apply to all specimens; the feeding
in no way impeded. Secondly, a permanent change is produced in the
direction of the precoracoid bars, in such a way that each bar is curved
tailwards and rests with its ventral half upon the coracoid; owing to this
forcible bending the clavicles do not meet each other. There is, of course,
not so much space gained by this slight rearrangement of the
shoulder-girdle as Espada implies, but we have here, perhaps, an
illustration of direct correlation between two originally independent
organs, namely, shoulder-girdle and vocal sacs. Repeated distension of the
throat-bag during every breeding season, while the whole organisation of
the male is in a highly excitable condition, has pressed the clavicular
bars back, or rather has staved them in, and this at first pathological and
abnormal condition has at last become a fixed feature. It is to be
regretted that we know next to nothing about the habits, especially the
mode of breeding, of the other genera which likewise have reflected or very
feeble precoracoids and clavicles. Their weakness or even complete absence
must have a reason, or rather must have had a cause.
The pairing and oviposition, and the manner in which the eggs are conveyed
into the gular sac, have not yet been observed. Espada examined five males
with young, the number of which varied from five to fifteen. In one male
with eleven embryos the most developed tadpoles measured 13.5 mm. from the
snout to the end of the tail, and they were lying within the chest of the
father, the less advanced in the farther recesses of the bag. Three of the
tadpoles had already completely-formed fore- and hind-limbs, while the arms
were still hidden. The least developed were still globular, a proof that
the eggs are conveyed into the bag. Another male with fifteen embryos
looked as if it had gorged itself with the almost fully-formed tadpoles,
which measured 14 mm. They were quite irregularly distributed, and nowhere
{230}attached to the walls of the bag. None of them had horny
jaw-armaments, and not even the smallest specimens showed any traces of
gills, resembling in this latter character those in the female brood-pouch
of _Nototrema_. The intestine of the tadpoles is short and thick, coiled up
spirally and filled with yolk, certainly not with vegetable or other
foreign matter. Consequently the entire development from the egg to the
complete stump-tailed little creature is undergone within the pouch; and
this, after the young have escaped, probably shrinks back to its original
size and acts as a gular vocal sac.
_Phryniscus._–About ten species of this tropical American genus are known;
they extend from Costa Rica to Buenos Aires. They differ not inconsiderably
in various details. The tongue is elliptical, entire, and free behind. The
palate is smooth. The tympanic disc is absent. Fingers and toes more or
less webbed, sometimes with swollen tips, without, however, forming
adhesive discs. In a few species the first toe is quite indistinct. The
male has a subgular vocal sac. The mouth is small, and there is a short
snout. The general appearance varies much. _Ph. nigricans_ of Uruguay,
etc., is stout and has very short hind-limbs; the skin of the upper parts
is black, spotted with white, and covered with warts. Most of the other
species are slender, with larger hind-limbs and a perfectly smooth skin,
the coloration of which ranges from dull uniform brown, or black with
crimson markings, to bright green with purple spots. The under parts are,
as a rule, conspicuously coloured, a rare feature in Anura, the favourite
colours being orange, yellow, or even crimson, with or without black
patches.
_Phryniscus nigricans_ has been observed in Paraguay by Budgett,[100] who
gives the following account. This is a brilliantly coloured frog of
toad-like appearance, and about 33 mm. in length. The ground-colour is
black, with yellow spots or patches on the upper parts, the under parts are
black, with scarlet blotches, the palms of the hands and soles of the feet
are scarlet. At the breeding season both sexes utter a call-note which
consists of two clear musical "rings," followed by a long descending
"trill," like that of our British Greenfinch. This frog, which at ordinary
times is the slowest and boldest of frogs, is now active and excessively
shy. Swimming rapidly between the blades of grass, it climbs a {231}tuft,
and dilating its throat, repeats its call; but if in the least disturbed,
it is suddenly gone. The eggs are laid in quite temporary pools in grassy
ground, and form separate globules of jelly, which float on the surface of
the water, and are heavily pigmented. The development is excessively rapid.
The segmentation beginning at 10 A.M., they were hatched and wriggling
about by 7 A.M. the following day. They are probably washed down into
deeper pools by the retreating waters, and for this purpose the manner in
which the eggs are laid, namely, in separate globules of jelly, seems
especially suited.
_Brachycephalus ephippium_ in Brazil, the only species, is remarkable for
the development of a broad dorsal shield of bone, which is fused with the
processes of the second to seventh vertebrae, an ossification which
strongly resembles that of several species of the likewise Brazilian
_Ceratophrys_, a genus of the Cystignathinae.
_Stereocyclops_ is remarkable for the peculiar formation and protection of
the eyeballs. The anterior portion of the sclerotic is ossified into a
ring, which surrounds the transparent cornea. Another peculiarity lies in
the metasternum, which is so much broadened out that its cartilage is in
wide contact with the posterior edge of the coracoids. The epidermis is
everywhere "thickened by a chitin-like deposit." The only species, _S.
incrassatus_, found near Rio Janeiro, is an altogether aberrant creature.
Its general appearance recalls that of _Pipa_. The gape is large, with a
slightly projecting muzzle; the limbs are so short that the upper arms and
the thighs scarcely stand out from the broadened and flattened body, which
is leathery brown, with a narrow white median line extending dorsally from
the nose to the vent.
_Engystoma_, with about five species in the Southern States, Central and
South America, is the type-genus of the whole family, chiefly on account of
priority of name. It is fairly characteristic in so far as the mouth forms
a narrow, somewhat projecting snout; the precoracoids, the clavicles, and
the omosternum are absent, the palate is devoid of teeth, the lining of the
mouth forms a dermal ridge across the palate and another in front of the
oesophagus, the tympanum is hidden, the sacral diapophyses are moderately
dilated, and the tongue is elliptical and free behind. The pupil is
vertical. The fingers and toes are free, ending in slightly dilated or
blunt tips; the terminal phalanges are simple {232}and the hind-limbs are
short. The male has a subgular vocal sac.
The most northern species is _E. carolinense_, living in the Southern
United States, concealed under the bark of fallen trees or in old fences.
The skin is smooth, but forms a fold across the head, behind the eyes. The
general colour is brown, with light, whitish dots on the under parts. Total
length 1 inch.
_Breviceps_ is a South African genus with three species. The coracoids are
very strong and directed backwards, but so broadened that they form a long
and strong symphysis, touching in front that of the precoracoids, which
stand transversely and are well developed. The metasternum is cartilaginous
and decidedly small. The sacral vertebra has much dilated diapophyses and
is co-ossified with the coccyx. The general appearance is extremely stout
and short, the head being almost drawn into the nearly globular body, and
ending in a short snout with a small mouth-opening. The tongue is long and
oval, not nicked, but slightly free behind. _B. mossambicus_ is about 2
inches long, and looks like an overstuffed round bag, out of which the
short arms and legs project from the elbows and knee-joints only. The
tarsus is provided with a strong horny, spade-like tubercle, which enables
the creature to dig into the ground, and into the nests of termites, which
seem to be its chief food. Peters found this species in enormous numbers,
during the tropical rains, coming out of the ground, whither they withdraw
again completely for the dry season. The skin is smooth, reddish brown
above, with darker patches; the under parts are dull white, with a large
black patch on the throat.
_Hemisus_ is another African genus, with two species, _H. guttatum_ in
Natal, and _H. sudanense_ in East and West Africa. This genus is so
exceptional in its shoulder-girdle, that Cope separated it from all the
other Anura as a special sub-order Gastrechmia. The precoracoids are
extremely strong, and form a broad symphysis from which springs the long
cartilaginous omosternum; the coracoids are slender, very long, and
converge backwards to a narrow symphysis, and there is no metasternum. The
two symphyses are connected by a narrow cartilaginous median bar, probably
produced by the much modified epicoracoid cartilages. However, except for
the reverse development shown by the omo- and meta-sternum, it is easy to
connect this apparently quite anomalous shoulder-girdle of _Hemisus_ with
that of _Breviceps_. {233}(cf. Fig. 5, 5 and 6, p. 25). The sacral
diapophyses are slightly dilated; the fingers and toes are free and end in
points. The tongue is triangular, broader in front. The lining of the mouth
forms a transverse ridge across the palate, and another in front of the
oesophagus. The male has a subgular sac. The general shape is stout, the
head small and ending in a pointed snout. Colour brown above, with whitish
spots. Total length about 2 inches.
_Glyphoglossus_ has a peculiar tongue. It is elongated, notched behind and
in front, divided into two lateral halves by a deep groove; moreover, the
tongue is not only extensively free behind, but also slightly so in front.
The skin of the palate forms a transverse serrated ridge. The precoracoids
and the omosternum are absent; the metasternum is a well-developed
cartilaginous plate. The sacral diapophyses are moderately dilated; the
terminal phalanges are simple. _G. molossus_, the only species, is
olive-brown above, marbled on the sides; the under parts are uniformly
whitish. This creature, about 2 inches in length, looks like a roundish
bag, with a ridiculous, short face. The type-specimen, still the only one
known, was taken by Dr Theobald under the following circumstances:–"I had
halted one day within the tidal portion of the Irawaddy delta, to enable my
boatmen to prepare their dinner. One of my servants, having cooked his
rice, poured out the hot water as usual on the ground, and some of it went
down a hole that happened to be near the spot. No sooner, however, had the
hot water disappeared than out scrambled in great haste a fine
_Glyphoglossus_, only, alas! to be transferred to a collecting jar."
_Phrynella._–The tongue is heart-shaped, free behind. The palate is smooth
and toothless. The fingers and toes end in small discs, supported by
T-shaped phalanges; the fingers are free, the toes extensively webbed.
Precoracoids absent; metasternum cartilaginous. Pupil horizontal. Malay
Peninsula.
_Ph. pollicaris_ is dark olive brown above; an oblique yellow line runs
from the eye to the angle of the mouth; a pale yellow mark, across the
forehead, through the eyes, and down the sides of the body. A dark-centred
yellow patch on the anal region. The limbs are banded yellow and brown. The
under parts are brown, with paler specks, dark on the throat. Iris red
brown. The whole coloration changes considerably.
"They inhabit the hills of Perak from 3000 feet upwards, {234}and live in
holes in trees, which are so situated as to contain more or less
rain-water. They have a loud flute-like, musical note, which they utter at
irregular intervals, principally during the night. The form and size of the
hole in which they are seem to have a great deal to do with the loudness of
the note, as specimens when extracted from their holes have far more feeble
vocal powers than they had when in them. These frogs blow themselves out
with air, and look more like bladders than anything else. When inflated
they float on the surface of the water, and will remain motionless for a
long time, with legs and arms stretched out."[101]
_Callula._–The tongue is round, entire, and free behind. The palatine bones
form an acute, sometimes toothed ridge across the palate; two dermal
serrated ridges in front of the oesophagus. Fingers free, sometimes with
dilated tips, supported by T-shaped phalanges. Precoracoids and omosternum
absent; metasternum cartilaginous. Pupil round. About seven species in the
Indian region.
_C. pulchra._–The following account has been extracted from Mr. S. S.
Flower's observations:[102]–
This pretty creature inhabits most of the warm portions of the continental
Indian region, from India and Ceylon to South China and Malacca. The back
is a rich dark brown, divided from the yellow of the head by a narrow black
line which extends from eye to eye and forwards to each nostril. A
conspicuous yellow band runs from the eyes to the hind-limbs. The sides of
the body and the limbs are mottled yellow and brown. The under parts are
dirty buff; the throat of the male is black. The intensity of colouring
varies individually and from time to time, the contrast between the brown
and yellow being occasionally very brilliant. Total length up to 3 inches,
the male being the smaller sex.
"I have been told by both English and natives that this frog was unknown in
Singapore until some nine or ten years ago, when it was introduced by a
half-caste (why, it is not known), and that it rapidly spread about the
island. It is now well known as the 'Bullfrog' by the English in Singapore,
and detested for the noise it makes at night. The voice of these rotund
animals can be heard every night after heavy rain; it is {235}a deep
guttural croak, 'wau-auhhhh,' very strident and prolonged. The males croak
while floating on the surface of the water, the single vocal sac under the
mouth inflated like a globe, and the arms and legs extended. They can hop
well on land and are good swimmers. The skin is excessively slimy; the
secretion comes off profusely, and dries on the hand into a sort of white
gum, with a faint aromatic smell. This gum dissolves in hot water and
coagulates in cold. The general appearance of these frogs is very stout,
their girth being about twice the length from snout to vent. The tongue,
which is oblong in spirit specimens, in life is very elastic, assuming,
when extended, a vermiform shape and reaching about 4 cm. in length. They
appear after sunset, crawling on old wood and feeding on white ants."
SUB-FAM. 2. DYSCOPHINAE.–_With teeth in the upper jaw._
This small group of nine genera, with scarcely more than one dozen species,
all with one exception living in Madagascar, has been separated by
Boulenger from the Engystomatinae merely on account of the presence of
teeth on the upper jaw and on the vomerine margin of the palatine bones. He
himself remarks that _Calluella_ may be considered a toothed _Hypopachus_,
and _Plethodontohyla_ a toothed _Callula_. These are obvious cases of
convergent analogy. Except for the teeth, the Indian _Calluella_ would be
merged into the American _Hypopachus_, and this would present an instance
of the most puzzling geographical distribution. In the case of the other
two genera, one Indian and Malayan, the other Malagasy, no such suspicion
would arise, since there are many other instances of such a coincidence of
distribution. There is the same divergence or unsettled condition in the
modification of various parts in the Dyscophinae as in the Engystomatinae.
The precoracoid bars are weak and curved backwards, and closely pressed
against the strong coracoids, in _Dyscophus_, _Calluella_ and _Platypelis_,
while these elements are reduced to unossified bars, and the clavicular
portions completely lost, in _Plethodontohyla_ and in _Phrynocara_. The
omosternum is absent and the metasternum is small in all except
_Dyscophus_, in which both these parts are exceptionally well developed and
large, although remaining unossified. The palate of _Dyscophus_ and
_Calluella_ is provided with curious, serrated dermal folds like those
which are so common in the Engystomatinae; and well-developed discs on the
fingers and toes, supported by T-shaped phalanges, are {236}possessed by
_Platypelis_, _Cophyla_ and others. The sacral diapophyses are dilated. The
pupil is either horizontal or vertical. Those which are provided with discs
to the fingers and toes are climbers, and mostly slender and long-legged,
sometimes of very small size, for instance _Cophyla_, the body of which is
scarcely one inch in length.
The genera can be determined by means of the following key:–[103]
_A_. Pupil vertical. Palatine teeth in long transverse series.
_a_. Precoracoids ossified. Tips of fingers and toes not dilated.
Sternum very large. Madagascar .......... _Dyscophus._
Sternum small. Burmah .......... _Calluella._
_b_. Precoracoids not ossified. Tips dilated ..........
_Plethodontohyla._
_B_. Pupil horizontal.
_a_. Palatine teeth in long transverse series.
α. Precoracoids ossified. Tips dilated.
Fingers and toes free. Precoracoids entirely ossified ..........
_Mantipus._
Fingers and toes webbed at the base. Precoracoids semi-ossified
.......... _Platyhyla._
β. Precoracoids not ossified. Tips not dilated ..........
_Phrynocara._
_b_. Palatine teeth in one or two small groups.
Precoracoids ossified. Tips dilated.
Two small groups of palatine teeth .......... _Platypelis._
One single group in the middle of the palate .......... _Cophyla._
No teeth on the palate .......... _Anodontohyla._
_Dyscophus antongili._–Madagascar. General appearance stout, with short
legs and a wide mouth. Total length about 3 inches. The skin is mostly
smooth, and forms a broad glandular fold which extends from the eye to the
groin. The upper parts are beautiful magenta red, with a purplish streak
beneath the lateral folds; the under parts are yellowish white, with minute
grey specks. Red or pink colours, and the lateral folds, occur also in most
of the other members of this family, for instance in the Indian genus
_Calluella_.
SUB-FAM. 3. GENYOPHRYNINAE.–_With very small teeth on the anterior portion
of the lower jaw._
_Genyophryne thomsoni._–Pupil horizontal. Tongue oblong and entire. With
teeth on the palatine bones, and a serrated transverse dermal ridge in
front of the oesophagus. Sternum cartilaginous. Precoracoids absent. Sacral
diapophyses moderately {237}dilated. Tympanum hidden. Head large and much
depressed. Heel with a triangular dermal flap. The smooth skin is pink
brown above, with blackish marks; a light line extends on each side from
the eye along the back. Under parts black. About 32 mm. in length. Sudest
Island, between New Guinea and the Louisiade Archipelago.
FAM. 7. RANIDAE.–Frogs, in the true sense, are all well diagnosed as
_Firmisternia, with cylindrical sacral diapophyses_. According to the
presence or absence of teeth in the jaws they can be subdivided as
follows:–
SUB-FAM. 1. CERATOBATRACHINAE, with teeth in the upper and in the lower
jaws. The sole representative is the genus _Ceratobatrachus_.
SUB-FAM. 2. RANINAE, with teeth in the upper, but none in the lower jaw.
These are the Ranidae of Boulenger in the Catalogue of Batrachia Salientia.
SUB-FAM. 3. DENDROBATINAE, without teeth in the upper and lower jaws.
SUB-FAM. 1. CERATOBATRACHINAE.–Teeth present in both jaws. Those of the
lower jaw, between 20 and 30 in number in _Ceratobatrachus_, the only
genus, are nearly all inserted upon the articular bone; only 2 or 3 are
carried by the dentary element, which, although large, enters into the
formation of the upper border of the jaw at the anterior end only. In the
small extent of the share of the dentary in the formation of the edge of
the lower jaw, and in its anterior "toothlike" process, _Rana adspersa_ of
Africa bears unmistakable resemblance to this genus. The tongue is deeply
notched, and free behind. Pupil horizontal. Vomers furnished with teeth.
Tympanum distinct and large. Precoracoids present. Omosternum and
presternum with a bony style. Sacral diapophyses cylindrical. Fingers and
toes free, with swollen tips. Outer metatarsals united. Male with two
internal vocal sacs.
_G. guentheri_, Solomon Islands, the only species, has an enormous mouth
and a triangular head not much smaller than the rest of the body. The skull
is furnished with prominent ridges and a small curved spine at the angle of
the jaws. The hind-limbs are rather short. The skin of the upper parts
shows linear ridges, variously arranged; that of the belly is granular. A
triangular dermal flap on the tip of the muzzle, one on the {238}upper edge
of the eyelids, others on the heel and above the vent. The colour and
markings are very variable, the ground-colour is yellowish to pink, brown,
grey or olive, with darker and lighter markings. Total length of the males
3 inches, of females 3½ inches.–Guppy, the discoverer of this peculiar
creature, remarks that "horned Frogs are very numerous in these islands,
and so closely do they imitate their surroundings in colour and pattern,
that on one occasion I captured one by accidentally placing my hand on it
when clasping a tree."
SUB-FAM. 2. RANINAE.–The vertebrae are procoelous and devoid of ribs. The
precoracoids are always present and ossified from the clavicles, and are
parallel with the much stronger and ossified coracoids. The omosternum
usually possesses a bony style, but in the Indian genera _Nannobatrachus_
and _Nannophrys_ and in _Phyllodromus_ of Ecuador it remains cartilaginous,
and in _Colosthetus_ of Colombia it is absent. The metasternum also
possesses a bony style, but it remains cartilaginous in the Indian genera
_Oxyglossus_, _Nannophrys_, _Nannobatrachus_ and _Phyllodromus_, in the
last two genera rather reduced and slender, while in the Ecuadorian and
Colombian genera _Hylixalus_, _Prostherapis_ and _Colosthetus_, it is
reduced to a membranous piece. In quite a number of genera the normal
number of phalanges is increased by one owing to the intercalation of an
extra phalanx between the terminal and the otherwise penultimate
phalanx.[104] This is the case in all the species of _Cassina_,
_Hylambates_, _Rappia_, _Megalixalus_, _Rhacophorus_, _Chiromantis_,
_Ixalus_ and _Nyctixalus_, but it is doubtful if all these genera are
thereby more nearly related to each other than to the rest of the Raninae.
The structure of the tips of the fingers and toes exhibits more variety.
The terminal phalanges are mostly simple, with slight swellings at the
ends, or they are Y- or T-shaped in conformity with more or less developed
adhesive discs; in the African genus _Hylambates_ only they are
claw-shaped, as in the Hylidae.
_Gampsosteonyx batesi_, recently described by Boulenger from the Gaboon,
shows a unique modification of the terminal phalanges of the second to the
fifth toes. They are transformed into sharp and curved claws, like those of
a cat, but instead {239}of horny sheaths, it is the bone itself which is
thus sharpened and perforates the skin, an anomaly reminding us of the ribs
of _Triton waltli_. Total length of the type-specimens, about 3 inches.
Adhesive discs are common, and are best developed in _Rhacophorus_,
_Ixalus_, _Rappia_, and _Megalixalus_. In the Neotropical genera, excepting
_Colosthetus_, the discs are very peculiar, being provided on the upper
side with leathery scales which are separated by a fissure. The fourth and
fifth metatarsals either diverge and are connected by a distinct web, or
they lie close together with only a groove between them, or lastly they
appear externally united.
[Illustration: FIG. 46.–Map showing distribution of the Ranidae.]
The tympanic disc is very variable, large, small or quite hidden. Vomerine
teeth are present or absent. The pupil contracts into a horizontal slit
except in some Palaeotropical genera. The tongue is universally free
behind, mostly deeply notched, and can be well protruded; only in the
Indian _Oxyglossus_ and in the Neotropical genera, excepting _Hylixalus_,
its posterior margin is entire.–There are terrestrial, arboreal, and
aquatic members in this large sub-family. The geographical distribution of
the Raninae, which comprise about twenty genera with at least some 270
species, is almost entirely Arctogaean. None, with the exception of three
species in the Papuan subregion, occur in the Australian region; and only
four genera, with one or two species each, inhabit the tropical Andesian
district, the {240}remainder of South America being without any Raninae.
All the species of the whole Periarctic region belong to the genus _Rana_
except in Eastern Asia, where the closely allied genus _Rhacophorus_ occurs
also. The entire sub-family of Raninae is, in its fulness and diversity of
development, essentially Palaeotropical.
Many of the genera, even in the present more liberal sense as interpreted
by Boulenger, are based upon unimportant characters, and in reality run
into each other. This is for instance the case with _Rana_ and
_Rhacophorus_.
The following tabular arrangement is merely a key for determination and
does not necessarily express relationships. The presence or absence of
vomerine teeth is a character easily ascertained, but it separates closely
allied genera, for instance, _Rhacophorus_ from _Ixalus_ and _Micrixalus_
from Rana.
The genera with extra, interpolated phalanges are marked *.
KEY FOR THE DETERMINATION OF THE GENERA OF RANINAE.
I. Pupil vertical.
_A_. With vomerine teeth.
_a_. Omosternum very slender and cartilaginous. Small discs. India
and Ceylon, 3 species .......... _Nannobatrachus._
_b_. Omosternum with a bony style.
α. Outer metatarsals webbed. Small discs. South India, 2 species
.......... _Nyctibatrachus._
β. Outer metatarsals close together. Africa.
Fingers and toes with interpolated phalanges.
Without terminal discs. 2 species .......... _Cassina._*
With discs supported by claw-shaped phalanges, 10 species
.......... _Hylambates._*
Fingers and toes without interpolated phalanges; without discs.
Toes webbed .......... _Trichobatrachus robustus_,
p. 271.
Toes free, with sharp claws .......... _Gampsosteonyx batesi_,
p. 272.
_B_. Without vomerine teeth. Discs well developed. Outer
metatarsals united. Tropical Africa and Madagascar, 7 species
.......... _Megalixalus._*
{241}II. Pupil horizontal.
_A_. With vomerine teeth.
_a_. Outer metatarsals webbed together.
Fingers free, toes webbed .......... _Rana_, p. 249.
Fingers and toes more or less webbed. Always with discs ..........
_Rhacophorus_,* p. 245.
Two fingers opposed to the others. Africa ..........
_Chiromantis_,* p. 244.
_b_. Outer metatarsals united, or separated by a groove only.
Omo- and meta-sternum with a bony style .......... _Cornufer_,
p. 243.
Omo- and meta-sternum slender and cartilaginous.
Ceylon, 2 species .......... _Nannophrys._
Mozambique .......... _Phrynopsis boulengeri._
_B_. Without vomerine teeth.
_a_. Palaeotropical.
α. Tongue narrow and entire. No discs. Outer metatarsals webbed.
India, 3 species .......... _Oxyglossus_.
β. Tongue oval, feebly nicked. Large discs. Solomon Islands
.......... _Batrachylodes vertebralis._
Karin Hills .......... _Phrynoderma asperum._
γ. Tongue deeply notched. Outer metatarsals united by a web.
Discs none or very small.
Africa, 3 species .......... _Phrynobatrachus._
Borneo .......... _Oreobatrachus baluensis._
With regular discs.
Number of phalanges normal. India, 5 species ..........
_Micrixalus._
With an extra, interpolated phalanx. India, 18 species
.......... _Ixalus._*
Two fingers opposed to the others. Karin Hills ..........
_Chirixalus doriae._*
δ. Tongue heart-shaped. Outer metatarsals united.
Fingers and toes free, tips blunt. Africa, 8 species ..........
_Arthroleptis_, p. 242.
Fingers and toes more or less webbed, with regular discs. Africa
and Madagascar, 23 species .......... _Rappia._*
{242}_b_. Neotropical. Metasternum small, cartilaginous or
membranous. With discs.
1. With a pair of dermal scales on the discs. Omosternum with a
bony style.
Tongue heart-shaped. Ecuador, 2 species .......... _Hylixalus._
Toes free. 5 species .......... _Phyllobates_, p. 242.
Tongue entire. Ecuador and Colombia, 3 species ..........
_Prostherapis._
Omosternum cartilaginous. Ecuador .......... _Phyllodromus
pulchellus._
2. Discs without scales. Omosternum absent. Colombia ..........
_Colosthetus latinasus._
_Phyllobates._[105]–This is one of the few Neotropical genera, and like
nearly all of these has peculiar adhesive discs on the fingers and toes,
each disc bearing on its upper surface two dermal scales. The tympanum is
distinct. Vomerine teeth are absent. The general appearance of the five
species is that of tree-frogs. One species, _Ph. bicolor_, yellowish above,
dark brown beneath, lives in Cuba. The others inhabit Central America and
Venezuela. They seem to have peculiar nursing habits. _Ph. trinitatis_ of
Venezuela and Trinidad carries its tadpoles on its back, on to which the
young fix themselves by means of their suckers. Nothing is known about
their breeding habits, for instance whether the young are hatched on the
back, or, as seems more likely, if the parents (the specimen described by
Boulenger[106] is a male) only give their offspring a temporary lift in
order to convey them from a drying-up pool to a healthier place. It is
remarkable that several species of Dendrobatinae, which inhabit the same
countries, have precisely the same habits.[107]
_Arthroleptis._–Slender and long-limbed little frogs, about one inch in
length. The fingers and toes are free, very slender, and end in slightly
dilated tips, the supporting phalanges being simple. The tympanum is
variable. The skin is smooth or finely granulated. The colours are
inconspicuous, brown or grey tones usually prevailing. About ten species
are known, mostly {243}from Continental Africa, a few from Madagascar and
the islands in the Indian Ocean.
_A. seychellensis._–Brauer[108] has discovered the mode of nursing of this
frog. He found a specimen of _A. seychellensis_ which carried nine tadpoles
on its back, in the month of August, in the Seychelles, about 1500 feet
above sea-level, upon an old tree-fern. The little ones were already
provided with long tails, the hind-limbs were partly free, the fore-limbs
still covered by the skin, and they held on by their bellies; not, like the
young of _Phyllobates_, by their "suckers." Another specimen carried young
which were still further developed. He also found an old frog, near which
was lying a little heap of eggs, not enveloped in a common mass of jelly.
The old frog escaped, but the eggs were taken care of in a vessel with
moist sand at the bottom. By the following morning the eggs were hatched
and the tadpoles were clinging by their bellies on to the walls of the
glass. Brauer concludes that the young, when hatched, creep on to the
parent's back, he or she waiting near the heap of eggs until the latter are
ready. Curiously enough, he did not find out the sex of the nurse, nor are
we told if the young are taken to the nearest water to finish their
metamorphosis, or if they remain upon the parent's back until they hop off
as baby-frogs. The yolk is very large. When the four limbs are already
developed, the gill-cavity possesses no gills and no outer opening; and
since the lungs are only just beginning to sprout, the tadpole must needs
breathe by means of its skin. The jaws have no horny coverings. The adults
live on the ground between moist leaves, and eat chiefly termites.
[Illustration: FIG. 47.–_Arthroleptis seychellensis_, carrying Tadpoles. ×
1. (After Brauer.)]
_Cornufer_, with about twelve species, is an essentially Austro-Malayan and
Polynesian genus, but one species, _C. johnstoni_, has been found in the
Cameroons. The fingers and toes are free, and their T-shaped phalanges
support adhesive discs. The tympanum is distinct. The general shape is
frog-like, usually with slender and very long hind-limbs and toes, the
discs of the latter being much smaller than those of the fingers. The
coloration is dull, mostly brown, more or less marbled, whitish below. The
{244}upper eyelid of some species, _e.g._ of _G. unicolor_ of New Guinea,
has a small tubercle, hence the generic name. The skin of the back is
glandular and granular, forming slight folds on the back and on the sides
of the head in some species. The male has one or two internal vocal sacs.
_C. corrugatus_ is one of the most widely distributed species, inhabiting
the Philippines, New Guinea, and Duke of York Island. The granular skin
forms longitudinal folds on the back, one of which reaches from the eye to
the shoulder. Brownish above with darker markings, below yellowish, with or
without brown spots on the throat.–Three species inhabit the Fiji Islands.
Of _C. solomonis_ of the Solomon Islands little is known about the
propagation, although the large size of the egg, which measures 5 mm. in
diameter, suggests that the young undergo most or the whole of their
metamorphosis within the egg.
_Chiromantis_ is distinguished by the peculiar arrangement of the fingers,
the first and second being opposed to the others; their terminal phalanges
are obtuse and support small knobs or discs. The general shape is that of a
frog with long and slender hind-limbs. The tympanum is distinct.
_Ch. xerampelina_, the type-species, was discovered by Peters at
Mozambique; it is a middle-sized frog, about 2 inches in length, brown
above with reddish spots on the sides; the male is devoid of vocal sacs.
_Ch. petersi_, a native of East Africa, differs from the preceding by the
possession of an internal vocal sac. _Ch. rufescens_ = _guineensis_ shows
very little of the typical grasping arrangement of the fingers; the two
inner ones are separated from the two outer fingers by a wide gap, but they
all lie in the same plane, are much webbed and possess large discs, so that
by the latter two characters a link is formed with _Rhacophorus_, to which
the present genus is closely allied. Total length about 2½ inches.
Buchholz[109] has observed the peculiar breeding habits of this rather
large, brown, and slender tree-frog in the Cameroons. In the month of June
he found on the leaves of a low tree, standing in the water, a white foamy
mass, like the froth of a broken egg, containing a number of newly hatched
larvae and quite transparent eggs. Within three or four days this mass
became {245}fluid, and the larvae, provided with external gills and a long
tail, swam about in the slime. In the natural course of events the larvae
are probably washed down into the water by the rain. He found that the
female deposits the eggs in the foamy mass at night, during the months of
June and July, on various kinds of trees, either between the roots or in a
cavity formed by gluing together several leaves, sometimes 10 feet and more
above the water, or near the margin. On one occasion the mother was seen
sitting upon the foamy mass, clasping the same with its four limbs.
_Rhacophorus._–This large genus, containing more than forty species, has a
curious distribution. At least one dozen species are found in Madagascar,
eight or nine in Ceylon, the rest in Southern India, the Himalayas, the
Malay Islands and Philippines, extending northwards through China and
Southern Japan. Therefore this genus, with the three species of the African
_Chiromantis_, extends over the whole of the Palaeotropical region. The
generic name has reference to the possession by many species of little
dermal flaps, especially at the inner side of the heel, and it has nothing
to do with the parachute-like use of the hands and feet of certain species,
to be mentioned presently.
The terminal phalanges are generally bifurcated, rarely obtuse, and support
well-developed adhesive discs. The fingers and toes are webbed to a
variable extent. The two outer metatarsals are likewise connected by a web.
The tympanum is distinct. The general appearance is that of tree-frogs, and
many of them are green. The males have one or two internal vocal sacs. Not
all the species have dermal appendages. _Rh. maximus_, for instance, the
largest of all, living in the Himalayan forests, has none. A heel-flap
occurs in some half-dozen Indian species; and _Rh. madagascariensis_ has
these flaps on the heels and on the elbows. Some have queer little lappets
above the vent, or on the edges of the arms and legs; in others the bend of
the arm is fringed. The small size of these appendages, in comparison with
the webs and discs, makes them practically useless so far as increase of
surface is concerned, and they have most likely some other, although
unknown meaning, especially the flaps over the vent. Lastly, in the
majority of species the fingers are not more than half-webbed, or even
less, and in a few only, the webs reach down to the discs.
{246}Several species of this genus are remarkable for two reasons. First,
the great enlargement of the fully-webbed hands and feet, which are then
used as parachutes; secondly, the mode of propagation.
Greatly exaggerated notions are, however, entertained about the parachutes,
ever since Wallace's description[110] of the first "flying frog." The
creature was brought to him in Borneo by a Chinese workman. "He assured me
that he had seen it come down, in a slanting direction, from a high tree,
as if it flew.... The body was about four inches long, while the webs of
each hind-foot, when fully expanded, covered a surface of four square
inches, and the webs of all the feet together about twelve square inches."
[Illustration: FIG. 48.–_Rhacophorus pardalis_, × about 1. (From Wallace,
_Malay Archipelago_.)]
The species in question is _Rh. pardalis_, an inhabitant of Borneo and of
the Philippine Islands. Specimens from Wallace's Collection are in the
National Collection and the largest specimen {247}shows the following
measurements. Total length 6.5 cm. or 2½ inches, not 4 inches.
Area covered by one fully-expanded hand 3.4 square cm.
" " " foot 6.0 " "
–––
9.4 square cm.
_i.e._ for the four limbs 18.8 square cm. = about 3 square inches, and not
78 square cm. or 12 square inches. By some unfortunate oversight Wallace
must have mixed up the total expanded area with that of the four hands and
feet! In Brehm's _Thierleben_ the 78 square cm. have increased to 81 cm.,
and the artist has in the somewhat larger species _Rh. reinwardti_ improved
upon this, and has produced a truly startling picture by a further
exaggeration based upon the figure given by Wallace.
_Rh. reinwardti_ lives in the forests of the mountains of Java and Sumatra.
It reaches 3 inches in length, and is grass-green above, yellow below.
Younger specimens are further adorned with large blue patches on the webs
of the hands and feet and behind the armpits. Besides the flap on the heel
and the curious cutaneous fringe on the forearm, suggestive of an incipient
flying-membrane, the skin forms a projecting fringe on the inner side of
the fifth toe and a transverse flap above the vent.
Of _Rh. leucomystax_, Annandale, who accompanied the Skeat Expedition to
Malacca, gives the following account:–"This frog, which is called by the
Malays of Lower Siam either 'Berkata Pisang' (banana-frog) or 'Berkata
Rhumah' (house-frog), lays its eggs either on leaves of branches
overhanging the water, or on the mud surrounding buffalo-wallows. The ova
are enclosed in a round mass of yellow froth, which afterwards becomes
steel-grey, about as large as a cricket-ball. Should they be placed
judiciously in a position sheltered from the sun, the tadpoles may either
hatch, and reach a considerable degree of development, before the mass is
washed into the water, or the froth may be melted almost as soon as it is
formed and the eggs be carried into a pool by a shower of rain. Very often,
however, the whole mass is dried up by the heat of the sun before the rain
comes. During the breeding season, which seems to occur as often as the
land is flooded under the trees, for I have never seen the eggs of this
frog on the bank of a river, the {248}males croak loudly, producing a sound
which can hardly be distinguished from the chattering of the large black
and yellow squirrel, _Sciurus bicolor_."
These arboreal frogs have a peculiar mode of nursing the young and taking
care of the eggs. _Rh. maculatus_ of Ceylon, Malacca, etc., and _Rh.
schlegeli_ of Japan, lay their eggs in a foamy mass, the size of a fist, on
the margins of ponds, and the whole process has recently been described by
Ikeda.[111] He observed the Japanese _Rh. schlegeli_ depositing the eggs in
soft, muddy ground covered with grass, and in wet, muddy banks of
paddy-fields, ponds, and similar localities near Tokyo. Sometimes they are
deposited between the leaves of trees, near the ground. The breeding season
extends from the middle of April to the middle of May. Towards the evening
the female, bearing the much smaller male on her back, retires underground
for the deposition of the eggs. The spots chosen are 10-15 cm. above the
surface of the water; the female digs a spherical hole 6-9 cm. wide.
Sitting thus concealed underground, the frogs assume a dark colour and the
spawning takes place during the night, whereupon the parents leave the
nest. The eggs are enveloped in a white mass of jelly full of air-bubbles,
the whole frothy lump looking like the well-beaten white of a hen's egg,
with the yellowish eggs scattered through it, and measuring some 6 cm. in
diameter. The air-bubbles are 2-3 mm. large. The froth is originally very
elastic and sticky, but it gradually sinks down, becomes liquid and
ultimately runs out of the hole. It is produced in the following peculiar
manner. During and after the deposition of the eggs the female puts her
feet upon the sticky jelly, part of which adheres and is then pulled out as
a thin, transparent membrane stretching between both feet. The latter are
then thrust backwards, the membrane is folded downwards and becomes a
vesicle of 5 to 10 mm. in width. By repeated working of the limbs the
successively formed bubbles are trodden and kneaded into froth, which
ultimately surrounds and at the same time separates the eggs.
The female of _Rh. reticulatus_ of Ceylon attaches the eggs, about twenty
in number, to the under surface of her belly, on the skin of which they
leave little cellular impressions. What becomes of the tadpoles is not
known.
{249}_Rh. leucomystax_ is found in the Malay Archipelago, Farther India,
and the Philippine Islands.
S. S. Flower[112] found the tadpoles about Singapore, from January to
April, in small ponds and in rain-water butts. The spiracle lies on the
left side, directed backwards and upwards, nearer the anus than the end of
the snout. The anus opens on the right side. Exceptionally large tadpoles
measured 46 mm. in total length, the recently transformed young only 14-18
mm.
"A cheerful little frog of most graceful build. It comes out from its
hiding-places shortly before sunset, and remains abroad all night. The
males are easily found as they sit on shrubs or trees, or on the edges of
the rain-water butts under the verandahs of the houses, and from time to
time utter a single, rather musical, short croak. In March and April they
can be found both by day and night in embrace, in the ponds. This species
changes both its colour and markings very rapidly and frequently, but dark
bands across the legs can always be more or less distinguished; the lower
parts are some shade or other of buff, but the principal variations of the
upper part are as follows: pale bronze, either uniform or with four
longitudinal dark-brown or black lines; uniform, almost orange, bright
bronze; chocolate, with darker mottling; pale brownish green or olive, with
irregular dark spots; yellowish green, mottled with darker or brown." The
females are considerably larger than the males; the largest male caught was
48 mm. from snout to vent, and the largest female 68 mm.
_Rana._–The following combination of characters should be a sufficient
diagnosis: pupil horizontal; tongue deeply notched and free behind; vomers
with teeth; fingers free, toes webbed, fourth and fifth metatarsals
diverging and webbed together.
In conformity with the great number of species and the wide distribution of
this genus some of the organs vary considerably, indeed so much so that
many of these modifications have been deemed sufficient to be of generic
importance. Fortunately the species are so numerous that these characters
mostly form an uninterrupted series from one extreme to the other.
The terminal phalanges are mostly simple and pointed; sometimes
transversely dilated or T-shaped, according to the presence of more or less
developed discs. Such discs are, for {250}instance, present in the Malay
species _R. erythraea_ and _R. chalconota_ and in the Indian _R.
corrugata_. The tympanum occurs in every stage from a conspicuous, free
disc to being quite hidden by the skin. The vomerine teeth either form a
pair of tiny, mostly transverse rows, between the choanae, or they are
arranged in two oblique series which extend beyond the hinder edges of the
choanae.
The vocal sacs vary greatly. Many species, e.g. _R. agilis_, have none at
all. Most species have a pair of internal sacs, and in comparatively few,
about a dozen, these sacs have become external, a feature which indicates
no relationship of the species thus distinguished, for instance the
European _R. esculenta_, the Japanese _R. rugosa_, the Indian _R.
hexadactyla_, _R. cyanophlyctis_ and _R. Chloronota_, the Bornean _R.
glandulosa_, the African _R. oxyrhynchus_ and _R. mascareniensis_, the
Mexican _R. montezumae_. In _R. esculenta_, and perhaps in a few others,
even the female has some traces of these otherwise male organs, indicated
by slit-like folds of the outer skin below the angles of the lower jaw.
Nuptial excrescences on the inner metacarpal tubercle and on the inner
fingers of the male are common; they reach their greatest development in
the Himalayan _R. liebigi_, the male of which is "remarkable for the
extreme thickness of its arms, the inner sides of which are studded with
small conical black spines, each supported on a rounded base produced by a
swelling of the skin. A large patch of similar spines exists on each side
of the breast."[113]
Specific glandular complexes in the skin are mostly restricted to a pair of
lateral or dorso-lateral folds; they are often absent, but a few species,
e.g. _R. glandulosa_ of Borneo, _R. temporalis_ of Ceylon, _R. elegans_ and
_R. albolabris_ of West Africa, have a pair of large flat glands at the
base or inner side of the arms.
All the species of _Rana_, except those in the Solomon Islands, spawn in
the water, where the development of the tadpoles takes its course. Those of
some Indian species, notably _R. alticola_ and _R. afghana_ of the
Himalayas, and _R. curtipes_ of Malabar, are very peculiar, being provided
on either side of the shoulders with a large oval parotoid-like gland, well
defined and crowded with pores; _R. alticola_ possesses in addition an
unpaired, sharply {251}marked glandular complex on the top of the root of
the tail, or rather upon the future coccyx. These complexes gradually
disappear with age.
The genus _Rana_, with about 140 species and subspecies, is distributed
over the whole of Arctogaea so far as this is available for Amphibian life,
while there are only a few stragglers in Notogaea, namely, a few species in
Ecuador and in the Peruvian or Upper Amazon district. None exist in the
rest of the Neotropical region, including the Antilles, and practically
none in Australia; but _R. arfaki_ and _R. papua_ inhabit New Guinea and
the northern corner of Australia, _R. kreffti_ the Solomon Islands. A few
species are restricted to Madagascar, and a few others live there and on
the continent of Africa.
So far as number of species is concerned, the home of the genus _Rana_ is
the Palaeotropical region; about one dozen (some of them with a very wide
range) live in the Palaearctic sub-region, scarcely more in the Nearctic
sub-region, and a few in Central America.
_R. temporaria_ (the common European Brown Frog or Grass-frog).–The
tympanum is distinct, two-thirds the diameter of the eye in size. The first
finger is slightly longer than the second, which is shorter and weaker than
the others, whilst the fourth is the longest. All the fingers are quite
free. When the hind-limbs are laid forwards along the body, the ankle-joint
reaches to a point between the eye and the tip of the snout. The five toes,
which are about half webbed, increase in length from the first to the
fourth, while the fifth is about equal to the third. The sole of the foot
has a small, blunt, inner metatarsal tubercle; the outer one is scarcely
visible. The skin is smooth, always moist, owing to the minute mucous
glands; but a series of larger glands forms a pair of folds along the upper
sides of the back; beginning behind the eyes they converge slightly beyond
the shoulders, diverge a little in the sacral region, and converge again
towards the vent. Another, much feebler, Λ-shaped ridge lies between the
shoulders.
The male has two internal vocal sacs, which, when in use, bulge out the
skin of the throat beneath the angles of the mouth like a pair of globes.
It is further distinguished from the female by the stronger muscles of the
arms and by a pair of swollen pads on the inner side of the first finger.
During the pairing {252}season these pads are enlarged into cushions
covered with black horny rugosities.
The iris is golden, with dark specks. The coloration is, generally
speaking, brown above, with black-brown irregular spots, especially on the
sides of the body, and with cross-bands on the legs. The under parts of the
male are white or pale yellow, with a bluish tinge on the throat, while the
female is more yellow instead of white, inclining to orange. In both sexes
the under parts are mostly spotted with darker colours. A large dark-brown
patch, extending from behind the eye over the tympanum towards the
shoulder, is always present and has given this frog its specific name.
Otherwise the coloration varies considerably; more or less according to the
locality and nature of the surroundings, and to individual variation and
temporary change of colour.
Some specimens are almost spotless above and of a rich brown, or almost
yellow colour, the spots being restricted to the sides below the lateral
folds. Others have very few spots, but these are then arranged in two
interrupted streaks on the back. The under parts, especially the flanks,
may be lemon yellow instead of whitish, and the darker markings may be
almost absent. Boulenger has figured a beautiful specimen, almost orange
red, with red spots and vermiculations on the yellow under surface. I have
found similar red specimens of unusually striking appearance between Berlin
and Spandau in a forest-glade, through which run little streams with banks
of red ferruginous soil. Specimens which live in woods with rich black soil
are often very dark, all the brown and reddish tints being absent. The
variations are, however, really endless, and it is difficult to find two
individuals exactly alike, even amongst a great number collected in the
same locality. Moreover, they change colour. Warmth makes them paler, cold
causes the chromatophores to expand and the whole frog appears darker.
During the breeding season the males assume a delicate bluish hue,
especially on the throat, but this film quickly fades away when they are
taken out of the water. It is caused by the swelling of the cutaneous
lymph-spaces which extend their ramifications into the epidermal layer, and
it is not a question of pigmentation or of chromatophores, but a case of
interference-colours, blue being frequently the result of the light passing
through a cloudy, colourless, but not {253}quite transparent and thin
stratum, in this case the turgid epidermis.
The habits of the Grass-frog are essentially terrestrial. It spends most of
its time on land, preferably in damp places, but local fashion permits of a
great deal of freedom, as these frogs are sometimes found not only in very
wet, naturally irrigated places, but also in the water itself. However, the
Grass-frog when pursued rarely takes to the water for safety. It trusts to
flight, first by a few long and fast jumps, and then to concealment by
squatting down between grass, under leaves; it rarely creeps into a hole,
even if there be one near. The jumps soon become shorter and shorter after
a few dozen repetitions. It swims well, but cannot climb. The food, which
consists chiefly of insects, snails, and worms, must be moving to excite
interest; then the frog, whose favourite position is half squatting, half
supported by the arms, erects itself, and, facing the insect, turns round
upon its haunches, adjusts its position anew by a shifting of the legs, and
betrays its mental agitation by a few rapid movements of the throat. All
this time the prey is watched intently until it moves; then there follows a
jump, a flap of the tongue and the insect is seen no more. As a rule these
frogs do not crawl, they jump or hop, even whilst stalking, and this takes
place at any time of the day; in fact they are very diurnal, although they
become more active towards the evening. When caught they are at first very
wild and, like all true frogs, very impetuous, committing acts of
astonishing stupidity without any apparent sense or appreciation of
distance or height. The captive will not only jump off the table, whilst a
toad stops at the edge and looks carefully down, but without hesitation he
jumps out of the window, regardless of the height above the ground. This is
due to sheer fright; he loses his head. When at large in his native
surroundings, nothing will induce him, although hotly pursued, to commit
suicide by jumping down a precipice. But all this wildness calms down
wonderfully soon. The captive no longer dashes his head against the glass,
he does not struggle or twist when taken up; on the contrary, he makes
himself at home, watches your coming with intense expectation, and without
hesitation accepts the proffered mealworm, maggot, butterfly or earthworm;
in short, he shows what a jolly and intelligent fellow he really is.
{254}The Grass-frog has many more obvious enemies than perhaps any other
Amphibian, and it is not even slightly protected by any appreciable
poisonous secretion. Nevertheless it is extremely common. A whole host of
birds eat it–for instance, buzzards, harriers, and above all storks. Foxes,
polecats, and stoats are not averse to it, and the Grass-snake derives its
main sustenance from it. In fact the enemies of the little frog are legion,
one of the worst being Man. In France, Italy, and other parts of the
Continent, the skinned fleshy hind-limbs are turned into a by no means
disagreeable ragoût, or into dainty morsels when fried in butter and
encrusted with bread-crumbs. This frog, together with its cousin the
Water-frog, also suffers from the distinction of being one of the chief
martyrs to science. Perhaps the story is true that Galvani was led to his
investigations into animal magnetism and electricity by observing that the
legs of a number of skinned frogs, strung up by his wife upon the bronze
railings of the balcony, jumped whenever the scissors, which cut off the
feet, touched the other metal. Frogs have suffered ever since. Easily
procured and of a convenient size, they are used in every biological
laboratory, and the young student is supposed to be initiated into the
mysteries of Vertebrate structure by the careful dissection and study of
this, the worst of all the so-called types. Next to Man there is no animal
which has been studied so minutely, and has had so many primers and
text-books written on it, as this frog. In spite of all this it is very
little understood, thanks to its rather aberrant and far from generalised
structure.
However, the frog, by reason of its fertility, holds its own. Early in the
year, sometimes while there is still ice and snow, the frogs leave their
hibernating places (mostly holes in the ground, under moss, or in the mud),
and they begin to pair in standing or slowly flowing, mostly shallow,
waters.
They are not always very careful in the selection of the spawning locality,
many of them lay their eggs in a ditch, or even in the shallowest puddle,
which is sure to dry up, and thus to cause the destruction of the whole
brood. This carelessness is all the more surprising when there are large
pools or lakes in the immediate vicinity, perhaps only one hundred yards to
the other side of the road. The Natterjack is, by the way, equally
careless, while other toads and the tree-frogs are very circumspect.
{255}[Illustration: FIG. 49.–_Rana temporaria._ Eight successive stages in
the development from the egg to the almost complete Frog, × 1.]
Both sexes can croak, and this sound is frequently produced under water;
but there are no regular concerts, although many collect in the same pond
or spring, which is perhaps the only suitable place for miles around. The
male puts its arms around the chest of the female, behind her arms, and the
embrace is so firm that nothing will induce him to loosen his hold. The
process becomes an involuntary reflex-action, a cramp which may last for
days, or even for weeks, if sudden cold weather sets in, until the female
is ready to expel the eggs, an act which is quick and soon over. The usual
time of spawning in Middle Europe is the month of March, earlier in warm,
later in cold seasons; in southern countries, February or even January, but
in Norway not until May. Although the males of this species are not more
numerous than the females, and therefore should be able to mate without
much trouble, their ardour is so great that they occasionally get hold not
only of the wrong kind of frogs, but of toads or even fishes, and, if taken
off by force, they fasten on to anything else, a log or on to your own
fingers. The eggs measure 2-3 mm. in diameter, are black with a whitish
spot on the lower pole, number from 1000 to 2000, and sink at first to the
bottom. Their gelatinous cover soon swells to a large globe more than 10
cm. in width, and the whole mass, as large as a man's head, floats on the
surface, often stained with mud and other impurities. During the cold
weather which often prevails in the spring, the dark brown larvae are slow
in their development; and provided with rather large branched external
gills and a well-developed tail, they wriggle about in the dissolving slime
for three or four weeks. Fischer Sigwart[114] has timed and measured them
as follows.–The eggs were laid on the 10th of {256}March. On the 15th the
larvae were 4 mm. long and began to leave the eggs. On the 19th they
measured, body 4, tail 9, total 13 mm.; on the 5th of April 10, 16, and 26
mm. respectively. On the 13th of May they were 40 mm. long and the
hind-limbs appeared; the fore-legs burst through on the 25th, when the
tadpoles had reached their greatest length, namely 45 mm., the body
measuring 15 mm. On the 31st of May they left the water, still provided
with a rather long tail of 20 mm., the total length being reduced to 35 mm.
The larvae of this set developed unusually fast, perhaps owing to
artificial conditions. The whole development is, however, mostly finished
in three months, so that the little stump-tailed baby-frogs swarm about
well before midsummer, and have time enough to grow to the size of 20 mm.
or ¾ inch before they begin to hibernate in October.
In higher localities and in northern countries the tadpoles are sometimes
obliged to winter in the unfinished condition.
In spite of the unusually hot summer of 1899 I found plenty of tadpoles on
the 10th of September in the tarns of the hills of North Wales, 1500 feet
above the level of the sea; while thousands of little frogs, with and
without stumpy tails, were hopping about in the surrounding bogs. The water
of these tarns is always very cool. Cold and rainy weather set in by the
middle of the month, and on the 26th the tadpoles, all rather small,
measuring only 35 mm., with the four limbs developed, but still with a
broad fin on the tail, had all settled down under stones at the bottom of
the now very cold water, prepared for hibernation. A few were taken home
and kept in a glass vessel with water, cool, but less so than that of their
native tarns. Within two days they lost the fins on their tails; before the
end of a week they left the water, and crawled on to the moss, and the
tails were reduced to little stumps. By the 10th of October the
metamorphosis was complete, the little frogs measured only 13 mm. in length
and showed no desire to hibernate in the genial atmosphere of the
greenhouse.
This species has a very wide distribution. It ranges from the west of
Ireland to the islands of Saghalin and Yezzo, being found everywhere in the
enormous stretch of intervening countries, practically the whole of Central
and Northern Europe and the middle belt of Asia. Its most northern extent
is the whole of Sweden and Norway. I have found it to the east of the
{257}Dovrefjeld, at an elevation of 4000 feet, well-nigh the snow-line. In
conformity herewith it ascends the Italian Alps up to 10,000 feet. The
southern limit in Europe is the Cantabrian range and the hilly province of
Galicia. In the rest of the peninsula, in Italy and Lombardy, Greece and
Turkey, and on the Mediterranean islands it is absent.
_R. arvalis_ is often confounded with _R. temporaria_, as it differs from
the latter only by the following characters. The snout is rather more
pointed and is narrower; the inner metatarsal tubercle is large,
compressed, and hard; the dorso-lateral glandular folds are more prominent
and the belly is white and immaculate; lastly, it scarcely reaches 3 inches
in length, a size which is not rarely surpassed by the other species. There
are also some differences in habits. _R. arvalis_ prefers moist, boggy,
open localities, and does not ascend beyond 2000 feet in Central Europe. It
pairs as a rule later in the spring and the eggs are smaller, only 1½-2 mm.
in diameter; they do not swell up so much, and the whole mass does not
float but remains at the bottom of the shallow water. The coloration much
resembles that of _R. temporaria_, and is likewise subject to much
variation, except that the pale vertebral stripe is perhaps more common.
This species is distributed over the whole of Central Europe, Russia, and
Western Siberia, south of the 60th degree of latitude, living side by side
with _R. temporaria_. Between the rivers Elbe and Rhine it becomes
decidedly rare, and the latter river is practically its western boundary,
while the Bavarian Alps and the Danube form its southern limits.
_R. agilis_ is still more frequently confounded with both the two former
species. It differs from either by the absence of the two internal vocal
sacs of the male, and by the decidedly longer hind-limbs, the tibio-tarsal
joint reaching often a little beyond the tip of the snout. The inner
metatarsal tubercle is as prominent as in _R. arvalis_. Total length up to
3 inches. The prevailing colour of the upper parts is rather yellow or
pink-brown with few and small blackish spots; a Λ-shaped dark mark on the
neck is often present, and the large dark patch on the temporal regions is
always conspicuous. The under parts are white, inclining to lemon yellow on
the flanks and thighs. The iris is golden yellow in its upper half, dark
brown in the lower half.
{258}This species has a much smaller range than the first two:–from France
through Middle and Southern Germany, Switzerland, and Lombardy to Hungary
and Greece. The specific name refers to the quick and long leaps of this
pretty, or rather delicately coloured frog, which prefers woods and wooded
glens to large open places. Their voice differs much from the croak of the
common Brown Frog, and agrees with that of _R. arvalis_, which is
transcribed by Boulenger, who has kept them alive, as a rapidly uttered
"co-co-co," or "cor-cor-cor." According to the same authority, the pairing
takes place as in _R. temporaria_, but is of much shorter duration, the
females usually resorting to the water only at night and when quite ready
to spawn. Specimens in embrace are therefore seldom found in the daytime.
The eggs resemble those of _R. temporaria_ in size, but they do not swell
up so much and they do not float.
These three species of European brown frogs, difficult enough to
distinguish, have of late been increased by three more, thanks to the
sagacity of Boulenger. These latter inhabit South Europe, and the males all
lack the internal vocal sacs.
_R. iberica_ has a very small range, namely the north-western portion of
the Iberian peninsula, from the Tagus northwards into Galicia, but south of
the main extension of the Cantabrian chain. The rest of the Peninsula south
of these mountains has no brown frogs, the only species of _Rana_ being _R.
esculenta_. _R. iberica_ is rather local, being restricted to those hilly
and mountainous districts which are well watered. A favourite haunt is the
numerous streams in the wooded parts of the Serra Gerez, the red,
disintegrated granite of which suits this little, extremely active, and
reddish frog to perfection. The prevailing ground-colour varies according
to the district, from pale to dark reddish or orange brown, with red specks
and larger, dark brown spots, which in some specimens begin with the
Λ-shaped mark between the shoulders. Dark spots on the flanks are very
variable; the hind-limbs show the usual darker cross-bars, and the temporal
region has the conspicuous dark patch. The ground-colour of the under parts
is whitish, suffused with a pink tinge, and the throat is much speckled
with brown; the toes are pink. The size of this pretty frog amounts to 2
inches. The breeding time is the month of March. When caught and squeezed
they emit a slight "co-co-co."
{259}_R. graeca_ inhabits Italy and the Balkan peninsula from Rosina to
Morea, together with _R. agilis_, from which it is very difficult to
distinguish except that it is a little smaller, remaining below 2½ inches,
and is generally more uniformly pale grey brown to yellowish and pinkish
brown above, with scarcely any, or only a few, small dark specks on the
back and limbs. The temporal patch is likewise paler than in the other
species. The flanks are spotless, their colour gradually passing into the
light buff of the under parts, which are more or less marbled with grey.
The iris is golden, speckled with dark brown.
_R. latastei_ of Lombardy and Northern Italy down to Florence is the last
of these closely allied frogs. Its affinities lie with _R. iberica_ and _R.
agilis_. The latter and _R. latastei_, although living side by side in the
same locality, for instance near Turin, are said not to interbreed. The
voice is a rapidly uttered "keck-keck-keck;" the length remains below 2½
inches. The ground colour is greyish or reddish brown with a dark brown
Λ-shaped mark between the shoulders, and a few red, orange, or blackish
spots on the back. The flanks are without definite dark spots. The under
parts are whitish, with a strong pink tinge, especially along the middle of
the throat and on the chest, the paler portions being mottled with pale
grey brown.
Perhaps the least unsatisfactory way of distinguishing between _R. agilis_,
_R. graeca_, and _R. latastei_ (_R. iberica_ need not be confounded with
them on account of its distribution) is the size of the tympanum, and its
distance from the eye. The tympanum is smallest in _R. graeca_, its
diameter being about half that of the eye and from ¾ to the whole of its
width distant from the eye. In _R. latastei_ the tympanum is a little
larger, and about ½ to ⅔ its own width distant from the eye. _R. agilis_
has the largest tympanum, measuring about ¾ of the diameter of the eye, and
the distance between the two organs amounts to only ⅓ of the size of the
tympanum.
Brown land-frogs of the _R. temporaria_ group are found in most countries
of nearly the whole Periarctic and Oriental regions, and by the time their
races and varieties have been studied as minutely as those of Europe are
now being scrutinised, the number of species will indeed be great.
_R. silvatica_ is the chief representative in North America. It closely
resembles _R. agilis_, but is smaller, only 2 inches in length, {260}and
possesses a pair of internal vocal sacs. Its specific name refers to its
predilection for forests of oak, among the dried leaves of which it
conceals itself so successfully that it is discovered with difficulty. _R.
japonica_ of Eastern Asia is almost indistinguishable from this American
species and from the European _R. agilis_.
_R. opisthodon_ of the Solomon Islands has the vomerine teeth in two
oblique series entirely behind the level of the choanae. The general shape
of this large frog is stout, the type specimen of the male measuring 78,
that of the female 125 mm. = 5 inches. The upper surface of the female is
covered with small, flat warts, that of the male is much smoother. The
upper parts are dark brown, while the under surface is brownish white. The
male has two internal vocal sacs.
This species is interesting as affording another instance of shortened
development, the whole metamorphosis being gone through within the egg. Mr.
Guppy, its discoverer, has supplied the following notes: "During a descent
from one of the peaks of Faro Island I stopped at a stream some 400 feet
above the sea, where my native boys collected from the moist crevices of
the rocks close to the water a number of transparent gelatinous balls,
rather smaller than a marble. Each of these balls contained a young frog,
about 4 inches in length, apparently fully developed, with very long
hind-legs and short fore-legs, no tail, and bearing on the sides of the
body small tufts of what seemed to be branchiae. On my rupturing the ball
or egg in which the little animal was doubled up the tiny frog took a
marvellous leap into its existence, and disappeared before I could catch
it. On reaching the ship an hour after, I found that some of the eggs which
I had put in a tin had been ruptured on the way by the jolting, and the
liberated frogs were leaping about with great activity. On placing some of
them in an open-mouthed bottle, 8 inches long, I had to put the cover on,
as they kept leaping out."
Boulenger[115] has figured and further described the eggs and young. The
egg measures 6-10 mm. in diameter, and is a transparent capsule in which
the young frog is coiled up in the same way as figured by Peters in
_Hylodes martinicensis_; but none of the specimens, which are in an
advanced stage of development, show anything of a tail. There are no gills,
but on each side {261}of the abdomen are several regular transverse folds,
the function of which is probably that of breathing organs, like the tail
of _Hylodes_. The tip of the snout is furnished with a small conical
protuberance projecting slightly through the delicate envelope of the egg,
and evidently used to perforate that envelope.
_R. guppyi_, likewise an inhabitant of the Solomon Islands, is a giant
among frogs. It was discovered by Mr. Guppy on the Shortland Islands. The
type-specimen measures 165 mm. = 6½ inches in length! The skin of the upper
parts is covered with minute warts, and forms a strong fold above the
distinct, but small, tympanum. General colour dark olive brown above, dirty
white below.
_R. tigrina_ is a common species of Eastern Asia, including the Malay
Islands. On account of the strength of its voice, and its size, which is
said to reach 7 inches, it is called the "Indian Bullfrog." Mainly aquatic,
it has a strong cutaneous fringe along the outer side of the fifth toe. The
skin of the back is thrown into longitudinal folds, and a strong fold marks
the upper border of the tympanum. The general colour above is olive brown,
with dark spots, often with a light vertebral line; the under parts are
white. The male has a pair of large external vocal sacs.
_R. gracilis_ has the same distribution, but it remains much smaller, and
the toes are only half, instead of fully, webbed.
_R. catesbiana_ is now the settled name of _the_ "Bullfrog" of North
America, the much more appropriate name of _mugiens_ having been sacrificed
to the fetish of priority. The tympanum is extraordinarily large, at least
equal to the size of the eye, largest in the male. The first finger does
not extend beyond the second; the toes are connected by a broad web down to
the ends, and there is a small inner, but no outer, metatarsal tubercle.
The upper parts are olive brown, clouded with dark brown or blackish spots;
the under parts are yellowish white, often marbled with brown, especially
on the throat. The iris is reddish, with an outer yellow ring. The male
possesses two internal vocal sacs. Total length of adult specimens about 5
inches, but there are giants on record 7 inches in length, while the
stretched hind-limbs measure another 9 or 10 inches. Its home extends over
the whole of the United States, East of the {262}Rocky Mountains,
southwards into Mexico, northwards into Canada.
According to Holbrook the Bullfrogs are solitary in their habits, only
collecting together in the breeding season, when hundreds may be seen in
the same small pond; and then the croak uttered by the males is so loud as
to resemble the distant roaring of a bull, and can be heard on still
evenings at a distance of half a mile. The voice is a hoarse bass "brwoom,"
playfully translated into "more rum." "They cannot be said to abound, but
are found commonly enough sitting half immersed in water, or on the banks
of ponds, waiting for their prey. If alarmed they hop suddenly into the
water, but do not conceal themselves at once, frequently skimming along the
surface for several yards before they dive below." They are the most
aquatic of all the North American frogs, and Holbrook has known specimens
to live in wells for years, where they could not rest a moment on solid
ground above the water.
The Bullfrog is voracious, and takes almost anything that lives or gets
into his own pond–Mollusca, Crustacea, fishes and, above all, frogs. There
is no doubt that they drag down and swallow a good many ducklings and the
young of other water-fowl, but certainly not the half-grown birds which
have a way of disappearing from the farms wherever there are negroes and
other farm-hands about. In turn the bullfrog has sufficient enemies to keep
its numbers down, in fishes, birds, otters, and snakes, and, in the South,
alligators. Although easily kept and growing comparatively tame, they are
dull, having to be kept in solitary confinement on account of their
greediness, which knows no limits. Two of our specimens each swallowed a
full-grown _Salamandra maculosa_, and died within the same night, probably
not understanding the meaning of the conspicuous black and yellow warning
colours of the European.
_E. clamata_ s. _fontinalis_, likewise an inhabitant of Eastern North
America, may be called a smaller edition of the Bullfrog, its usual
full-grown size being about 3½ inches. The tympanum is conspicuously large,
but the toes are webbed to a lesser extent, and the skin forms a glandular
fold which extends from the shoulder in a curve to the flank. This species
is partial to the neighbourhood of running streams; it is said to be
{263}exceedingly timid, and to utter a short cry when disturbed and making
its enormous leaps.
Another North American relation is _R. halecina_ s. _palustris_,
frequenting the neighbourhood of ponds and rivers, very lively and capable
of jumping 8 to 10 feet. The tympanum is smaller than the eye, but there is
the same glandular lateral fold as in _R. clamata_. The vocal sacs are
internal and decidedly small.
[Illustration: FIG. 50.–_Rana clamata_, × ⅔.]
_R. esculenta._–The common Water-frog of nearly the whole Palaearctic
region is closely allied to the American Water-frogs described above, and,
like most of them, has the vomerine teeth in two small oblique rows between
the choanae and extending a little beyond their posterior border. But the
males have a pair of external vocal sacs. The tympanum is distinct, about
two-thirds the size of the eye. The first finger is slightly longer than
the second. The toes are entirely webbed. Besides the usual subarticular
phalangeal tubercles, the sole of the foot is provided with two metatarsal
tubercles, the outer of which is very small, while the inner is much
larger, although varying in size from a soft oval to a long, curved,
shovel-shaped structure. The skin is smooth, except for a pair of prominent
glandular folds which extend from behind the eye along the dorso-lateral
line. The coloration varies considerably. The upper parts are mostly
greenish brown, with black brown spots on the back, and larger patches on
the limbs. Most specimens have three lighter stripes along the back, the
middle one mostly green, the two lateral bronzy brown and coinciding with
the glandular folds. The tympanum is brown, and there is occasionally a
dark temporal patch. The posterior aspect of the thighs is invariably
{264}spotted with black and white or yellow, in opposition to the _R.
temporaria_ group, where these parts are never spotted.
The total length of this species varies much. Specimens 2½ inches in length
are certainly mature, those of 4 inches are unusually large, and Boulenger
has received a giant from Damascus, which measured 125 mm., or nearly 5
inches. The females are larger than the males.
The variations in colour are not only local but also individual, moreover
the colours are changeable. The ground-tint ranges from dull brown through
olive to bright green, the dark spots being more or less pronounced and
numerous; the light vertebral line is olive-yellowish, bright green, or
altogether absent.
Those which inhabit waters with plentiful vegetation, like water-lilies and
other luxuriant plants, are generally prettier and more vividly coloured
than those which live in swamps and ponds with dark mud, or where the
prevailing vegetation has a sombre aspect. Cold and dull, warm and sunny
days also influence the water-frogs, and those which have been kept in a
dark tank look very different from the bright assembly which had been put
in some weeks before.
Various attempts have been made at subdividing _R. esculenta_ of Linnaeus
into sub-species, and Boulenger has now, after the attentive study of an
enormous material, arranged them in four principal and recognisable races.
The chief differences are the relative length of the femur to the tibia and
the size of the metatarsal tubercles.
1. Var. _ridibunda_, Pallas.–The right and left heels overlap each other
when the thighs are stretched out at right angles to the vertebral column,
and the tibia is closely folded up against the thighs. When stretched
forwards, the heel reaches the eye or even the tip of the snout. The inner
metatarsal tubercle is feebly developed, very small and blunt; the outer
tubercle is absent.
That part of the thighs which is concealed by the legs when the animal is
at rest is whitish or pale greenish, marbled with dark olive, or bronze, or
of the latter colour with or without small light spots. No trace of yellow
is ever to be detected on that region, nor at the axillae or on the groin.
The vocal sacs are strongly pigmented with black, when inflated they are
pale grey. The iris is a mixture of black and gold.
{265}This form or race has the widest distribution, namely, all over Europe
with the exception of England, the northern half of France, the Rhine
countries, Denmark, and Italy. Southwards it extends from France through
Spain and Portugal into the Sahara, eastwards into Turkestan. It attains a
larger size than the others, but only in certain localities in various
countries, where circumstances favour its development. Eastern countries
produce the largest of all; those of the Volga are said to be very large.
German physiological laboratories prefer those from the Danube, from
Bohemia, and from the lakes and broad expansions of the Spree, to specimens
from other localities.
2. Var. _typica_ (_esculenta_, Linnaeus).–The heels just meet, but do not
overlap. The inner metatarsal tubercle is strong, compressed, and
prominent. A small outer tubercle is present. The heel reaches to the eye
or a little further; the hinder surface of the thighs is "marbled with
black, usually with more or less bright yellow pigment" in the living
specimens; the vocal sacs are white or feebly pigmented. This race inclines
to rather more green than the others, the males especially are often dark
grass-green, with scarcely any markings. The vertebral stripe is then
yellowish, and the lateral stripes almost golden. The range extends over
the whole of Central Europe and the kingdom of Italy. Its northern limit is
the southern end of Sweden. In the greater portion of Germany, Poland, and
Austria it overlaps the var. _ridibunda_, with which it does not seem to
pair, owing to a difference in the time of spawning; the var. _typica_
being about a fortnight later, and beginning to spawn when the other has
finished.
3. Var. _lessonae_, Camerano.–Except that the inner tubercle is stronger,
while the outer one is near the vanishing point, and that the fourth toe is
proportionally longer, this variety is really not distinguishable from the
typical form, and Boulenger himself confesses that the distinction is
arbitrary. The var. _lessonae_ seems to have a rather sporadic
distribution. It has been found in Piedmont and other parts of Italy, in
Hungary and Transylvania, near Vienna, Halle, Upper Bavaria, on the Rhine,
near Brussels, Paris, and what is of especial interest to us, in a few
places in the eastern counties of England.
According to Boulenger's "Notes on the Edible Frog in England,"[116] the
individuals of _R. esculenta_ which live in Foulmire {266}Fen in
Cambridgeshire, near Stow Bedon, and between Thetford and Scoulton in
Norfolk, and are generally supposed to have been introduced from France,
belong to the Italian form of var. _lessonae_. "It used to be found in
Cambridgeshire, in Foulmire Fen, where it was discovered in 1844; and
Bell[117] assures us that his father, who was a native of Cambridgeshire,
had noticed the presence of these frogs many years before at Whaddon and
Foulmire, where they were known from their loud croak as 'Whaddon organs'
and 'Dutch nightingales.' The species was afterwards rediscovered in
Norfolk, between Thetford and Scoulton, where it is now still very
abundant, and from inquiries made by Lord Walsingham, must have existed for
the last seventy (80) years at least. These frogs belong to the var.
_lessonae_, and differ widely (by the much stronger inner metatarsal
tubercle) from those found in a few other places in Norfolk, which are
undoubtedly the descendants of a number imported from France and Belgium in
1837, 1841, and 1842, and turned loose in the Fens at Foulden and in the
neighbourhood.... Within the last ten years large numbers of all the three
forms have been imported from Brussels, Berlin, and Italy, and liberated in
various localities in West Surrey and Hampshire. Berlin specimens of the
var. _ridibunda_ have also been introduced in Bedfordshire, and Italian
ones in Oxfordshire."[118]
Leaving aside the question whether the so-called var. _lessonae_ is merely
sporadically developed out of the typical form, the inquiry of the possible
origin of the English specimens of the var. _lessonae_ is of special
interest. Have they been introduced, as has been suggested, from Lombardy,
or are they the last lingering descendants of native English frogs? The
suggestion as to their Italian origin has naturally lost in value since
similar specimens have been found in Belgium and near Paris; but we must
remember that there existed considerable intercourse between East Anglia
and the monks of Lombardy, who, to mention only one instance, came
regularly to the old Priory of Chesterton, near Cambridge, in order to
collect their rents. If the frogs were introduced by them for culinary
purposes into various suitable localities their descendants would remain as
local as they, and as the undoubtedly introduced French typical specimens
actually are. On the other {267}hand, if we assume the _lessonae_ specimens
to be the last living descendants of English natives, it is inconceivable
why they should now be restricted to that eastern corner while there are
hundreds of other suitable places in England and Wales which, if on the
Continent, would be perfect paradises for Water-frogs. The same vegetation,
the same insects, the same climate, and–an enormous advantage to the
frogs–no storks.
These English specimens are "olive-brown or bronzy-brown above, with black
spots, strongly marked on the flanks, where a light longitudinal area
remains unspotted; glandular folds lighter; the sides of the head and the
ground colour of the flanks are sometimes green; tympanum chestnut-brown; a
pale yellow or pale green vertebral line, frequently edged with black; the
dark cross-bands on the limbs usually very irregular, sometimes absent;
lower surfaces more or less profusely spotted with blackish; iris golden.
Length of a male from Stow Bedon, 64 mm. or 2½ inches; of a female, 78 mm.
or 3 inches."[119]
4. Var. _chinensis_, Osb.–Distinguished by short glandular folds along the
back, in addition to the long dorso-lateral pair. The metatarsal tubercle
is large and shovel-shaped. Distribution from Corea and Japan to Siam.
All these Water-frogs are decidedly aquatic. They make short excursions on
land when their homes are dried up, but as a rule they remain in the lake,
pond, river, morass, or ditch in which they were born. Their favourite
resorts are the broad floating leaves of water-plants, for instance
water-lilies, or a prominent stone, a tussock of grass, or the banks of
their homes, where they sit motionless, basking for hours in a half-erect,
alert position, watching for insects and other small fry, which are secured
by a jump, and then lapped up. Sunshine is sure to bring them out, and on
our approach they make straight for the water, either by one tremendous
leap or with quick bounds, but without the slightest hesitation or stopping
on the way. With folded arms they take a header, swim, with the arms still
folded, for some distance under water, and conceal themselves in the mud,
between stones, or in the vegetation. We perhaps have not seen them at all,
whilst their watchful eyes and keen ears have noticed our approach, and the
pond might appear uninhabited if we had not heard the plumping noise. If we
{268}keep quite still, and they have not been disturbed previously, one
after another will wriggle out of the mud, rise slowly to the surface under
cover of the plants, and, without causing a ripple, rise just enough for
the prominent eyes and the nose to clear the surface. Then one scrambles
partly on to a leaf, but the sight of the huge human figure strikes him as
uncanny, as it certainly does not belong to the scenery, and he doubles
back, the broadly-webbed feet making a little splash. But another appears,
jumps on to a leaf in the middle, or at the farther end of the pond,
settles down, and utters a little croak, somewhat like "ooaar," and soon
the whole company appear one after another, each taking up its favourite
position. After all, their observing powers cannot be very great. If we
ourselves keep still we may wield a rod and fish for them. There is no need
of a hook, a piece of red cloth tied to the end of the line and skimmed
over the water causes a lively commotion. The new bait is noticed at once,
and arouses their curiosity; several jump at it, and the one which swallows
the bait can be lifted out before it has time to let go. However, this is
after all poor sport; the game is too eager. When a boy I have often caught
them with a noose of slender wire at the end of a long hazel rod. They do
not mind the rod at all, their attention being fixed on the person; they
allow the noose to be slipped over their heads, and a sudden jerk secures
the captive. In this way they can be singled out individually. Old frogs
are more wary and experienced than the younger members; they take up safer
positions, and by their sudden plunges give the alarm.
[Illustration: FIG. 51.–_Rana esculenta._ × 1. Three stages of the movement
of the tongue.]
The males are great musicians, singing for sheer enjoyment not only during
the pairing time, but throughout the months of June and July. Warm moonlit
nights are the favourite times {269}for the concert, which takes place in
the water, beginning at sunset, and continuing until the early dawn. A few
individuals here and there utter a single note, "gwarr, oo-arr," or
"coarx," but these are only preliminaries. The precentor–the country-folk
in North Germany firmly believe that in each pond one old male holds the
dignified position of choir-master–begins with a sharp-sounding "brekeke,"
and this is the signal for all the others to chime in with the same notes,
varied with all sorts of other sounds, bass, tenor, and alto, each
performer filling its resounding vocal sacs to bursting size, and these
bags then look as if they acted as floats. When there are several hundred
of these sociable creatures, the din is continuous, and may be heard more
than a mile off. There can be too much of this, just as there can be too
many nightingales; and a well-stocked pond in the neighbourhood may become
a perfect nuisance. There are accounts of servants having been employed in
the Middle Ages for the sole purpose of keeping the noise down by beating
the pond, throwing stones into the water, or otherwise disturbing the
frogs. Sometimes more vigorous and lasting measures seem to have been
taken; the monks exorcised them in order not to be disturbed in their
vigils. Near the former monastery of Chorin, in the province of
Brandenburg, the frogs have still the reputation of keeping very quiet on
account of some powerful abbot who threatened them with awful consequences
if they did not forego their concerts.
[Illustration: FIG. 52.–_Rana esculenta._ Male with inflated external vocal
sacs. × 1.]
The length of life which these frogs can attain is quite unknown. They do
not reach maturity until the fourth or fifth year, but this is long before
they stop growing, and it is no exaggeration to say that few, if any, frogs
die of old age, since they have so many enemies. The stork is their king in
the fable, and his daily visits to his realm strike dire distress amongst
his subjects, which soon learn to know his conspicuous white and black
garb, and seek imperfect safety at the bottom of shallow ponds and ditches,
not too deep for the long-legged and long-billed despot. Numbers are taken
by birds of prey; snakes and tortoises hunt them up in the water, and they
are good bait for pike and other voracious fishes. The specific {270}name
_esculenta_ needs no comment, and this species is as much a martyr to
science as the brown Grass-frog. The destroyers of tadpoles and young frogs
are unlimited. In their turn the frogs themselves, especially the old ones,
are very rapacious, and eat any living creature they can master,–insects,
worms and snails, other frogs, especially the brown kind, and the young
brood of fishes.
Recently caught Water-frogs are wild beyond description, much more so than
the Grass-frog, but even they calm down after some time, learn to know
their keeper, and allow him to handle them without trying to commit suicide
by jumping on to, into, and down anything. However, they do not thrive well
in captivity, and it is rare that they can be induced to breed, unless
their enforced new home affords them ample freedom, and plenty of water and
fresh air.
The Water-frogs appear in Germany rather late in the year, not before the
middle of April, first the younger, then the adult members. In Southern
Europe they show themselves earlier, and still further south they do not
hibernate at all. The breeding season begins in Germany towards the end of
May and continues well into June, the var. _ridibunda_ beginning mostly a
fortnight earlier. The male clasps the female under the arms, throwing its
own round her breast, the nuptial grey excrescences on his inner fingers
pressing against her skin, the palms being turned outwards. The embrace
does not last long, rarely extending over a few days. The eggs, to the
astonishing number of 5000 to 10,000 in full-grown specimens, are expelled
in several masses, which sink down and remain at the bottom. The eggs
measure only 1.5 mm. and are yellowish-grey above, pale yellow below; their
gelatinous cover swells to 7-8 mm. in width. The embryo escapes on the
fifth or sixth day as a very small larva, in which, however, the mouth,
eyes, and beginnings of the external gills are already discernible. At the
age of two weeks the gills have shrunk away, the left-sided "spiracle" is
completed, and the well-tailed tadpoles, olive brown above, yellowish white
below, still hang with their suckers on to plants and stones, or lie at the
bottom, nibbling away at any rotting animal matter or scraping off the
green algae.
It may here be mentioned that small tadpoles of any kind can with advantage
be used as cleaners of delicate and small {271}skeletons. The object is put
into a vessel, and the tadpoles will soon nibble and rasp away all the
edible portions, leaving the skeletal framework beautifully cleaned. But
they require attention lest they rasp away the cartilage.
The tadpole stage lasts three to four months; but cold, absence of
sunshine, and scarcity of food delay the metamorphosis well into the end of
summer, or force them to hibernate in the unfinished condition. They are
very gregarious, and when the tadpoles of several families combine, they
make imposing shows. By the time that their hind-limbs begin to sprout,
they frequently combine into large shoals, and instead of always feeding
they swim about in their tens of thousands, all moving in the same
direction, and making almost regular evolutions. Mill-ponds with steep
banks are good places for watching these peculiar habits. The tadpoles
reach a considerable size, the total length averaging 2½ inches, or some 60
mm. the tail taking up ⅔ of the whole length. Specimens which measure more
than 3 inches are rare. The baby-frogs hop on land while still provided
with a stumpy tail; when this is resorbed the little creature is scarcely
half-an-inch long, and for the rest of the available season leads a rather
more terrestrial life than ever after.
_Ex Africa semper aliquid novi!_ Quite recently Boulenger has received a
consignment of Anura from the French Congo, amongst which were several new,
remarkable genera, notably _Trichobatrachus_ and _Gampsosteonyx_. Both are
true Ranidae. Pupil vertical, with vomerine teeth. Omosternum with a bony
style. The outer metatarsals are bound together. In _Trichobatrachus
robustus_ the toes are webbed, and both sexes have the flanks and
corresponding portions of the thighs covered with numerous darkly
pigmented, filamentous, cutaneous excrescences; these are several
millimeters in length, giving the flanks and thighs a "hairy" appearance.
Mr. F. F. Laidlaw has examined these structures. Their most remarkable
feature is the presence in them of a great number of ordinary flask-shaped
cutaneous glands, whilst such glands are scarce on the surrounding skin.
They differ in no way from those seen in sections of the skin of the Common
Frog. The fibrous connective tissue is dense and vascular; the
pigment-cells are most plentiful at the base. Contrary to expectation no
nerve-endings were found in these filaments.
{272}_Gampsosteonyx_ has free toes. The terminal joints of the digits stand
out beyond the skin, and end in sharp, bony claws, like those of a cat.
SUB-FAM. 3. DENDROBATINAE.–About one dozen arboreal little frogs have been
separated from the Raninae proper on account of the entire absence of
teeth. This mere loss of teeth, and the geographical distribution suggest
that these frogs do not form a natural group, but have been developed
independently from other Ranidae, the Neotropical _Dendrobates_ from some
likewise Neotropical genus like _Prostherapis_, the Malagasy _Mantella_
from an African form like _Megalixalus_.
The sacral diapophyses are cylindrical. The omo- and meta-sternum are well
developed. The fingers and toes are free, their terminal phalanges are
T-shaped and carry regular, round, adhesive discs. The tympanum is
distinct, although sometimes, in _Dendrobates_, very small. The pupil is
horizontal.
_Dendrobates._–The tongue is elongate, entire and free behind. The
omosternum has a weak, semi-ossified style, but the metasternum remains
cartilaginous. The males have a subgular vocal sac. Seven closely-allied
species inhabit tropical America.
_D. tinctorius._–This pretty little species, scarcely 1½ inch in length, is
quite smooth, varies much in coloration, and forms local races to a certain
extent. Some are quite black, others are grey above, black on the sides and
under parts; or they are grey with large black patches. A fourth variety is
black above with several white or pink longitudinal stripes, while the
under parts are grey, spotted with black. In others, again, the
ground-colour is black, with white stripes and spots above, marbled below.
But this enumeration does not exhaust the list, since living specimens are
sometimes much more conspicuously coloured, some being black with large
patches of saturated yellow on the head and back, while the limbs are
orange red and black. This species has a wide range, from Panama to Ecuador
and to the mouth of the Amazon. It owes its specific name to the peculiar
use made by man of the strongly poisonous secretion of the tiny glands of
the otherwise smooth skin. Other species are doubtless employed in the same
way. The poison is mainly used for "dyeing" the green Amazon-parrots. This
is done as follows:–The green and blue feathers on the head and neck, or
other parts, according to the fancy of the {273}operator, are plucked out,
and these places are rubbed with the poison, often simply with the living
frog, certainly not with its blood, as is sometimes asserted. This
operation may be repeated when the new, young feathers begin to bud. The
result is that these appear yellow instead of green, and since the
Brazilians, and to a certain extent the Portuguese, are rather partial to
these artificially-produced freaks or "contrafeitos" as they call them, the
industry is kept up. That the poison is also used for arrows has been
mentioned on p. 38.
[Illustration: FIG. 53.–_Dendrobates tinctorius_, three colour-variations.
× 1.]
_D. trivittatus_, chiefly in Northern Brazil, has the first finger slightly
longer than the second. It likewise varies considerably in its coloration,
being either quite black, or spotted with white and brown, or with a
whitish forehead and several white patches on the back and hind-limbs. _D.
typographus_ of Central America is vermilion red, with small dark marks on
the back; the legs are black.
The various species of _Dendrobates_ take remarkable care of their young.
_D. braccatus_ lives in Brazil in "varzeas," _i.e._ moist but waterless
places, and carries its tadpoles on its back, to which they are attached by
a peculiar secretion. The same is said to be true of _D. trivittatus_,
which sits down in a drying-up puddle, lets the little tadpoles, when they
are only 6-7 mm. long, fasten themselves on, and conveys them to a safer
locality, where the water is calculated not to evaporate before the
metamorphosis is completed.
{274}_Mantella._–Both omo- and meta-sternum possess a bony style. The
tongue is free and distinctly mitred or cut out behind. The skin is very
granular. Several species, in Madagascar, were formerly put into the same
genus as the American forms, until Boulenger established the genus
_Mantella_ for them. The coloration is strikingly pretty. _M.
madagascariensis_ is a rare instance of difference in colour between the
two sexes. The male is bluish black, with light blue spots on the belly,
while the thighs and the inner sides of the legs are beautifully red. The
female is deep black, with a light green spot at the base and in front of
the limbs; the rest is coloured like the male.
_Cardioglossa gracilis_, quite recently discovered at the Gaboon, has
likewise to be added to the Dendrobatinae, on account of the absence of
teeth. It is a small, slender, arboreal frog, bearing an unmistakable
resemblance to the other genera by its general appearance and conspicuous,
contrasting coloration of black and white.
PART II
REPTILIA
"Cada uno es como Dios le hizo,
y aun peor muchas vezes."
"We are all as God made us
and many even worse."
SANCHO PANZA,
_Don Quixote_.
{277}CHAPTER VII
REPTILIA
DEFINITION AND CHARACTERS–POSITION OF THE CLASS REPTILIA IN THE PHYLUM
VERTEBRATA–CLASSIFICATION–SKULL AND VERTEBRAE.
The recent Reptiles comprise, broadly speaking, the Crocodiles, Tortoises,
Lizards, and Snakes. They are the only Vertebrates which are cold-blooded,
breathe by lungs, and have a median occipital condyle. Another equally
sufficient diagnosis is the following:–Tetrapoda, with a median occipital
condyle, with nucleated red blood-corpuscles, and with complete right and
left functional aortic arches. A still shorter diagnosis is:–Monocondylia
with a scaly skin.
If our diagnosis is to include the fossil Reptiles we have not only to
discard the characters drawn from the soft parts as unavailable, but we are
forced to treat the condition of the occipital condyle with caution, since
there exist, or must have existed, transitional stages between Reptiles and
Amphibia and Mammals; and the winged class Pterosauria does not permit us
to use the wings as a differential character for the Birds. In fact, while
the Reptilia are sufficiently separated from the Amphibia by their
absolutely gastrocentrous vertebrae, it is difficult to distinguish them as
a class from the Birds; hence the term SAUROPSIDA, which is intended to
indicate the close relationship of the Reptiles to the Birds in opposition
to the Mammalia, and to the ICHTHYOPSIDA or Amphibia and Fishes. However,
the Reptilia take up a very central position in the evolution of the main
classes of the Vertebrata. On the one hand, there is not the slightest
doubt that they are evolved from some branch of {278}the Stegocephali,
whilst on the other hand the Reptiles, probably through some branch of the
Theromorpha, have given rise to the Mammals; some other Reptilian branch,
at present unknown, has blossomed out into the Birds.
PRINCIPAL CHARACTERS OF THE REPTILIA.
1. The vertebrae are gastrocentrous.
2. The skull articulates with the atlas by one condyle, which is formed
mainly by the basioccipital.
3. The mandible consists of many pieces and articulates with the cranium
through the quadrate bones.
4. There is an auditory columellar apparatus fitting into the fenestra
ovalis.
5. The limbs are of the tetrapodous, pentadactyle type.
6. There is an intracranial hypoglossal nerve.
7. The ribs form a true sternum.
8. The ilio-sacral connexion is post-acetabular.
9. The skin is covered (_a_) with scales, but (_b_) neither with feathers
nor with hairs; and there is a great paucity of glands.
10. Reptiles are poikilothermous.
11. The red blood-corpuscles are nucleated, biconvex, and oval.
12. The heart is divided into two atria and an imperfectly divided
ventricle. It has no conus, but semilunar valves exist at the base of the
tripartite aortic trunk.
13. The right and left aortic arch are complete and remain functional.
14. Respiration is effected by lungs; and gills are entirely absent, even
during embryonic life.
15. Lateral sense-organs are absent.
16. The kidneys have no nephrostomes. Each kidney has one separate
ureter.
17. There is always a typical cloaca.
18. The eggs are meroblastic.
19. Fertilisation is internal, and is effected, with the single exception
of _Sphenodon_, by means of male copulatory organs.
20. An amnion and an allantois are formed during development.
Numbers 1, 2, 6, 7, 8, 14, 16, 18, 20 separate the Reptiles from the
Amphibia. Cf. also pp. 4 and 5.
Numbers 9 (_b_), 10, 12, and 13 separate them from the Birds and
Mammals.
Numbers 3, 8, and 11 separate them from the Mammals.
The EVOLUTION OF THE CLASSIFICATION OF THE REPTILES has to a certain extent
been already treated on pp. 7-9. For a long time only Chelonia or
Tortoises, Ophidia or Snakes, and Saurii were recognised as their principal
divisions. Then the Crocodiles were separated from the Lizards; later the
Coeciliae were removed from the Snakes and referred to the Amphibia,
{279}and ultimately _Sphenodon_ was recognised as deserving a separate
position, equal in rank to the other groups. Stannius showed that the
Crocodiles and Tortoises are relatively near allies in opposition to the
likewise closely allied Lizards and Snakes (_Sphenodon_ was then unknown),
and he expressed this by the term Monimostylica, or creatures with fixed
quadrate bones, for the former, and Streptostylica, creatures with movable
quadrates, for the latter combination. The fossil Reptiles were hardly
allowed proper places in the system. In various zoological text-books they
were, or are even now, treated as inconvenient, outlying, or supernumerary
members. A long time elapsed before, thanks to the labours of H. von Meyer,
Owen, Huxley, Marsh, Cope, Zittel, and Seeley, it was recognised that the
extinct groups form the preponderant mass of Reptiles, and that it is the
recent groups which, in spite of the bewildering number of species of
Lizards and Snakes, are the comparatively few and much-reduced members of a
once flourishing class. With the exception of the Lizards and Snakes, which
are on the ascending branch, the modern _Sphenodon_, the Crocodiles and the
Tortoises are a mere fraction, comprising a few survivals of
richly-developed groups, while all the others, the overwhelming majority,
have died out.
The classification adopted in this volume is as follows:–
CLASS REPTILIA.
Sub-Class I. Proreptilia.
" II. Prosauria. Orders: Microsauri, Prosauri.
" III. Theromorpha. Orders: Pareiasauri, Theriodontia,
Anomodontia, Placodontia.
" IV. Chelonia. Orders: Athecae, Thecophora.
" V. Dinosauria. Orders: Sauropoda, Theropoda, Orthopoda,
Ceratopsia.
" VI. Crocodilia. Orders: Pseudosuchia, Parasuchia, Eusuchia.
" VII. Plesiosauria. Orders: Nothosauri, Plesiosauri.
" VIII. Ichthyosauria.
" IX. Pterosauria.
" X. Pythonomorpha. Orders: Dolichosauri, Mosasauri.
" XI. Sauria. Orders: Lacertilia, Ophidia.
The eleven principal groups are here called "sub-classes" to emphasise the
undeniable fact that these Reptilian groups are of much greater
morphological value than those which are most generally called "Orders" in
the Mammalia, that class which we consider as the standard or model of
classificatory units.
{280}[Illustration: FIG. 54.–Diagrams of skulls, showing especially the
composition of the bony arches of the orbito-temporal region.
A, C, D, E, THEROMORPHA. A, _Elginia_, p. 305; C, _Cynognathus_,
p. 306; D, _Gordonia_, p. 310; E, _Dicynodon_, p. 310.
B, G, PROSAURIA. B, _Sphenodon_, p. 294; G, _Palaeohatteria_, p. 291.
F, CROCODILIA, p. 434.
H, I, K, CHELONIA, p. 316. H, _Chelydra_, p. 338; I, _Chrysemys_,
p. 346; K, _Cistudo_, p. 361.
_E_, Epiotic; _F_, frontal; _IT_, infratemporal fossa; _J_, jugal, shaded
vertically; _L_, lacrymal; _M_, maxillary; _N_, nasal groove; _Na_, nasal
bone; _O_, orbit; _P_, parietal; _Po_, postorbital, dotted; _Pf_,
post-frontal; _Pm_, premaxillary; _Pr_, prefrontal; _Ptg_, pterygoid; _Q_,
quadrate; _Qj_, quadrato-jugal; _So_, supra-occipital; _Sq_, squamosal,
shaded obliquely; _St_ (in B-E), supratemporal fossa; _St_ (in A),
Supratemporal bone.]
{281}[Illustration: FIG. 55.–Diagrams of skulls, showing especially the
composition of the bony arches of the orbito-temporal region.
L, PYTHONOMORPHA. _Clidastes_, p. 490.
M, N, O, LACERTILIA, p. 496. M, _Varanus_, p. 543; N, _Uromastix_,
p. 524; O, _Lacerta_, p. 550.
P, ICHTHYOSAURIA, p. 479. _Ichthyosaurus_, p. 483.
Q, PTEROSAURIA, p. 484. _Dimorphodon_, p. 486.
R, AVES, generalised, for comparison.
S, MAMMALIA, generalised, for comparison.
T, OPHIDIA, p. 581.
_C_, Condyle of mandible; _Col_, columella cranii; _F_, frontal; _I_,
interparietal or pineal foramen; _I.A_, Inner angle of mandible; _J_,
jugal, shaded vertically; _L_, lacrymal; _M_, maxillary; _N_, nasal groove;
_Na_, nasal bone; _O_, orbit; _O_{1}_, preorbital fossa; _P_, parietal;
_Pf_, postfrontal; _Pm_, premaxillary; _Pr_, prefrontal; _Ptg_, pterygoid;
_Q_, quadrate; _Qj_, quadrato-jugal; _Sq_, squamosal, shaded obliquely;
_St_, supratemporal bone.]
{282}The families cannot well be changed, and terms like super-families and
super-orders are sometimes resorted to by those who do not like to look
stern facts in the face.
The sequence of the groups, although arranged as much as possible in
ascending order, is of necessity as unnatural as that of the maps in an
atlas. We cannot yet construct a satisfactory phyletic tree of the
Reptiles. The Proreptilia connect them with the Amphibia. Next follow the
Prosauria with _Sphenodon_ among the Prosauri as the key to most other
groups. Then follow the Theromorpha, and it is probable that from various
branches of these have arisen the Chelonia, Dinosauria, Crocodilia, and
Plesiosauria. The descent of the Ichthyosauria is very problematic. The
same applies to the Pterosauria and to the Pythonomorpha, but it is
possible that they, together with the Sauria, are connected with the
Prosauria.
With all reserve these hypothetical affinities may be expressed by the
following diagram:–
Lacertilia Ophidia
| /
Ichthyosauria Plesiosauria | /
\ \ | /
\ \ Crocodilia |/
? \ | Sauria
\ | |
Chelonia \| | Pterosauria
\ Dinosauria Sphenodon | /
\ | | | /
\ | | | / Pythonomorpha
\ | | |/ |
Theromorpha |–––––––––––––––
| |
Prosauria
|
Proreptilia
The eleven sub-classes of the Reptilia present so many important
differences that it is not advisable to give here a further general account
of their structure. The diagrammatic figures A to T on pp. 280, 281,
representing various types of skulls, are intended to explain their chief
modifications, all referable to Proreptilian and to certain Theromorphous
conditions. One of the most important features is that the mandible, which
is always composed of many pieces (cf. Fig. 142, p. 550), is invariably
carried by the quadrate bone. Diagrams of the generalised skulls of a Bird
and a Mammal have been added for comparison.
{283}[Illustration: FIG. 56.–Composition of vertebrae of Reptiles,
illustrated by the first and second cervical vertebrae. (1) Atlas (first
cervical) and axis (second) vertebra of _Crocodilus_. (2) Atlas and axis of
_Metriorhynchus_, a Jurassic Crocodile. (3) Analysis of the first two
cervical vertebrae of a Crocodile; 2, second basiventral complex or
"intercentrum" continued upwards into the meniscus or intervertebral pad.
(4) Diagram of the fundamental composition of a Reptilian vertebra; compare
this and (6) with Fig. 1 (8 and 9) on p. 13. (5) The first three cervical
vertebrae of _Sphenodon_. (6) Trunk-vertebrae of _Eryops_, a Permian
Proreptile; typically temnospondylous; _cp_, articular facet of the
capitulum of a rib. (7) The complete atlas of an adult _Trionyx hurum_; the
second basiventral (intercentrum) is attached to the posterior end of the
first centrum, which, not being fused with the second centrum, is not yet
an odontoid process. (8) The complete atlas of an adult _Trionyx
gangeticus_; still typically temnospondylous. (9) The first and second
cervical vertebrae of an adult _Platemys_. (10) The complete atlas of a
_Chelys fimbriata_. _Az_, Anterior zygapophysis; _B.D_, basidorsal; _B.V_,
basiventral; _C_{1}_, _C_{2}_, _C_{3}_, first, second, and third centra,
formed by the interventralia; _Cp^1_, _Cp^2_, articular facets of the
capitular portions of the first and second ribs; _I.V_, interventral;
_N_{1}_, _N_{2}_, _N_{3}_, first, second, and third neural arch, formed by
basidorsalia (_B.D_); _Od_, odontoid process = first centrum; _Pz_,
posterior zygapophysis; _R_{1}_, _R_{2}_, ribs; _Sp_, detached spinous
process of the first neural arch; _t_{1}_, _t_{2}_, tubercular attachments
of the first and second ribs; 1, 2, 3, 4, "intercentra" = basiventrals;
_I_, _II_, _III_, position of the exit of the first, second, and third
spinal nerves.]
As mentioned on p. 278 the vertebrae of the Reptilia and those of all other
Amniota are _gastrocentrous_; that is to say the centra or bodies of the
vertebrae are formed by the pairs of interventralia, while the
basiventralia are reduced, persisting either as so-called intercentra or
wedge-bones, or as intervertebral pads, or disappearing altogether. At the
earlier stages of development the gastrocentrous vertebrae behave in the
{284}same way as that described on p. 12 (Fig. 1), except that the
interdorsal elements are suppressed from the beginning. If the remaining
three pairs of constituent elements of each vertebra (the basidorsalia,
forming the neural arch; the interventralia, forming the body or centrum;
and the basiventralia) remain separate, the vertebrae are called
_temnospondylous_ (τέμνω, I cut, σπόνδυλος, a vertebra). If the neural
arches and the centra are suturally united or are fused with each other,
the vertebrae are called _stereospondylous_ (στερεός, solid). In many
Amniota the atlas or first vertebra remains in a relatively primitive,
embryonic condition, and is temnospondylous but for the usual modification
that its centrum becomes attached to that of the second vertebra, and forms
the odontoid process of the latter. The composition of gastrocentrous
vertebrae (cf. p. 282) is best illustrated by the first and second cervical
vertebrae of the Crocodile (Fig. 56, 3, p. 283).
Concerning GEOGRAPHICAL DISTRIBUTION, even a cursory study shows that the
sub-classes have come into existence at very different geological periods,
and have each followed their own lines of dispersal.
{285}CHAPTER VIII
PROREPTILIA–PROSAURIA–THEROMORPHA
_SUB-CLASS I.–PROREPTILIA._
_Permian Temnospondylous Reptiles with well-developed limbs and girdles of
the terrestrial type._
The two genera _Eryops_ and _Cricotus_ of the North-American Permian
formation had until recently[120] been relegated to the Stegocephali. By
grouping them and their nearest allies together as Proreptilia it is
intended to indicate that they are the lowest known Reptiles and that they
probably link this class to the Amphibia. The superficial resemblance of
their tri- or bi-partite vertebrae, and their occurrence in the Lower
Permian, have caused the error of classing them with the Stegocephali, but
the composition of their typically gastrocentrous vertebrae leaves no doubt
as to their affinities. After all, we feel certain that Reptiles have
arisen from Stegocephalous Amphibia, and it is in the Lower Permian,
exactly where these debatable creatures lived side by side with
Stegocephali, undoubtedly likewise temnospondylous, that the change from
Amphibia into Reptiles seems to have taken place. Both are referable to
Amphibia with quadripartite vertebrae. The condition of the occipital
condyles determines nothing. This greatly exaggerated character has lost in
importance since we have known the condylar modifications of the
Theromorpha; moreover, _Cricotus_ itself seems to have possessed a single
condyle. We should even expect the Proreptilia to present many
Stegocephalous inheritances, for instance the condition of the skull roofed
in by dermal bones, a ventral dermal armour, a very complete pectoral arch
still without a sternum, and only one sacral vertebra.
{286}Until more genera are better known than they are now, it is premature
to divide the present sub-class into orders.
[Illustration: FIG. 57.–Trunk vertebrae of _Eryops_ (cf. Fig. 56, 4,
p. 283). _Cp_, Articular facet of the capitulum of a rib.]
_Eryops_, with several species in Texas and New Mexico. _E. megacephalus_
is the most abundant and the largest species, its broad and flattened skull
measuring more than 18 inches in length and 12 in width. With the exception
of the nostrils and the small orbits, the skull is entirely encased in
bone, with a rough, pitted surface, but without any distinguishable
sutures. The absence of mucous canals, so common in the Stegocephali, is
worthy of note. The quadrates extend obliquely outwards and backwards, so
that the joint with the mandible lies in a plane behind the occiput. The
mandibles are devoid of a projecting angular process. The teeth are
numerous, small, and pointed. The vertebrae are typically temnospondylous,
consisting each of three pairs of separately ossified pieces, which,
although closely packed together, are not suturally connected. The neural
arches possess high spinous processes, they articulate by short and broad
zygapophyses and are, with their triangular bases, wedged in between the
two ventral pieces, the posterior of which (the united interventralia) is
in broader contact with the neural arch and lies behind it; the anterior
piece (the united basiventrals) appear as typical, but large, intercentra,
and bear on their posterior, dorsal margin the facets for the ribs. The
latter are short, but are broad at their proximal ends, which are not
bifurcated; they extend their articulation from the "intercentra" upon the
short lateral processes of the neural arches. The tail is short and ends in
a pointed coccyx, owing to fusion of the last vertebrae.
The pubes and ischia are heavy, the former flattened and broadened out. The
limbs are of an almost ideal pentadactyloid type; strongly developed for
terrestrial locomotion. The ulna possesses a large olecranon. The carpus
consists of ten separate pieces, ulnare, intermedium, radiale, two
centralia and five distal carpalia. The latter support only four
metacarpals and fingers, the second finger being completely abolished, an
explanation suggested by Cope and corroborated by Emery.[121]
{287}_Cricotus_, with several species in Texas and Illinois. _C.
heteroclitus_ was perhaps 10 feet long and probably aquatic. The skull has
a long, narrow, depressed snout, the margins overhanging those of the lower
jaw; its surface is encased in dermal bones, most of which still show
sutures, so that for instance postfrontals, postorbitals, supratemporals
and squamosals can be distinguished; all these are in contact with the long
parietals and with the quadrato-jugal arch, covering the temporal region;
but the supratemporals have a free projecting border, like the squamosals
of the crocodiles. According to Cope's description the basioccipital is
connected with the first vertebra by an undivided discoid "intercentrum,"
probably the true centrum, while the first basiventral mass, which would
be, if independent, the first true intercentrum, is more probably connected
with the first neural arch, thus constituting the ring of the atlas.
The vertebrae are still temnospondylous, but no longer tripartite. The
neural arch is fused with the interventralia into one mass, which carries
the capitula and tubercula of the ribs, while the united basiventrals still
remain as separate intercentral wedges. In the tail these wedges carry
chevron-bones, and are enlarged into thick almost complete discs, or rather
rings, while the whole vertebral column is still perforated, as also in
_Eryops_, by the chorda dorsalis. The tail is long. The digits are devoid
of claws.
Remains of dermal armour exist on the throat in the shape of several large
gular plates, while the whole belly is covered with many closely packed
bony scales, which are arranged in chevron-shaped transverse rows.
Probably several other genera of American Permian and also of European
Permian strata will, when better known and critically examined, have to be
referred to the Proreptilia. Thus for instance the European _Melosaurus_
may have affinities with _Eryops_, while _Diplovertebron_ of Bohemia seems
to be allied to _Cricotus_. The difficulty of division will lie with those
Lower Permian Amphibia which, like _Archegosaurus_, _Euchirosaurus_,
_Actinodon_, possess tripartite vertebrae, which at first sight are
strikingly like those of _Eryops_. But the tail-vertebrae permit of no
mistake, and since these are quadripartite in _Archegosaurus_,
_Chelydosaurus_, and _Sphenosaurus_, these genera are safely to be classed
with the Amphibia, unless, indeed, for mere argument's {288}sake, it be
assumed that the intercentral discs of _Diplovertebron_ and _Cricotus_ are
formed by the fusion of Amphibian interdorsals with interventrals. Anyhow,
simply to state that the tripartite vertebrae of _Eryops_ are the same as
those of _Actinodon_, would be as convincing as saying that the English and
French flags are essentially the same, both containing the same colours,
but one is white, red, and blue, the other blue, white, and red. Tripartite
Amphibian vertebrae are composed of basidorsals + basiventrals +
interdorsals, those of Reptiles are made up of basidorsals + basiventrals +
interventrals. (Cf. Fig. 56, p. 283, and Fig. 1, p. 13.)
_SUB-CLASS II.–PROSAURIA._
_Mostly extinct Reptiles, with deeply amphicoelous but stereospondylous
vertebrae, with movable chevron-bones in the tail and frequently with
intercentra in the trunk._ Sphenodon, _the only recent genus, has no
copulatory organs_.
ORDER I. MICROSAURI.
_Extinct, small Reptiles, mostly Carboniferous and Permian, with dermal
armour on the dorsal and ventral side and with bifurcated ribs._
We retain this term of Dawson's for those small, newt-shaped, chiefly
Permian reptiles, which are allied to _Hylonomus_, after elimination of
contemporary forms like _Keraterpeton_ and _Urocordylus_, which belong to
the Branchiosaurian order of the Stegocephali. Until recently[122] all
these creatures had been classed with the Stegocephali. The Microsauri in
the present restricted sense reveal themselves, however, as reptiles by the
movable chevron-bones in their tail, their broad neurocentral sutures, the
possession of two sacral vertebrae (_Petrobates_), the bifurcated ribs
which always articulate with the centra (most clearly shown in
_Orthocosta_), and the possession of five fingers and toes.
Considering the age of these little creatures and their low position in the
reptilian scale–in fact, they stand almost as low {289}as the
Proreptilia–it is not to be wondered at that they still retain a number of
amphibian features. The skull is encased in dermal bones as in the
Stegocephali, and the dermal armour of the trunk and tail is composed of
many bony, sculptured scales, which cover back, sides, and under surface.
The middle rows on the back are the largest, while the scales on the belly
are arranged in transverse rows, which imbricate and converge obliquely
headwards. Special gular plates seem to be absent. The skull has an
interparietal foramen. The jaws and the palate are furnished with small,
simple teeth, and there is a large parasphenoid bone, an eminently
amphibian character. The occipital condylar articulation is supposed to be
double. The centra of the vertebrae are deeply amphicoelous, elongated, and
constricted in the middle, just like those of the Aistopoda and
Branchiosauri. The dorsal spinous processes are strongly developed, and
with the zygapophyses are very reptilian. Transverse processes are absent
or very short, the tubercular portions of the ribs articulating with the
centra, the capitula mostly intervertebrally, in any case close to the
anterior end of the centra. The tail-vertebrae possess very typical,
movable chevrons, placed intervertebrally, and bear an extraordinary
resemblance to those of Geckos. The ribs are long and slender, but there is
no sternum. The fore- and hind-limbs are pentadactyle, in opposition to the
invariably four-fingered Stegocephali. The shoulder-girdle consists of
scapulae, coracoids, clavicles, cleithra, and a T-shaped interclavicle. The
pelvis also resembles that of certain Stegocephali by the separately
ossified, somewhat disc-shaped, flat ischia and pubes, which seem to have
been joined together by cartilage into one broad mass.
_Hylonomus_, Dawson's type of Microsauri, was found in the Coal-measures of
Nova Scotia, within decayed tree-stumps. Closely allied, if not identical,
but much better known is _Hyloplesion_, e.g. _H. longicostatum_ of the
uppermost Permian of Nyrschan in Bohemia. Total length under 4 inches; eyes
with bony sclerotic rings; neck short. The truly Permian genera _Dawsonia_,
_Melanerpeton_, _Orthocosta_, and _Seeleya_ are allied forms, the last
scarcely one inch in length, but well preserved. _Petrobates_ of the
Triassic Lower Red Sandstone of Saxony has an arrangement of the ventral
dermal armour closely resembling abdominal ribs.
{290}ORDER II. PROSAURI
Mostly extinct, chiefly Permian and Triassic, terrestrial, unarmoured
reptiles with deeply biconcave vertebrae, numerous intercentra and
chevron-bones, fixed quadrates, complete pentadactyle limbs and
shoulder-girdle, entepicondylar foramina, acrodont teeth, and many small
abdominal ossifications.
The Prosauri differ from the Microsauri, with which they are closely
allied, by the more advanced solidification of the vertebrae, the reduction
of the tubercular portions of the ribs, the presence of an entepicondylar
foramen in the humerus, and the loss of the dermal ossifications on the
upper surface.
Their ancestors are the Microsauri, whilst they themselves seem to be very
near the root whence have sprung most, if not all, other main branches of
the reptiles, notably Crocodilia, Dinosauria, and Sauria. In fact the
Prosauri, although apparently few in number, seem to represent the central
stem of the reptilian tree. Only one of them is still surviving, the famous
_Sphenodon_, now represented by a single species in New Zealand.
SUB-ORDER 1. PROTOROSAURI.–The ventral half of the pelvis seems to have
formed one broad, continuous mass of cartilage in which the pubic bones are
represented by a pair of oval, rather disc-shaped ossifications, while the
ischia are more elongated. The pelvis consequently still bears a great
resemblance to that of the Microsauri, and thereby also to the
Stegocephalous condition, but the ilium seems to be attached to more than
two vertebrae. The vertebrae are deeply biconcave, perhaps even with a
persistent continuous chorda. The neural arches bear high, laterally
compressed spines, but no diapophysial or lateral processes, the ribs being
placed mostly intervertebrally and having lost their tubercular portions.
The ribs are continued to about the sixth caudal vertebra. Intercentral
wedges exist in an unbroken series between all the vertebrae from the atlas
to the tail, where they are represented by movable chevrons. A costal
sternum seems to be absent, unless it was quite cartilaginous. The
shoulder-girdle is complete, consisting of a long interclavicle, clavicles,
disc-shaped coracoids, and scapulae; but there are no cleithra, and no
indication of precoracoids or even notches in the coracoids. The fore- and
hind-limbs are complete and primitive, with five digits. The abdomen is
protected by numerous oat-shaped little {291}ossifications, which are
arranged in many transverse or rather chevron-shaped rows, still greatly
resembling the condition prevailing in the Microsauri, except that they
have sunk deeper into the skin, being no longer directly covered by the
scales. The skull, being no longer completely encased by bones, and
possessing now wide supra- and infra-temporal fossae, appears at first
sight much like that of a generalised lizard, except that it possesses
three very conspicuous and distinct arcades in the temporal region: namely,
the orbito-squamosal bridge across the temporal fossa, formed by the
postorbital and squamosal; the arch formed by the squamosal with the
postero-lateral buttress of the parietal; and the infratemporal arch or
jugal bridge. The jugal itself is long, connecting the quadrato-jugal with
the maxillary and lacrymal, and sending up an ascending process to the
postorbital bone, thus taking a considerable share in the formation of the
orbit. The quadrato-jugal is small, apparently fused with the quadrate,
which itself is firmly overlaid by the squamosal. The quadrates are further
fixed by being buttressed by the pterygoids, which rest upon short
basisphenoid processes and extend far forwards, meeting the vomers and
separating the palatines. The premaxillae are short, the nares small and
terminal, the nasal bones are large. There is a small interparietal
foramen. The teeth are acrodont and pointed, forming unbroken series on the
premaxillaries, maxillaries, palatines and dentaries, and there are
scattered little teeth on the vomers.
_Palaeohatteria longicaudata_ from the Lower Red Sandstone of Saxony. Total
length about 18 inches, with six cervical, twenty trunk, three or four
sacral, and about fifty caudal vertebrae. The teeth are ankylosed with the
supporting bones. The five fingers have 2, 3, 4, 5, 3 phalanges
respectively. For the skull see Fig. 54, G, p. 280. _Telerpeton elginense_
from the Triassic sandstone of Scotland, and perhaps _Saurosternon_ of the
South African Karroo sandstone seem to be allied.
_Protorosaurus_ (πρῶτος = first, ὤρα = spring, or dawn, not
_Proterosaurus_) apparently several species, e.g. _P. lincki_ in the Upper
Permian (marl-slate and magnesian limestone) of Thuringia and Durham. About
4 or 5 feet long, and in its general appearance rather like a
Monitor-lizard, with about eight cervical vertebrae, most of which carry
slender backwardly-pointing ribs, sixteen long-ribbed trunk-vertebrae,
followed by three or four {292}sacrals and more than thirty caudals, some
of which have bifurcated spinous processes.
SUB-ORDER 2. RHYNCHOCEPHALI.–The ventral pelvic bones resemble those of
lizards and enclose a wide pubo-ischiadic foramen. There are only two
sacral vertebrae. The abdominal ribs are closely packed, each transverse
set consisting of only three rod-shaped pieces instead of many small
oat-shaped nodules. The intercentra are sometimes suppressed in the
trunk-region.
_Rhynchosaurus_ from the Upper Trias of Warwickshire and Shropshire, and
_Hyperodapedon_ of the same age, found at Elgin, in Warwickshire, and also
in Central India, are rather large, _H. gordoni_ measuring 6 feet in
length. Both have a short, broad, and stout cranium, and curved down,
toothless premaxillae, hence the name Rhynchocephali; the nares are
confluent; the teeth are numerous and small, and are liable to be worn down
so that the animals ultimately bite with the edges of the jaws, to which
the teeth are ankylosed. The premaxillaries of _Rhynchosaurus_ are curved
downwards over a slightly upcurved, likewise toothless process of the
mandibles, which form a strong symphysis. All the teeth are very small,
absent, or minute on the mandibles, forming one series on the maxillae,
several rows on the vomers and especially on the palatines, which latter
remain separated from each other. _Hyperodapedon_ seems to have lost the
intercentra; its vertebrae are solid, those of the neck are opisthocoelous.
The interparietal foramen is likewise abolished. The hook-shaped end of the
curved-down premaxillae fits into a bifurcation of the mandibles in front
of their stout symphysis. The teeth are similar to those of the other
genus. Whilst these, the earliest known genera of Rhynchocephali, are
already in various ways rather specialised, _e.g._ the hooked beak and the
loss of the intercentra, the two following fossil genera, although of much
later date, namely Upper Triassic, are more closely allied to the recent
_Sphenodon_.
_Homoeosaurus pulchellus_ and other species in Germany are only 6 to 8
inches long. The vertebral column consists of twenty-three presacral and
many caudal vertebrae. The first five cervicals are devoid of ribs.
Intercentra are restricted to the neck and the anterior portion of the
tail. The mandibles are not fused together. The nares are divided by a bony
septum. Each premaxillary has one rather broad tooth.
{293}[Illustration: FIG. 58.–_Sphenodon punctatum._ × ⅓.]
{294}The teeth of the maxillaries and mandibles are triangular, much worn
down in front. The ribs are devoid of uncinate processes. Closely allied
but larger is _Sauranodon_ of France, which has lost the upper teeth and
uses the sharp margins of the jaws instead.
_Pleurosaurus_ of Germany and France, about 5 feet in length, is remarkable
for the shortness of its still pentadactyle extremities, for its short
neck, and very long tail;–an interesting parallel to what has happened in
many genera of recent lizards.
_Sphenodon_ s. _Hatteria_ is the sole surviving member of the whole group
of Prosauria, and is represented by one species only, _S. punctatum_, in
New Zealand. As the last living witness of bygone ages this primitive,
almost ideally generalised type of reptiles, this "living fossil," deserves
a detailed description.
Total length of very large male specimens up to two feet and a half; in
general appearance like many a stoutly built lizard. The general colour of
the skin is dark olive-green with small white or yellowish specks on the
sides. A series of slightly erectile spines of yellowish colour extends
from the top of the head to the end of the tail, but is interrupted on the
neck; they are cutaneous, covered with a thin sheath of horn. The under
surface is covered with numerous scales, arranged in transverse rows; the
rest of the body is rather granular. The tail is thick, slightly compressed
laterally. The eye is large, dark brown, with a vertical pupil.
Those who are satisfied with superficial resemblances still group this
creature with the lizards, but it reveals itself as a primitive reptile or
Prosaurian by the following characters, every one of which distinguishes it
from the lizards:–The temporal region is bridged by three bony arcades. The
large vomers, palatines, and pterygoids form a broad bony roof to the
mouth; the large quadrates are firmly fixed by the pterygoids, squamosals,
lateral occipital bones, and by the jugal bridge. The vertebrae possess an
unbroken series of intercentral wedge-bones. There is an elaborate system
of abdominal ribs. The humerus has an entepicondylar foramen, and there is
also, in contradistinction to the fossil Rhynchocephalia, an ectepicondylar
foramen for the passage of the radial nerve. The carpus still has the
primitive number of ten bones, all of which remain separate, including the
intermedium. Of soft parts are to be mentioned above all the entire absence
of external copulatory organs, _Sphenodon_ being the {295}only recent
reptile which is devoid of them; a most primitive condition, sufficient by
itself to separate this creature from all the other living reptiles.
[Illustration: FIG. 59.–A, Dorsal; B, ventral; C, left-sided view of the
skull of _Sphenodon_. × 3/2. _Col_, columella auris; _Cond_, occipital
condyle; _E.P_, ectopterygoid; _F_, frontal; _Jug_, jugal; _Max_,
maxillary; _Na_, nasal; _No_, anterior nasal opening; _Pal_, palatine;
_Par_, parietal; _Pmx_, premaxillary; _Prf_, prefrontal; _Pt.f_,
postfrontal and postorbital; _Ptg_, pterygoid or endopterygoid; _Q_,
quadrate and quadrato-jugal; _Sq_, squamosal; _Vo_, vomer. See also Fig.
54, B, p. 280.]
The supratemporal bridge is formed by the squamosal and postorbital (Fig.
59, C, _Pt.f_), the latter being continued forwards and fused with the
postfrontal (A, _Pt.f_). The postorbital joins the ascending branch of the
jugal, both together forming the hinder border of the orbit; this is
bordered below chiefly by {296}the maxillary, which is long, while the
anterior process of the jugal is much reduced. There is no pre-orbital
fossa. The nares are terminal and lateral, well separated by the
premaxillaries. The posterior temporal bridge is formed by the squamosal
and parietal, the bridge extending laterally over the quadrate and
enclosing a wide space between itself and the buttress-like expansion of
the lateral occipital bone. The space enclosed between this occipital
buttress, the quadrate, and the pterygoid support of the latter is likewise
very large; it is of course the cavity of the middle ear, and as such is
crossed by the columellar chain of the ear. The infratemporal bridge or
jugal arch is formed by the jugal, which joins the descending process of
the squamosal, and by the quadrato-jugal, which is small and fused with the
quadrate. The latter is consequently very firmly fixed.
The teeth are acrodont, ankylosed in one series with the supporting bones,
triangular and much worn down in older specimens. Originally there seem to
be several in the premaxilla, but the adult bite with the somewhat
curved-down portions of the premaxillaries themselves, or with what remains
of the fused bases of the original teeth, which then, together with the
bone, look like one pair of large chisel-shaped incisors. The lateral edges
of the palatines likewise carry teeth, those of the mandibles fit into the
long slit-like space between the palatine and the maxillary teeth. Young
specimens have a few small teeth on the vomers, which are large, and
separate the long choanae from each other. The pterygoids form an anterior
symphysis, posteriorly they rest upon short processes of the basisphenoid
and send short flanges to the quadrates.
The vertebral column is very primitive. The atlas is still typically
temnospondylous. The first intercentrum or fused pair of basiventrals is
broad and thick, and forms the ventral half of the atlas-ring, which
articulates with the first centrum and with the second intercentrum. The
irregularly shaped neural arches remain separate from each other and from
the centrum; they carry on the dorsal side a pair of disconnected
supradorsals, the so-called pro-atlas. The second intercentrum is fused
with the first and second centrum. The second to ninth intercentra have low
median ridges or knobs, and are as a rule more firmly attached to the
cranial ends of the centra. Those of the trunk are small. From the third or
fourth caudal vertebra {297}backwards they appear as chevrons, articulating
more with the vertebra in front than with the one behind. The bases of the
right and left chevrons are frequently fused across so that the caudal
canal is completely surrounded by bone, a feature common in Dinosaurs.
Every intercentrum, be it a pair of chevrons, or an unpaired nodule, or
crescent, extends dorsalwards into a fibro-cartilaginous ring which
surrounds the chorda. The centra of the vertebrae are deeply amphicoelous,
the cavity being filled throughout life by the chorda; but the middle of
the centra is solid. Most of the caudal vertebrae are transversely divided
into two parts, the posterior of which carries the greater share of the
arches; they resemble in this respect those of lizards, and the lost tail
is likewise reproduced. The first three ribs are represented by bands of
connective tissue. The first is attached to the side of the first
intercentrum; the second arises from the second intercentrum, and forms a
small tubercle on the side of the second centrum; the third behaves
similarly. The vertebral arteries and lateral strands of the sympathetic
nerve-chain pass through these double basal attachments of the reduced
ribs. The other ribs are osseous; they possess short capitula which retain
their partly intercentral attachment, while the short tubercula are carried
by low processes of the centra, not of the neural arches. Already in the
thoracic region both capitulum and tuberculum merge into one facet, at
first dumb-bell shaped, further towards the tail oval, gradually shifted
backwards and dorsalwards upon the middle of the centrum, until the facet
reaches and ultimately lies right across the neuro-central suture. The
first few caudal vertebrae also possess ribs, which are however very short
and fuse with the diapophyses, immediately below which lies the
neuro-central suture.
[Illustration: FIG. 60.–The first three cervical vertebrae of _Sphenodon_.
1, 2, 3, 4, Intercentra; _C_{1}-C_{3}_, centra; _N_{1}-N_{3}_ neural
arches.]
The whole column consists of twenty-five presacral, two sacral, and about
thirty caudal vertebrae. Some of the thoracic ribs have cartilaginous
uncinate processes. Three or four pairs of ribs join a typical sternum,
into the antero-lateral portion of which are let in the coracoids. The
sternum is raised into a low median crest which fuses with the posterior
branch of the {298}T-shaped interclavicle, while the lateral branches of
the latter fuse with the clavicles. The coracoids are broad and entire,
still without fenestrae or notches indicative of precoracoids. The
parasternum is very elaborate; it extends from the sternum to the pubic
bones, and consists of about twenty-four transverse rows, each of which is
composed of a median and two lateral splint-bones. They are irregularly
shaped, partly with imbricating hooks, and are firmly attached to, in fact
still connected with, the deeper portions of the cutaneous scales of the
belly. The three pairs of pelvic bones are fused together at the
acetabulum. Pubes and ischia each form one symphysis, and these are
connected with each other by partly ossified cartilage and ligaments, so
that the originally heart-shaped space is divided into a pair of ovals. The
lateral processes of the pubes are thick, but very short. The ischia have
postero-lateral processes. There is also a mostly cartilaginous, unpaired
hypo-ischium.
The fore- and hind-limbs are still primitive in structure; both
pentadactyle. The carpus consists of ten, sometimes eleven pieces,
according to the single or double nature of the central element. The
proximal series is formed by the radiale, intermedian, and ulnare, with a
pisiform. The ulna and radius remain separate. The humerus has the usual
ectepicondylar in addition to the entepicondylar foramen common to all the
Prosauri and Theromorpha. The hind-limbs are typically plantigrade.
The tail is capable of regeneration, as in many lizards.
The development of this reptile has recently been studied and described by
Howes,[123] who quotes the literature bearing upon the whole subject.
A good account of the occurrence and habits of the "Tuatera" has been given
by Newman.[124] The Maoris call it "ruatara," "tuatete," or "tuatara," the
latter meaning "having spines." Formerly common on the main islands of New
Zealand, they are now apparently restricted to some of the islets in the
Bay of Plenty, North Island. Bush-fires, wild pigs, dogs and cats,
reptile-eating Maori tribes, and the advance of civilisation, have swept
them away except on some of the small uninhabited islands, difficult of
access, where they dig burrows, into which they retreat at the slightest
sign of danger. They sleep during the {299}greater part of the day, are
very fond of lying in the water, and they can remain below for hours
without breathing. They live strictly upon animals, but these are only
taken when alive and moving about. The kind of food seems to vary according
to the custom or fancy of the individuals. Sir W. L. Buller observed that
some of his captives stubbornly refused to eat until one day, rather
accidentally, minnows were offered. Others eat insects and worms; those
which live near the seashore not improbably eat also crustaceans. From
November to January they lay about ten eggs–white, hard-shelled, long and
oval–about 28 mm. long, in holes in the sand, where they can be warmed by
the sun. They are as a rule lazy in their movements. The usual pace is a
slow crawl, the belly and tail trailing on the ground, but when chasing
prey they lift the whole trunk off the ground. After running, or rather
"wobbling" three or four yards, they grow weary and stop. They cannot jump
the smallest obstacle.
Von Haast[125] has carefully examined their habitations on the Chicken
Islands. The Tuatara excavates its own hole, and this is shared sociably by
various kinds of Petrels. The entrance to the chamber is generally 4 or 5
inches in diameter, and the passage leading into the inner chamber is 2 to
3 feet long, first descending and then ascending again. The chamber itself
is one foot and a half long, by one foot wide and 6 inches high, lined with
grass and leaves. The petrel lives usually on the left side, the Tuatara on
the right side of the inner chamber. Whilst very tolerant of the bird with
its egg and young, it does not allow another of its own kind to live in the
same hole, which it is ready to defend by lying in such a manner that the
head is placed where the passage widens out into the chamber. On putting
one's hand or a stick into the burrow the Tuatara bites at them furiously.
They can run very fast, and defend themselves with great pluck against dog
or man by biting or scratching. As soon as the sun has set they leave their
holes to seek food. During the night, and especially during the pairing
season, they croak or grunt.
The eggs, having been deposited during the Southern summer, from November
to January or February, in holes on a sunny and sandy spot, contain nearly
ripe embryos in the following August. They are, however, not hatched until
about thirteen {300}months old. In the meantime they seem to undergo a kind
of aestivation. The nasal chambers become blocked with proliferating
epithelium, which is resorbed shortly before hatching.
I have kept half-a-dozen specimens in a green-house for several years, and
have come to the conclusion that they are dull, not companionable
creatures, in spite of their imposing, rather noble appearance when, with
their heads erect, they calmly look about with their large, quiet eyes.
Each dug its own hole in the hard ground underneath and between large
stones. At dusk they sat in front of the holes or walked leisurely to the
pan with the earthworms which formed their principal food. Meat they did
not touch, but they killed and chewed up lizards and blind-worms. Sometimes
they soaked themselves for many hours in the shallow, warm water. The skin
is shed in flakes. I never found them basking in the sun, and the pineal
eye, still so well developed in these strange creatures, caused them no
distress when bright light was thrown upon it. They grew tame enough not to
run away when found roaming about at night, but they did not like being
handled, and they inflicted the most painful bites when taken up
carelessly. The biggest, a male, was rather quarrelsome, grunted much, and
worried the others.
_SUB-CLASS III.–THEROMORPHA._
The Theromorpha comprise a great number of extraordinary, extinct reptiles,
which as a group had a wide range in space and time. The earliest known
occur in the Lower Red Sandstone of Thuringia and Bohemia, and in the
middle Permian strata of Russia. The majority have been found in strata
transitional between the Permian and the Triassic age, notably in the
Karroo sandstone of South Africa and in corresponding levels of North
America. Closely allied to them are those of the Triassic sandstone of
Elgin in Scotland, and of India. They seem to have died out with the
Muschelkalk or Middle Trias.
The various genera exhibit such a diversity of structure, shape, and size,
and many are still so imperfectly known, that {301}any diagnosis is liable
to be faulty, even assuming that they are a homogeneous group. To avoid
confusion, we characterise the Theromorpha as _Reptiles with a firmly fixed
quadrate, a single temporal arch, an interparietal foramen, and a pelvis in
which the pubes and ischia form one stout, ventral symphysis_.
The dentition is most abnormal, and permits the division of the Theromorpha
into two or three main groups. In the Pareiasauri the teeth of the upper
and lower jaws form rather even series of nearly equal size; smaller teeth
are carried by the palatal bones. In the Theriodontia the teeth are
differentiated in a truly Mammalian fashion into incisors, prominent
canines, and multicuspid or tubercular molars. Each tooth, and this applies
to all Theromorpha, is implanted in a separate alveolus; _Tritylodon_ only
seems to have double-rooted molars. The lower canines cross in front of the
upper, just as in Mammals. In _Placodus_, which probably belongs to this
assembly, the teeth are few in numbers, very broad and flat, especially
those of the palate. In _Dicynodon_ and _Gordonia_ the teeth are restricted
to a pair of conical, sometimes very large, tusk-like upper canines, and in
_Oudenodon_ the whole mouth is toothless.
The configuration of the skull shows two main types. In the Pareiasauri it
is completely roofed in by dermal bones, the only holes on the surface
being the nostrils, orbits, and the interparietal foramen.
The most striking feature of the second type of skull is the tendency to
form an almost Mammalian zygomatic arch by the junction of the much
elongated squamosal with the jugal bone, both abutting against a downward
process of the postfrontal bone. The skull shows a pair of wide
supratemporal foramina bordered by the parietals, squamosals, and
postfrontals. The composition of the temporal arch varies considerably in
detail, and in _Cynognathus crateronotus_ at least there is a small hole
within the arch, between the squamosal and jugal, probably the last remnant
of the otherwise absent infratemporal foramen. Except in the roofed-in
skulls of _Pareiasaurus_ and _Elginia_ there is no separate quadrato-jugal
element. The quadrate is firmly fixed by the overlapping squamosal, and the
whole pedicle for the support of the mandible is rather elongated, and
either stands vertically or slants forwards. The mandible itself is
compound. The pterygoids extend backwards so as to approach or reach the
{302}distal portion of the quadrate; separate ectopterygoids do not seem to
be developed. The shoulder-girdle consists on either side of a large
scapula, which is mostly directed obliquely backwards, and is fused with
the coracoid; a precoracoid is present or at least indicated by a notch or
foramen; it is usually fused with the other bones. At least some genera
possess a T-shaped interclavicle and clavicles; _Pareiasaurus_ possesses
also a pair of cleithra.
The pelvis is in every respect constructed upon the Mammalian plan. The
three constituent parts meet at the acetabulum, and the ventral bones,
pubes and ischia, form one broad symphysis, leaving two, sometimes very
small, obturator-foramina. The ilium is attached to one to five sacral
vertebrae, and since the whole pelvis slants obliquely downwards and
backwards, this sacral attachment is distinctly pre-acetabular, perhaps
most markedly so in _Dicynodon_. The limbs are mostly stout, humerus and
femur with strong crests; the feet are thoroughly plantigrade, with five
fingers and toes. The details of the carpus and tarsus are not well enough
known to permit of generalisation, but there is a tendency to form a heel,
and to develop the cruro-tarsal joint into the chief joint of the hind
feet. The vertebrae are amphicoelous, sometimes with rather thin-walled
centra, so that in these cases the chorda was continuous. Intercentral
wedges, or basiventral elements, are frequent in the cervical and caudal
regions. Most of the ribs, especially those of the neck, have a tuberculum
attached to the neural arch, and a distinct capitulum which articulates
either with the centrum or with the intercentrum, or lastly, if the latter
is absent, between two centra. The axis and atlas vertebrae are united.
The occipital condyle exhibits every stage between the single median knob
(_Pareiasaurus_) formed almost entirely by the basioccipital bone, a triple
condyle (_Dicynodon_) to which both lateral and the basioccipital bones
contribute, and a kidney-shaped or double condyle (_Cynognathus_) from
which the middle or basioccipital portion is more or less withdrawn.
Dermal bony armour reached an extraordinary development on the head of
_Pareisaurus_ and _Elginia_; whether other parts of the body were protected
is doubtful, but the flattened tops of the neural spines of _Pareiasaurus_
suggest that they carried bony scutes. Abdominal protective ossifications
are unknown. {303}Many of the Theromorpha[126] reached a considerable size,
massive skulls of one foot in length being not uncommon. The tail was
comparatively short.
The many resemblances of these strange creatures to Mammals have naturally
suggested that the Mammalia have sprung from some such Theromorpha or
"beast-shaped" animals. The resemblances are chiefly the dentition, the
zygomatic arch, the pelvis, the cruro-tarsal joint, the scapula which is
sometimes possessed of a spine, and the occasionally double occipital
condyle. The general shape of the skull of _Cynognathus_ is indeed
strikingly like that of a Carnivorous Mammal, and the shape of the whole
body suggests rather a Mammal than a reptile; and when we have to deal with
the fragmentary skulls of _Tritylodon_ (cf. p. 309) it is, indeed,
difficult to decide to which of the two classes such a creature belongs.
But the Theromorpha possess a number of important characters by which they
reveal themselves at once as reptiles: (1) the large and fixed quadrate
bone, which is still the sole support of the lower jaw; (2) the compound
mandible, which is composed of at least an articular, dentary, angular,
supra-angular, and splenial element; (3) the interparietal foramen; (4) the
possession of prefrontal and postfrontal bones, sometimes also postorbital,
supratemporal, and quadrato-jugal bones. Of course, any of these ancestral
bones may be lost, and the interparietal hole may be closed as in tortoises
and crocodiles. We can also imagine that the quadrate may be relieved of
its jaw-bearing function and become loosened, but this is not easy,
considering the strong development of the squamoso-quadrate pedicle. Those
Theromorpha in which the quadrate itself is small, whilst the squamosal
reaches down, or at least approaches the mandible, as in _Dicynodon_ and
_Gordonia_, are so hopelessly pledged, or specialised in other directions,
that it is impossible to connect them ancestrally with Mammals.
However, it is beyond reasonable question that the Mammals have sprung from
some reptilian stock (the attempts to derive {304}them from Amphibia,
without the intervention of Reptiles, are as gratuitous as they have proved
futile), and the Theromorpha undoubtedly comprise creatures which of all
animals approach nearest to Mammals, and coincide with them in most
important features. But we have not yet found a single Theromorph which can
claim to be a direct ancestor of Mammals. Since the latter occur already in
the Trias, we have to look for their reptilian forefathers at least in the
Lower Permian, and this naturally excludes all the known forms. The filling
up of this gap is but a question of time.
The ancestry of the Theromorpha themselves is also shrouded in mystery.
Attempts have been made to connect them with the Permian _Protorosaurus_,
_Palaeohatteria_, and _Eryops_. On the other hand, some retain various
Stegocephalous reminiscences (_e.g._ the roofed-in condition of the skull
by membrane-bones, amongst which, besides others, supratemporals and
postorbitals can be recognised; occurrence of cleithra in _Pareiasaurus_;
distinct epiotic bones in _Elginia_). Although they have died out as a
group, they have perhaps given rise to several side-branches, one of which
(leaving aside the question of Mammalian origin) seems to have flourished
as the Dinosauria.
We divide the Theromorpha into four orders, which are, however, liable to
run into each other, and it is reasonably to be hoped that many forms may
be discovered which will connect not only these provisional orders with
each other, but also with other sub-classes.
ORDER I. PAREIASAURI
Cranium completely roofed in by membrane-bones. The only foramina are the
nostrils, orbits, and the interparietal foramen. The teeth are
comparatively small, and stand in even series in both jaws.
_Pareiasaurus_, several species from the Karroo sandstone of South Africa.
_P. baini_ was an extremely clumsy brute, of most uncouth appearance,
standing between 2 and 3 feet high, and measuring with the short tail
nearly 8 feet in length. The skull is very massive, 18 inches long and
slightly broader, with a rugose, deeply pitted surface. The teeth are
thickly enamelled, serrated at the margin, with many pointed cusps; those
{305}of the vomer, palatines, and pterygoids are recurved and arranged in
several longitudinal rows. There is a small incisive foramen in the
premaxilla; the choanae lie within the pterygoids. The palate has a pair of
large lateral vacuities. Between the squamosal and quadrate is a small
foramen, as in _Belodon_ and _Sphenodon_. The nares are terminal, bordered
behind by the nasals, and divided by the premaxillaries. The occipital
condyle is a single knob, but the lateral occipital bones also partake in
its formation. The shoulder-girdle is strong. The scapula slants backwards,
is broad, and possesses a longitudinal spine, an almost exclusively
Mammalian character. The scapula, coracoid and precoracoid are fused
together, and are united ventrally with those of the other side. There is a
T-shaped interclavicle, a pair of clavicles, and a pair of slender, long
cleithra, which extend along the upper anterior margin of the scapulae. The
humerus possesses enormous crests. The broad ilium is attached to two, or
perhaps three, sacral ribs. The acetabulum is closed. The pubes and ischia
are united into one broad mass of bone, and the obturator-foramina seem to
be just large enough to permit of the passage of the nerve. Both fore- and
hind-limbs are plantigrade and five-toed. The tibia articulates with one
large bone, which is supposed to represent the united astragalus and
calcaneum, the latter being without an indication of a prominent heel,
although there is a tendency to develop the crurotarsal into the chief
joint. The number of vertebrae amounts to eighteen presacrals, eight to ten
of which are cervicals. There are two or three sacral and about twenty-four
mostly shortened caudal vertebrae. The latter possess intercentral wedges
and chevron-bones; wedges occur also between the cervical and some thoracic
vertebrae. Some of the posterior cervical ribs are very peculiar–straight,
broadened out, turned backwards, partly overlapped by one another, and 18
inches long, recalling the first two ribs of the crocodiles. Sternum and
abdominal ribs are unknown.
_Elginia mirabilis._–The skull (Fig. 54, A, p. 280)–nothing else is
known–indicates one of the most remarkable reptiles hitherto found on this
side of the Atlantic. It was discovered in the Red Sandstone of Elgin
(Lower Trias). The skull reminds us in its general shape and by its spikes
and horns of the little American Iguanoid lizard, _Phrynosoma_. The length
of the cranium is about 6 inches, the distance between the tips of the two
largest {306}horns measures 9 inches. The teeth are small and resemble
those of an _Iguana_ in their shape and finely serrated edges, indicating
herbivorous habits, but there are also several rows of smaller teeth on the
palate, the configuration of which is not unlike that of _Sphenodon_. The
top and sides of the skull, except the interparietal foramen, the orbits,
and nostrils, are completely encased by rugose, pitted, dermal bones, most
of them with strange, horn-like spikes. In the encasement of the temporal
region can be discerned a postfrontal, parietal and squamosal, a conically
projecting epiotic, a postorbital and supratemporal, a jugal and a
quadrato-jugal, which latter almost completely covers the quadrate bone.
The interparietal foramen lies far forwards, almost on a level with the
orbits. The nostrils are terminal, surrounded by the short nasals, the
maxillaries and the premaxillaries, which latter divide them.
ORDER II. THERIODONTIA.
The cranium is not roofed in, but shows a pair of large supratemporal
fossae, bordered below by the zygoma, which is formed mainly by the
squamoso-jugal bridge, and is shut off from the orbit by the postfrontal
joining the bridge. The teeth are differentiated into incisors, canines,
and molars (Fig. 54, C, p. 280). The lower canines close in front of the
upper.
_Cynognathus_, Karroo formation of South Africa. _C. crateronotus_ has a
skull about 16 inches long, looking like that of a ferocious Carnivore;
there are four incisors, huge canines, and nine molars, the latter with
serrated edges and anterior and posterior cusps. The wide supratemporal
fossa is bordered and closed behind by the broad lateral extension of the
parietal, which joins a similar extension of the squamosal bone. The latter
is very long, extending to the postfrontal and to a bone which, bordering
the orbit posteriorly, is either an upward branch of the jugal, or a
postorbital bone; the latter interpretation is made probable by the
occurrence of a suture with the jugal in _C. platyceps_. The jugal bone is
very long, beginning at the quadrate, running along the squamosal, and
forming the lower border of the orbit.
The number of vertebrae is large, there being as many as twenty-nine
presacrals, six of which belong to the cervical region. {307}The atlas is
fused with the axis; most of the thoracic ribs articulate partly upon the
intercentra. The lumbar ribs are very peculiar; they are much expanded
horizontally, and overlap each other, forming thereby intercostal foramina.
The broad ilium is attached to three or four sacral ribs. The acetabulum is
closed. The ventral side of the pelvis shows a broad symphysis and has a
pair of obturator-foramina. The scapula is large, directed backwards, and
shows a distinct, very Mammalian spine; it is fused with the coracoid and
precoracoid.
The occipital condyle of _C. platyceps_ is kidney-shaped, with the
concavity directed upwards; in _C. berryi_ it is separated into two
distinct knobs, the middle, basioccipital portion being apparently wanting.
The mandible possesses a long coronoid process which ascends obliquely into
the temporal fossa.
_Aelurosaurus_, _Lycosaurus_, _Galesaurus_, and many others, likewise of
the Karroo formation. In the first genus the splenial bones help to form
the symphysis of the lower jaw; teeth are also found on the palate, in
opposition to _Lycosaurus_. This has a skull 6 inches in length; the dental
formula on either side is _i._ 4/3, _c._ 1/1, _m._ 5/5; the molars are
slender, conical, and recurved. _Galesaurus_ seems to have been rather
small, the low, triangular skull measuring only 2 to 3 inches in length,
with four or five sharply pointed incisors, prominent canines and four or
five small multicuspid or deeply serrated little molars.
_Endothiodon_, with several species from the Karroo formation, is of
uncertain systematic position, only imperfect skulls being known. The
animals must have been large and bulky, the skulls being very massive and
at least one foot in length. The premaxillaries and the maxillaries are
toothless, their alveolar borders forming cutting, prominent edges. The
same applies to the very strong lower jaw; but there is a pair of
tooth-like stout projections in the upper and lower jaws in the place of
canine teeth. True, enamelled, small, apparently conical or low and perhaps
blunt teeth occur on either side in one or three longitudinal series upon
the palate, and in corresponding positions on the inner sides of the two
halves of the lower jaw. It is doubtful if the upper teeth are carried by
the palatines or by the broadened inner flanges of the maxillaries. The
choanae seem to lie between the pterygoids and the palatines, incompletely
roofed in by ventral extensions of the latter towards the middle line.
{308}Direct affinity of _Endothiodon_ (ἐνδοθί, within) with _Placodus_ is
unlikely; the same applies to the Dicynodontia, although the restriction of
the teeth to the palate seems to point as much to the former genus as do
the toothless cutting edges of the jaws to the forms like _Oudenodon_.
Other Theriodont reptiles have been described from the upper Permian of
Russia, for instance _Deuterosaurus_ and _Brithopus_, but the determination
rests upon insufficient fragments. North America has yielded many strange
Theromorphous fossils, some of which may belong to the Theriodont order,
while others seem to be intermediate between this and the other orders.
_Diadectes_ of Texas, for instance, seems to be a Theriodont creature;
while in _Empedias molaris_, with a skull about 8 inches in length, the
teeth form an uninterrupted series without distinct canine tusks, and the
incisors are distinguished from the molars only by the transversely
broadened shape of the latter. Very small teeth are arranged along the
median line of the vomer and united palatine bones. In _Clepsydrops_,
_Dimetrodon_, and _Naosaurus_ of Texas the teeth are differentiated into
incisors, canines, and molars, although not so regularly as in the typical
Theriodont forms described above, one or more pairs of teeth being enlarged
into canine-like tusks. In the latter two genera the spinous processes of
the thoracic vertebrae are enormously elongated, standing up vertically to
a height of 2 feet, while the centra of the vertebrae measure only one inch
in diameter. In _Naosaurus claviger_ these upright spines carry on either
side half a dozen transverse projections. _Stereorhachis_ of the Permian of
France is typically Theriodont in the structure of its shoulder-girdle,
humerus, and pelvis, but the dentition is composed of 3/3 incisors, no
canines, and 6/10 pointed molars.
The following genera have been placed by Seeley in the family
Gomphognathidae. _Microgomphodon_, with broader and less prominently
multicuspid teeth than those of the typical Theriodonts, seems to lead to
_Gomphognathus_, which has the following dentition: _i._ 3/3, _c._ 1/1,
_m._ 12/12, with a long diastema between the canines and molars, some of
which latter are nearly as broad as they are long, and have comparatively
low tubercles on the crowns. The skull is remarkably like that of a
Carnivorous Mammal. There are incisive foramina behind the premaxilla. The
maxillaries and palatines form a united palatal roof, and behind them open
the {309}choanae. The occipital condyle is kidney-shaped. The mandible is
most extraordinary, approaching that of the Mammalian, especially the
Marsupial type, except that it is still composed of several pieces. The
articular facet for the mandible is borne by an outward or lateral
projection, while the bulk of the posterior half of the jaw projects
inwards like a broad flange, undoubtedly recalling the so-called inner
inverted angle of the Marsupial jaw. The coronoid process is large and
extends far into the temporal fossa. Nearly the whole skeleton of
_Microgomphodon_ is known; the lumbar ribs are broadened and overlap as in
_Cynognathus_, and the mandible is typically compound, so that there is no
doubt about the affinities of this genus with the Theriodontia. It throws
light upon _Gomphognathus_ and the three likewise South African genera
_Diademodon_, _Trirachiodon_ and _Tritylodon_, which are all known from
imperfect skulls only. Their teeth are restricted to the jaws, the molars
have flat, multitubercular crowns and bear an extraordinary resemblance to
those of Mammals. Some of the molars of _Tritylodon_ are said even to
possess two roots, but this point, absolutely unique in Reptiles, but
common in Mammals, is not certain. The few upper incisors of _Tritylodon_
are rather large, chisel-shaped, and extend like those of the Rodent-type
back into the maxillaries; canines are absent, leaving a diastema.
_Trirachiodon_ has prominent canines, the five upper molars are
multitubercular, rather flat, and much broader transversely than in the
longitudinal direction. Still, even these creatures, with skulls of the
size of that of a small fox, possessed distinct prefrontal and postfrontal
bones, and are, at least in this respect, typical Reptiles.
ORDER III. ANOMODONTIA.
The cranium is not roofed in. The pedicle for the suspension of the lower
jaw is much elongated, slants slightly forwards, and is composed of the
long quadrate, which is laterally overgrown by the squamosal bone. The
teeth are restricted to a pair of strong, tusk-like canines, or they are
altogether absent. The margins of the upper and especially those of the
lower jaw are trenchant, and were possibly furnished with a thick horny
armature like those of tortoises.
{310}_Dicynodon_, with many species from the Karroo formation of South
Africa, reached formidable dimensions. The thick, curved skull is in size
and outline not unlike that of a large lion, hence _D. leoniceps_, _D.
tigriceps_, etc. The zygomatic arch is almost mammalian, except that the
posterior boundary of the orbit is formed by a distinct postfrontal bone.
The nostrils are lateral. The canine tusks (Fig. 54, E, p. 280) are very
large. The choanae open behind the rhomboid vomer and between the separated
palatine bones, which are posteriorly confluent with the medially united
pterygoids. The latter send out flat extensions, along the lateral side of
the palatines; these extensions reach the maxillaries and probably
represent the ectopterygoids. The occipital condyle is distinctly triple,
being equally composed of the basi- and latero-occipital bones.
The three bones of the shoulder-girdle meet at the glenoid fossa; the
scapula has the indication of a spine. The pelvis is stout, attached to
four or five vertebrae, converting the latter into a very Mammalian-like
sacrum, the position of which lies distinctly in front of the acetabulum.
The latter is closed, composed by the three pelvic bones. The pubes and
ischia are fused together, leaving only a very small obturator-foramen. The
limbs are plantigrade and pentadactyle, very stout; the humerus and femur
have enormous crests.
_Oudenodon_, of which several species have been described, is so much like
_Dicynodon_, except for the complete absence of teeth, that it has been
suggested that these skulls belong to females of this genus. This view is
strengthened by the fact that tusk-like canines exist, or are absent in
some of the species which have been described as _Cistecephalus_, a genus
closely allied to _Dicynodon_. The latter, which, like _Oudenodon_ and
_Cistecephalus_, occurred in Africa, extended also into India, _D.
orientalis_ having been found in the Panchet formation of Bengal, of
transitional age between the Permian and Triassic epochs. _Oudenodon
rugosus_, on the other hand, has been described from the Ural.
_Gordonia_ and _Geikia_, of the New Red Sandstone of Elgin, are known from
their skulls only, but these are so well preserved that there is no doubt
about their close relationship to the typical South African Dicynodontia.
The skull of _Gordonia_ is about 7 inches long and 4 inches high. The
canines (Fig. 54, D, p. 280) are reduced to short, but thick, conical
tusks. The most {311}remarkable feature is the very elongated
squamoso-jugal arch, which arises moreover from the dorsal end of the long
squamoso-quadrate pedicle. The two wide and long temporal fossae are
dorsally divided by narrow parietal crests. There is a distinct
interparietal bone, and the usual interparietal foramen. The choanae are
united and lie within the palatines, which themselves are united; the large
lateral palatal foramina are otherwise enclosed by the pterygoids,
quadrates, and laterally by the squamoso-jugal arch.
ORDER IV. PLACODONTIA.
These are the latest and last members of the Theromorpha, unfortunately
known from skulls only, from the Muschelkalk or Middle Trias of Germany and
Russia. The skull of _Placodus gigas_ is about one foot long, rather high
and triangular owing to the lateral expansion of the temporal arches, which
diverge posteriorly. The squamoso-jugal arch is very broad, and most of the
posterior border of the orbit is formed by the large postorbital bone. The
maxillary bone seems to extend back to beyond the level of the orbits. The
choanae lie behind the premaxillaries. The palatines and pterygoids are
fused in the middle line, forming a broad bony palate, which, owing to the
broad, posteriorly extended wings of the pterygoids, much resembles that of
the crocodiles. The teeth are very remarkable. There are two or three
stout, conical, or chisel-like teeth in each premaxillary bone, and three
to five broad and flat maxillary teeth; three pairs of huge, broad, and
quite flat teeth are crowded together and fill up the whole vomerine and
palatine portion of the palate. These crushing teeth indicate that
_Placodus_ probably lived upon hard-shelled molluscs, and this would be in
conformity with its occurrence in the Muschelkalk, which is a strictly
marine deposit and full of shells. Another closely allied genus is
_Cyamodus_, one species of which is known from Russia. The teeth are fewer
in number and not so large as those of _Placodus_.
{312}CHAPTER IX
CHELONIA–ATHECAE–THECOPHORA
_SUB-CLASS IV.–CHELONIA._
There is no mistaking a tortoise. The shell and the horn-covered toothless
jaws separate them from all other four-footed creatures.
They may be described as terrestrial or aquatic, pentadactyle reptiles,
with walking limbs or with paddles; ribs with capitular portions only, two
sacral vertebrae, humerus with entepicondylar foramen, pubes and ischia
forming symphyses, quadrate bones fixed, jaws without teeth, but with
cutting horny sheaths. Trunk encased in a bony shell, composed of numerous
dorsal and ventral dermal bones, forming a carapace and a plastron, which
may or may not be covered with horny shields. Copulatory organ unpaired,
cloacal opening more longitudinal than round, never transverse. Oviparous.
It is customary to distinguish the marine, paddle-limbed kinds as
_Turtles_, the others as _Land-_ and _Water-tortoises_.
Tortoises occur already in the Trias. They reached their greatest
development towards the end of the Mesozoic and in the earlier Tertiary
periods. They are now comparatively reduced in the number of families and
genera, although they are still represented by about 200 species. The
sub-class as a whole is cosmopolitan, but does not occur in the colder
regions.
Their origin is quite unknown. Of recent groups only the Crocodilia and the
Rhynchocephalia come into consideration. Combination of these groups with
the Chelonia leads to some unknown forms whence also the Theromorpha have
arisen. Palaeontology does not help us, all the leading, main groups of
Chelonia having been in existence in the earlier Mesozoic ages, {313}and
Palaeozoic Chelonia are still unknown. We can, however, to a certain
extent, reconstruct an ideal primordial Chelonian by assigning to it all
the ancestral characters actually observed in recent and fossil kinds, and
by reducing to simpler conditions those features which we know to be more
or less exaggerated specialisations. It is reasonable to assume that
originally each metamere, except those of the anterior half of the neck and
the posterior half of the tail, carried a transverse series of dermal
plates, covered with horny shields, while the trunk, according to the
greater bulk of the body, increased in size, converging towards the root of
the neck and tail. By concentration, reduction of the number, and increase
in the size of some of the remaining plates and shields, the skull assumed
its characteristic box-like shape, the neck and tail becoming at the same
time free. Chelonia are without doubt descendants of terrestrial, or at
least semi-aquatic reptiles, and the marine paddled forms subsequently
developed from terrestrial kinds.
CLASSIFICATION OF CHELONIA.–After many vicissitudes it was recognised that
the Chelonia cannot naturally be divided according to the modification of
their feet. The TRIONYCHOIDEA were clearly separated from the rest by
Stannius in 1854. Cope, in 1870, was the first to emphasise the important
character of the mode in which the neck is either bent sidewards
(PLEURODIRA) or withdrawn in an S-shaped curve in a vertical plane
(CRYPTODIRA); and he also separated _Sphargis_ as ATHECAE from all the
other Chelonians, for which Dollo in 1886 proposed the term THECOPHORA. The
division of the latter into recognisable families, based upon reliable,
chiefly internal, skeletal, characters, has been effected by
Boulenger;[127] and his classification has been adopted in the present
volume, after intercalation of the more important fossil forms. The
relationships between these various families may perhaps be indicated as
follows:–
{ ATHECAE Sphargidae
{
{ { _Pleurodira_ { Pelomedusidae
{ { { Chelydidae–Carettochelydidae
{ {
CHELONIA { THECOPHORA { _Cryptodira_ { Chelydridae–Dermatemydidae–
{ { { Cinosternidae
{ { { Platysternidae
{ { { Testudinidae–Chelonidae
{ {
{ { _Trionychoidea_ Trionychidae
{314}The guiding taxonomic characters are fully mentioned at the head of
the different families, and are mostly internal. The following "key,"
adapted from Boulenger, and based upon external characters, is preferable
for practical purposes.
_For the position and names of the horny shields_ see Fig. 61 on p. 315.
Shell covered with horny shields.
Digits distinct, with 5 or 4 claws.
Pectoral shields separated from the marginals by inframarginals.
Tail long and crested. Plastron small and cruciform.
North America _Chelydridae_, p. 338.
Tail long, covered with rings of shields.
Plastron large. Indo-China _Platysternidae_, p. 345.
Tail short. North and { _Dermatemydidae_, p. 341.
Central America { _Cinosternidae_, p. 342.
Pectoral shields in contact with the marginals.
Plastral shields 11 or 12, without an intergular.
Neck retractile in an p. S-shaped vertical curve
_Testudinidae_, p. 345.
Plastral shields 13, an intergular being present.
Neck bending sideways under the shell
{ _Chelydidae_, p. 399.
{ _Pelomedusidae_, p. 390.
Limbs paddle-shaped, with one or two claws _Chelonidae_, p. 378.
Shell without horny shields, covered with soft, leathery skin.
Digits distinct, broadly webbed, but with only
three claws _Trionychoidea_, p. 404.
Limbs paddle-shaped.
Shell composed of regular series of
bony plates. Two claws _Carettochelydidae_, p. 404.
Shell composed of very many small plates arranged like
mosaic. No claws _Sphargidae_, p. 333.
The VERTEBRAE are, sometimes in the various regions of the same individual,
amphi-, opistho- or pro-coelous, or even biconvex. Traces of the chorda
remain longest in the middle of the centra. Intercentra occur regularly on
the first two or three cervicals, and then again in the tail as paired or
unpaired nodules, or as short chevrons. The latter occasionally fuse with
the caudal end of their centra. Intercentral discs of fibrous cartilage
occur regularly in the neck and tail. The ribs develop originally in the
same transverse level with these discs, and frequently the anterior
thoracic vertebrae retain this intercentral or intervertebral position
throughout life. Farther back they often show a gradual change from the
intercentral to a more central and ultimately {315}remarkable to a purely
neural attachment. In all the Chelonia the ribs are devoid of the
tubercular portion.
[Illustration: FIG. 61.–Various plastra and their horny shields. 1,
_Testudo ibera_; 2, _Macroclemmys temmincki_; 3, _Cinosternum odoratum_; 4,
_Sternothaerus nigricans_; 5, _Chelodina longicollis_; 6, _Chelone mydas_.
_a_ or _an_, Anal shield; _abd_, abdominal shield; _f_ or _fem_, femoral;
_g_ or _gul_, gular, unpaired in Fig. 3; _h_ or _hum_, humeral shield; _i_
or. _int.g_, intergular; _im_, infra-marginals; _m_, marginals; _p_ or
_pect_, pectoral; _x_, in Fig. 1, inguinal shield constituting, with the
axillary _xx_, the last trace of infra-marginals.]
The cervical vertebrae have no ribs, except mere traces in the shape of
small nodules. On the tail the ribs are often large, and, when fused with
their neural supports, look like transverse processes; the whole
arrangement exactly resembles that of Crocodilia. The first pair of
thoracic ribs, those borne by the ninth vertebra, are peculiar. They arise
from the anterior portion of the centrum, are much reduced, sometimes to
mere threads of bone, and lean against the anterior rim of the second pair
of ribs, in many cases without reaching the carapace. The next following
ribs, those of the tenth to the sixteenth vertebra, are intimately involved
in the formation of the first to seventh costal plates. The ribs of the two
sacral vertebrae sometimes remain quite distinct throughout life, just
touching the upper {316}ends of the iliac bones; but since these find a
much more effective support in the shell, the distal ends of the sacral
vertebrae fuse with the eighth, or so-called last, pair of costal plates.
The neural arch of the ninth vertebra rests upon its centrum; but the
neural arches of the other trunk-vertebrae, although long, rest upon two
centra; retaining, like the ribs, their original intercentral position; and
in most cases the neuro-central sutures remain throughout life. The atlas
and the last cervical vertebra deserve special attention. In many
tortoises, _e.g._ _Trionyx_, _Clemmys_, _Testudo_, the three constituent
parts of the atlas, namely, the neural arch, the centrum, and the
intercentrum or first pair of united basiventralia, do not ankylose, but
remain loosely connected; and the first centrum, instead of forming an
odontoid process, remains movably attached to the second centrum, although
it sometimes carries, and fuses with, the second intercentral piece. In
other tortoises, _e.g._ _Platemys_ and _Chelys_, however, all the parts of
the atlas co-ossify and form a complete, solid vertebra which articulates
by a concavo-convex joint with the centrum of the second vertebra. The
normal number of cervical vertebrae is eight in all Chelonians. The first
spinal nerve issues between occiput and atlas, all the others behind the
neural arches of their vertebrae. The last, or eighth cervical, owing to
the retractility of the neck, forms elaborate joints; its centre fits with
a knob into a cup of the ninth, and its post-zygapophyses form broad,
curved articulating concave facets for the reception of the anterior
zygapophyses of the fixed ninth vertebra. In the Trionychidae the
zygapophyses are most elaborate, and they alone articulate with the ninth
vertebra, while the centra do not join, but remain, or rather become,
separated by partial resorption. In the Chelonidae, in conformity with the
non-retractile and short neck, all the cervical joints are much reduced.
[Illustration: FIG. 62.–1, The complete atlas of an adult _Trionyx hurum_.
The second basiventral (white) is attached to the posterior end of the
first centrum, which, not being fused with the second centrum, is not yet
an odontoid process. 2, The complete atlas of an adult _Trionyx
gangeticus_, still typically temnospondylous. 3, The first and second
cervical vertebrae of an adult _Platemys_. 4, The complete atlas of a
_Chelys fimbriata_.]
{317}[Illustration: FIG. 63.–Skull of _Chelone mydas_. A, from the left
side; in B, the postfrontal and squamosal bones have been removed, and the
broad expansions of the jugal, quadrato-jugal, parietal, and quadrate bones
have been reduced in order to reduce the skull to more primitive
conditions. _F_, Frontal; _J_, jugal; _L.o_, lateral occipital; _Mx_,
maxillary; _Op_, opisthotic; _Pal_, palatine; _Par_, parietal; _Prf_,
prefrontal; _Pro_, pro-otic; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_,
quadrate; _Qj_, quadrato-jugal; _S.o_, supra-occipital; _Sq_, squamosal.]
The SKULL (cf. Fig. 54, H, I, K, p. 280) agrees fundamentally with that of
_Sphenodon_ and of the _Crocodilia_, but it is characterised by several
special features. There are no ectopterygoids or ossa transversa; no
lacrymal bones, no interparietal or pineal foramen; the vomer is unpaired
and the nasal bones are mostly absent, unless they are fused with the
prefrontals. The premaxillae are very small. The single vomer forms a
septum between the choanae; and these are, except in _Sphargis_, ventrally
roofed over by wings sent out by the palatines. The latter form a
continuous bony roof to the mouth with the pterygoids, and these diverge
posteriorly, being connected suturally with the quadrates, lateral and
basi-occipital bones, and with the unpaired basi-sphenoid, which appears
between the basi-occipital and the diverging pterygoids, but is in most
cases to a great extent overlapped by the latter. The occipital condyle is
distinctly triple; the basi-occipital sometimes helps to border the foramen
magnum. The supra-occipital sends out a long vertical blade, directed
backwards and generally projecting far over the neck, for the attachment of
the powerful cranio-cervical muscles. The quadrate is very peculiar. Firmly
attached, and hemmed in on nearly all sides by the neighbouring bones, it
stands nearly vertically and forms a broad articulating surface for the
mandible. Its posterior side shows either a transverse, horizontal groove,
in which lies the columella auris, or the groove is transformed into a more
or less closed canal. Moreover, the hinder lateral margin of the quadrate
forms most of the tympanic frame; its margins being curved backwards,
leaving in the Cryptodira, however, a {318}wide notch behind; in the
Pleurodira this part of the quadrate is transformed into a trumpet, the
wide rim of which, forming a complete ring, carries the tympanic membrane.
The tympanic cavity thus formed often leads into a deep recess which
extends beneath the squamosal towards the opisthotic and bears some
resemblance to the intricate tympanic recesses which pervade that region of
the Crocodilian skull.
Dorsally the quadrate is broadly overlaid by the squamosal, which
frequently forms an arch with the parietal. Anteriorly the quadrate is
connected through a variably sized quadrato-jugal with the jugal; and this,
by joining the maxilla and postfrontal, helps normally to form the
posterior rim of the orbit. All the bones which border the temporal fossa
vary much in extent in the different groups of Chelonia. The extremes are
represented by _Cistudo_ and _Geoemyda_, in which the bony infratemporal
arch is absent, owing to the loss of the quadrato-jugal; and on the other
hand by the Chelonidae and by _Sphargis_, in which the whole temporal
region is covered over by an additional "false cranial" roof. This roof is
produced chiefly by lateral wing-like expansions of the parietal and
postfrontal bones, which meet the likewise much expanded jugal,
quadrato-jugal, and squamosal bones. In the lower diagram of Fig. 63
(_Chelone mydas_) the squamosal has been removed, and the other bones have
been reduced to their normal, or rather primitive condition, for comparison
with the external view of the complete skull of the same animal. The lower
diagram shows also the connexion of the pterygoid with a descending process
of the parietal; this column, paired of course, usually contains a separate
bone, the epipterygoid, the portion between _Ptg_ and _Par_.
The hyoidean apparatus is well developed, and sometimes assumes large
dimensions, especially in _Chelys_. The two pairs of "horns" are the first
and second branchial arches, whilst the hyoid arches are reduced to a pair
of small, frequently only cartilaginous, nodules attached near the anterior
corners of the basis linguae, which generally fuses with the os entoglossum
in the tip of the tongue.
The PECTORAL ARCH consists of a pair of long coracoids sloping obliquely
backwards, the distal cartilages of which scarcely touch each other in the
middle line, and the scapulae. The upper end of the scapula frequently
touches the inside of the {319}first costal plate, protected by a
cartilaginous pad. Near the glenoid cavity arises a long process (PC in
Fig. 65), placed transversely and approaching its fellow. The distal end is
connected with that of the coracoid by a fibro-cartilaginous band. The
homology of this scapular process is not quite clear. The band just
mentioned favours the idea that the process represents the precoracoid, but
its being an outgrowth from the scapula suggests that it is merely the much
enlarged acromion. It certainly does not represent the clavicle, which
forms part of the plastron: and this is not in contact with the
shoulder-girdle at all.
[Illustration: FIG. 64.–Diagram of the skeleton of _Testudo elephantopus_,
after removal of the left half of the carapace. The plastron is roughly
indicated by a section through the middle line. _Fe_, Femur, foreshortened;
_Fi_, fibula; _H_, humerus; _Il_, ilium; _Is_, ischium; _P.P._, pubis; _R_,
radius; _Scap_, scapula; _Tb_, tibia; _u_, ulna; 3, third cervical
vertebra; 1, 3, 5, first, third, and fifth fingers; _XIII_, thirteenth
(fifth thoracic) vertebra.]
The PELVIS is strong. Ilium, pubis, and ischium meet at the acetabulum. The
dorsal end of the ilium is generally broadened, and is attached to one or
both sacral vertebrae, but it is also in contact with the superimposed last
costal plate. This additional connexion often becomes predominant and the
sacral vertebrae are partly or completely relieved of the iliac support,
fusing in this case more or less with the costal plates. The pubes have
strong lateral processes, directed obliquely forwards and downwards. The
pubes and the ischia, which latter are much smaller, form broad symphyses,
and these are connected with each other by a longitudinal cartilaginous
band (_Chelone, Trionyx_); or the connecting bridge is broad and quite
ossified (_Testudo_), forming in the latter case two roundish
obturator-foramina. Cartilage frequently remains at the anterior end of
{320}the pubic symphysis, and a smaller, longer, and narrow piece of
cartilage extends sometimes backwards from the ischiadic symphysis, as the
so-called hypo-ischium. In the Pleurodira the ends of the ilia, and those
of the lateral processes of the pubes, are much broadened and firmly
ankylosed with the posterior costal plates and with the xiphiplastron
respectively.
[Illustration: FIG. 65.–Ventral view of the bony shell of _Chelone mydas_,
the Green Turtle, after removal of the plastron (Fig. 66). The costal
plates are marked by cross lines to distinguish them from the ribs. _C_,
coracoid; _Fe_, femur; _Fi_, fibula; _H_, humerus; _Ma._1-_Ma._12, marginal
plates, some of which are fused together; _Nu_, nuchal plate; _PC_,
"precoracoid"; _R_, radius; _Sc_, scapula; _I_, _V_, first and fifth
digits; _IX_, Ninth vertebra or first thoracic.]
The LIMBS are typically pentadactyle and complete, and are most primitive
in water-tortoises, e.g. _Chelydra_ and _Emys_, in which the carpus
consists of the typical ten separate elements, including the pisiform. In
_Testudo_ the centrale is fused with the intermedium, and the first three
distal carpals are also fused together. In the marine turtles the limbs are
transformed into paddles, but all the bones retain their independence; the
pisiform {321}and the first metacarpal are enlarged and flattened, thereby
giving additional width to the paddle. The tarsus remains less primitive;
the centrale and the proximal elements have a tendency to fuse together,
most completely in land-tortoises; the fifth distal carpal is enlarged, and
stands out hook-like from the rest. The number of the phalanges of the
fingers and toes varies slightly. It is noteworthy that none of the
Chelonia possess more than three phalanges. The three middle fingers and
toes have mostly three phalanges; the pollex and hallux have always two;
the number of phalanges of the fifth finger varies from three to one, of
the fifth toe from two to none. The greatest reduction occurs in _Testudo_
and its allied genera of typical land-tortoises, _Homopus_, _Pyxis_, and
_Cinixys_, the formula for the fingers being 2, 2, 2, 2, 2 or 1, and 2, 2,
2, 2, 0 for the toes. In _Pelomedusa_ all the fingers possess two phalanges
only, owing to fusion of the first and second phalanges with each other.
[Illustration: FIG. 66.–The bones composing the plastron of _Chelone
mydas_. On the right side the position of the covering horny shields[128]
is indicated by dotted lines. _a_, Anal horny shield; _ab_, abdominal; _f_,
femoral; _g_, gular; _h_, humeral; _ig_, intergular; _im_, infra-marginals;
_p_, pectoral.]
The SHELL, which is the most characteristic feature of the Chelonia,
consists of the dorsal "carapace" and the ventral "plastron." Each is
composed of a considerable number of bony plates which arise as
ossifications of nearly the whole thickness of the cutis, only a thin layer
of subcutaneous connective tissue remaining soft and lining the inside of
the shell. We restrict ourselves to a description of the shell of the
Thecophora, leaving the discussion of the peculiar shell of _Sphargis_ to
p. 336 f. Very young tortoises are still soft, and the plates which are
beginning to ossify are not yet suturally united. The plastron (Figs. 66
and 67) consists of the paired epi-, hyo-, hypo-, and xiphi-plastral
plates, and the unpaired endo-plastral plate.
{322}[Illustration: FIG. 67.–Bony shell of _Testudo ibera_. A, Ventral; B,
dorsal; C, left-side view. In B, and on the right half of A, the position
of the horny shields is indicated by dotted lines. The underlying bony
plates are marked by strong lines. In B the 1st neural and costal plates,
the 4th neural, costal, and 6th marginal plates, and the 7th neural plate
are shaded. 1, 4, 6, First, fourth, and sixth neural plate; _M_, in C,
fifth left marginal plate; _Nu_, nuchal plate.]
The latter is homologous with the interclavicle, the epi-plastra are
homologous with the clavicles of other Reptiles, while the other pieces are
genetically derived from, and are further modifications of, the so-called
abdominal ribs of the Crocodilia and Prosauria, These plastral plates are
never in direct contact with the shoulder-girdle or with any other parts of
the internal skeleton. In the young of all tortoises, and in the adult of
the Chelonidae and Trionychidae, the several plastral plates enclose large,
irregularly-shaped fontanelles. These are more or less filled up in the
other groups; and in the Testudinidae especially the whole plastron forms
one continuous mass. The navel is situated between the hyo- and
hypo-plastrals. Both these pairs are broader than the others, and are
connected with the carapace by {323}means of several marginals. The
connecting region is called the bridge. In several tortoises, e.g. _Emys_,
the connexion with the marginals is formed by ligaments only and remains
movable. In others, transverse, more or less perfect hinges are formed
across the plastron. A rather imperfect joint between the hypo- and
xiphi-plastrals develops with age in _Testudo ibera_. In _Cistudo_ and
_Cyclemys_ a very effective hinge lies below the hyo- and hypo-plastrals,
just in front of the bridge; and the anterior and posterior lobes of the
plastron can be closed against the inner rim of the box, fitting tightly in
_Cistudo_. In _Pyxis_ the front lobe only is movable.
[Illustration: FIG. 68.–A, Diagrammatic transverse section through the
shell of _Testudo_. On the right side the horny shields have been removed,
on the left are shown the neural, costal, marginal, and pectoral shields.
The bony dermal plates are dotted. _Cap_, Capitular portion of rib; _Sp.C_,
position of spinal cord. B, Vertical section through part of the shell,
magnified and diagrammatic. B, Bony layer of the cutis; L, leathery layer
of the cutis; M, cells of the Malpighian layer; P, star-shaped
pigment-cells; SC, stratum corneum, composing the horny shields.]
The carapace is composed of one median series, a right and left lateral
series of costal plates, and a series of marginals which surround the
whole. The median series consists of one large nuchal plate, normally eight
neurals and one to three supracaudal plates. The characteristic feature of
the neural plates is that they are firmly fused with the broadened neural
spinous processes of the underlying vertebrae. The nuchal plate lies in
front of the first thoracic or ninth vertebra; it overlies the last
cervical vertebrae, with the eighth of which it is connected by ligament
only; but the posterior corner of the plate often fuses with the spine of
the ninth vertebra. In the Chelydridae, and still {324}more in the
Trionychidae, the nuchal sends out a pair of long rib-like processes, which
either extend to below some of the neighbouring marginals, or their ends
overlap those of the ribs of the second thoracic vertebra (e.g. _Trionyx_),
or, lastly, they are in turn overlapped by the first costal plates (e.g.
_Cyclanorbis_). Such rib-like processes are also present, well developed in
the young, shorter in the adult, in the Dermatemydidae and Cinosternidae.
It is possible that the nuchal plate represents the fused neural of the
eighth and the costal plates of the ninth vertebrae. An indication of the
compound nature of the nuchal may be found in the fact that two nuchals
have been described in _Chelydropsis carinata_, a Miocene relation of
_Chelydra_. Somewhat similar modifications have taken place in the
post-sacral region. The one to three supracaudal plates are, namely,
neurals which have lost their connexion with, or perhaps have never been
fused with, the spinous processes of the movable tail-vertebrae. The number
of neural plates is mostly eight, but there are sometimes individually nine
or ten, the gradual suppression taking place first in the sacral region.
When such a plate is suppressed the neighbouring costal plates usually
close up and meet in the median line. In _Cistudo_, for instance, there are
only seven normal neurals, the eighth pair of costals meet, and the
original eighth neural is transformed into a supracaudal. In _Cinosternum_
the sixth to eighth costals meet, separating the one supracaudal widely
from the remaining five neurals. The meeting of the last pair of costals,
with co-ordinate reduction of the neurals to seven, is almost universal in
the Pleurodira; and this tendency is carried out to an extreme in the
Brazilian _Platemys_ and in the Australian _Chelodina_ and its allies, in
which all the costals meet in the middle line, and the neurals are
completely suppressed. Every stage intermediate between complete neurals
(_Sternothaerus_) and interrupted, vestigial, and vanished neurals, is
still represented by some genus. This process takes place independently,
both in America and in Australia, and is one of the most recently
introduced modifications.
The costal plates arise, like the neurals, independently in the cutis, but
they soon come into contact with the underlying cartilage of the ribs,
which are long enough to reach the marginals. The ribs flatten, become
surrounded by the growing membrane-bone of the plates, and the cartilage of
the ribs, {325}instead of ossifying, undergoes a process of calcification.
Ultimately this is more or less absorbed, its place is taken by the dermal
bone, which forms so to speak a cast of the rib, preserving in many cases
the shape of the vanished rib, only the capitular portions of which remain
unaffected. The number of costal plates is very constant, namely eight on
each side, but some fossils have nine or ten, and there are still
individual variations in recent forms, indicative of that number. In a
large _Chrysemys concinna_ I find the last pair of costals clearly composed
of at least two pairs, and this same specimen has nine distinct neural
plates.
The marginal plates are originally paired, almost always eleven pairs, very
rarely ten or twelve; an unpaired posterior plate, the pygal, is always
present, and is probably the result of fusion. In the Chelonidae large
fenestrae remain between the costal and marginal plates, only covered by
leathery unossified cutis, and of course by the horny shields. In the
Indian fresh-water genus _Batagur_ similar windows are gradually filled up
with age, and the horny shields become extremely thin and almost confluent.
On the other hand, in _Testudo polyphemus_, the bony shell, always very
thin, becomes still thinner with age and finally fenestrated by absorption.
Great reduction has taken place in the carapace of the Trionychidae. The
American species of _Trionyx_ have only seven pairs of costal plates; in
_Cyclanorbis_ the neurals are reduced to two. The whole dorsal shell is
much smaller than the body, and marginal plates are absent or merely
vestigial. It is doubtful if the ossifications in the posterior half of the
marginal flap of some genera are homologous with true marginals.
Externally the whole shell is covered, except in the _Trionychidae_, in
_Sphargis_ and _Carettochelys_ with horny, epidermal shields. These are
phylogenetically older than the dermal plates, and they do not correspond
with them either in numbers or in position, although there exists a general
resemblance in their arrangement. On the plastron we distinguish an
unpaired or paired gular, and a pair of gular, humeral, pectoral,
abdominal, femoral, and anal shields (Fig. 66). Sometimes there are also
intergulars, paired in _Macroclemmys_ and _Chelys_, unpaired in _Chelone_;
in many of the Pleurodira an unpaired intergular lies behind the gulars.
{326}The carapace of most Chelonians is covered with five neural, four
pairs of costal and twelve pairs of marginal _shields_, the last of which
often forms an unpaired pygal. In front of the first neural lies the nuchal
shield, very variable in size, often absent. The Chelydridae,
Dermatemydidae, Platysternidae, and Cinosternidae possess moreover several
inframarginals, intercalated on the bridge between the marginal and some of
the plastral shields. In many of the other families these inframarginals
are restricted to the anterior and posterior corners of the bridge, as the
so-called axillaries and inguinals, mostly small and variable. Lastly,
_Macroclemmys_ has several small supramarginals.
There are consequently eleven longitudinal rows of shields in all; by
elimination of the supra- and infra-marginals they are reduced to seven
rows. It is absolutely certain that the number of transverse rows also was
originally much greater than it is now. The mode of reduction of the number
of the neural and costal shields has been studied in _Thalassochelys
caretta_ (cf. p. 388.) The accompanying illustration (Fig. 69) shows some
of the main stages actually observed in the reduction of these shields. The
chief point is that certain shields are squeezed out, or suppressed by
their enlarging neighbours. The ultimate result is the formation of fewer,
but larger shields.
Each shield grows individually as follows. Every year, or rather during
every periodically recurring period of growth, the area of the Malpighian
layer belonging to each shield increases peripherally in size, and at the
same time produces a new layer of horn. The original little shield, with
which the tortoise is born, remains for years, often throughout life, as
the so-called "areola;" it increases in thickness owing to the new layer of
horn added from below, and peripherally the increase in size is indicated
by the overlapping concentric rings. Each ring represents a year's growth,
at least in tortoises which live in temperate zones, where hibernation
means a complete suspension of growth. It is not known if the same applies
to tropical species, which grow either throughout the year, or which
undergo one or more periods of rest. The areola does not remain central;
the growth is uneven. With age the oldest layers of the areola are
frequently rubbed off, and the areola then appears enlarged.
{327}[Illustration: FIG. 69.–Diagrams illustrating the progressive
reduction of the horny shields in various Chelonians. The shields, the fate
of which it is desired to follow, are indicated by distinctive shading. I.
Hypothetical, primitive stage. Eight neural (including the nuchal) and
eight costal shields. Both neurals and costals lie in the same transverse
planes. II.-VII. Successive stages in the reduction and suppression of
various shields, observed in specimens of _Thalassochelys_, the normal
condition of which is represented by VII. VIII. Six neurals and only four
costals. The normal condition of _Chelone_. IX. The nuchal shield has
become very small and the resulting gap has been filled up by an
enlargement of the first pair of marginals. This is the normal condition of
most Cryptodirous tortoises. X. The first marginals meet in front and the
nuchal is either suppressed (X_a_[X^a in diag]), _e.g._ in several species
of _Testudo_, or it is surrounded by the marginals (X_b_), _e.g._ in
_Sternothaerus_. (From Willey's _Zool. Results_, 1899.)]
{328}For the first dozen years or so the annual rings can be easily
followed, but when the creature approaches maturity each shield adds very
little to its growth, and the rings become very fine, crowded and
irregular. Only by careful counting and comparison of the rings on the
costals, marginals, and plastrals, can a reliable average be arrived at. In
some tortoises, e.g. _Chrysemys_, the whole outer layer of the shields
peels off periodically; only a thin smooth layer like mica or tracing-paper
remains, of course without any indication of rings. The pigment is formed
in the Malpighian layer, but it frequently diffuses into the horny shields
themselves, notably in _Chelone imbricata_, which yields the beautiful
"tortoise-shell." The colour of the pigment is either black, yellow, or
red, with resulting combinations. The green colour, often so beautiful in
baby-specimens of _Chrysemys_, is optical, produced, according to Agassiz,
by a network of black pigment, spread over a layer of yellow oil.
Horny scales, sometimes forming spines, and covering a nodule of dermal
ossification, are also common on other parts of the skin, especially on the
limbs of land-tortoises, and also on the tail of _Chelydra_. Sometimes the
end of the tail is protected by a claw-like nail, for instance in _Pyxis_.
In some of the gigantic land-tortoises, and in _Chelone mydas_, this nail
assumes large dimensions, and several of the terminal caudal vertebrae are
fused together into a regular urostyle. In some subfossil specimens of
Mauritian tortoises, these ankylosed complexes are 12 cm. long and more
than 5 cm. broad!
Before leaving the description of the shell, it is worth while to draw
attention to the enormous correlative changes in other organs produced by
this case. Nearly the whole organism has been altered. The hard, firm
carapace has partly rendered the supporting functions of the vertebral
column unnecessary or impossible. In many tortoises, especially in the
large land-tortoises, the vertebrae and the capitular portions of the ribs
are reduced to mere bony outlines; the reduction to thin paper-like bony
lamellae proceeds with age. The iliac bones find a better support in the
costal plates; the contact with the sacral ribs is given up, and these ribs
fuse partly with the costal plates, or they are absorbed. The whole mass of
muscles of the trunk is completely lost in the region of the shell, but
traces of them exist in young specimens. Neck, limbs, and tail can in most
cases be withdrawn and hidden in the shell. When this is not possible it is
due to secondary changes. The neck is withdrawn either by being tucked away
{329}sideways (Pleurodira[129]), or by being bent in an S-shaped curve in a
vertical plane. In a left-sided profile-view of the animal, the head
represents the tail of the S. The neck is withdrawn by long muscles, which
are inserted into the ventral side of the middle of the neck, and extend in
the shape of vertical ribbons far back into the shell, arising from the
centra of some of the middle or even more posterior thoracic vertebrae.
Lastly, a few remarks on the PARTIAL REGENERATION, or the mending of
injuries to the shell. If part of the horny covering is badly bruised, torn
off, or rubbed through, or if part of the shell is crushed, the underlying
portion of the bony plate becomes necrotic, and the horny covering also
dies so far as its Malpighian layer is destroyed. Soon, however, the
uninjured Malpighian cells, around the margin of the wound, multiply, grow
into and beneath the injured portion of the bone, and form a new horny
layer, casting off the necrotic portion. After several months the
deficiency is patched up; new bone has grown in the deeper remaining strata
of the cutis, and the outside is covered by a continuous horny layer,
without, however, reproducing the original concentric moulding of the
shields. In badly crushed shells sometimes almost one-third of the whole
shell is thus cast off and mended within one or two years. The regeneration
of the forcibly stripped-off shields of _Chelone imbricata_ is described on
p. 386. Bitten-off tails and limbs, rather frequent occurrences in
water-tortoises, are of course not reproduced, but the wounds are healed
and covered again with scaly skin.
SENSE-ORGANS.–The EYE is by far the best developed sense-organ. It is
comparatively small. The pupil is round. The iris is mostly dark in
terrestrial forms, while in water-tortoises it is often brightly coloured,
for instance pale yellow in _Chelodina_, greenish and mottled with black,
pale grey, brown, etc., in various species of _Chrysemys_. _Cistudo_
presents a curious sexual dimorphism; the males have red, the females
brown, eyes. The sclerotic wall contains a ring of numerous small ossified
plates. There is no trace of a pecten. The eye is protected externally by
the two lids and the nictitating membrane. In some water-tortoises, notably
in _Chelodina_, the lower lid is transparent. Lacrymal and Harderian glands
are present.
{330}The SENSE OF HEARING is apparently not very acute, although tortoises
and turtles are frightened by noise, and can distinguish sounds; otherwise
they would have no voice, which is very tiny and piping in most tortoises
during the pairing season. In most water-tortoises the tympanic membrane is
thin and quite exposed; in land-tortoises it is often thick and covered by
the ordinary skin; lastly, in _Chelone_ the tympanic cavity is filled with
a plug of the much-thickened skin, possibly in adaptation to the
water-pressure when these creatures dive to considerable depths. The
ossicular chain is mostly reduced to a long, bony, columellar rod.
The SENSE OF SMELL is well developed. All Chelonians carefully smell their
food, in the air as well as under water. The individual predilection shown
by many species for different kinds of animal and vegetable food,–since
they are, for instance, able to distinguish between the various sorts of
cabbage, cauliflower, sprouts, etc.,–proves that they possess a
considerable amount of smell and taste.
Tortoises have a fine sense of touch; even the slightest tap on the shell
is noticed, and the skin of the soft parts is extremely sensitive. Tickling
of the sides of the tail, or of the hinder surface of a thigh, produces
ridiculous scratching actions of the same or of the opposite foot.
The DIGESTIVE APPARATUS is simple. Only a few peculiarities need be
mentioned. The tongue is mostly broad and soft; it cannot be protruded. The
oesophagus of the Chelonidae is covered with many conical projections
pointing towards the stomach. The latter is simple, except in _Sphargis_.
The intestine is devoid of a caecum, but the difference between the small
intestine and the rectum is very marked and often abrupt. The cloaca is
very roomy. It contains the large copulatory organ, which is unpaired,
grooved on its dorsal side, and is altogether constructed like that of the
Crocodilia. The large bladder opens ventrally into the urodaeum, a recess
of the cloaca; near its base open the urinary and genital ducts. Many
water-tortoises possess also a pair of lateral thin-walled sacs, the
so-called anal sacs, dorso-lateral diverticula of the walls of the
urodaeum. These sacs, which have highly vascularised walls, are incessantly
filled and emptied with water through the vent, and act as important
respiratory organs. When such a water-tortoise, for instance an _Emys_ or a
_Clemmys_, is suddenly taken out of the water, it squirts out a {331}stream
of this water, which is not, as is generally supposed, the urine from the
bladder.
The mode of RESPIRATION is interesting. The lungs are very complicated,
highly-developed, spongy structures. They are attached by their whole
dorsal surface to the inner lining of the shell. As they cannot expand
through their own initiative, and since the shell has made costal and
abdominal expansion impossible, the tortoise has to resort to other means
of producing the necessary vacuum. This is done partly by the neck and the
limbs, which act like pistons in being drawn in and out; partly by the
greatly developed hyoidean apparatus, by which, when the neck is stretched
out, the throat is alternately inflated and emptied, the air being
swallowed, or pumped into the lungs. Additional respiration, besides that
of the anal sacs mentioned above, is effected in various aquatic tortoises
by slightly vascularised recesses of the pharyngeal region. Most Chelonians
can exist for a very long time without breathing; sulky individuals remain
for hours or days under water. _Cistudo_ can shut itself up for an equally
long time. Nevertheless this and other land-tortoises easily get drowned.
All Chelonians lay white EGGS, round or oval, according to their kind, but
the shape of the eggs of one set sometimes varies within the greatest
limits. The shell varies from a parchment-like, flexible, scarcely
calcareous cover to a hard, well-polished case. As a rule the eggs,
imbedded in the ground, are hatched after a few months, but in some of the
northern kinds, e.g. _Emys orbicularis_, the hatching is deferred until the
next spring, the embryo's development being arrested during the winter. How
such eggs, buried a few inches only below the surface, withstand the often
very severe North German and Russian winter is a mystery. Whilst the
plastron is generally flat, it is more or less concave in the males of many
species, notably in _Testudo_, _Cistudo_, and _Emys_.
The general conclusions which can be drawn from the present GEOGRAPHICAL
DISTRIBUTION of the Chelonia are as few and unsatisfactory as those
applying to the Crocodilia, since all the main groups of Chelonians, and
many more extinct families, occurred together in bygone ages in the same
countries, for instance in Europe.
{332}[Illustration: FIG. 70.–Geographical distribution of Cryptodirous
tortoises.]
[Illustration: FIG. 71.–Geographical distribution of Pleurodirous
tortoises.]
The marine forms are naturally cosmopolitan, but the _Testudinidae_ are
likewise cosmopolitan, except in the Australian region. The _Chelydridae_,
now restricted to North and Central America, occurred formerly also in
Europe. The _Pleurodira_, in Mesozoic times plentiful in Europe, India, and
North America, are now restricted to South America, Australia, and Africa;
the _Pelomedusidae_ to Africa, Madagascar, and South America; the
_Chelydidae_ to South America and Australia. In the latter country all the
Chelonians belong to the Chelydidae. The _Trionychoidea_, occurring since
the Cretaceous epoch in North America, in Early and Mid-Tertiary times in
Europe, are now restricted to North America, Asia, and Africa. The country
richest in Chelonians is America; North and Central America together
possessing representatives of all the families except the Pleurodira, and
these we know to have died out there. The _Dermatemydidae_,
{333}_Cinosternidae_, and Chelydridae are now restricted to the Nearctic
sub-region (including Central America). Poorest in genera and species, all
of them Chelydidae, is the Australian region, where no fossils of other
families have yet been discovered. Europe, with its few Testudinidae, does
not come into consideration; Asia has at least Testudinidae and
Trionychidae, and in addition the solitary _Platysternum_ in Indo-China,
representative of a family whose affinities with the Chelydridae again
proclaim the validity of the Periarctic region.
[Illustration: FIG. 72.–Geographical distribution of Trionychidae and
Chelydidae.]
ORDER I. ATHECAE.
_The vertebrae and ribs are not fused with, but are free from, the
carapace, which consists of numerous small polygonal plates and is covered
with leathery skin without any epidermal shields. The limbs are transformed
into paddles. The neck is not retractile. Marine._
FAM. SPHARGIDAE.–_Sphargis_ s. _Dermatochelys coriacea_, the Leathery
Turtle or Luth, is the only recent species and is the largest of all recent
Chelonians. The biggest specimen in the national collection is about six
feet and a half long, from the nose to the end of the shell, which latter
is about four feet long; such a specimen may weigh half a ton. Agassiz,
however, says that he has seen some "weighing over a ton." The general
colour is dark brown, either uniform or with yellow spots. The Leathery
Turtle has a wide distribution, ranging over all the intertropical seas,
but it is rare everywhere; least so perhaps in the Western Atlantic from
Florida to Brazil and in the Indian Ocean.
{334}[Illustration: FIG. 73.–_Sphargis coriacea_, the "Leathery Turtle,"
young specimens, ventral and dorsal views. × 1.]
According to Agassiz it breeds regularly every year in the spring on the
Bahamas, on the Tortugas, and on the coast of Brazil, depositing its many
eggs on the sandy shore like other turtles. Accidentally it visits the
northern coast up to Long Island, and specimens, perhaps carried with the
Gulf Stream, have been caught on the coasts of Europe, for instance off
Dorsetshire. One was caught near Nantes in 1729, and is said to have made a
terrible noise when being killed. This is perhaps the reason why Merrem in
1820 invented the generic name _Sphargis_, supposed to be derived from
σφαραγέω (I make a noise). It has also been recorded from the
Mediterranean. It seems to be entirely carnivorous, living upon Molluscs,
Crustacea, and fish. The flesh is supposed to be unwholesome. It is a very
curious fact that of this rare species only large specimens, besides a very
few baby-turtles, are known or preserved in collections, while individuals
of intermediate size, say from four inches to three feet in length, have
never been recorded. If it were not for the fact that they are still known
to breed, it would look as if the {335}species were dying out. Perhaps they
are very shy, leading a pelagic life, diving at the least sign of danger,
and coming near the land only for the sake of breeding.
The structure of _Sphargis_ is so peculiar in many respects that it
deserves a somewhat full account. The neuro-central sutures persist on all
the vertebrae. The eight cervicals are short. All the ten trunk-vertebrae
carry ribs, and these, with the exception of the last, articulate between
the centra and with the neural arches; the first and tenth ribs are short,
the others are long and flattened, but not broad, with wide spaces between
them. The tail is short, although it consists of about twenty vertebrae;
these are devoid of chevrons.
The skull superficially resembles that of _Chelone_, chiefly owing to the
completely roofed-in temporal region. The supraoccipital crest is rather
short, covered completely by the parietals, the posterior margin of which
is rounded off instead of forming, as in the Chelonidae, a long projecting
triangular crest with the supra-occipital. The parietals are in broad
contact with the postfrontals, posteriorly they are just reached by the
squamosals. The quadrato-jugal is small, separated from the postfrontal by
the meeting of the squamosal with the jugal. The quadrate is notched
behind, and it separates the opisthotic from the squamosal. The
basisphenoid is large and broad, extending far forwards so as to separate
the pterygoids widely from each other except in their anterior portions,
which, instead of sending a lateral arm to the jugal and maxillary, as in
_Chelone_, are widely separated from these bones by the palatines. The
choanae lie on either side of the anterior half of the vomer, and are not
roofed over by ventral vomero-palatine wings.
The limbs and their girdles are essentially like those of the Chelonidae,
but are not derivable from them. The most remarkable feature is the shell.
The dorsal and ventral halves are directly continuous, forming one unbroken
case all round, which is composed of many hundreds of little bony plates,
irregularly polygonal, fitting closely into each other with their sutural
edges, and giving the shell a beautiful mosaic appearance. On the dorsal
side are a median row and three pairs of lateral rows of larger plates, and
these form seven longitudinal blunt ridges which all converge towards the
triangularly pointed tail-end of the shell. The ridges are not so much
produced by thickened {336}or spine-like edges of the plates, but by the
right and left halves of the plates being actually bent at an angle. This
is most conspicuous at the sides of the shell where it passes into the
ventral portion. The latter has two pairs of lateral and one median ridge.
The whole shell has consequently twelve ridges. The mosaic plates are
deeply imbedded in the cutis, being externally as well as internally
covered or lined with dense leathery skin. The epiderm is thin, and shows
no indications of horny scales. In young specimens the whole shell is soft
and very imperfectly ossified, later on it is quite rigid, although
comparatively thin. It is nowhere in contact with the internal skeleton,
except by a nuchal bone, which by a descending process articulates with the
neural arch of the eighth cervical vertebra.
The affinities of the Sphargidae and their position in the system are still
debatable. Whilst some authorities, _e.g._ Cope, Dollo, and Boulenger look
upon _Sphargis_ as the sole remnant of a primitive group in opposition to
all the other recent Chelonia, Baur considered it the most specialised
descendant of the Chelonidae. Dames agreed with him. Van Bemmelen has
modified this view in so far as he regards _Sphargis_ as the most
specialised Chelonian, but considers the differences between it and the
Chelonidae great enough to conclude that both Sphargidae and Chelonidae
represent two independent, partly parallel, branches which have arisen from
two different groups of terrestrial tortoises. Case,[130] from the study of
_Protostega_ and other fossil forms, tends towards Baur's view. He believes
that _Sphargis_ is the culminating form of a branch which through
_Psephophorus_ and with _Eosphargis_ has sprung from some creature like
_Lytoloma_, which at the same time is the starting-point of another branch
which culminates in the genera _Thalassochelys_ and _Chelone_, while lastly
a third branch contains _Protostega_, _Protosphargis_, and
_Pseudosphargis_. In other words, he considers them all Chelonidae. If he
is right we have of course no business to separate _Sphargis_ with its
fossil allies from the rest of the Chelonia as "Athecae."
However, Case has not proved his point. It is easy enough to understand
that the characters of the cranium and plastron of _Sphargis_ are in a
condition which by partial reduction can be derived from that of typical
Chelonidae. The structure of the {337}cervical vertebrae, the absence of
the marginal plates and the peculiar articulation of the nuchal with the
last cervical vertebra can be explained as convergent analogies, just like
the paddles of _Carettochelys_. But the shell of _Sphargis_ is
fundamentally different from and not homologous with that of the others.
Cope was therefore quite justified in distinguishing the Sphargidae as
"Athecae" in opposition to the others which Dollo later on, by contrast,
named "Thecophora." Unfortunate names, since both groups are undeniably in
possession of a θήκη or shell. Both authors meant, however, by Theca the
epidermal shields, but even this distinction is rendered invalid by
_Carettochelys_.
The most reasonable explanation has been suggested by Hay.[131] The mosaic
polygonal components of the shell of _Sphargis_ are, so to speak, an
earlier generation of osteodermal plates than the later generation of
longer and broader bony plates which in the Thecophora come into contact,
and fuse with, the neural arches and ribs. The osteoderms of _Sphargis_
belong to the same category as the dermal ossifications in the scutes of
Crocodilia, whilst the plates of the carapace and plastron of the
Thecophora belong to the category of the abdominal ribs. _Sphargis_ has the
first kind in its peculiar shell, the second kind in the deeper lying
plastron and in its nuchal plate. But it has lost, or perhaps had never
developed, the horny shields. The only difficulty is, however, the presence
of a plastron and of a typical neural plate in _Sphargis_. This difficulty
is not very serious. The plastron is a very old institution. It occurs
together with the more superficial osteoderms in _Caiman_, and the nuchal
plate may be the oldest of all dorsals. We can scarcely imagine that the
direct ancestors of _Sphargis_ had developed both kinds of shells, and that
comparatively recently the inner shell of the carapace was lost, leaving
only the nuchal plate. Fossils do not support such an assumption. Undoubted
ancestral forms of _Sphargis_ are very rare. _Psephophorus_ of the
Oligocene and Miocene of Europe had a continuous mosaic shell much
resembling that of _Sphargis_; _Eosphargis_ is represented by a
well-preserved skull from the London clay. Then follows a wide gap until we
come to _Psephoderma_ of the Rhaetic, or Upper Trias of Bavaria; the large
fragment of whose dorsal shell is composed of about 200 mosaic pieces. If
this fragment really formed part of the shell {338}of a Chelonian, its age
would speak greatly in favour of the Athecae being a very primitive and
independent group.
ORDER II. THECOPHORA.
_Thoracic vertebrae and ribs united with a series of median or neural and a
paired series of lateral or costal plates. Parietals prolonged downwards,
meeting the pterygoids directly or by interposition of an epipterygoid._
SUB-ORDER 1. CRYPTODIRA.–_The carapace is covered with horny shields. The
neck, if retractile, bends in an S-shaped curve in a vertical plane. The
pelvis is not fused with the shell._
FAM. 1. CHELYDRIDAE.–The plastron is small and cross-shaped (Fig. 61, 2,
p. 315); the bridge is very narrow, and the displaced abdominal shields are
widely separated from the marginals by a few irregularly shaped
inframarginals. The tail is long. The limbs, neck, and head are so stout
that they cannot be completely withdrawn into the shell. Snout with a
powerful hooked beak. American; only two genera, each with one species.
The temporal region is roofed very incompletely and only anteriorly by the
expanded parietals and postfrontals, which form a long suture. The plastron
consists of nine bony plates, a small entoplastron being present; there are
lacunae in the middle line, the plates meeting imperfectly, and the horny
abdominal shields are likewise separated by soft skin. The carapace has a
nuchal with long rib-like processes which underlie the marginals; the
neural plates form a continuous series. There are twenty-three marginal
plates. The pubic and ischiadic symphyses remain separate, enclosing one
large heart-shaped foramen. The five fingers and toes are webbed and are
protected by claws except the outer toe, the nail of which is usually
suppressed.
_Chelydra serpentina_, the Snapping Turtle, attains a large size, namely, a
shell-length of more than one foot, and a total length from the nose to the
tip of the tail of more than three feet. Its range extends from the
Canadian lakes east of the Rocky Mountains, through the United States and
Central America. The carapace of young specimens has three very marked
series of keels, which gradually disappear with age, until in very old
individuals the shell becomes quite smooth. The skin is very warty,
especially on the neck, and there is a pair of minute {339}barbels on the
chin. The tail carries three series of originally triangular horny crests,
which with age are transformed into blunt knobs. The general colour of this
rather ugly creature is olive, mottled with dark brown above and with
yellowish below.
According to Holbrook the Snapping Turtle is found in stagnant pools, or in
streams where the waters are of sluggish motion. Generally they prefer deep
water, and live at the bottom of rivers; at times, however, they approach
the surface, above which they elevate the tip of their pointed snout, all
other parts being concealed; and in this way they float slowly with the
current, but if disturbed they descend speedily to the bottom. They are
extremely voracious, feeding on fish, reptiles, or any animal substance
that falls in their way. They take the hook readily, whatever may be the
bait, though most attracted by pieces of fish; in this way many are caught
for the market. It is, however, necessary to have strong hooks and tackle,
otherwise they would be broken, for the animal puts forth great strength in
his struggles to escape, both with his firm jaws and by bringing his
anterior extremities across the line. When caught they always give out an
odour of musk, which in very old animals is sometimes disagreeably strong.
Occasionally the Snapping Turtle leaves the water, and is seen on the banks
of rivers or in meadows, even at a distance from its accustomed element. On
land his motions are awkward; he walks slowly, with his head, neck, and
long tail extended, elevating himself on his legs like the Alligator, which
at that time he greatly resembles in his motions; like the Alligator also,
after having walked a short distance, he falls down to rest for a few
moments, and then proceeds on his journey. In captivity they prefer dark
places, and are exceedingly ferocious; they will seize upon and bite
severely anything that is offered them, and their grasp upon the object
with their strong jaws is most tenacious.
The Snapping Turtles, or "Snappers," are feared on account of the ferocious
bites which they inflict, and they are hated because of the destruction of
valuable fish and water-fowl. They in turn atone for this damage by being
eaten, especially the younger half-grown individuals, the flesh of the
older ones being too much tainted with the odour of musk. The round eggs,
which are laid to the number of twenty to thirty in the summer {340}(in the
Northern States about June), are likewise good to eat. The first act of the
young creature on leaving the shell is said to be snapping and biting. In
captivity they are often very sulky, and refuse food stubbornly for many
months, perhaps for a whole year, and apparently without much harm to
themselves, since they lie quietly in the distant corner of the tank, now
and then slowly rising to the surface to breathe. Fresh-water algae grow on
the shell and in the mud which settles on it, and since this happens also
in the wild state, they are rendered as inconspicuous as old rotten logs.
In order to attract fishes they protrude a pair of worm-like, pale pink
filaments from the tip of the tongue.
[Illustration: FIG. 74.–_Macroclemmys temmincki_, "Alligator Turtle." × ⅙.]
_Macroclemmys temmincki_, the "Alligator Turtle."–In size and general
appearance much like the other Snapping Turtle, but the dorsal shields have
each a strong and prominent keel, and these three series increase in size
with age. The costal shields are separated from the marginals by an
additional series of about four supramarginals, well shown in the
illustration. The shields of {341}the cross-shaped plastron are subject to
much individual variation, small shields being frequently intercalated, or
rather retained, between the usual ones, especially between the pectorals
and abdominals, in the gular region, and on the narrow bridge, where the
inframarginals number one to three or even more. This species inhabits,
broadly speaking, the whole basin of the Mississippi and Missouri rivers.
This beast is as vicious as the other Snapping Turtle. According to Agassiz
it does not withdraw its head and limbs on the approach of danger, but
resorts to more active defence. It raises itself upon the legs and tail,
highest behind, opens the mouth widely, and throwing out the head quickly
as far as the long neck will allow, snaps the jaws forcibly upon the
assailant, at the same time throwing the body forward so powerfully as
often to come down to the ground when it has missed its object.
It lives mostly in the water, but makes considerable journeys overland.
Both in the water and on dry land the limbs move nearly perpendicularly,
and the body is raised high. On dry land a considerable part of the weight
of the body is borne by the long, strong tail.
"They are as ferocious as the wildest beast of prey, but the slowness of
their motions, their inability to repeat the attack immediately, their
awkwardness in attempting to recover their balance when they have missed
their object, their haggard look, and the hideous appearance of their
gaping mouth, constitute at such times a picture as ludicrous as it is
fearful and revolting. Their strength is truly wonderful. I have seen a
large specimen bite off a piece of a plank more than an inch thick. They
take hold of a stick with such tenacity that they may be carried for a
considerable distance suspended to it free above the ground. Fishes and
young ducks are their ordinary prey. They lay from twenty to forty or more
round eggs only about the size of a small walnut in holes which they dig in
sloping banks not far from the water" (Agassiz).
FAM. 2. DERMATEMYDIDAE.–The pectoral shields are widely separated from the
marginals by inframarginals, the gular shields are very small or absent,
and the tail is extremely short. Only two or three genera, with three or
four species in Central America.
The plastron is composed of nine plates. In _Dermatemys mawi_ it is large,
firmly joined to the carapace, covered with {342}eleven or more shields,
and there are four inframarginals; in _Staurotypus salvini_ of Mexico the
plastron is cruciform, with the anterior lobe movable, covered with seven
or more shields, according to the fusion of the anal shields and the
presence or absence of the gulars; there are only two inframarginals. The
pubic and ischiadic symphyses remain separate; the temporal fossa remains
widely open, the postfrontals scarcely touching the parietals. There are 23
marginal shields in _Staurotypus_, 25 in _Dermatemys_, including the
unpaired nuchal. The nuchal plate has a pair of rib-like processes like
those of the Chelydridae, but some of the posterior costal plates,
sometimes only one pair, meet in the middle line, overlying or suppressing
the corresponding neural plates. The shell of these aquatic tortoises is
rather flat, more or less keeled, especially in young specimens, and in the
fully adult condition is about one foot in length.
FAM. 3. CINOSTERNIDAE, represented by the single genus _Cinosternum_, with
about ten species in North and Central America, and one in Guiana. Closely
allied to the two previous families, with which it agrees by the separation
of the pubic and ischiadic symphyses, the presence of an ento-plastral
plate, the possession of inframarginal shields (Fig. 61, 3, p. 315), the
widely open temporal fossae, and the rib-like pair of processes to the
nuchal plate. It agrees with the Dermatemydidae in the interruption of the
neural plates by the meeting of several pairs of the costal plates. There
are 23 marginal shields; five or four shields, according to the presence or
absence of the gular on the plastron, and in some species these plastral
shields become, with age, more and more separated from each other by soft
skin (see Fig. 75). The shape and size of the plastron differ considerably
in the various species; in most of them, e.g. in _C. pennsylvanicum_ and
_C. leucostomum_, but not in _C. odoratum_, the anterior and posterior
lobes are movable, with transverse soft hinges, so that the animal can
completely close its shell. The skin of the legs and neck is so baggy and
loose that these parts slip in, the skin rolling off, when the creature
withdraws into its shell. They lay only a few–from three to five–elliptical
eggs, which have a shining, glazed, and thick, but very brittle shell.
{343}[Illustration: FIG. 75.–_Cinosternum odoratum_, young specimens. × ⅔.
A and B, males; C, female.]
_Cinosternum odoratum_, the Mud-Turtle, or Stinkpot Terrapin, so called on
account of the disagreeable smell which exudes from the inguinal glands.
The head is disproportionately large, with the snout rather compressed
laterally, and pointed underneath, with several short barbels. The neck is
long and slender. The carapace of the young is keeled, each of the neural
shields being raised in the middle line; but in full-grown specimens the
shell becomes quite smooth and rounded. The horny shields of the plastron
are relatively largest in the young, but they soon leave ever-increasing
spaces between them, which are then filled with soft skin only, which
thinly covers the underlying bone. The {344}fore- and hind-limbs,
especially the latter, are extensively webbed, and are provided with five
short claws. The general colour of the shell is horny brown, either uniform
or with darker spots or streaks. The neck and limbs are mottled brown. The
only ornamental colouring is a pair of clear yellow broad lines on each
side of the head, and a similar streak on each side of the lower jaw. On
the chin and upper throat are two pairs of small tentacles. The tail of the
male is of about the length of the hind-limbs, while that of the female is
so short that its tip scarcely reaches beyond the hinder margin of the
carapace. Length of the shell of full-grown specimens between four and five
inches. Very young specimens have a rather droll appearance, owing to the
long and slender neck with the large head, and the humpy back.
This species is common in the eastern half of North America, from Canada to
Texas. It is mainly aquatic, and is one of the dullest and shyest species.
My own specimens spend most of their time in the water, invariably in the
darkest corners, preferably under a stone or a log, and they do not leave
their hiding places until dark, in search of worms, meat, and all sorts of
animal food. For months I could never induce them to take food from a
stick, or even to eat in my presence, and it was not until after many weeks
that one of them at last protruded its head far enough to exhibit the
yellow stripes. When taken out of the water they draw in their heads, just
allowing the vicious little eyes to be visible, and opening the sharp-edged
mouth widely to bite deliberately and furiously at the unwary finger. Some
spent the winter in the water, in the greenhouses, feeding as usual, others
crept on land, hiding under moss, half buried in the soil, where they slept
for several months, but with interruptions in order to soak and to drink.
When spring is well advanced they prefer the water for their regular
sojourn. Some which had been sent over from New York arrived in a
deplorably dried-up condition, the skin being quite flabby and shrivelled,
but after a few hours' soaking they came round, and increased considerably
in weight, the limbs and neck becoming turgid.
_C. pennsylvanicum_ of Eastern North America has a larger, more oval
plastron. The head is not so strikingly large as in the other species and,
like the neck, is brown with yellowish spots, and often has streaks on the
sides. The tail of the male ends in a {345}nail-like horny point. The lobes
of the plastron are well hinged in the adult.
_C. leucostomum_ of Central America is larger, with a shell-length of six
inches. The plastron is not at all cruciform, but has a broad bridge, and
fills the box, moreover it has an anterior and a posterior hinge, so that
the box can be completely closed. Hence the vernacular name of the
Box-Terrapin.
FAM. 4. PLATYSTERNIDAE, represented by the single species _Platysternum
megacephalum_ in Burma, Siam, and Southern China.
The pectoral shields are widely separated from the marginals by
inframarginals, the plastron is large, oblong, not cruciform, and the tail
is long.
The plastron consists of nine plates, and is covered with six pairs of
shields, the most anterior of which are the broad gulars. The nuchal plate
has no rib-like processes. The neurals form a continuous series, and there
are twenty-three marginal scutes. The temporal fossae are completely roofed
over, owing to the long sutures formed by the parietals with the
postfrontals, moreover the postfrontals expand laterally so much that they
posteriorly come into broad contact with the quadrato-jugals and
squamosals, anteriorly with the maxillaries, so that the jugals are
completely surrounded by bones, and are shut off from the orbits and from
the temporal fossae. This is a unique arrangement, found nowhere else in
Tortoises. The pubic and ischiadic symphyses are connected with each other
by ligaments only.
The general appearance of this water-tortoise is rather curious, since the
carapace is much depressed, looking, especially in younger specimens, as if
it had been crushed in. The head, provided with very strong hooked jaws, is
strikingly heavy and large, and is covered above with one single large
shield. The tail is longer than the shell, which, in full-grown specimens,
reaches about six inches in length; it is, throughout its length, covered
with rings of squarish shields. A large specimen measures 14 inches in
total length, of which only five fall to the shell.
FAM. 5. TESTUDINIDAE.–The shell is always covered with well-developed horny
shields. Those which form the plastral bridge are in direct contact with
the marginals. The plastron is composed of nine bones. The digits have four
or five claws. The neck is completely retractile. The skull is devoid of
parieto-squamosal arches.
{346}This large family is cosmopolitan, with the exception of the
Australian and the adjoining Austro-Malayan countries. It contains genera
which form a continuous gradation between absolutely terrestrial and
thoroughly aquatic tortoises; and many are truly amphibious. As a general
rule the typically terrestrial kinds have a more curved or arched shell,
the digits are short, the eggs are more oval or round, and they are chiefly
herbivorous; the essentially aquatic kinds have a flatter or depressed
shell, webbed feet, with longer, often slender claws, the eggs are more
cylindrical, and they live on animal diet. About 20 genera, with more than
110 species, are recognised by Boulenger, but their essential characters
are nearly all internal, and therefore of no avail for the determination of
live or entire specimens.
_Chrysemys._–One of the most typical and widely distributed genera of
American Terrapins or water-tortoises. The carapace is flat; the plastron
is quite immovable, with a strongly developed bridge. Feet well webbed.
Tail short. Skull with a broad, complete, lateral, temporal arch. About one
dozen species, mostly in the eastern half of the United States, but the
whole genus ranges from Canada to Argentina.
Most of the young _Chrysemys_ are very pretty, the ground-colour of the
upper shields being green, variegated with yellowish-brown or blackish
markings, which often form exquisitely delicate patterns, either
concentrical (_Ch. concinna_, _Ch. rubriventris_), or more longitudinal
(_Ch. elegans_), or apparently quite irregular. The ground-colour of the
plastron is yellow, but the various species are best distinguished, at
least in very young individuals, by the arrangement of the dark brown spots
and patches. There are, for instance, several pairs of bold lateral and
several median patches in _Ch. rubriventris_; five pairs of ocellated spots
in _Ch. elegans_; only small median patches, where four plastral shields
meet, in _Ch. concinna_; while the plastron of _Ch. picta_ is uniformly
yellow.
These water-tortoises are very lively and shy, most so perhaps _Ch. picta_,
which is very quick and active. The food varies, often according to
individual fancy. Most of them eat fish. _Ch. picta_ is partial to insects,
but it also takes worms. Some of my specimens refused meat for a long time,
but ultimately they became so fond of it and of worms, that they came out
of the pond to take the food from the fingers; those in the Zoological
{347}Gardens of London have developed a taste for biscuits. One of my
largest _Ch. concinna_ fasted deliberately for eight months, refusing
worms, insects, meat, and frogs, only occasionally sniffing at the food,
until it was tempted with whitebait, which it took greedily. It refused,
however, smelts and pieces of soles, but after another month it
condescended to take meat regularly. Very young individuals live chiefly on
flies, which they watch for near the surface of the water; and they are
fond of smooth caterpillars, maggots, the larvae of humble-bees, and
similar soft creatures. They all spend most of their time in the water,
preferably floating near the surface, hidden between weeds; and they are
fond of basking. Some of them spend the night in the water, lying
motionless on the bottom, with heads and limbs turned in. Others prefer
hiding under moss. Those species, which, like _Ch. concinna_ and _Ch.
picta_, are common in the North, are of course perfectly hardy. For the
winter they dig themselves holes in the banks near the water, and they do
not come out again until the spring is well advanced. The eggs are
hard-shelled, mostly long and oval, and they are hatched before the end of
the summer. The larger species of Terrapin are eaten.
_Ch. picta_ (Fig. 76), the "Painted Terrapin," of the Eastern United
States, _e.g._ of New York and Long Island, is easily recognised by the
much depressed shell, which is absolutely smooth, and without a trace of a
keel. The colour above is dark olive-brown or blackish, with broad yellow
bands across the anterior ends of the neural and costal shields. Three or
four of these transverse bands are very conspicuous. The marginals are red,
with more or less concentric black and yellow markings. The pretty red
colour, with some black stripes, extends over the bridge, but the plastron
itself is uniformly yellow. The soft parts are likewise prettily marked,
the ground-colour is black-brown, with delicate bright yellow and red
stripes on the sides of the neck, limbs, and tail. The stripes are
originally yellow, but they develop an orange or red line in the middle, so
that each red stripe is ultimately narrowly edged with yellow; or the
yellow and red stripes alternate, for instance on the tail, which is short,
narrow, and pointed. The head is further adorned with a pair of conspicuous
bright yellow patches behind the eyes, and a smaller pair on the occiput.
The black and yellow stripes run across the gape of the mouth, some of the
lines even looking as if they had been {348}painted across. The nuchal
shield is elongated and very narrow, its anterior edge and that of the
neighbouring marginals are finely serrated. Very young individuals are at
once recognised by the prominent longitudinal median stripe of bright
orange extending over the nuchal and neural shields; the yellow transverse
bands are still absent; they appear when the longitudinal line vanishes.
[Illustration: FIG. 76.–_Chrysemys picta_, "Painted Terrapin." × ½.]
The "Painted Terrapin" is one of the few species of which, thanks to L.
Agassiz,[132] complete data of growth from the new born to old age are
known. During the first six or seven years the rate of growth is so uniform
that numerous specimens collected at the same time are readily arranged in
sets of the same age, simply by the differences they show in their size.
The successive lines of growth on the shields indicate the number of years.
After the seventh year the age is much more difficult to distinguish in
those tortoises, which, like _Ch. picta_, have a perfectly smooth
epidermis. This smoothness is due to the fact that the shields undergo a
process of moulting. An upper, quite {349}transparent layer of each shield
peels off completely like a piece of mica. I have been able to confirm
Agassiz' statement on _Ch. concinna_ in their third and fourth springs, and
on a number of adult _Ch. picta_. The latter were not allowed to hibernate,
being kept in a warm tank; they peeled completely during the late autumn,
and then the red and yellow colours underlying the newly formed shields
appeared very vividly; others moult at midsummer.
Growth of _Ch. picta_, after Agassiz.
+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+
| Year. | Length of | Breadth of | Height of | Length of |
| | carapace. | carapace. | box. | tail. |
+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+
| | millim. | millim. | millim. | millim. |
| Second | 26.5 | 25 | 12 | 16.5 |
| Third | 42 | 39.5 | 17 | 17.5 |
| Fourth | 51 | 49 | 21.5 | 20.5 |
| Fifth | 54 | 51 | 23.5 | 21.5 |
| Sixth | 59 | 56 | 25 | 23.5 |
| Seventh | 66 | 60 | 26.5 | 26 |
| Eighth (♂) | 72.5 | 61 | 28 | 27.5 |
| Ninth (♂) | 74 | 62 | 28 | 27.5 |
| Tenth (♂) | 77 | 64 | 30 | 28 |
| Eleventh (♂) | 80 | 67 | 30 | 28.5 |
| Fourteenth (♂) | 92 | 74.5 | 33 | 28.5 |
| Twenty-fifth (♀) | 121 | 92 | 43 | 34 |
| Old ♀ | 129 | 96 | 47 | 37 |
| Very old ♀ | 163 | 113 | 59 | 53 |
+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+
The size of the eggs varies considerably, from 26 by 17 to 30 by 16
millimeters; sometimes they are perfectly round, 17 mm. in diameter.
_Ch. concinna._–The specific character by which this Terrapin may be easily
recognised is a pair of orange-red broad streaks, which extend from above
the eye to the sides of the neck. The general colour is olive-brown above,
variegated with yellowish dark-edged lines, which, together with numerous
rugosities, radiate from the middle field of each shield. The plastron is
yellow, often with blackish symmetrical patches, and sometimes these become
confluent and preponderant. Very young specimens are extremely pretty, the
ground-colour of the carapace being green, each shield with darker,
somewhat concentric markings, most conspicuous and regular on the upper
surface of the marginals, where the marks of the adjoining shields form one
pattern-system across the dividing lines. The plastron is either uniform
yellow or has a few pairs of blackish spots {350}which stand so closely
together that they form almost median patches.
The carapace is rough. The horny shields become very thin with age. The
anterior margin of the small nuchal and the neighbouring marginals is
faintly serrated. The posterior marginals form slight notches or
indentations between their edges. The plastron is almost square behind. The
edges of the jaws are nearly smooth, without hook and receiving-notch. The
tail is short.
[Illustration: FIG. 77.–_Chrysemys concinna_, in its third summer, × 1.]
[Illustration: FIG. 78.–_Chrysemys concinna_, in its third summer, × 1.]
This species inhabits the South-Eastern States of North America, from
Missouri and North Carolina to the Gulf of Mexico. Very large female
specimens have a shell sixteen inches in length. The eggs measure from 33
by 25 to 39 by 25 mm. or about 1½ inch in the long diameter.
_Emys._–The plastron is movably united to the carapace by ligament, and in
the adult has a slightly flexible hinge across the middle, between the hyo-
and hypo-plastral plates and the pectoral and abdominal shields. The
plastron is large, but does not quite close the box. Besides the small
nuchal there are twelve pairs {351}of marginal shields. The head is covered
with smooth skin; the temporal arch is complete. The limbs are extensively
webbed. The tail of the very young is nearly as long as the shell, but it
becomes relatively shorter with age, being reduced in the males to about
two-thirds, in the females to half the length of the shell. Only two
species are found in Europe, the other, _E. blandingi_, in Canada and
north-eastern U.S.A.
_E. orbicularis_ s. _europaea_ s. _lutaria_, the European
Pond-tortoise.–The shape and coloration of the shell change likewise much
with age. In the very young the shell is round, and the shields are rough
and slightly keeled, uniform dark brown above, black below, with a yellow
spot on each marginal and plastral shield. When half grown the dorsal
shields become quite smooth, and are striated or spotted, with yellow upon
a dark ground. The head, limbs, and tail are dark, with yellow or light
brown spots and small dots. In very old specimens all these yellow marks
disappear on the shell, which then becomes uniform brown or almost black.
The coloration is subject to much local and individual variation, and there
are two main types, the spotted and the radiate. It is difficult to say
which of the two is the prettier. One male which I caught in the Alemtejo
was very beautiful. The shell was almost black with a greenish shine when
in the water, and had many bright yellow and whitish spots. In the radiate
type the yellow is sometimes preponderant, so that each shield becomes a
study of delicately painted yellow, brown, and blackish lines radiating
from the centre. This variety seems to prevail in the south of Spain,
decidedly so in the Marismas, also in Northern Italy, whence most of the
European markets are supplied. The largest shell in the British Museum is
19 cm. = 7½ inches long. Fischer Sigwart received one from Naples which was
about 9 inches long, and this seems to have been kept as a pet, since its
shell had been gilt. Specimens about 5 inches in length may be considered
as fully adult. There are very few reliable observations on the growth of
individuals. One of F. Sigwart's grew in eleven years only about 2.5 cm. =
1 inch, when its shell was 13.4 cm. = 5¼ inches long–total weight of the
tortoise 491 grammes, about 1 lb. One of my own grew from 11 to 13.2 cm.
shell-length, and 8.3 to 10.6 cm. in width within eight years, but this was
one of the specimens which, living in a greenhouse, {352}did not hibernate.
This European pond-tortoise is now restricted to Southern and Middle
Europe, extending eastwards towards St. Petersburg and into Asia Minor,
southwards into Algeria. Formerly it had a much wider range, having been
found in post-glacial deposits in Southern Sweden, Denmark, the
Netherlands, and in East Anglia. Specimens have been found in the peat of
the fens of Norfolk and Cambridgeshire, contemporary with bones of the
Beaver, Roe-deer, and Pelican. The same applies to North Germany, where its
gradual disappearance from the western and central parts is obvious. Except
in Central France it is now practically unknown to the west of the Elbe
river. The country between the Elbe and Oder is now debatable ground,
_Emys_ being exceedingly rare. Some fifty years ago this seems to have been
different, to judge from the fact that farmers were rather fond of keeping
a tortoise in the water-troughs of the cattle to keep the water free from
worms and other impurities. Hence arose a silly superstitious custom. It
was considered equally conducive to the health of the pigs to keep a
tortoise in the foul tub into which all the dish-water and
kitchen-refuse–as potato-peels, sour milk, etc.,–were collected before the
mess was given to the pigs.
A specimen is still occasionally caught in the Havel and Spree rivers. I
myself have heard of one or two in the backwaters of the Oder near
Frankfurt, but they are vanishing, and it is difficult to say exactly why.
The universal lowering of the water-level owing to better drainage cannot
quite account for it, since there are thousands of suitable ponds, swamps,
and backwaters left. In Poland and in Eastern Prussia the tortoise is still
common.
This creature lives on a strictly animal diet. Worms, insects, frogs,
fishes form its main sustenance. Fishes are regularly stalked. The tortoise
watches its opportunity, slowly it half crawls, half swims along the
bottom, rises imperceptibly by a few gentle movements of the widely
spread-out webbed feet, then opens its sharp cutting jaws wide, and makes a
grab at the belly of the fish. Frogs are most easily stalked when they sit
upon a floating leaf. The tortoise rises from below, and often waits with
the nostrils and eyes just above the water and close to the frog. After a
while it sinks, and rises again, this time actually touching the toes of
the non-suspecting frog, smelling at them and deliberately biting with a
sideward turn of the head.
{353}[Illustration: FIG. 79.–_Emys orbicularis_, European Pond-tortoise
(left), and _Clemmys leprosa_, Iberian Water-tortoise (right). × ½.]
{354}What the jaws have got hold of is not allowed to escape again. The
tortoise holds on and tears the prey to pieces with the sharp-clawed
fingers. This takes a long time, only the scraped-off flesh and the
intestines being eaten. The skeleton remains and sinks to the bottom, while
in the case of a fish, the air-bladder floats away on the surface, and
remains there as one of the surest signs of the existence of tortoises in
that locality. The bones are cleaned with wonderful neatness. Some of my
grass-snakes shared this fate, their backbones, with the hundreds of pairs
of ribs, being picked or rather scraped clean, scarcely less well than if
they had been prepared for a museum.
As a rule the prey must be in motion to be seized, unless the tortoise has
watched it before, and even then the latter prefers to smell it before
biting. In captivity they soon learn to eat meat, and they become very
tame, but in their native haunts they are extremely shy and cautious. Fond
of basking upon a stone or on the banks, with the four limbs sprawling, or
with the hind-limbs stretched backwards, and with the webs spread out so as
to offer as large a surface as possible to the rays of the sun, they lie
motionless for hours and appear fast asleep. But the slightest noise, or
any other sign of our approach, is sufficient to send them plumping into
the water, and to make them scuttle along with unsuspected agility. Nothing
but the audible plump of the flat body and the widening rings of the
disturbed water indicate their presence. After a long time of waiting we
give it up, and turn away. That very instant we see a little ripple, caused
by the withdrawing of the tortoise, which had come to the surface and had
been watching us, with only the nose and eyes peeping out of the water, the
rest being concealed between the floating vegetation. Apparently they
cannot see us well with their eyes still under water, owing to the
difference of refraction, otherwise they would not peep out and then at
once turn back. It is certainly not for the want of air, since they can
remain below for many hours without breathing.
Although they generally feed in the water, they come on land when tame and
hungry enough to take the offered food. Sometimes they make long
migrations, perhaps because their old home is dried up or does not yield
food enough. They hibernate during the cold season, buried in the mud, and
they do not appear until {355}the spring is well advanced. During the
pairing season, on warm spring nights, they emit short piping sounds, and
when they have found each other, the couple swim about together. The white,
hard-shelled, long, oval eggs, averaging 25 to 15 mm., and about ten in
number, are laid on land. This is a very laborious and curious business.
The female having selected a suitable spot, not loose sand, but rather hard
soil free from grass and other dense vegetation, prepares the ground by
moistening it from the bladder and the anal water-sacs. Then it stiffens
the tail and bores a hole with it, moving the tail but not the body. The
hind-limbs then scoop out the hole, the broad feet moving alternately and
heaping up the soil on the side, until the hole is about five inches deep,
that is as far as the hind legs will reach. The eggs are laid at the bottom
in one layer, divided and distributed by the feet. Lastly, the soil is put
in again, and the tortoise, by repeatedly raising its body and falling
down, stamps the soil firm and flat, roughens the surface a little with its
claws, and leaves the nest to its fate. Nothing but an accident leads to
its discovery. The young are hatched, according to locality and the kind of
season, either in the same autumn or not until the next spring. Eggs laid
in a garden at Kieff, in Russia, were hatched eleven months later. This
implies hibernation of the embryo within the egg, and this is probably the
usual course of events, resembling the conditions of the development of
_Sphenodon_ (cf. p. 299). The pretty little creatures, scarcely larger than
a shilling-piece, are exceedingly difficult to rear. They require a tank
with green vegetation, stones to bask on and to hide under, and also dry
ground and moss for a change. They eat flies, tiny worms, tadpoles, etc.,
greedily enough, but for some occult reasons they do less well than many
another kind of water-tortoise. Miss Durham has, however, succeeded in
rearing one, which is now in its fourth year; the shell is 2 inches long,
and each shield shows three annual rings around the areola. This specimen
spent the winters in an unheated room under moss, not in the water.
_E. blandingi_, the North American species, has a more elongated and
decidedly higher carapace than its smaller European relation. The carapace
is dull black with many pale yellowish spots; the plastron is yellow, with
a large dark patch on the outer and hinder corner of each shield. The head
is dark brown above, bright {356}yellow below and on the throat, a contrast
which gives this tortoise a striking appearance. This species is extremely
voracious, becomes easily tame, and spends a great part of the day on land,
hiding under grass to avoid great heat, and withdrawing into the water for
the night.
_Clemmys._–The plastron is immovably united with the carapace, and is
devoid of any transverse hinge. The skull has a complete bony temporal
arch. This genus, consisting of eight species, is otherwise very much like
_Emys_, and is truly Periarctic.
[Illustration: FIG. 80.–Skull of _Clemmys leprosa_. × 3/2. _A_, dorsal
view; _B_, from the left side; _F_, frontal; _J_, jugal; _M_, maxillary;
_Par_, parietal; _Pr.f_, prefrontal; _Pt.f_, postfrontal; _Q_, quadrate;
_Qj_, quadrato-jugal; _Sq_, squamosal.]
_C. leprosa_ s. _sigris_ (Fig. 79).–The upper jaw has a median notch for
the reception of the upturned point of the lower jaw; the cutting edges of
the powerful beak are smooth. The shell is flat and long-oval, nowhere
serrated. The plastron does not quite fill the box. In the young the shell
is nearly round, and the horny shields form three series of keels, of which
the lateral pair disappear early; the shields are olive-brown, each with an
orange spot or streak; the plastron is dark brown, with a yellowish margin.
The adult looks very different. The shell has become much more oval, with
the greatest width behind the bridge. The long shields are smooth, and in
elderly specimens are without any trace of the original connective rings of
growth. The general colour of the shell is uniform pale olive-grey,
inclining to yellow on the plastron. The ground-colour of the soft parts is
olive-grey, but the sides of the head are adorned with orange-red or yellow
marks, the patch between the eye and ear and three or {357}four stripes on
the neck being especially conspicuous. The limbs have pale yellowish
streaks. All these markings are, however, subject to much individual
variation. While, for instance, the half-grown creatures are distinctly
agreeably coloured, often with a rich brown, nicely sculptured shell, and
with conspicuous orange and yellow marks on the skin, the very old ones
become rather ugly, the prevailing colour varying more and more into dull
uniform pale olive-grey.
The "Iberian Water-tortoise" is typical of the Iberian Peninsula, and
extends through Morocco and Algeria far into North-Western Africa. Unknown
to the north of the Cantabrian range, decidedly scarcer than its cousin
_Emys_ in the northern half of the Peninsula, it becomes common in the
south. In the Alemtejo, in the lower parts of Andalucia and in Morocco,
there is scarcely a pool, stream, or river in which it is not found,
feeding on any living thing it can master, although fishes and frogs are
its principal prey. When the streams and watercourses run dry, during the
hot and dry season, the tortoises crowd together into the remaining pools,
which soon become stagnant and filthy. But even these havens of refuge are
not of lasting avail. They are soon cleared of anything edible, and the
stinking water becomes dirtier and hotter day by day. Ultimately the
tortoises leave the pool to hide under ledges of rocks, where they
aestivate for months. This life in the muddy, slimy pools renders these
tortoises peculiarly liable to the attacks of a certain fresh-water alga,
which enters through the cracks in the horny shields and then flourishes in
the Malpighian layer, and even in the underlying bone itself. This becomes
gangrenous in patches, and the whole shell assumes a leprous appearance,
hence the specific name of _leprosa_. Everything combines in favour of this
destructive little alga. The tortoise, covered with mud, basks in the hot
sun, the horny shields become brittle and crack, often peeling off in thin
flakes. But those happy individuals which inhabit permanent rivers, or
pools which do not dry up, are, and remain, as clean as other
water-tortoises.
_C. leprosa_ has a most disagreeable, offensive smell, something like
concentrated essence of fish, due to the secretion of a pair of large
glands situated beneath the skin of the inguinal region, and opening behind
the bridge. Freshly caught specimens stink horribly, but when they have
become accustomed to being {358}handled, they no longer void these glands.
They always withdraw into the water for the night, and the cold season is
spent in the mud. Their time of propagation is still somewhat doubtful.
Very young tortoises are met with in the Peninsula in March, when they are
already in the rivers. Those which I imported in the summer and autumn
invariably dug their nests and laid their long, oval eggs (28 to 33 mm.
long) in the month of November, pairing having taken place some two or
three months previously. The mode of making the nest is exactly the same as
that described for _Emys_. As most of my specimens were kept in a
greenhouse with a permanent current of warm water through their tanks, they
never hibernated, nor did they pass through a torpid time in the summer,
but they showed an irresistible love for the hot-water pipes, huddling
together by the dozen, so that the pipes had to be screened off to prevent
the creatures from getting burnt. Until this precaution was taken, they
heated themselves so much that the shields and even the bones of the
plastron were injured. The artificial warm temperature and the complete
suppression of seasonal rest had no bad influence, most of the tortoises
living with undiminished appetite for more than twelve years, but the
sexual period became disturbed, pairing occurring ultimately at all times
of the year. The eagerness of the males, however, had a peculiar evil
secondary influence upon the females. The male tries to fasten on to its
mate by biting into the collar-like fold of the neck into which the head is
withdrawn, and this repeated irritation produces sores and swellings, which
latter in their turn prevent the female from wiping the eyes with the back
of the fore-limbs, a habit common to most, if not all, tortoises.
Ultimately the eyes fester, and the tortoise, becoming practically blind,
falls off its feed, leaves the water, which makes matters worse, and is
very difficult to cure.
In other respects they are very hardy, and they stand acclimatisation in
England perfectly. Some, thriving in a deep concreted pond, passed through
the very severe winters of several years ago, hiding in the mud below the
ice, and appeared in the spring in perfect health. They can also
successfully pass the winter under moss and a heap of loose garden-rubbish.
_C. caspica_ is closely allied to _C. leprosa_, which it represents in the
Balkan Peninsula and in Asia Minor. It differs from the south-western
species chiefly by having the cutting edges of the {359}upper jaw finely
denticulated, and by its prettier coloration, each shield being ornamented
with yellowish streaks which form a kind of ∞ on the costals, and a ring on
the marginals. The plastron is black in the young, with yellow and black
patches in the adult. The head and sides of the neck are striped with
yellow lines, narrowly edged with black, and the rest of the soft parts is
marbled dark olive and yellow. A few other species occur in China, Japan,
and North America.
_Clemmys insculpta_, one of the American species, ranging from Maine to
Pennsylvania and New Jersey, is easily recognised by the peculiar
reddish-brown and brick-dust colour of the soft parts. The strongly keeled,
posteriorly emarginate carapace is reddish brown, with radiating yellow
lines. Each shield is delicately sculptured. The plastron, which is notched
behind, is yellow, with a large black patch on the outer corner of each
shield. Length of a full-grown specimen 8 inches. They frequent the rivers
and ponds, but are also very fond of leaving the water, sometimes remaining
for months in dry places.
_Malacoclemmys_ of North America, with three species only, is closely
allied to _Clemmys_, from which it differs chiefly by the very broad
alveolar surface of the upper jaw, and by the more forward position of the
entoplastron, this being placed anteriorly to the humero-pectoral suture.
We mention this genus since one of its species, _M. terrapin_, is so
extensively eaten in the Eastern United States. The shell is oval, slightly
emarginate behind, obtusely carinated along the middle line. The upper
parts of the shell are brown or greenish, with dark concentric lines; the
marginals are yellow below, each with a ring of dark grey, and forming a
peculiarly up-turned rim. The plastron is yellowish, either with concentric
stripes and dusky lines or uniform yellow. But it is the colour of the soft
parts which gives this otherwise dull-looking creature its delicately
pretty appearance. The skin is, namely, greenish white with countless small
black dots. The males remain much smaller than the females, and have the
concentric stripes more pronounced. This species, the choicest of the
edible Terrapins, frequents the salt marshes of the east coast of North
America, from Rhode Island to the Gulf of Mexico, being most abundant
around Charleston.
The following is a condensed account of an article which appeared in the
New York Sun, 18th September 1898, the data {360}of which were supplied by
the manager of the terrapin-farm at Beaulieu, Georgia. The continued
hunting and the unfailing demand for them are making them very scarce, so
that enterprising men have established terrapin-farms or "crawls" for the
keeping and breeding of terrapins. The "crawls" in question are near the
river. The larger is 310 by 60 feet, and is divided into three compartments
for three sizes. The smaller "crawl" is for the babies, and is 100 by 8
feet. Through both "crawls" runs a ditch connected with the river and
making a circuit of the farm. The bottom of the "crawls" is on a level with
the low tide, and is covered with a layer of mud about six inches deep.
Into this the terrapins burrow in the winter. The average population of
terrapins is about 40,000, one half "bulls" and the other half "heifers."
The latter are much better eating, and grow to a much larger size, namely,
eight inches on the plastron, while the "bulls" rarely grow over five
inches long. When a female reaches six to eight inches it is called a
"count." Those between five-and-a-half to six inches long are known as
"two-for-threes," while those from five to five-and-a-half inches are known
as "halves." They are fed exclusively on shrimps and crabs on account of
the flavour, although they will eat almost anything. The 40,000 consume on
an average twenty bushels of crustaceans a day. They are quite indifferent
to cold. The manager saw some placed in a block of ice and frozen fast to
it; after four or five days they were chopped out, thawed, and were soon as
lively as ever. The statement that it takes these terrapins only seven
years to attain full commercial growth is surprising, and is probably an
underestimate. At the end of the large "crawl" is a board to enable the
females to creep into a sand-pit, where they lay the eggs from April to
June, eight to twelve forming a set. It is necessary to get the babies away
from their parents as soon as they hatch, else they will be eaten. The
young must not be exposed to the cold. The old ones have a large amount of
curiosity. The best way of catching them is for two men to go out in a boat
with a net. They row carefully along until they come to a likely spot. Then
one man raps several times sharply on the boat with a stick, and if there
are any terrapin about they will come to the surface just as fast as they
can get there to see what is going on, and the other man scoops them up
with a little net. Another {361}way, used in the salt marshes, is for the
negroes to go tramping through the mud and water. If they pass any terrapin
these will rise out of the mud to see what the disturbance is. The captives
are then fattened in the "crawl." When the men go in to feed them they
whistle, and terrapin from all over the "crawl," thousands of them, come
swimming through the water, piling over each other in their efforts to get
close to the man with the shrimps and crabs.
_Cistudo._–The plastron, without forming a bridge, is connected with the
carapace by ligaments, and is divided into two movable lobes, the
transverse hinge being so perfect that the box can be completely closed
after head, legs, and tail have been withdrawn. The nuchal shield is very
small; the first four neurals are large and broad, the fifth much broader
than long. There are twelve pairs of marginal shields. The carapace is high
and arched. The digits are almost completely free. The tail is very short.
The skull is without a bony temporal arch, the quadrato-jugal and the jugal
being absent. Only two species, in North America.
_C. carolina_ of the Eastern United States is a very interesting species.
Closely allied by its internal structure to the water-tortoises, it has
become absolutely terrestrial; and the shape of the head, the convex shell
which is coloured black and yellow or orange-brown, and the short webless
fingers are all terrestrial features. But the rather long toes, provided
with long and sharp claws, the broad and flat feet, enlarged by a broad
fold of skin on the outer margin, the long oval eggs, the smooth covering
of the head, and the preponderant animal diet, still proclaim the aquatic
relationship of this tortoise. It is in fact a genus which has changed
habits and features from aquatic to terrestrial life. The head is covered
with a smooth skin, and the upper beak, especially in old specimens, is
strongly and broadly hooked. The eyes of the males are red, those of the
females are brown. The plastron of the males is concave, that of the
females is flat. Large females reach a length of nearly six inches. The
young are nearly round, with high, arched back and prominent keels. The
keels of the middle line remain a long time, but they gradually flatten
down with age, being prominent only at their posterior ends. Each dorsal
shield is originally nicely sculptured, with a well-marked areola and
concentric rings. Very old individuals {362}become much flatter on the top
of the shell, but the sides remain steep, so that the whole shell roughly
resembles a somewhat oblong box with the corners rounded off, and the whole
upper surface rubbed down quite smooth. The variations of colour are almost
endless, and they occur in the same localities. I have a number of all ages
from Long Island, near New York. The half-grown are beautifully reddish or
orange-brown with dark patches, median keels prominent, plastron uniform
black-brown. In others the dark-brown prevails over the lighter markings,
which are yellower and more spotted or dotted than patched. Some of the
oldest, with quite smooth shells, are black, with small, round, light
yellow spots. Others are vermiculated or striped with yellow and black. The
soft parts vary to the same extent, some showing on the neck a beautiful
intricate pattern of yellow, reddish and brown, while in others these
colours are arranged more or less in longitudinal stripes.
These "Box-tortoises" are often caught in the States and kept as pets in
the gardens, and their owners mark them by cutting their initials into the
plastron. These marks heal up and widen in time like letters cut into the
bark of a tree. One of my specimens, certainly a very old one to judge from
his hooked beak, perfectly smooth and flat shell, and from the condition of
the marginals, which have the edges rubbed down quite smooth and rounded
off, has two initials and the date 1837 on its plastron. Of course there is
no proof that the date had been cut in that year, more than sixty-three
years ago, but it was done a long time ago. The scars on those parts of the
shell which touch the ground are almost effaced, and the letters and
figures have become somewhat distorted owing to the usual unequal, not
concentrical, peripheral growth. Moreover, this tortoise must have been
already adult, although not quite fully grown, since the marks are large
and were evidently put in such a size and position as to fit the available
space. I may mention that this record tortoise was, when I got it, not kept
in confinement, but had been picked up at large.
These Box-tortoises become very tame. Although fond of drinking quantities
of water in long and slowly repeated draughts, they do not go into the
water, and if they fall in accidentally they are liable to get drowned.
They enjoy a mixed diet, but animal food predominates, consisting chiefly
of snails, the shells of {363}which are passed, slugs, earthworms, maggots,
and soft caterpillars. Their fondness for slugs is all the more remarkable
since scarcely any other Vertebrate eats these slimy, sticky molluscs; but
a Box-tortoise will make a meal of two or more fat specimens of the black
slug _Arion_, and it will eat dozens of small slugs. It first deliberately
smells the prey, turns the head sidewards and gives a bite, whereupon first
the intestines and then the rest are eaten. The slime is later on scraped
off with the fore-limbs, or the head is rubbed against the grass. The
favourite time of feeding is towards dusk or in the early dewy morning, and
they are especially lively during a soft, warm rain. They also relish
various kinds of fungi and fruit, for instance half-rotten bananas. Close
observation of their habits gives us indications as to how the change from
carnivorous to herbivorous habits may have taken place. Accidentally many a
blade of grass is bitten off and swallowed together with the molluscs, also
bits of rotten wood and moss, and their excrements are often full of such
more or less digested matter. They are not very fond of basking, although
they love warmth, creeping into the grass, where they make a shallow form
by moving the shell backwards and forwards. During the cooler nights they
frequently retire into a hole or under a log of wood. They require to
hibernate. If kept in a warm house they become restless in the autumn,
refuse food, drink and feed again after some weeks, but are liable to die
during the winter. If they can find a cool place they bury themselves and
sleep for several months. If left out of doors they dig into the ground,
creep into a hole, at the bottom of which they half bury themselves, or
they hide under a heap of garden-rubbish well out of the reach of frost.
Warm April days bring them out, and the first requirement is a drink.
When walking about in search of food they assume a curious attitude, with
the shell well above the ground, the long neck stretched out and raised
high. Their temper varies individually. Some become tame readily and lose
all shyness, and creep up to their friend to take food from his fingers.
Others are decidedly shy and sulky, withdrawing with a hiss into the shell,
which in some specimens shuts almost hermetically all round, and they do
not come out until all imaginary danger is past. One of my males sulked
thus for several months, at least we never saw anything of it except the
closed shell, but it did not starve itself. {364}Propagation takes place in
the summer, the long oval hard-shelled eggs being laid in June and July.
The TYPICAL LAND-TORTOISES are easily recognised by their feet. The digits
are short, have not more than two joints, and are without any trace of
webs; the metacarpals are scarcely longer than broad. The hind-feet are
club-footed. The skin on the anterior side of the fore-limbs is covered
with strong horny scales, frequently with dermal ossifications. The
plastron is united suturally by a broad bridge with the usually strongly
arched carapace. The skull has complete postorbital and temporal arches.
The top of the head is covered with shields. The tail is short. There are
only a few recent genera, modifications of the central and typical genus
_Testudo_. The latter is cosmopolitan in the warmer temperate and tropical
regions, except in the Australian and Austro-Malayan countries.
_Cinyxis_ (Fig. 82) with a few species in Tropical Africa from the Gambia
and from Abyssinia to the Equator is remarkable for the unique modification
of its carapace, the posterior portion of which is movable, the hinge
passing between the seventh and eighth marginal and the fourth and fifth
costal plates, externally behind the seventh marginal and the second costal
shields. In the middle of the back the hinge is imperfect, the parts being
merely flexible enough to permit the posterior half of the box to be
closed. The head is covered with shields.
[Illustration: FIG. 81.–Skull of _Testudo nigrita_ s. _elephantopus_, from
the Galapagos Islands. × ½. _M_, maxillary; _Op_, Opisthotic; _Pr.f_,
prefrontal; _Pr.o_, prootic; _Pt.f_, postfrontal; _Q_, quadrate; _S.o_,
supra-occipital.]
_C. belliana_, of Northern Tropical Africa, has a small nuchal shield, and
the margin of the carapace is smooth. Length of shell up to seven or eight
inches. _C. homeana_, of West Africa, has likewise a small nuchal shield,
but the posterior portion of the carapace descends vertically, and the
marginals are strongly reverted and serrated. _C. erosa_ (Fig. 82), also
from West Africa, has no nuchal shield; the marginals are reverted and
serrated, but the posterior part of the carapace is sloping, and the
anterior {365}portion of the plastron is strongly forked in front, and
projects beyond the anterior border of the carapace. This peculiar creature
reaches a length of nine inches. When withdrawn within the shell, which is
closed behind and depressed in front, with the jagged edges of the plastron
and the anterior marginals protecting the drawn-in head, it has a very
quaint appearance. It lives entirely on fruit and other vegetable matter,
and is said to prefer to lie in the water, while _C. belliana_ is supposed
to be entirely terrestrial.
[Illustration: FIG. 82.–_Cinyxis erosa._ × ½.]
_Pyxis arachnoides_, of Madagascar, a small land-tortoise, only four inches
in length, has an immovable carapace, but the front lobe of the plastron is
hinged.
_Testudo._–The plastron is immovable, except that in old individuals of
some species, e.g. _T. ibera_, the hinder lobe develops a transverse
flexible hinge. They have existed since the Oligocene of North America and
Europe; and are now represented by nearly forty species in all the tropical
and warmer temperate countries excepting the Austro-Malayan and Australian
region. Typically terrestrial, herbivorous and frugivorous, although
occasionally varying their diet with worms, molluscs, and insects. The eggs
are hard-shelled, mostly less oval than those of the aquatic and
semi-aquatic tortoises. The males generally remain smaller than the
females, have a slightly longer tail, and have a concave instead of a flat
plastron. Most land-tortoises hibernate in the ground during the cool and
cold seasons, or they aestivate during the hot and dry months of tropical
countries, but this is not an invariable rule.
_T. graeca_, the common "Greek Tortoise." The shell is very convex, without
keels, and has a smooth, not serrated margin. {366}The nuchal shield is
narrow. The fifth or last neural shield is much broader than the others.
The supracaudal is usually divided in the median line, so that this is
really the last pair of marginals. The plastron is notched behind; the
axillary and inguinal shields are small. The scales on the anterior surface
of the fore-limbs are small, and form from half-a-dozen to ten longitudinal
rows. The hinder surface of the thigh is quite smooth. The tip of the tail
ends in a conical, horny spur. The coloration of the shell varies somewhat,
but the ground-colour is yellow, each shield with a dark brown centre and
irregular patches or confluent spots towards the margin. The plastron has
an irregular, broad black border. The soft parts are grey-yellowish. Some
specimens are rather pale, almost lemon yellow with little black; others
incline towards orange with more or less black. The middle fields of the
shields of young specimens are granular, although this area is rubbed
smooth with age; but the rest shows clearly marked concentric lines of
growth. The eyes are dark, with a brown or bluish tinge, sometimes
inclining to dark grey in very old specimens.
Full-grown females have a shell six inches in length. This species inhabits
the northern half of the Balkan Peninsula, parts of Asia Minor and Syria,
Italy, and most of the islands of the Mediterranean, from the Grecian
Archipelago to the Balearic Islands.
_T. ibera_ is closely allied to _T. graeca_, from which it differs chiefly
in the following points. The last pair of marginal shields are fused into
an unpaired supracaudal, the median line of division being almost
obliterated. The fifth neural shield is not broader, and generally a little
narrower than the others. The posterior lobe of the plastron develops with
age a transverse ligamentous hinge, and is thus rendered slightly movable,
especially in the females. The posterior margin of the carapace is slightly
expanded in old specimens. The scales of the fore-limb are large and
imbricating, and form only four or five longitudinal rows. On the middle of
the exposed posterior surface of the thighs the skin carries a strong,
conical, horny tubercle. The coloration is much like that of _T. graeca_,
except that the yellow of the young inclines to pale olive. Some specimens
are uniform brownish. This species reaches a much larger size than _T.
graeca_, old females often measuring eight inches, {367}rarely more than
nine inches in length. Its home is Morocco and Asia Minor, extending into
Persia. It also occurs in certain parts of Southern Andalucia, where it
breeds regularly, for instance, in the sandy pine-forests of the Marismas,
near the mouth of the Guadalquivir. Whether it has been introduced from
Morocco, or is indigenous, is an open question. Its specific name refers to
its Iberian home.
_T. marginata_ is worth mentioning, since it is the Greek tortoise,
although not that of the European markets, which are supplied by the other
two species. _T. marginata_ is restricted to Greece proper, where it is the
only land-tortoise. It is less closely allied to _T. graeca_ than to _T.
ibera_, of which it may be called an exaggerated form. The posterior margin
of the carapace is much expanded or flanged, and serrated. The supracaudal
is undivided, the posterior lobe of the plastron is movable, but the large
conical spur on the thighs is absent. The dorsal shields of adult specimens
are black with a small yellowish patch; the ventral shields are yellowish,
each with a large black triangular patch. The British Museum possesses a
shell 28 cm. = 11 inches in length.
The habits of these Moorish and Greek tortoises are very much alike, and
since they enjoy the distinction of frequently being kept as pets in
gardens, where they are allowed to look after themselves, a great many
incidental and odd observations have been made on them. They are
essentially vegetable feeders, but their taste varies individually and with
the season, also according to the vegetation of the country they happen to
come from. Most of them enjoy juicy plants, for instance, lettuce and
cabbage; the flowers of the dandelion attract them not merely by their
bright colour; clover is also a favourite food, and an enclosure of
grass-land with clover in it is soon cleared of the latter; grass is also
taken, in default of anything better. Some of my specimens gradually bite
large holes into gourds and pumpkins; and in Morocco I found them in the
autumn feeding entirely on the terribly astringent green fruits of the
dwarf palm _Chamaerops humilis_. The larger specimens bolted the fruit with
the stones, passing the latter. In close captivity they often learn to take
and to like bread soaked in milk or water. They drink slowly and at length,
but scarcely ever when they have succulent food. There is one thing which
they do {368}not eat, namely, "black beetles," although they are warranted
to do so by the men who hawk them in the streets. Worms, slugs, etc. are
often mentioned as part of their occasional diet, but I am not aware that
any of the hundreds which I have watched have taken such creatures, in
spite of every opportunity. Their habits are very regular. They learn to
know the geography of their domain thoroughly, and the spot selected for
sleeping will be resorted to over and over again, be it underneath some
broad leaves, under a bushy fir-tree, between a cluster of wallflowers, or
between some tussocks, or even in an almost bare corner, the attractions of
which are not at all obvious. Although their mental capacities cannot
possibly be called brilliant, they soon learn to distinguish between
different persons, and they will come up to be fed; but their memory for
localities is surprising. Here is only one instance. A tortoise which had
been put into an outhouse for hibernation was six months later taken to its
usual large enclosure, and in the afternoon it tucked itself away on the
top of a mound under precisely the same low bush where it used to sleep
during the previous autumn. It could not see that spot from where it had
been put down, and it did not meander about during the day, but after
having enjoyed the warm sun it made straight for its favourite place. Dr.
Girtanner of St. Gallen in Switzerland testifies to their appreciation of
music. When the town-band began to play on the square adjoining his garden,
all his tortoises crept as fast as possible towards the fence and remained
there motionless with heads and necks erect. When the piece was finished
they moved about, but when the next number began they were again
spellbound. This he has observed, not on one but on many occasions. That
they can hear, although their ears are not visible, but covered by the
ordinary skin, is obvious enough from the fact that during the pairing
season they emit feeble piping sounds.
They are extremely fond of basking in the hot sun, sometimes allowing
themselves to be almost baked in it, but then again at other times they
seem to be anxious to seek the shade. They rise late and go to bed early,
being absolutely diurnal. In the summer they leave their quarters when the
sun is well up, making for a sunny spot to graze. Then they lie still and
bask, unless a shower causes them to retreat under shelter. {369}After some
hours' rest they feed again, and in the afternoon, long before sunset, they
go to bed. Some winters in England are of course much more severe than any
which these tortoises experience in their native countries. Still they
manage to survive them, provided they find a place which they can burrow
into, deep enough to be out of the reach of frost; and if there is a heap
of mould, rotting weeds, and leaves, they are probably safe. Sometimes they
are restless, coming out again in unusually mild winters without, however,
taking food. If they appear too early in the spring, they run the risk of
terrible colds on prolonged wet and cold days, but in the autumn they are
hardier, and can stand several degrees of dry frost.
The pairing season begins in May, but lasts far into the summer. In Morocco
I found them pairing as late as the month of September. The preliminaries
extend over many days. The male becomes unusually active, makes a piping
sound, runs after the female, draws in its head, and knocks with its shell
against that of the female. This is repeated many times, until the female
is excited enough to raise itself upon its hind-limbs. The eggs, only two
to four in number, are laid several weeks later, and are buried in the
ground. They are roundish-oval, hard-shelled, and vary according to the
size of the female. Those of _T. graeca_ measure on the average 30 by 24
mm.; those of a large specimen of _T. ibera_ 32 to 36 by 30 mm. The
newly-hatched little creatures are still quite flexible, and apparently
soon bury themselves before beginning their active life in the ensuing
spring.
The age which these tortoises can reach is quite unknown, but there are
reliable data of individuals having been kept for many years. Rumpf[133]
kept two _T. graeca_ in his garden at Frankfort-on-the-Main, and let them
hibernate in a box with hay in the cellar. One lived 33, the other 23
years. The most famous specimen of _T. ibera_ is "Gilbert White's
Tortoise,"[134] which had been kept for more than 40 years before it came
into his possession. It used to bury itself in November and to come out in
April. It died in 1794, having reached an age of fifty-four _plus_ an
unknown number of years, since there is no record of its size when it came
to England. The same applies to every other specimen which has been, and is
being, observed as a pet. My {370}largest Morocco female, which has a shell
7 inches long, shows at least 25 concentric rings of growth on the shields;
the last half-dozen rings are very narrow, while some of those of the
central area have been rubbed down. This creature is not improbably 30
years old. A small female, which is only 5¼ inches long, has already 14
rings on its still perfect shields. Lastly, a little one, only 4 inches
long, shows 7 rings. They grow fastest when they are about 6 to 7 inches
long, and they then seem to be at their prime. White's tortoise, now
enshrined in the National Collection, was unusually large, the shell
measuring 25 cm., or nearly 10 inches; around the much-enlarged,
rubbed-down areola of each shield are about 30 very narrow rings.
_T. horsfieldi_ is easily recognised by its possessing only four claws on
the fore- and hind-limbs. It is closely allied to the species last
mentioned, which it seems to represent in the sandy districts of
Transcaspia and the Kirghiz Steppes to Afghanistan.
_T. elegans_, the "Starred Tortoise" of the southern half of India and
Ceylon, is easily recognised by the very convex carapace without a nuchal
shield, and by the beautiful markings of the other shields, each of which
has a yellow areola, whence radiate yellow streaks upon a black ground.
Moreover, the dorsal shields often form humps. It reaches the length of one
foot. Old specimens lose the beautiful yellow radiation, owing to a
considerable amount of peeling off of the horny layers.
The habits have been carefully watched by Captain Thomas Hutton,[135] who
gives the following account. The tortoises live in the grassy jungle at the
base of the hills, but owing to their colour being so blended with the
rocky nature of the ground, they are with difficulty distinguished.
Moreover, they remain concealed beneath shrubs or grass during the heat of
the day. In the rainy season they are most active, wandering about all day,
feeding and pairing. At the approach of the cold weather they select a
sheltered spot and conceal themselves by thrusting their shell into some
thick tuft of grass, remaining there in a sort of lethargic, but not
torpid, inactivity until the hot season, at which time they remain
concealed only during the heat of the day, coming out about sunset to feed.
During the hot season Hutton's captives often soaked themselves {371}in
water, and they drank a great deal. Copulation lasted about ten minutes;
the females received the males from the end of June to the middle of
October. On the 11th of November a female dug a pit at the root of a tuft
of grass, having previously watered the spot, then digging with the
hind-limbs alternately, and continuing to water the soil. In two hours she
had made a hole six inches deep and four wide; she then laid four pure
white eggs, each about 1¾ inches or 45 mm. long, and filled the hole again
with the prepared mud, pressing it well in with the feet and with the
weight of the body. The whole operation took four hours. From December to
the beginning of February these tortoises were listless, they then took
water and some lucerne, but did not come out again until the middle of
April, well in the hot season. Both males and females wrestled in a curious
way. One confronted the other, with the head and fore-limbs drawn into the
shell, and with the hind-limbs planted firmly on the ground, and in this
manner shoving against each other in any narrow space. Sometimes, if one
succeeded in placing its shell beneath the other, he tilted his adversary
over on his back, from which position he had great difficulty in recovering
himself.
_T. polyphemus_, the "Gopher Tortoise" of the south-eastern States of North
America, is one of the few American species. It is characterised by the
shape of the front lobe of the plastron, which is bent upwards, and extends
beyond the carapace. The nuchal shield is present, not narrow; the
supracaudal is undivided. The shell is much depressed, and flattened along
the vertebral region, with rounded margins. The fore-limbs are armed with
very strong claws. The general colour is very dark brown above, inclining
to black; brownish yellow below, with blackish patches. The length of the
shell is about one foot, or even eighteen inches.
The Gopher is interesting for its habits, which are described by Agassiz,
Schnee, and others. Its domicile consists of an excavation, the mouth of
which is just sufficient to admit the animal, the burrow running in an
oblique direction to the depth of about four feet. The whole passage is
sometimes more than two yards long. It expands from the entrance, and ends
in a roomy space, sometimes with a few branches of fir trees which have
been dragged in either for food or as a lining. The burrow {372}is
inhabited by one pair only. When the dew is on the grass, or after rain,
they emerge in search of food, which consists of grass, succulent
vegetables, fruit, etc. They also eat the gum that exudes from trees,
especially the resin of the pine. The eggs are laid in June, not in their
domicile, but in a separate cavity near the entrance; a set consists of
five eggs, almost round, and very large, namely, 40 mm., or more than one
inch and a half in diameter. To capture the Gopher a deep hole is dug at
the mouth of their home, into which they fall as they emerge for food. In
Southern Texas and neighbouring parts of Mexico they are represented by a
smaller and lighter coloured species.
_T. tabulata_, widely spread over Tropical South America, whence it is
often brought over as a curiosity, reaches a large size, specimens nearly
two feet in length being not uncommon. The shell is flat on the top, and is
very elongated, without a nuchal, but with an undivided supracaudal shield.
The carapace is very dark brown or black, each shield with a yellow or
orange centre; the plastron is brown and yellow, the dark colour being
mostly confined to the middle portion. The ground-colour of the skin of the
limbs is blackish, but the scales are orange or red. The head is yellow and
black. This species inhabits the forests, and lives chiefly on the fruits
of trees; in captivity they are said to take bread soaked in milk or water,
lemons, apples, bananas, cabbage, gourds, and also meat, at least the
males.
GIGANTIC LAND-TORTOISES differ from the others in no essential points
except their large size. The term gigantic is, however, applied to many of
them by courtesy only, since they do not exceed the dimensions of large
Turtles. A truly gigantic species, _T. atlas_, has left its remains in the
Sivalik Hills of late Miocene or early Pliocene date. The skull is between
seven and eight inches long, and is well preserved, but the correctness of
the dimensions of the specimen, as it now stands, restored in the National
Collection, is open to doubt. The shell was probably not more than six feet
long. Miocene and Pliocene Europe was also inhabited by large tortoises,
with shells about four feet long, _e.g._ _T. perpigniana_, whose bony
plates are one inch thick; others have been found in North America. Such
large tortoises are now restricted to two widely separated regions of the
world, namely the Galapagos Islands (which have received their name from
these creatures, _galápago_ being one of the Spanish terms for
{373}tortoise), and the islands in the Western Indian Ocean, namely the
Mascarenes (Bourbon, Mauritius, and Rodriguez), the Comoros, Aldabra, the
Amirantes, and the Seychelles. When they became extinct in Madagascar is
not known, but _T. grandidieri_ was a very large species of apparently very
recent date. Of the other islands the Comoros only were inhabited by man,
the others were devoid of any but small and harmless Mammals. It was on
these peaceful islands that large tortoises lived in incredible numbers,
and, like the Dodo of Mauritius and the Solitaire of Rodriguez, grew to a
size far beyond that of their less favourably placed continental relations.
The same applies to the tortoises of the Galapagos Islands. Plenty of food,
a congenial equable climate, and absence of enemies enabled them to enjoy
existence to the fullest extent. There was nothing for them to do but to
thrive, to feed, to propagate, to grow, and to vary. At least there was
nothing to check variation within reasonable limits. Scattered over the
many islands, they were prevented from inter-breeding, and thus it has come
to pass that not only every group of islands, but in the case of the
Galapagos almost every island, has or had its own particular kind, be these
called varieties, races, forms, or species.
There are four features of special interest. First, these tortoises grow to
a large size, and there are no small species on any of these islands.
Secondly, they vary much individually. Thirdly, each island or group of
islands has developed its own kind. Lastly, there is the widely spread
tendency to reduce the thickness of the bony plates of the carapace, in
spite of its size. In some cases, notably _T. vosmaeri_ of Rodriguez, the
bony shell is reduced to apparently the utmost limit compatible with
mechanical safety. The horny shields are, or were, however, well developed,
sometimes much more so than in other recent land-tortoises. Whatever were
the original reasons for the development of a strong shell in tortoises,
they cannot have prevailed in these islands.
Where did all these tortoises come from, and how did they get to these
oceanic islands? Accidental transport or migration are out of the question.
Land-tortoises are drowned within a few hours. Moreover, there are none of
their kind on the continents of Africa, Asia, and South America, although
they had a much wider distribution in past geological ages. Consequently we
have to assume that they are descendants of tortoises once populating the
land which, except the islands, lies now below {374}the western Indian
ocean. The existence of this, "Lemuria" or "Gondwana," came to an end in
Mid-Tertiary times. The large tortoises on the remaining continents died
out–in any case they are gone, while those which lived on, or retreated to,
what became the present islands, survived and flourished.
The tortoises were not left in peace with the advent of man, who found that
they were good to eat. They were first exterminated on the Mascarene
Islands. In 1759 four small vessels were specially appointed for the
service of bringing tortoises from Rodriguez to Mauritius; one vessel
carried a cargo of 6000; and altogether more than 30,000 were imported into
Mauritius within the space of eighteen months. Dr. Günther very properly
remarks that many of these tortoises must have been small-sized specimens,
and that many of them were probably used for provisioning passing
Government vessels. Anyhow an inter-insular traffic was carried on, and
there are records of superfluous tortoises having been turned loose, at the
end of the voyage, in distant islands, even in Java. Importation and
exchange of choice specimens, by way of presents, seems also to have taken
place. All this makes it now actually impossible to trace the original
habitat of the few surviving specimens with anything like certainty. At the
beginning of this century the large tortoises had been nearly cleared off
most of the islands, and at the present time only the south island of
Aldabra enjoys the reputation of still possessing some really indigenous
tortoises. The few survivors on the other islands are said to have been
introduced. The small stock at Aldabra is now under Government protection.
Representatives of various species will linger on for a little time to
come, when they are kept as pets on some tropical islands, but those which
have been brought to Europe are of course doomed.
We can mention only a few of the large tortoises which have become famous,
not to say historical. A fascinating résumé of the whole complicated
question has been given by Dr. Günther.[136]
_Testudo gigantea_ s. _elephantina_ s. _hololissa_ s. _ponderosa_,
originally confined to the North Island of Aldabra, where this {375}kind
has been completely exterminated, is now still to be found in the
Seychelles in considerable numbers, introduced there by planters, and kept
in a state of semi-domestication. A very large specimen was received by the
Hon. Walter Rothschild, at Tring, in 1893. In 1897 its shell measured 40¼
inches in length, 52¼ over the curve, and 50 inches across the curve
transversely; it weighed 358 lbs. The measurements taken in previous years
are unfortunately not free from mistakes. "Whenever the temperature was
over 60° F. this tortoise had a free run of 350 acres of grass park, and
when the temperature showed permanently below 58°, it was kept in an orchid
house from September to June. When at liberty in the park it lived entirely
on grass, but in the hothouse it fed on carrots, cabbage, lettuce, and
several other vegetables"; it was also very fond of rotten fruit. To this
species belongs the large tortoise which has been living at St. Helena for
more than the last hundred years.
_T. daudini_ is the species of the South Island of Aldabra. Voeltzkow, in
1895, succeeded in carrying off seven specimens. He gives the following
description:–The island is an atoll, cut through in three places, with a
greatest length of about twenty miles. The chief hindrance in the search
for the tortoises is the impenetrability of the island. The soil consists
entirely of sharp water-worn corals, with their points uppermost, while the
whole is covered with such thick masses of low scrub, that a way has to be
cut with an axe, so that an extended search over a large area is out of the
question. To land on the outside is dangerous, on account of the heavy
surf; while landing from the inside of the atoll is much hindered by the
dense thickets of mangrove trees. As drinking water, and that very bad, is
only found in one place, rainwater has to be collected from the natural
hollows, and carried along in tanks. Thousands of mosquitoes prevent one
remaining over night in those places which the tortoises frequent. Then at
last, when one has discovered, by a stroke of luck, one of these creatures,
in the thick scrub, where they hide during the heat of the day, the real
hard work begins, namely, the conveyance of the beast. Six reached Europe
alive, two of them were sent to Frankfort, and the four others to Hamburg.
Mr. Rothschild received a male of _T. daudini_, which, until its recent
death, was the largest living tortoise known. The length {376}of its shell
was 55 inches, or 67½ inches over the curve; total weight 560 lbs. This
specimen had a chequered career. Although its original home must have been
the Aldabra atoll, it had been known for many years on Egmont Island, one
of the Chagos Islands. According to tradition, it had been there some 150
years, but the first settlement on that island was formed from Mauritius
only at the beginning of this century. The owner of the tortoise, M.
Antelme, took it to Mauritius, whence it came to England. On the Egmont
Island it used to bury itself for six months in the ground without eating
anything.
[Illustration: FIG. 83.–_Testudo daudini_ (above) and _T. abingdoni_
(below). × 1/20.]
_T. sumeirei._–This kind is supposed to have been the species peculiar to
the Seychelles. In 1766 five large tortoises were brought from the
Seychelles to Mauritius by Chevalier Marion de Tresne. Of these only three
were alive in 1898, two in {377}Mauritius and one in London; the latter
specimen soon died in the Zoological Gardens. One of the two survivors, the
last of their race, is famous. It was kept at Port Louis, and when
Mauritius became a British possession in 1810, the tortoise was especially
mentioned and taken over. It still lives there in the grounds of the
barracks of the garrison. According to the proverbial oldest inhabitants it
had in 1810 already reached its present size, namely, a shell-length of
about 40 inches with a greatest circumference of 259 cm. = 8 feet 6 inches.
Total weight 160 kilo = about 358 lbs. When walking it stands 63.5 cm. =
25.4 inches high, with the plastron about 15 cm. or 6 inches above the
ground, and it can then carry with ease two full-grown men on its back.
This old male is now nearly blind, but is otherwise of regular habits and
in good health. Although it has been known for nearly 150 years it had to
wait for its scientific name until the year 1892.
Another famous individual is the Colombo tortoise. It is supposed to have
come to Colombo from the Seychelles in 1798. It died in 1897. To judge from
photographs, this specimen, a male, may possibly belong to _T. sumeirei_,
in spite of the very flat shell, which is 53½ inches in length.
Leaving aside the remains of sub-fossil tortoises, _e.g._ the thin-shelled
_T. vosmaeri_ of Rodriguez, and several kinds which have been dug out in
the Mare-aux-songes of Mauritius, one of which had a markedly forked and
prolonged anterior plastral lobe, rather resembling that of the Pliocene
Sivalik _T. atlas_, we now turn to the tortoises of the Galapagos Islands.
They existed in enormous numbers towards the end of the seventeenth
century, when Dampier visited those islands. Hundreds were exported and
scattered early in the nineteenth century. When the islands became a penal
settlement of Ecuador, the introduction of convicts and pigs proved
detrimental to them, but Darwin found them still present in 1835 on most of
the islands. His classical account of these old giants is to be found in
the _Voyage of the Beagle_. They lived on the succulent cactus plants,
leaves of trees, berries, and a kind of _Usnea_, a lichen pendant from the
trees. They collected regularly at certain pools and springs, leading to
which were regular well-trodden paths, formed by the coming and going of
the tortoises. He calculated that they could walk a distance of about four
miles in one day. During {378}the time of propagation the males emit a
hoarse bark, which can be heard a hundred yards off. The round eggs measure
about 5 cm. or 2 inches in diameter, and are laid in the month of October,
about one dozen making a set.
Nearly every island had apparently its own kind. They are all remarkable
for their small head and the length of their neck, which is decidedly
longer and more slender than that of the Eastern tortoises. The most
peculiar looking are or were _T. ephippium_ and _T. abingdoni_, the shell
of which is extremely thin, with large lacunae in the osseous plates. The
profile of the shell is somewhat saddle-shaped, with the horny shields
partly concave and turned upwards at the sides. The general colour of these
and the other Galapagos tortoises is black. _T. ephippium_ still survives
on Duncan Island. Of _T. elephantopus_ s. _vicina_ Baur collected
twenty-one specimens in 1893 on Albemarle Island. Some of them are still
comparatively young, only 16 inches long. A large one was killed, and,
being hard up for water, Baur and his companions drank the five cups full
of fluid contained in the pericardial sac; they found it most refreshing,
and tasting somewhat like the white of an egg. One monster is said to have
measured 56 inches over the curve, with a skull 7.12 inches in length. Mr.
Rothschild received one of this kind alive–a much-travelled specimen. It
came to England from Sydney, whether it had been brought in 1880 from
Rotuma Island, north of the Fiji group. There it had probably been left
with others by Captain Porter, who, on his voyage from the Galapagos in
1813, distributed several young tortoises from his stock among the chiefs,
and permitted a great many to escape into the bushes and among the grass.
The shell of this specimen measured 49½ inches in length, 56 over the
curve.
FAM. 6. CHELONIDAE (_Turtles_).–The limbs are paddle-shaped, and the shell
is covered with horny shields. Only two recent genera, with three species,
widely distributed in the seas.
The neck is short and incompletely retractile. The temporal region of the
skull is completely roofed over above and laterally by the parietals,
postfrontals, squamosals, quadrato-jugals and jugals. All these bones are
much expanded, and form the additional or false roof. The parietals are
especially large, and are in broad contact with the squamosals. Nasals are
absent. The nares are bordered by the small premaxillaries, the
maxillaries, {379}and the prefrontals. The choanae are enclosed by the
palatines, which are separated by the vomer, and are posteriorly in broad
contact with the pterygoids. The latter are connected with descending
processes of the parietals by epipterygoids. The foramen magnum is bounded
not only by the supra-occipital and the lateral occipitals, but also by the
basi-occipital. For the skeleton see Fig. 65, p. 320. The pubic and
ischiadic symphyses are connected by a narrow cartilaginous band. The pubis
has a large, broad, lateral process, but the ischium is devoid of such a
process. The paddles of the fore- and hind-limbs are produced by an
elongation of the metacarpal and metatarsal bones and of most of the
phalanges, and these have no condyles; most of the carpal and tarsal
elements are flattened, and additional width is given to the hands by the
much enlarged pisiform bone. The number of phalanges of the five fingers is
2, 3, 3, 2, 2; that of the five toes, 2, 3, 3, 3, 2.
[Illustration: FIG. 84.–Skull of _Thalassochelys caretta_; cf. also Fig.
63, p. 317. _A_, Dorsal view; _B_, ventral view; _F_, frontal; _Jg_, jugal;
_Mx_, maxillary; _Op_, opisthotic; _P_, parietal; _Pal_, palatine; _Pr.f_,
prefrontal; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate; _Quadr_,
articular surface of quadrate; _Qj_, quadrato-jugal; _S.o_,
supra-occipital; _Sq_, squamosal.]
The carapace is heart-shaped and very flat. The nuchal plate has no
rib-like processes. The eight neurals form a continuous series, and the
short tail is covered by two or three pygal plates besides the unpaired
last marginal. The number of all the {380}marginals is 23, sometimes 25
individually. The plastron (Fig. 66, p. 321) is composed of the usual nine
plates, which, however, remain entirely free from the marginals, and are
only loosely connected with each other, enclosing a very large unossified
space. The horny shields covering the plastron number 13, and there is a
series of about 5 inframarginals (Fig. 61, 6, p. 315). There are normally
12 pairs of marginal shields, a nuchal, 5 neural, and 5 or 7 costal
shields. Whilst the number of these dorsal shields is pretty constant in
_Chelone_, it is subject to an astonishing amount of individual variation
in _Thalassochelys_.
The Chelonidae are a highly specialised offshoot of the Cryptodira adapted
to marine life. Fundamentally they agree most with the Testudinidae,
paradoxical as this may appear at first sight. There is nothing primitive
about them except the complete series of inframarginal shields. Fossil
forerunners of marine turtle-like creatures appear in the Upper Jurassic
deposits of Europe and North America. The numerous genera have been grouped
together as Thalassemydidae and Chelonemydidae. They are more or less
intermediate between Chelonidae and _Emys_-like Testudinidae, the carapace
being not too much flattened and broadened out, the fontanelles between the
ribs are mostly small, the plastral bones are still broad, enclose a
smaller ossified space, and there is still a bony bridge in most cases. The
paddle-shape of the limbs is less pronounced, and sometimes only indicated.
In some forms, especially _Lytoloma_, from the Upper Cretaceous and Eocene
of North America and Europe, the anterior portion of the skull is much
longer than in the Chelonidae, the vomer and the premaxillaries are
elongated, and the anterior portion of the roof of the mouth, with the
corresponding parts of the lower jaw, seems to have carried crushing pads.
Some of the best-known Upper Jurassic genera are _Eurysternum_ and
_Idiochelys_; _Plesiochelys_ from the Purbeck and Wealden; _Allopleuron
hofmanni_ from the Upper Cretaceous of Belgium approaches _Chelone_ by the
large fontanelles between the small marginal and the short costal plates.
True Chelonidae are very rare and imperfect in the Mid-Tertiary strata, but
both recent genera seem to have existed since Pliocene times.
The few recent Chelonidae are entirely marine, going on land only in order
to deposit their eggs in the sands of unfrequented shores. Their
distribution, in conformity with their oceanic life, {381}is almost
cosmopolitan within the warmer zones, but not a few find their way far into
the temperate seas. They are all eagerly hunted by man either for food or
for the sake of the tortoiseshell.
_Chelone._–With only four pairs of costal shields. Carapace with large
persisting fontanelles between the costal and marginal plates. Two species.
_Ch. mydas_ (the "Green or Edible Turtle"), has when adult a nearly smooth
shell, all the shields being juxtaposed, fitting closely into each other,
and becoming quite smooth with age. The neural shields of younger specimens
have a feeble keel. The twenty-five shields which surround the carapace
form a smooth, or but indistinctly serrated rim. The head is covered with
one pair of prefrontal shields, the others are small. The horny beaks of
the upper and lower jaws have denticulated outer edges, those of the upper
jaw having two pairs of strong denticulated ridges. The limbs have
generally only one claw, namely on the first digit. This claw, although
sometimes curved and thick, and more than an inch in length, is blunt. The
general colour is olive or brown above, with yellowish spots or blotches;
the under parts are pale yellowish. This species attains a large size, with
a length of shell of nearly four feet, but the usual length of full-grown
specimens is three feet, and these weigh, when in good condition, more than
three hundredweight. Their home is in the Atlantic, Indian, and Pacific
Oceans, but there are certain regions in which they are more common than in
others. Famous centres are the Island of Ascension, the West Indies, and
the coast of Mosquito, at least for commercial purposes. As they require
sandy, easily accessible beaches for the deposition of their eggs, they
congregate in certain parts of the world more than in others, and being
strictly vegetable feeders, they are naturally bound to the coasts,
although they are sometimes met with far out at sea. Their chief food
consists of algae, and of _Zostera marina_, the edible "Dulce," which grows
plentifully in the lagoons of the coast of Florida. When they have eaten
their fill, they are said to chop off more of these plants, and roll them,
together with the adherent mud, into balls of the size of a head, and these
balls, receding with the tide, are followed by the Turtles.
Whilst in the water they are caught in various ways, with {382}nets or
harpoons. In some parts of the world the natives follow them in a boat, and
when they espy a turtle crawling along the bottom, a man, attached to a
rope, dives in, clasps it, and is brought up by his companions together
with his prey. Turtles are fond of basking asleep, floating on the surface,
and they are then harpooned from a stealthily approaching boat. The most
original mode of catching them is that used by the natives of Torres
Straits, Madagascar, and Cuba. The turtle-fishers go out in the boat to a
spot frequented by grazing turtles; a long string is tied to the tail of a
fish, _Echeneis_, a member of the Mackerel family, and the _Echeneis_,
anxious to get away to protective shelter, makes for a turtle, and attaches
itself to the turtle's plastron by means of the large sucking apparatus on
the top of its head and neck-region. The men are guided by the string, and
the turtle is gently coaxed up towards the surface or followed into shallow
water, where it is either harpooned or dived for. It is curious that this
use of the _Echeneis_ exists in such widely separated parts of the world,
the natives of which cannot have any knowledge of each other. These modes
of catching turtles are sportsman-like, but the greatest and most wanton
destruction is practised at their breeding places. In conformity with the
wide distribution of these creatures, the time of breeding is not the same
everywhere. In the West Indian region, and in the Straits of Malacca, it
falls within the period of April to June; on the coast of West Africa it
occurs from September to January. The females come to their breeding places
from afar, reconnoitre the beach carefully, are extremely wary and shy,
taking alarm at the slightest disturbance, and at last crawl on land. Well
out of the reach of the tide the female scoops out a hole in the sand,
deposits about one hundred or more of its round, rather parchment-shelled
eggs, covers the nest carefully, obliterating all traces of the dug-out
sand, and makes again for the sea by another route. At least they are said
to make a sort of circuitous route so that nobody can tell the position of
the nest, which may be anywhere beneath the broad trail left by the heavy
creature on its way from and back to the sea. The nest is discovered by
probing the sand with sticks. The time of incubation is not known, but
according to Agassiz, lasts at least seven weeks.
{383}[Illustration: FIG. 85.–Three turned Turtles, a Seal, and Albatrosses,
Laysan Islands, north-west of the Sandwich Islands. From a photograph
belonging to the Hon. W. Rothschild.]
{384}The "turning" of turtles is a cruel and wanton operation, since
frequently many more are turned over and left to perish than are taken
away. Men lying in ambush watch the beast, or they approach the lonely
sandy shore by boat, and rush the helpless creatures when these are
surprised in sufficient numbers. It takes several men to lift a full-grown
specimen. It is therefore necessary to secure them by turning them over
with poles or by their flippers, lest they should crawl away. On board ship
they are either put into tanks or tied with ropes on deck, covered with a
moistened cloth; and occasionally a piece of bread, soaked in sea-water, is
thrust into the parched mouth. In London they are kept in large tanks,
often in considerable numbers, but since they take no food in captivity, or
rather because it is difficult to supply them with the right sort, they are
not kept long. After the head has been cut off, the body is suspended for a
day or two, in order to drain it of the blood. It is not only the meat and
the fat which are used for the making of the famous soup, but also the
thick and dense layer of subcutaneous tissue which lines the inside of the
shell.
Tennent describes a revolting spectacle exhibited in the markets of Jaffna,
in Ceylon. The flesh of the turtles is sold piecemeal by the Tamil
fishermen, while the animals are still alive. At certain seasons, says the
same authority, the flesh of turtle on the south-west coast of Ceylon is
usually avoided as poisonous, but some lamentable instances are recorded of
neglect of this, and consequent sickness, followed by coma and death. In
the Gulf of Manaar specimens are frequently found between four and five
feet in length; and on one occasion, in riding along the seashore north of
Putlam, he saw a man in charge of some sheep, resting under the shade of a
turtle shell, which he had erected on sticks to protect him from the sun.
In connexion with this curious sight, Tennent quotes Aelian's statements,
copied by him from Megasthenes' _Indica Frag._ lix. 31, that in the Indian
ocean turtles occur which measure fifteen ells, so that not a few people
may find ample shelter beneath a single shell.
_Ch. imbricata_ ("Hawksbill Turtle").–The number of shields covering the
carapace is the same as in _Ch. mydas_, but they strongly imbricate, or
overlap each other from before backwards, until the animal is very old,
when the shields become juxtaposed.
{385}[Illustration: FIG. 86.–_Chelone imbricata_ ("Hawksbill Turtle"),
young. × ½.]
In young specimens, under one foot in length, each of the neural and costal
shields is strongly keeled, the three rows of keels converging towards the
posterior end of the shell. The neural series of keels is almost
continuous, and remains longest, even in half-grown specimens. The twelve
pairs of marginal shields form at first a strongly serrated sharp edge; the
serrations disappear gradually on the front portion, but remain on the
posterior half of the shell. The horny covers of the jaws form a hooked
beak, with sharp but smooth or feebly denticulated margins. The fore- and
hind-flippers have two claws. The young are pale brown above, blackish
below; the shell of the adult is beautifully marbled with yellow on a rich
dark-brown ground; the plastron is yellow. The shields and scales of the
head and limbs are dark brown, with yellow margins. The top of the head is
covered by a large unpaired frontal and a pair of prefrontal or
interorbital shields. This Turtle does not reach the size of the green or
edible kind; the largest shell on record is in the National Collection, and
measures 85 cm. = 34 inches in length. They range over all the tropical and
subtropical seas. They are apparently strictly {386}carnivorous, living
upon fish and molluscs, the shells of which they crunch. Although not
eaten, they are much persecuted on account of their shells, the horny
shields of which are the "tortoiseshell" of commerce. A large specimen
yields up to 8 lbs. Few of the shields are, however, thick enough to be
manufactured into the larger articles which art and fashion delight in, but
if heated in oil, or boiled, they can be welded together under pressure,
and be given any desired shape. In genuine articles of Oriental manufacture
these welds can generally be detected, or their compound nature is
indicated by the beautiful pattern, which is too regular in the imitations
now common. Even the shavings and leavings can be welded and moulded into
large pieces. The stripping of the shields has been described by Sir E.
Tennent. "If taken from the animal after death and decomposition, the
colour of the shell becomes clouded and milky, and hence the cruel
expedient is resorted to of seizing the turtles as they repair to the shore
to deposit their eggs, and suspending them over fires till heat makes the
plates on the dorsal shields start from the bone of the carapace, after
which the creature is permitted to escape to the water. At Celebes, where
the finest tortoise-shell is exported to China, the natives kill the
turtles by blows on the head, and immerse the shell in boiling water to
detach the shields. Dry heat is only resorted to by the unskilful, who
frequently destroy the tortoise-shell in the operation." The cruel process
described above is resorted to "for economy's sake," the Singhalese
believing that such maltreated turtles regenerate the shields, to be caught
and shipped again. Since none of them are actually re-caught in the
mutilated condition, this is looked upon as a proof of the correctness of
the treatment. It is more likely that they die.
New shields can be reproduced only if the underlying Malpighian layer of
cells (_cf._ Fig. 68, B, p. 323) is not killed by the roasting. However,
Dr. Charles Hose, with his long experience in Borneo, is positive that
numerous individuals are there caught which have imperfectly mended shells,
the shields of which do not imbricate, are thin, and almost worthless.
It is commonly believed that the same individuals return again and again to
the same spot for laying. This is very likely the case. Tennent mentions
that in the year 1826 a Hawksbill was taken near Hambangtotte, which bore a
ring attached to one of its fins, that had been placed there by a Dutch
{387}officer thirty years before, with a view of establishing the fact of
these recurring visits to the same beach. The same homing instinct has been
observed in some females of the Green Turtle, which, having been brought
from the Tortugas Keys to Key West off the south end of Florida, escaped,
and were, a few days later, re-caught at the Tortugas. On the other hand,
experiments made with turtles at Ascension are said to have had no result.
_Thalassochelys_, with five pairs of costal shields. The carapace is
completely ossified in the adult, leaving no fontanelles between the ribs
and the marginals.
_Th. caretta_ (the "Loggerhead Turtle").–The shields of the carapace
imbricate only in young specimens, in the adult they become smooth and
juxtaposed. The margin is serrated posteriorly. The carapace of the young
has three strong keels. The intergular shield is very small or absent. The
marginals, including the nuchal, usually number 23, rarely 25. The large
head is armed with hooked jaws, the crushing surface of the horny upper
beak has a median prominent ridge. The top of the head has a pair of
shields in front of the unpaired frontal. The flippers of the young have
claws on the first and second digits; in the adult usually only that of the
first digit remains. The general colour of the shell is uniform brown
above, yellowish below. Very young specimens are uniform dark brown or
blackish above and below.
Large individuals have a shell about three feet and a half in length. The
Loggerhead is carnivorous, and is commercially of no value. Its habits seem
to be the same as those of the other Turtles, but it has a much wider
distribution. Besides all the tropical and intertropical seas, it inhabits
the Mediterranean, and is an accidental visitor to the western coasts of
Europe, especially Portugal and the Bay of Biscay. It has been caught
several times on the coast of Belgium, and an old female containing 1150
eggs was captured in 1894 on the Dutch coast. In 1861 one was caught near
Penman, on the coast of Banffshire, and a second in the completely
land-locked Loch Lomond.[137] It has been more frequently recorded from the
coast of Devon and Cornwall.
The most interesting feature of the Loggerhead is the {388}astonishing
variability in the number of the horny shields of the carapace. The normal
number of shields of the carapace, leaving out the marginals and counting
the nuchal as the first neural, is 6 neurals and 5 pairs of costals, in all
16. The greatest number of dorsal shields observed is 8 neurals and 8 pairs
of costals, in all 24. Many of the intermediate combinations have been
observed, there being, for instance, specimens with 8 neurals and 16, 14,
13, 12, or 11 costals, the latter not being always in pairs, but unequal on
the right and left sides; or there are 7 neurals with 20 to 16 costals, or
6 neurals with 20, 19, 18, 17, or 16 costals. The interesting fact in
connexion with these variations is, moreover, that some of the shields are
much smaller than the others, sometimes mere vestiges in all stages of
gradual suppression, and that the abnormalities are much more common in
babies and small specimens than in adults. The importance of these
"orthogenetic" variations has been discussed on p. 326.
SUB-ORDER 2. PLEURODIRA.–_Neck bending laterally and tucked away in the
niche formed between the anterior portion of the carapace and plastron.
Pelvis ankylosed to the shell, the broadened tops of the ilia to the
carapace, the distal ends of the pubes and ischia to the plastron._
Freshwater tortoises, almost entirely carnivorous, inhabiting South
America, Australia, Africa, and Madagascar. Fossil forms are known from the
Jurassic epoch onwards.
Owing to the strong connexion of the iliac bones with the costal plates the
sacrum has become practically abolished, the sacral ribs being reduced to
one pair (the posterior of the original two pairs) or being absent. The
centra of the cervical vertebrae articulate by cup and ball joints. The
formation of the temporal region of the skull varies considerably in the
three families, some genera lacking the complete zygomatic arch, while
others have a narrow parieto-squamosal arch bridging over the temporal
fossa, or the latter is completely roofed over by the laterally expanded
parietal, which meets the jugal and quadrato-jugal. The quadrate is always
trumpet-shaped; the rim of the tympanum is complete, but the posterior part
of the trumpet remains open. The basisphenoid, pterygoids, and palatines
form a broad and flat roof to the mouth. The vomer is large, and separates
the palatines in the Chelydidae; it is very much {389}reduced or absent in
the Pelomedusidae, in which the palatines meet. All the Chelydidae, except
_Chelys_, have nasal bones which remain distinct from the prefrontals. The
choanae lie in front of the palatines, divided by the vomer when this is
present, but they are not roofed in ventrally.
The ilia are solidly ankylosed in the adult with the neighbouring costal
plates, mostly with the last two pairs, sometimes also with the pygal
plate. The lateral processes of the pubes fuse with the xiphiplastra. The
ischia are also attached to the same plastral elements.
The carapace is flat and completely ossified. The nuchal plate is always
conspicuous, much larger than the neurals, and these are often reduced by
being encroached upon by the eight pairs of costal plates, which then meet
in the dorsal line. In _Sternothaerus_ all the eight neurals are present
and form a continuous row. In most of the other genera they are reduced to
seven, the last being squeezed out. In _Rhinemys_ they are reduced to the
second, third and fourth and an isolated fifth, and in _Hydraspis_ they are
all gone. The pygal plate is always, even in _Sternothaerus_, separated
from the last neural by the eighth pair of costals. The marginals number
23, but in _Carettochelys_ only 21.
The carapace is covered with horny shields, except in _Carettochelys_. The
nuchal is absent in the Pelomedusidae and in a few Chelydidae (_Elseya_ and
a few species of _Emydura_). In _Hydromedusa_ the nuchal is shut in by the
anterior marginals, simulating a sixth neural. The plastron is composed of
the usual nine elements, but the Pelomedusidae possess an additional pair,
the meso-plastra, inserted between the hyo- and hypo-plastra. The bridge is
strong, connected with the carapace by suture. In _Sternothaerus_ the front
lobe of the plastron is movable. The intergular shield is always present;
it is terminal, forming part of the front margin, except in _Chelodina_,
where this shield, although large, is shut in behind the gulars (cf. Fig.
61, 4 and 5, p. 315).
Although the Pleurodira are a peculiarly specialised group, one of the
oldest Chelonian fossils known seems to belong to them. _Proganochelys_,
represented by a complete shell, nearly 2 feet long, has been found in the
Upper Keuper Sandstone of Würtemberg. _Plesiochelys_, of the Upper Jurassic
of Switzerland, has eight neural and three supracaudal plates, but is
without the {390}ischiadic plastral ankylosis. _Pleurosternum_, of the
English and Continental Purbeck beds, has meso-plastral plates like the
recent Pelomedusidae. _Rhinochelys_, of the Cambridge Greensand, has a
broad parieto-postfrontal roof, and large nasal bones. Forms like
_Podocnemis_, now restricted to South America, occur in the Eocene of
Europe. One of the most aberrant Chelonians is _Miolania_, from the
Plistocene of Queensland and from Lord Howe's Island, remarkable for its
huge size and the thick armour on the head and tail; the head especially
carries large paired projections, one pair of which extends horizontally
like powerful horns, recalling the queer Theromorphous _Elginia_.
We divide the recent Pleurodira into three families, of which that of
_Carettochelys_ stands apart by its paddle-shaped limbs and the absence of
horny shields. The Pelomedusidae and Chelydidae are closely allied. The
former are not Australian, and are externally distinguished by the absence
of a nuchal shield.
FAM. 1. PELOMEDUSIDAE.–Neck completely retractile within the shell.
Carapace without a nuchal shield. The plastron is composed of eleven
plates, there being besides the unpaired endo-plastron a pair of
meso-plastra, situated between the hyo- and hypo-plastra; but these
meso-plastra meet in the middle line in _Sternothaerus_ only, while in
_Podocnemis_ and _Pelomedusa_ they are restricted to small pieces on the
bridge, widely separated from each other by the usual hyo- and
hypo-plastral suture. A nuchal shield is absent; there are twenty-four
marginal and thirteen plastral shields, inclusive of the conspicuous
intergular. The temporal fossa is widely open, except in _Podocnemis_,
where it is partly roofed in by the meeting of the much-expanded
quadrato-jugal with the parietal. The palatine bones are in median contact,
not separated by the vomer. Nasal bones being absent, the large prefrontals
meet in the middle line. The second cervical vertebra is biconvex.
This family is now represented by only three genera, with about fifteen
species in Africa, Madagascar, and South America.
_Sternothaerus._–Skull without a bony supratemporal roof. Meso-plastra
large, extending right across the plastron. Anterior lobe of the plastron
movable, the hinge passing between the hyo- and meso-plastral plates, and
between the pectoral and abdominal shields. Fore- and hind-limbs with five
short digits and claws. Several species in tropical and southern Africa,
and {391}in Madagascar. _S. derbianus_ in West Africa, from the Gambia to
Angola, is the largest species, with a shell nearly one foot in length.
_Pelomedusa._–Skull with a slender parieto-squamosal arch. Meso-plastra
small and lateral. Plastron without a hinge. Fore- and hind-limbs with five
very short digits and five claws. Top of the head with one pair of shields
between the eyes, and with a large interparietal and a pair of parietals
behind.
_P. galeata_, the only species, occurs in Madagascar and nearly the whole
of Africa south of the Sahara, from the Cape to Abyssinia, and in the
Sinaitic peninsula. The shell, less than one foot in length, is much
depressed and is obtusely keeled; brown above with black spots;
brownish-yellow below. The short and broad head is coloured like the rest,
without ornamentation. In Somaliland this species sleeps hidden on land
during the dry seasons, from July to the end of September, and from January
to March, and appears at once after the rains have set in.
_Podocnemis._–With a supratemporal roof formed by the junction of the
parietal with the quadrato-jugal. Meso-plastra small and lateral. Fore- and
hind-limbs broadly webbed, with five and four claws respectively. The
fore-arms and the outer edges of the hind-feet with several conspicuous
shields, hence the generic name. Head with an interparietal, two parietals,
and a narrow unpaired shield between the eyes. The tail is very short. The
carapace is flat and broad, strongly serrated on the posterior margin. Chin
with one or two short barbels. Several species in South America, chiefly in
the basin of the Amazon, and one in Madagascar.
_P. expansa._–Very common in Tropical South America, east of the Andes. The
female, which is much larger than the male, has a shell nearly three feet
in length. Olive-brown above with darker patches; yellowish below. With a
few yellow spots above and behind the eyes, and on the parietal region. The
"Arrau" turtle is of great commercial importance on account of the eggs,
which are periodically collected in enormous quantities, chiefly for the
oil. This is either eaten, like the eggs themselves, or used for burning in
lamps, or as an addition to tar. The turtles are likewise eaten by man and
beast. Thousands of the little creatures are snapped up by Jabiru storks,
alligators, and fishes; the adults fall an easy prey {392}to the prowling
jaguar, which turns them over on to their backs and neatly cleans out the
flesh with its sharp and powerful claws.
Fertilisation takes place in the water, the eggs are deposited on land, in
sand-banks, the female digging a hole about two feet deep and covering up
the numerous soft-shelled eggs with sand. The time of deposition is the
early hours of the morning, but the season depends upon the beginning of
the principal rains, since the young are hatched shortly before the
torrential rains. This season differs considerably in the various
countries. The hatching takes about forty days; the eggs are consequently
laid in the Amazon countries during the months of September to November, in
the Orinoco district in March. This species lives in the pools of the
inundated forests, and when these are dried up, the animals retire into the
rivers themselves. Their food consists mainly of the fruit dropping down
from the trees.
Bates, in his delightful book, _The Naturalist on the River Amazon_, gives
the following lively and exhaustive account of his experience with these
turtles:–
"I accompanied Cardozo in many wanderings on the Solimoes, during which we
visited the 'praias' (sand islands), the turtle pools in the forests, and
the by-streams and lakes of the great desert river. His object was mainly
to superintend the business of digging up turtle eggs on the sandbanks,
having been elected commandant for the year by the municipal council of
Ega, of the 'praia real' of Shimuni, the one lying nearest to Ega. There
are four of these royal praias within the Ega district, a distance of 150
miles from the town, all of which are visited annually by the Ega people
for the purpose of collecting eggs and extracting oil from their yolks.
Each has its commander, whose business is to make arrangements for securing
to every inhabitant an equal chance in the egg harvest, by placing
sentinels to protect the turtles whilst laying, and so forth. The pregnant
turtles descend from the interior pools to the main river in July and
August, before the outlets dry up, and there seek in countless swarms their
favourite sand-islands; for it is only a few praias that are selected by
them out of the great number existing. The young animals remain in the
pools throughout the dry season. These breeding places of turtles then lie
20 to 30 or more feet above the level of the river, {393}and are accessible
only by cutting roads through the dense forest....
"We found the two sentinels lodged in a corner of the praia, where it
commences at the foot of the towering forest-wall of the island, having
built for themselves a little rancho with poles and palm-leaves. Great
precautions are obliged to be taken to avoid disturbing the sensitive
turtles, who, previous to crawling ashore to lay, assemble in great shoals
off the sand-bank. The men, during this time, take care not to show
themselves, and warn off any fisherman who wishes to pass near the
place....
"I rose from my hammock by daylight, shivering with cold; a praia, on
account of the great radiation of heat in the night from the sand, being
towards the dawn the coldest place that can be found in this climate.
Cardozo and the men were already up watching the turtles. The sentinels had
erected for this purpose a stage about fifty feet high, on a tall tree near
their station, the ascent to which was by a roughly made ladder of woody
lianas. They are enabled, by observing the turtles from their watch-tower,
to ascertain the date of successive deposits of eggs, and thus guide the
commandant in fixing the time for the general invitation to the Ega people.
"The turtles lay their eggs by night, leaving the water, when nothing
disturbs them, in vast crowds, and crawling to the central and highest part
of the praia. These places are, of course, the last to go under water when,
in unusually wet seasons, the river rises before the eggs are hatched by
the heat of the sand.... The hours between midnight and dawn are the
busiest. The turtles excavate with their broad webbed paws deep holes in
the fine sand; the first-comer, in each case, making a pit about three feet
deep, laying its eggs (about 120 in number), and covering them with sand;
the next making its deposit at the top of that of its predecessor, and so
on until every pit is full. The whole body of turtles frequenting a praia
does not finish laying in less than fourteen or fifteen days, even when
there is no interruption. When all have done, the area (called by the
Brazilians 'taboleiro') over which they have excavated is distinguishable
from the rest of the praia only by signs of the sand having been a little
disturbed.
"I mounted the sentinel's stage just in time to see the turtles retreating
to the water on the opposite side of the sand-bank, {394}after having laid
their eggs. The sight was well worth the trouble of ascending the shaky
ladder. They were about a mile off, but the surface of the sands was
blackened with the multitudes which were waddling towards the river; the
margin of the praia was rather steep, and they all seemed to tumble head
first down the declivity into the water.... Placards were posted up on the
church doors at Ega, announcing that the excavation on Shimuni would
commence on the 17th of October, and on Catuá, sixty miles below Shimuni,
on the 25th. By the morning of the 17th some 400 persons were assembled on
the borders of the sand-bank, each family having erected a rude temporary
shed of poles and palm-leaves to protect themselves from the sun and rain.
Large copper kettles to prepare the oil, and hundreds of red earthenware
jars, were scattered about on the sand.
"The excavation of the taboleiro, collecting the eggs, and purifying the
oil, occupied four days. All was done on a system established by the old
Portuguese governors, probably more than a century ago. The commandant
first took down the names of all the masters of households, with the number
of persons each intended to employ in digging; he then exacted a payment of
140 reis (about 4d.) a head towards defraying the expense of sentinels. The
whole were then allowed to go to the taboleiro. They ranged themselves
round the circle, each person armed with a paddle, to be used as a spade,
and then all began simultaneously to dig on a signal being given–the roll
of drums–by order of the commandant. It was an animating sight to behold
the wide circle of rival diggers throwing up clouds of sand in their
energetic labours, and working gradually towards the centre of the ring. A
little rest was taken during the great heat of mid-day, and in the evening
the eggs were carried to the huts in baskets. By the end of the second day
the taboleiro was exhausted; large mounds of eggs, some of them four to
five feet in height, were then seen by the side of each hut, the produce of
the labour of the family.
"In the hurry of digging, some of the deeper nests are passed over; to find
these out, the people go about provided with a long steel or wooden probe,
the presence of the eggs being discoverable by the ease with which the spit
enters the sand. When no more eggs are to be found, the mashing process
begins. {395}The egg, it may be here mentioned, has a flexible or leathery
shell; it is quite round, and somewhat larger than a hen's egg. The whole
heap is thrown into an empty canoe and mashed with wooden prongs; but
sometimes naked Indians and children jump into the mass and tread it down,
besmearing themselves with yolk, and making about as filthy a scene as can
well be imagined. This being finished, water is poured into the canoe, and
the fatty mass is then left for a few hours to be heated by the sun, on
which the oil separates and rises to the surface. The floating oil is
afterwards skimmed off with long spoons, made by tying large mussel-shells
to the end of rods, and purified over the fire in copper kettles.
"The destruction of turtle eggs every year by these proceedings is
enormous. At least 6000 jars, holding each three gallons of the oil, are
exported annually from the Upper Amazons and the Madeira to Para, where it
is used for lighting, frying fish, and other purposes. It may be fairly
estimated that 2000 more jarfuls are consumed by the inhabitants of the
villages on the river. Now, it takes twelve basketfuls of eggs, or about
6000, by the wasteful process followed, to make one jar of oil. The total
number of eggs annually destroyed amounts, therefore, to 48 millions. As
each turtle lays about 120, it follows that the yearly offspring of 400,000
turtles is thus annihilated. A vast number, nevertheless, remain
undetected; and these would probably be sufficient to keep the turtle
population of these rivers up to the mark, if the people did not follow the
wasteful practice of lying in wait for the newly-hatched young, and
collecting them by thousands for eating; their tender flesh, and the
remains of yolk in their entrails, being considered a great delicacy. The
chief natural enemies of the turtle are vultures and alligators, which
devour the newly-hatched young as they descend in shoals to the water.
These must have destroyed an immensely greater number before the European
settlers began to appropriate the eggs than they do now. It is almost
doubtful if this natural persecution did not act as effectively in checking
the increase of the turtle as the artificial destruction now does. If we
are to believe the tradition of the Indians, however, it had not this
result; for they say that formerly the waters teemed as thickly with
turtles as the air does now with mosquitoes. The universal {396}opinion of
the settlers on the Upper Amazon is, that the turtle has very greatly
decreased in numbers, and is still annually decreasing.
"The principal object of another expedition was to search certain pools in
the forest for young turtle. We started from the praia at sunrise on the
7th of October in two canoes, containing twenty-three persons, nineteen of
whom were Indians. The pool covered an area of about four or five acres,
and was closely hemmed in by the forest, which, in picturesque variety and
grouping of trees and foliage, exceeded almost everything I had yet
witnessed. The margins for some distance were swampy, and covered with
large tufts of fine grass. The pool was nowhere more than five feet deep,
one foot of which was not water, but extremely fine and soft mud.
"Cardozo and I spent an hour paddling about. The Indians seemed to think
that netting the animals, as Cardozo proposed doing, was not lawful sport,
and wished first to have an hour or two's old-fashioned practice with their
weapons. I was astonished at the skill which they displayed in shooting
turtles from little stages made of poles and cross pieces of wood. They did
not wait for their coming to the surface to breathe, but watched for the
slight movements in the water which revealed their presence underneath.
These little tracts on the water are called the siriré; the instant one was
perceived an arrow flew from the bow of the nearest man, and never failed
to pierce the shell of the submerged animal. When the turtle was very
distant, of course the aim had to be taken at a considerable elevation, but
the marksmen preferred a longish range, because the arrow then fell more
perpendicularly on the shell, and entered it more deeply.
"The arrow used in turtle-shooting has a strong lancet-shaped steel point
fitted into a peg, which enters the tip of the shaft. The peg is secured to
the shaft by twine, being some thirty or forty yards in length, and neatly
wound round the body of the arrow. When the missile enters the shell the
peg drops out, and the pierced animal descends with it towards the bottom,
leaving the shaft floating on the surface. This being done the sportsman
paddles in his canoe to the place, and gently draws the animal by the
twine, humouring it by giving it the rein when it plunges, until it is
brought again near the surface, when {397}he strikes it with a second
arrow. With the increased hold given by the two cords he has then no
difficulty in landing his game.
"By mid-day the men had shot about a score of nearly full-grown turtles.
Cardozo then gave orders to spread the net.... Three boat loads, or about
eighty, were secured in about twenty minutes. They were then taken ashore
and each one secured by the men tying the legs with thongs of bast.
"When the canoes had been twice filled we desisted after a very hard day's
work. Nearly all the animals were young ones, chiefly, according to the
statement of Pedro, from three to ten years of age; they varied from 6 to
18 inches in length, and were very fat. Cardozo and I lived almost
exclusively on them for several months afterwards. Roasted in the shell
they form a most appetising dish. These younger turtles never migrate with
their elders on the sinking of the waters, but remain in the tepid pools,
fattening on fallen fruits, and, according to the natives, on the fine
nutritious mud. We captured a few full-grown mother turtles, which were
known at once by the horny skin of their breast plates being worn, telling
of their having crawled on the sand to lay eggs the previous year. They had
evidently made a mistake in not leaving the pool at the proper time, for
they were full of eggs, which, we were told, they would, before the season
was over, scatter in despair over the swamp. We also found several male
turtles, or capitaris, as they are called by the natives. These are
immensely less numerous than the females, and are distinguishable by their
much smaller size, more circular shape, and the greater length and
thickness of their tails. Their flesh is considered unwholesome, especially
to sick people having external signs of inflammation."
The most recent account of these water tortoises is that published by Dr.
Goeldi from the MS. of João Martins da Silva Continho, a former resident at
Manáos on the Middle Amazon. The "Tartaruga" (the Portuguese name for
turtles) live from January to July in the inundated, quiet backwaters of
the forest-region, feeding upon the various seeds of palms as these ripen
and drop successively; rarely, and only when hard up, they are carnivorous.
The creatures hide under water below the trees, when they are espied by the
Indians, who dive down to a depth of twenty and more feet to catch them in
their arms. The {398}civilised Indians use a steel-pointed lance of hard
wood, about 10 feet in length. A string connects the point with the shaft
around which it is wound. When stuck into the tortoise the shaft and point
part; the string is either tied to the boat or to a little float of light
wood. In other districts an arrow with a string is employed.
In August, when the water subsides, the tortoises return to the rivers, and
the entrance of the lagoon is closed with nets. A number of boats with long
poles drive them with much noise towards the entrance. On their way to the
rivers the tortoises always go up-stream, and this is called the "arribaçaõ
das tartarugas," the ascent of the turtles. The fishermen post themselves
at shallow spots or on sand-banks, and wait for the creatures which come up
to find a place for landing and laying. The arrows employed are called
_sararaca_, _i.e._ a thing which can be disjointed; they are about 4 feet
long, and consist of a _gomo_ or internodium of wood 9 inches long with a
one- or two-barbed steel point, and the shaft into which the _gomo_ fits
loosely. The _gomo_ is, moreover, connected with the shaft by a string made
of palm-fibres about 30 feet in length, partly wound round the shaft, which
ultimately acts as a float.
The laying takes place from the end of September into October. Some of the
parents seem to reconnoitre on land for a few days. As a rule only females
do this, and the natives say that they are led by a "_mestra_." The laying
takes place early in the morning. The number of females is so great that
they often block the way of the boats, and make a great noise by knocking
against their neighbours' shells. Each digs a hole about 18 inches or 2
feet deep, and lays from 80 to 200 eggs. Sometimes the laying individual is
entirely buried by its neighbours which are scraping their own holes.
In some districts the eggs are wanted for "manteiga" (Portuguese for
butter); and the turning over, or _viraçaõ_ of the tortoises takes place
later. In other districts they are caught before the eggs are laid, and
this barbaric and destructive custom was formerly forbidden by the people
themselves. Although the provincial assembly tried to reinstitute the old
reasonable customs, the inspectors are often got over by bribery.
There are two ways of extracting the oil from the eggs. To get the thick
oil used, mixed with tar, for shipbuilding, caulking, {399}etc., the eggs
are heaped up for five days and then worked. The fluid oil for lighting is
made from fresh eggs, which are put into a boat and then trampled out with
the feet. The oil is drawn off into large earthen jars and put on the fire.
Then it is rapidly cooled. The best oil, used for frying fish, is that
which is gained from the roasted tortoises themselves. Fresh eggs are
either fried or taken with sugar, or mixed with manioca-flour and water.
The young, which are hatched in January, are likewise eaten fried, or they
are preserved in the fat of the parents.
An average tortoise yields 5 lbs. of fat, costing on the spot two milreis.
The whole full-grown animal, of one yard in length, costs the same, and its
meat is sufficient to sustain a family of six people for three days. To
make 24 lbs. of oil requires 3000 eggs. Two or three tortoises would yield
the same amount from their fat. Consequently the destruction of the eggs
causes an enormous waste, and is after all the least economical procedure.
In the year 1719, 192,000 lbs. were exported from the Alto Amazonas,
representing 24,000,000 eggs. In 1700 there were still plenty of tortoises
50 leagues above the mouth of the Para river. Now there is no assembly of
more than fifteen tortoises to be found anywhere within 300 leagues from
Para to the mouth of the Rio Negro. On the Rio Madeira, from the mouth to
the first cataract, 186 leagues distance, there are now only two regular
nesting localities. The upper Solimoes and the Rio Yapura are still rich.
Near Ega are regular tortoise-ponds, called "curral," which yield
sufficient support to their owners; the animals are fed with manioca-flour
and leguminous plants.
FAM. 2. CHELYDIDAE.–The neck bends under the margin of the carapace, but
remains partly exposed. The nuchal shield is absent except in two Northern
Australian species. There are twelve pairs of marginal shields. The
plastron is composed of nine plates, and is covered with thirteen shields,
one of which is the conspicuous intergular. The temporal region of the
skull shows great diversity. It is quite open in _Chelodina_, covered in by
broad expansions of the parietal bones in _Platemys_, _Emydura_, and
_Elseya_, or bridged over by a parieto-squamosal arch, which is very
slender in _Rhinemys_, strong in _Chelys_ and _Hydraspis_. The palatine
bones are separated by the vomer; the nasals are variable, mostly present,
but the prefrontals are always small, and separated {400}by the frontals.
The fifth and eighth cervical vertebrae are biconvex.
This family, still represented by nearly thirty species, which are divided
into eight genera, is restricted to Notogaea, namely, South America and
Australia.
[Illustration: FIG. 87.–Skull of _Chelys fimbriata_. × 1. A, Dorsal view of
skull; B, side view of skull and hyoid apparatus. _Cop_, copular piece;
_F_, frontal; _J_, jugal; _L.o_, lateral occipital; _Mand_, mandible; _Op_,
opisthotic; _Orb_, orbit; _Par_, parietal; _Pt.f_, postfrontal; _Ptg_,
pterygoid; _Q_, quadrate; _Qj_, Quadrato-jugal; _Sq_, squamosal; I, II,
First and second branchial arch.]
_Chelys fimbriata_, the "Matamata," the only species of this genus,
inhabits the rivers of Guiana and Northern Brazil. Besides the nuchal,
there are seven neural plates; the last pair of costals form a median
suture. Nasal bones are absent. The jaws are very weak. The Matamata has a
very peculiar appearance. The nose is produced into a long, soft tube, at
the end of which open the tiny nostrils. The eyes are very small, and the
orbits are placed very near the anterior end of the skull, while the
parietal {401}region is broad and much elongated (Fig. 87, p. 400). The
quadrates are drawn out into trumpet-shaped tubes. The hyoid apparatus is
very large, with enormous anterior and posterior horns. The head and neck
are as long as or even longer than the carapace, which is covered with
thick, lumpy shields. The skin of the thick neck, of the sides and under
parts of the head, is produced into many soft arborescent excrescences or
fimbriae, those of the chin and throat and the large ear-flaps being
movable at will, and probably used to attract fishes and other prey. The
tail is very short. The fore- and hind-limbs are webbed, the former with
five, the latter with four claws. Old specimens, which reach a total length
of three feet, are uniformly dark brown, and look like a log covered with
rough bark. The young are far less ugly, with black and yellow spots on the
shell, and with dark stripes along the neck.
[Illustration: FIG. 88.–_Chelys fimbriata_ ("Matamata"). × ⅒.]
Very little is known about the habits of this peculiar creature. It is said
to lie submerged in the water, waiting for fishes, frogs, or tadpoles,
which are attracted by the playing motions of its cutaneous excrescences.
The jaws being so weak, and being covered with a partly soft lip-like skin,
it is probable that they are not used for seizing the prey, but that the
latter is engulfed into the mouth with the inrush of water into the throat.
{402}That this can be widened enormously is indicated by the greatly
developed hyoid apparatus.
_Chelodina._–The neck is long and slender, the head small and smooth. The
nuchal is terminal; the intergular is large. The neural plates are
completely suppressed, all the eight pairs of costal plates meeting in the
middle line. The shell is very flat. Anterior and posterior limbs entirely
webbed, and with only four claws. The tail is very short. Three species in
Australia, one in New Guinea.
[Illustration: FIG. 89.–_Chelodina longicollis._ × ⅓.]
_Ch. longicollis_ reaches a shell-length of ten inches. It inhabits
Southern Australia. The illustrations make a detailed description
unnecessary. The colour of the dorsal shield is uniformly dark rich brown,
while the shields of the under surface are yellow, with broad dark brown
lines along the sutures. These "long-necked Chelodines" have a striking
appearance, when they swim or creep about, with the neck either stretched
out straight or bent horizontally in an S-shape. The whole creature looks
neat and elegant; the iris is pale yellow, and gives the eye a very
intelligent expression. They keep well in captivity, provided they are
given the choice of land and water. My own prefer to spend most of the day
on land, preferably under the ledge of a stone, or perched upon the stone
itself if the latter is in the shade, and not too much exposed to view.
There they lie motionless, with the neck neatly tucked under the shell,
either to the right or to the left. Although the eyelids may be closed,
they can see well enough, owing to the transparent condition of the lower
lid. They feed in the water upon soft animals, as for instance worms,
smooth caterpillars, cockroaches or little frogs; and they also take meat
readily, provided this is moved about. The food is invariably taken with a
quick sideward jerk of the neck and head.
{403}[Illustration: FIG. 90.–_Chelodina longicollis_ (Australian
long-necked Chelodines). × ¼.]
My specimens soon became so tame that they left the water, and ran up to me
with the necks stretched to their full length, then snatching the bit of
food, and retiring into the pond to swallow it. When left to themselves
they are rather nocturnal in their feeding habits. Now and then they tuck
themselves away for weeks without feeding, for instance when they go
through a regular term of {404}aestivation in the summer. The last winter
they spent buried in the moss, but occasionally, especially on bright and
sunny days, they went into the water for a few hours, chiefly to drink, but
sometimes also to take a little food.
_Hydromedusa_, a South American genus, has a neck even longer than that of
_Chelodina_, which it much resembles externally. But the nuchal shield,
large and broad transversely, is situated behind the anterior marginals,
looking therefore like a sixth neural shield. The neural plates form a
continuous row, only the last pair of costal plates meeting in the middle
line. _H. tectifera_ occurs in Southern Brazil, and in the La Plata. The
shell is dark brown above; yellowish, with dark spots, below; the head and
neck are olive-coloured, adorned with a broad white, black-edged band on
either side. Fore- and hind-limbs broadly webbed, and with four claws.
Total length of the shell about eight inches.
FAM. 3. CARETTOCHELYDIDAE.–The shell is covered with soft skin instead of
horny shields. The limbs are transformed into paddles, with elongated
digits, and have only two claws. The neck is short, and not retractile. In
other respects the skeleton, notably the plastron, pelvis, and skull,
conform with the Pleurodirous type. Only one species, _Carettochelys
insculpta_, still imperfectly known, from the Fly River, New Guinea. Length
of the shell of the only complete specimen about 18 inches. This peculiar
creature seems to stand in the same relation to the typical Pleurodira, as
do the Chelonidae to the Testudinidae, except for the complete reduction of
the horny shields upon the shell, recalling in this respect _Sphargis_ and
_Trionyx_.
SUB-ORDER 3. TRIONYCHOIDEA.–The shell is very flat, oval, or almost round,
and is covered with soft, leathery skin instead of with horny shields. The
limbs are broadly webbed, and only the three inner digits are provided with
claws. Carnivorous, found in the rivers of Asia, Africa, and North America.
The head and neck are completely retractile, bending by a sigmoid curve in
a vertical plane like that of the Cryptodira. The jaws are concealed by
soft, lip-like flaps, and the nose forms a soft short proboscis. The ear is
hidden. The skull, Fig. 91, is flat, with three long posterior processes,
formed by the supra-occipital above, and the squamosals on either side. The
whole temporal region forms a wide, shallow fossa, without any
{405}indication of being arched or bridged over. The premaxilla is
extremely small, unpaired, not even reaching the nasal cavity or the vomer.
The maxillaries are correspondingly enlarged, surrounding the choanae,
which are separated by the narrow vomer. The palatines form a median
suture, and are joined behind by the long basisphenoid, which separates the
long pterygoids from each other. The quadrate is trumpet-shaped, with a
posterior notch for the stapes. The zygomatic arch is complete, and is
formed by the quadrato-jugal and the jugal; the latter joins the maxillary
and postfrontal, mostly reaching the orbit; in some cases it also just
meets the parietal, thereby adding to the strength of the postorbital arch.
The prefrontals are large; nasals are absent. The mandible is remarkable
for the great development of the coronoid process.
[Illustration: FIG. 91.–Skull of _Trionyx hurum_. _A_, From above; _B_,
from the left side; _Cond_, occipital condyle; _Fr_, frontal; _J_, _Jug_,
jugal; _L.o_, lateral occipital; _Max_, maxillary; _Op.o_, opisthotic;
_Par_, parietal; _Pr.f_, prefrontal; _Pro_, prootic; _Pt.f_, postfrontal;
_Q_, quadrate; _Qj_, quadrato-jugal; _S.o_, supra-occipital; _Sq_,
squamosal.]
The pubic and ischiadic bones enclose a large heart-shaped foramen, and are
free from the plastron; the ilia are attached only to the sacral ribs. The
carapace is peculiar in so far as it is very incomplete peripherally, the
ribs extending considerably beyond the costal plates, nor are they joined
by marginal plates, which are absent, unless they are represented by a few
small ossifications imbedded in the posterior marginal flap of the disc
(_Emyda_ of India). The rim of the disc is always formed by a horizontal,
cutaneous, very flexible flap. All the dorsal plates have a rough upper
surface, vermiculated or rugose, as usual with such dermal bones, which
have lost most of or all their horny covering, and have sunk more deeply
into the skin. The {406}nuchal plate has usually a pair of rib-like
processes. The neurals form a continuous series, except in the African
_Cyclanorbis_, in which they are much reduced in size, and separated by the
costal plates.
The plastron is imperfect, all its constituent nine elements being only
loosely connected with each other, and there remains a wide median vacuity
between the lateral elements. Most of these plastral bones are reduced to
splints, which, instead of meeting by regular sutures, loosely
interdigitate with their jagged edges. In the young all these ventral
elements are deeply imbedded in the soft, leathery skin, and they do not at
all resemble in appearance those of the dorsal side. With age they develop
upon their ventral surface stronger and denser ossifications, which
ultimately broaden out, sometimes beyond the original underlying bone, and
assume the characteristic vermiculated surface-appearance. This is
undoubtedly a process of exostosis, a step towards revival of that armour
which had been much reduced ancestrally. To appreciate this condition, it
is at least suggestive that these mud-tortoises, when kept in the usual
hard-bottomed tanks, invariably become sore, the skin wearing through where
the imbedded plastral bones touch the ground. Thus what is crammed into the
short life of a captive individual, is in the natural course of events
spread over many generations, whereby it has ceased to be pathological, and
has become a comparatively new, tertiary, but regular feature.
It is not open to much doubt that the characteristic features of the
Trionychoidea are not primitive but secondary. This is indicated by the
whole structure and behaviour of the carapace and plastron. The softening
of the whole shell, the loss of the horny shields, the reduction of the
claws, are the direct and almost unavoidable results of life in muddy
waters.
Geologically they do not seem to be very old. They appear, already
referable to the genus _Trionyx_, in the Upper Cretaceous strata of North
America. In the Lower and Middle Tertiary strata many species existed in
North America and in Europe, and it is of great importance that in these
species the costal plates were much broader, and the marginal plates better
developed, than in the recent forms. Now their half-dozen genera, with
about twenty-four species, are confined to North America, the tropical and
warmer parts of Asia, and the Malay {407}Islands, and to Africa from the
Nile to the Senegal and to the Congo.
The habits of Trionychoidea have found few observers. According to L.
Agassiz,[138] they live in the muddy bottom of shallow waters, burying
themselves in the soft mud, with only the head, or a small part of it,
exposed. They breathe without moving the body, by raising up the long neck
and carrying the leathery snout above water. When moving through the water
they strike horizontally with both pairs of limbs, alternating, however,
the right and left; but when they start suddenly, the front limbs are seen
moving together towards the tip of the snout, and then striking
simultaneously backward with great power. As the shield does not project
forward, the fore-limbs usually move beyond the shield, and as its outer
edge is sharp, and the feet are broad, their webs reach above as well as
below the plane of that edge, so that the water is driven partly over and
partly under it. When they move along the bottom, the limbs still move
horizontally, the webs striking against the water, and the inner toes,
those with the claws, against the bottom. They also bury themselves
horizontally, becoming covered by only a thin layer of mud. They readily
resort to the shell for protection. The neck and head are withdrawn
entirely, the loose skin rolling off from the greater part of the neck; and
the skin of the legs also slips off, as far as the elbows and knees. In
confinement they exhibit great quickness; their movements are abrupt and
unsteady, except when they swim rapidly in one direction. They then dart
their long and slender neck quickly forwards or sideways and upwards, as
snakes do, and bite in the same way, striking suddenly. Their temper is bad
or even ferocious, and large specimens are quite dangerous.
Their food consists of all sorts of aquatic animals, fish, frogs, and
molluscs, for instance _Anodonta_ and _Paludina_. According to the
different diet, many species develop a peculiar kind of dimorphism, a
reasonable explanation of which has been given by Boulenger. In the young
the horny coverings of the jaws are sharp, with cutting edges, and in those
specimens which keep to a diet of fish and other soft creatures, the jaws
remain in the same condition. But in those which take to living upon
molluscs, the hard shells of which they have to crush, the horny edges are
{408}worn down; and broad, thick, horny, crushing pads are developed in
their stead, the supporting parts of the jaws becoming more massive. The
masticatory muscles are likewise enlarged, and a tubercle grows upon the
lower border of the jugal bone, whence arises part of the masseter muscle.
The eggs are round, thick-shelled, but very brittle; they are laid in the
sand above the level of the water, and this is the chief occasion on which
these tortoises creep on land.
_Trionyx._–The plastron has no special cutaneous valves for the concealment
of the hind-limbs. This is the principal genus, with the greatest number of
species and the widest distribution, the latter coinciding with that of the
whole family. The upper surface of the shell of young specimens frequently
forms numerous longitudinal ridges or series of little horny tubercles
which disappear with age.
_T. ferox_, the commonest "Soft-shelled Turtle" of the United States. Olive
above with scattered, small, round, black spots; young with conical,
spine-like tubercles, especially on the nuchal border and on the posterior
portion of the shell, which has a pale, black-edged border. A light,
black-edged streak passes through the eye and joins its fellow on the
snout. The limbs are olive brown, spotted and marbled with black. The under
parts of the shell are white. Very large specimens have a shell 18 inches
in length and 16 inches wide. Holbrook gives the following account of its
habits:–
"A voracious, carnivorous creature. They reside most constantly in the
water, swim with rapidity, and choose for their retreat holes under the
banks of rivers, or under rocks; and not unfrequently the trunk of some
huge forest tree, fallen into the stream, affords them shelter. Sometimes
they leave the water and conceal themselves in the mud: I have frequently
seen them thus buried to the depth of 2 or 3 inches, leaving only a small
breathing hole for the long neck and narrow head, which is occasionally
thrust out, but most commonly it is retracted so that one would pass near
without observing their habitation; and if seen, it might easily be
mistaken for the residence of some large insect. At other times they may be
seen in numbers on rocks in shallow water, basking in the sun, apparently
asleep. They bite severely when provoked, darting forward with great
velocity the long neck and head, and not unfrequently spring upward at the
same time and make a loud hiss.
{409}[Illustration: FIG. 92.–_Trionyx ferox_ (American Soft-shelled
Turtle). × ⅒.]
In the month of May the females seek sandy places along the banks of the
waters they inhabit to lay their eggs, generally about sixty in number; and
it is remarkable that, though their motions are slow and difficult on dry
land, yet at this season they sometimes mount hillocks several feet high.
The flesh affords the most delicate food, surpassing that even of the Green
Turtle. The geographical distribution is interesting. It inhabits the
Savannah as well as all those rivers that empty into the northern borders
of the Gulf of Mexico; it ascends up the broad Mississippi, and is found in
all its tributaries, even to the very foot of the Rocky Mountains; it
abounds in the chain of great northern lakes both above and below the Falls
of Niagara, and is common in the Mohawk, a tributary of the {410}Hudson
river; but it is not found in any other Atlantic stream between that and
the Savannah river, a distance of nearly 800 miles."
_T. triunguis_, the only African species, ranging from the Senegal and
Congo into the Nile-system, but occurring also in Syria, is perhaps the
largest of all Trionychidae, reaching a shell-length of almost 3 feet. The
adults are olive-brownish above, the throat and under parts of the shell
with round, white spots separated by a dark network. The young have whitish
specks and spots.
[Illustration: FIG. 93.–_Trionyx gangeticus_ (young). × ⅓.]
_T. gangeticus_ and _T. hurum_ are the principal Indian species. The former
is the larger of the two, with a shell of more than 2 feet in length; olive
above, the young with fine black vermiculations; head with a black
longitudinal streak from between the eyes to the nape, intersected by two
or three chevron-shaped black streaks; under parts yellowish. _T. hurum_ is
olive brown above {411}and below, in younger specimens with conspicuous,
large, yellow spots on the sides of the head. The young are ornamented with
two or three pairs of large round spots on the back, and the same applies
to the beautiful young of the Burmese, _T. formosa_.
[Illustration: FIG. 94.–_Trionyx formosa_ (young). × 1.]
The three genera, _Cycloderma_ and _Cyclanorbis_ of Tropical Africa, and
_Emyda_ of India, have a pair of cutaneous femoral valves or flaps on the
plastron, beneath which the hind-limbs are withdrawn.
{412}CHAPTER X
DINOSAURIA–CROCODILIA
_SUB-CLASS V.–DINOSAURIA._
_Mesozoic, long-tailed, toothed reptiles, with distal ischiadic
symphysis, terrestrial limbs, large fixed quadrate bones and bifurcated
ribs._
The Dinosaurs begin and end with the Mesozoic epoch, and have a world-wide
distribution. The name, "terrible Reptiles," refers to the gigantic
proportions which many of them attained, not a few of them surpassing in
size and shape the fantastic pictures of the dragons of our fables.
Although these creatures came to an end millions of years before the first
man-like beings appeared, it is reasonable to suppose that the
widely-spread myths of dragons are based upon the accidentally disclosed
skeletons of these monsters.
The skull is built after a plan which may be derived from a combination of
the Crocodilian and Rhynchocephalian skulls, but the detail varies
considerably in the many and much diversified members of this large
sub-class. There is as a rule a pre-orbital foramen, which is smallest in
the Ornithopoda. The orbit is completely encircled by bones, and the
temporal fossa is divided by a squamoso-postfrontal or post-orbital bridge
into a smaller supra-, and a much wider infra-temporal portion, the latter
being bordered below by the jugal and quadrato-jugal, and this is firmly
connected with the quadrate by an ascending process. The quadrate is long,
more or less vertical in position, slanting either forwards or backwards,
and firmly fixed above by the squamosal, perhaps also by a supra-temporal
bone. The orbit is bordered by the jugal, lacrymal, pre- and post-frontals.
The interparietal foramen seems to be {413}abolished. Teeth, mostly
alveolar and laterally compressed, are restricted to the dentary,
maxillary, and premaxillary bones. In the Orthopoda the latter carry no
teeth, or these are restricted to the lateral portion, leaving a wide
diastema. This toothless part plays upon a peculiar crescent-shaped bone,
the so-called predentary, which rests loosely upon the anterior ends of the
mandibular rami, which latter do not as a rule form an osseous symphysis.
The Ceratopsia possess in addition a similar upper toothless piece, the
prerostral, a kind of pre-premaxilla. The morphological value of these
extra pieces is quite obscure; they were in all probability provided with
thick, horny pads. The bones of the roof of the mouth recall in their
arrangement that prevailing in the Rhynchocephalia and the Parasuchia.
There are two pairs of large vacuities; one between the maxillae,
ectopterygoids and palatines; the other between the latter, the maxillae
and the usually small or slender vomers. The pterygoids are perhaps the
largest bones, and form a rather long symphysis; laterally and behind they
abut against the quadrate, anteriorly against the ectopterygoids and the
palatines, which latter they sometimes separate. A peculiar feature of some
skulls, _e.g._ _Ceratosaurus_ and _Triceratops_ is the great size of the
groove in which the large hypophysis of the brain is lodged.
The vertebrae are very variable, amphicoelous, opisthocoelous, nearly
plain, with a slight concavity behind, or occasionally procoelous in the
anterior region of the tail. Besides the usual pre- and post-zygapophyses
many Sauropoda and Theropoda possess on the posterior trunk-vertebrae
additional joints, effected by a vertical wedge, the hyposphene, which
extends backwards from between the post-zygapophyses and fits into a notch
between and below the anterior zygapophyses of the next following vertebra.
These additional articulations are analogous to the zygosphenes and
zygantra of snakes and iguanas, except that in these Sauria the wedges are
formed on the opposite, namely the anterior ends of the vertebrae. The
vertebrae of the neck and trunk are devoid of intercentra, but those of the
tail carry long chevron-bones. The number of sacral vertebrae is generally
increased to four or five. The ribs have well-developed capitula and
tubercula, and the former have the tendency to shift from the centra or
from their parapophysial processes on to the usually much elongated
diapophyses of the neural arches. This {414}arrangement, recalling the
Crocodilian condition, results in an increased capacity of the dorsal
portion of the body-cavity. Intervertebral articulation of the ribs does
not occur except sometimes in the sacral region. Abdominal ribs are rare,
but they occur in some of the Theropoda, _e.g._ in _Compsognathus_.
The sternum seems to have been mainly cartilaginous, with a pair of
irregular, disc-shaped ossifications. How the coracoids were attached is
unknown; they are small, generally with a foramen, but the scapulae are
always very strong and slant backwards. Clavicles and interclavicles seem
to be absent.
The fore-limbs are as a rule powerful, although often much shorter than the
hind-limbs, which are then enormously developed, and in many genera of two
of the main groups show a tendency towards a semi-erect gait. Some of the
Dinosaurs, e.g. _Iguanodon_ and _Brontozoum_, were absolutely bipedal.
Others seem to have hopped like Kangaroos. In correlation with this more or
less erect mode of progression the iliac bones are very strong, much
elongated horizontally, and attached to more than three, often to five or
even more, vertebrae. The pubic bones show two main types. Each consists
either of a single strong shaft, which is connected distally with its
fellow; or (Orthopoda) this main shaft sends out, below its point of
contact with the ischium, a long process, the so-called post-pubis, which
is directed downwards and backwards. In the latter case it runs parallel
and in close contact with the ischium. Such bifurcated pubic bones never
meet in the middle line. The ischia, on the other hand, are always
connected with each other, not so much by fusion as by syndesmosis.
The hind-limbs exhibit all stages from a simple, plantigrade and five-toed
state to a decidedly digitigrade, four, and even three-toed arrangement.
Many genera exhibit the tendency to form an intertarsal joint, a feature
elsewhere known in birds only, where it is typical and universal. The
astragalus sends up an ascending process which tends to fuse with the
anterior aspect of the distal end of the tibia, and the calcaneum is
sometimes more or less firmly attached to the fibula. In _Compsognathus_
even the distal tarsalia have begun to fuse with the metatarsalia, so that
this reptile at least has a typical intertarsal joint. The femur is
remarkable for the frequent possession of a "fourth" trochanter on the
middle of the inner aspect of the shaft, undoubtedly {415}for the insertion
of the long caudi-femoral or long adductor muscle.
Many Dinosaurs possess hollow instead of solid bones. The vertebrae have
large cavities in the Sauropoda, notably in _Brontosaurus_; in many
Theropoda, e.g. _Coelurus_, _Anchisaurus_, _Compsognathus_, the limb-bones
and the vertebrae are hollow, the latter being reduced to thin-walled
shells with a few inner partitions, the bones being at the same time much
swollen and enlarged. In the Ornithopoda the vertebrae are solid, but the
limb-bones are hollow. The reason of this hollowing out is not easily
found. Undoubtedly it results in a saving of material and weight, whilst at
the same time, without loss of strength, the surfaces for the attachment of
the necessarily powerful muscles are increased. But _Compsognathus_ is a
small, _Brontozoum_ a gigantic, creature. On the other hand, the bones of
the huge Stegosauri are solid. Most probably these cavities were, as in
birds, filled with air-sacs ultimately in communication with the lungs; and
it is by no means a baseless suggestion of Haeckel's that the Dinosaurs
were warm-blooded. Their mode of propagation can only be guessed at from
the circumstance that a rather well-preserved specimen of _Compsognathus_
contains in its abdomen what may possibly be an embryo. There is nothing
against the assumption that the Dinosaurs were viviparous; on the contrary,
it seems more natural than that, for instance, an _Atlantosaurus_ of more
than 100 feet in length and many tons in weight, should have laid eggs.
Some of the herbivorous Dinosaurs, namely, the Stegosauri and the
Ceratopsia, had a dermal armour of variable extent; the plates were loosely
imbedded in the skin, and reached their greatest size along the middle of
the back and tail, and these crested plates were probably covered with
horny scutes, obviously weapons of defence. The Ceratopsia were armed with
a pair of huge pointed horns on the head, and a smaller one on the nose
(see Fig. 102, p. 430). It is difficult to guess the use of the weapons of
these terrestrial monsters, unless they were employed against the equally
large carnivorous Dinosaurs or in the combats for the possession of their
charming mates.
About the ancestry of the Dinosaurs we know nothing except that their
affinities lie with the Crocodilia; but it is impossible to derive either
from the other. The oldest forms, in the {416}present state of our
knowledge–those which have left their three-toed spoors in the Trias of
Connecticut–were already much specialised by having attained to an upright
bipedal gait, while the Sauropoda, which except for their gigantic size are
the most generalised, are of comparatively recent date, none of them being
known from strata older than the Upper Jurassic. Twenty years ago, until
the discoveries of numerous kinds in the United States, our knowledge of
the whole group was very limited. There is a widely spread notion that the
birds have sprung from some Dinosaurian stock. Huxley was the first to show
clearly that birds were an offshoot of the reptiles, and he said of the
Dinosaurs, especially his Ornithoscelida (_Iguanodon_, _Scelidosaurus_,
_Megalosaurus_, _Compsognathus_, and others), that they "present a large
series of modifications intermediate in structure between existing reptiles
and Aves." Baur proved to his own satisfaction that we have to look for the
ancestors of the Ratitae among the herbivorous Dinosaurs, especially the
Ornithopodous forms, whilst the Carinatae are descendants of the Ratitae.
However, even he had to give up this absolutely unwarrantable view.
It is easy to select a considerable number of characters amongst the
various Dinosaurs which also occur in birds, and some of these have until a
recent date been considered as peculiar to birds. For instance, the double,
bifurcated pubic bones of the Orthopoda; the increased number of vertebrae
to which the horizontally elongated ilia are attached, especially in the
forms with an upright gait, and the bipedal feature itself; the possession
of an ascending process of the astragalus and its fusion with the tibia in
_Compsognathus_ and _Ceratosaurus_ among the Theropoda, and in
_Ornithomimus_; the attachment of the distal tarsalia to the metatarsalia,
_e.g._ in _Compsognathus_,–in fact, the formation of an intertarsal joint,
a feature otherwise characteristic of, and peculiar to, birds; the frequent
reduction of the fifth metatarsal bone; the backward position of the hallux
and the proximal reduction of its metatarsal in _Compsognathus_; the
elongation and partial fusion of the functional metatarsals in the latter
genus and in _Ceratosaurus_; the regular increase of the phalangeal numbers
of the first four toes from two to five in many of the Ornithopoda;–in
short, the great resemblance between the feet of some of the Dinosaurs and
those of the birds. However striking these arguments are, they are
instances of {417}convergent analogies. The upright walk, which has been
assumed and improved upon independently by members of both Theropoda and
Orthopoda, has produced the same, or nearly the same modifications in them
as in the birds.
It is easy to show that these features are mere coincidences. The oldest
bird known is _Archaeopteryx_ from the Upper Oolite of Bavaria.
Consequently all those Dinosaurs, which are of the same and of later date,
have to be excluded from the supposed ancestry, and they happen to be those
in which (as in _Ceratosaurus_, _Compsognathus_, _Ornithomimus_,
_Iguanodon_) the resemblances are greatest. There remains only
_Anchisaurus_ of the Upper Trias, more or less contemporary with the
_Brontozoum_, which left its three-toed footprints (_Archaeopteryx_ has
four well-developed toes) with _Zanclodon_. Moreover, the most bird-like
foot is either that of the Theropoda, which, like _Anchisaurus_ and
_Zanclodon_, differ from birds by the formation of the pelvis, or of some
of the latest Ornithopoda. What, then, is the good of selecting a number of
bird-like features from members of Dinosaurs which we are bound to class in
different groups, and which existed, some in the lower, others in the
middle, or even in the latest Mesozoic periods?
Lastly, the advocates of the Dinosaurian ancestry of birds cannot have
fully appreciated the enormous differences between the wing of
_Archaeopteryx_ and the fore-limb of any Dinosaur with the most avian
resemblances in the hind-limbs. The fore-limbs of these reptiles are
modified in a direction diametrically opposed to that from which a
bird-like wing could be developed. The skull presents another
difficulty,and here again _Compsognathus_, a contemporary of
_Archaeopteryx_, comes perhaps nearest to that of a generalised bird's
skull. The ancestors of the birds must have combined the following
characters:–Of not later than Mid-Oolitic age, with bifurcated pubic bones,
four functional toes, elongated metatarsals, complete clavicles,
premaxillary teeth, and free, not firmly fixed quadrate bones. But such
creatures are not Dinosaurs.
We divide the enormous number of Dinosaurs according to the formation of
the pelvis, that of the hind-limbs, and the dentition, into four orders.
{418}ORDER I. SAUROPODA.
_Pubes simple, with symphysis. Premaxillae with teeth. Plantigrade._
The teeth are mostly spatulate, laterally compressed, with sharp edges, but
without serrations. Skull with a pair of large pre-orbital fossae. The
centra of the vertebrae of the trunk have large lateral cavities. The fore-
and hind-limbs are pentadactyle, plantigrade, and hoofed, of the typical
walking type; the bones of the limbs are stout and solid; the femur is
devoid of an inner distal or fourth trochanter. The carpal and tarsal bones
are free. Herbivorous. The Sauropoda comprise some of the most gigantic
terrestrial creatures which have ever existed, compared with some of which
the bulk of an elephant appears almost insignificant. Their range in time
extends from the Lower Oolite into the Cretaceous, with a perhaps
world-wide distribution, namely, Western Europe, North America, Patagonia,
Madagascar, and India. Although they are, except for their size, the least
specialised of all Dinosaurs, none of the Sauropoda hitherto discovered are
old enough to claim to be the ancestors of the other Dinosaurs.
[Illustration: FIG. 95.–Skeleton of _Brontosaurus excelsus_. × 1/180.
(After Marsh.)]
_Brontosaurus excelsus_ of the Upper Jurassic of Wyoming was a giant at
least 60 feet long and about 10 feet high. The head is extremely small in
proportion, not so broad as the fourth of the thirteen vertebrae of the
long and flexible neck. The trunk is comparatively short, the tail longer
than the neck, and provided with numerous chevron-bones. Most of the
vertebrae are hollow, especially the five co-ossified sacrals. The spinal
canal of the sacral region is very wide, indicating a strong sacral
swelling in conformity with the huge posterior limbs. The pubic bones are
stronger than the ischia. The long axis of the {419}former stands almost
vertically like that of elephants, and the knee is scarcely bent in the
erect position. The shoulder-girdle consists of long scapulae, broad at the
base and small, almost square and perforated coracoids, which latter fit
into a pair of partly ossified plates representing the sternum.
_Atlantosaurus immanis_ of the Upper Jurassic of Wyoming and Colorado, is
supposed to have been 115 feet long, perhaps the biggest and bulkiest of
all animals, the femur measuring more than 6 feet in length and 2 in width
at the upper end.
_Morosaurus grandis_, of the Upper Jurassic of Wyoming, with allied forms
in the Purbeck and Wealden of England, reached a length of 30 feet; in
general appearance resembling _Brontosaurus_, but the sacrum consists of
four vertebrae only, and the ischia are bent backwards in their distal
halves, so that their symphysis is formed by the shafts instead of by their
ends.
_Ornithopsis_ and _Cetiosaurus_, likewise huge creatures, from the English
Wealden and from the Great Oolite respectively, are rather imperfectly
known, although several species of each, under many generic synonyms, have
been described.
[Illustration: FIG. 96.–Front view of the pelvis of _Morosaurus grandis_. ×
1/30. (After Marsh.) _a_, First sacral vertebra; _b_, "transverse process"
(rib) of first sacral; _il_, ilium; _is_, ischium; _nc_, neural canal;
_pb_, pubis.]
[Illustration: FIG. 97.–Skull of _Diplodocus longus_. × 1/12 (After
Marsh.)]
_Diplodocus longus_, of the Upper Jurassic of Colorado and Wyoming, is
almost completely known. More than 40 feet long, it had a head in its
general outlines not unlike that of a horse, the skull being about two feet
long. The outer nasal openings are confluent, elongated, and lie far back
on the top of the skull. There is a pair of large antorbital, and a pair of
smaller lacrymal fossae. The teeth, long and slender, are restricted to the
anterior portion of the mouth, with many successors, which, decreasing in
size, lie on the inner or lingual side of the functional tooth, like the
cartridges in a repeating rifle. The {420}functional teeth themselves are
implanted in sockets. The generic name refers to the peculiar
chevron-bones, each half of which diverges into an anterior and a posterior
branch.
It is difficult to understand how these huge, long-necked Sauropoda lived
and moved about. The long neck suggests at first sight predacious habits,
but the teeth, rather feeble in _Diplodocus_, and distinctly of the
plant-cutting type in other genera, put this out of the question. The high
position of the unpaired nasal opening, and the shortened nasal bones of
_Diplodocus_, are features indicative of aquatic habits, but the
short-toed, plantigrade limbs are absolutely adapted to terrestrial life,
and we cannot well assume that such enormous brutes as _Atlantosaurus_
could possibly have ventured into swampy ground.
ORDER II. THEROPODA.
_Pubes simple, with symphysis. Premaxillae with teeth. Digitigrade.
Carnivorous._
The teeth are pointed, recurved, laterally compressed and serrated. The
nasal openings are large, lateral, and nearly terminal. The vertebrae and
the large bones of the limbs are hollow. The fore-limbs are considerably
shorter than the hind-limbs, which are distinctly digitigrade, many of the
species having a pronouncedly upright gait. The proximal tarsalia show a
tendency to fuse with the tibia, and the astragalus has sometimes an
ascending process, by which the fusion with the tibia is strengthened. The
first and fifth metatarsals are often reduced, while the three middle bones
are elongated and sometimes even fused with each other, so that the whole
foot assumes a striking resemblance to that of birds. The terminal
phalanges are protected by curved claws. Owing to the shortness of the
fore-limbs, and the often considerable length of the hind-limbs, which are
strongly bent at the knee and the ankle-joint, these animals must have
progressed somewhat like clumsy kangaroos.
The Theropoda, of which a great number of genera are now known, from the
size of a slender cat to that of an elephant, lived from the Upper Trias to
the Upper Oolite, both in Europe and in North America.
_Brontozoum giganteum_, one of the oldest forms, is known {421}from its
foot-spoors only, which, together with other three-toed spoors in the
sandstone of the Connecticut valley, were originally described and figured
by Hitchcock as _Ornithichnites_ (ἴχνος = track, or spoor). Some of these
imprints are more than a foot in length, the right and left spoors
following alternately at a distance of from four to six feet. In some cases
the long trailing tail has left a furrow behind, and the large tracks are
accompanied or crossed by much smaller, and even by quite tiny tracks,
otherwise similar, and undoubtedly made by the young.
_Anchisaurus_, from the same locality, was still Sauropodous, in so far as
the metatarsals are still free, with two, three, four, and five phalanges
on the first four toes, but the fifth metatarsal is reduced, carrying a
vestige of only one phalanx, and the proximal tarsal bones are fused with
the tibia and fibula respectively. Total length some seven feet, of which
about four belong to the tail.
_Zanclodon_, from the Keuper of Würtemberg, about ten feet long, with
pentadactyle hands and feet. Ischia stronger than the pubic bones, which
are distally much broadened. The femur is nearly three feet long, and
possesses a fourth trochanter. The astragalus has an ascending process, and
is fused with the tibia. The toes are short, strong, and clawed. The
shoulder-girdle and fore-limb are strong, the latter well adapted to
grasping. The teeth are much compressed laterally, with sharp, finely
serrated edges. Several allied genera have been described from the Upper
Trias of France and England: others from corresponding strata of India and
South Africa.
[Illustration: FIG. 98.–Skull of _Anchisaurus coelurus_. × ¼. (After
Marsh.) _a_, Nasal fossa; _b_, antorbital, _c_, infra-temporal, _d_,
supra-temporal, and _o_, orbital fossa; _q_, quadrate bone.]
_Megalosaurus_, from the Trias to the Wealden in England and France, with
other species in Colorado and India, reached a considerable size, larger
than that of any other Theropoda, the scapula of _M. bucklandi_ being
nearly three feet long, and the femur still longer. The hind-limbs are
twice as long as the fore-limbs. The cervical vertebrae are short, the neck
being much shorter than the tail. Hands with five fingers, feet with four
toes. Pubic bones long and slender, with a broad symphysis. With
well-developed abdominal ribs, resembling those of crocodiles.
{422}_Allosaurus_, from the Upper Jurassic of North America, with only
three toes. Ischia and pubes united into one symphysis. Anterior
extremities very short. Sacrum consisting of four vertebrae. Total length
of some of the larger species about twenty feet.
[Illustration: FIG. 99.–Skeleton (× 1/40) and skull of _Ceratosaurus
nasicornis_. (After Marsh.) _a_, Nasal cavity; _b_, bony horn-supporting
excrescence; _c_, pre-orbital fossa; _d_, orbital fossa.]
_Ceratosaurus nasicornis_, from the Upper Jurassic of Colorado, is about
seventeen feet long. The generic and specific names refer to the nasal
bones, which are raised into an unpaired longitudinal crest. This, by its
rough surface, suggests that it was covered by a horny sheath, or carried a
horn. The large skull, about two feet in length, is armed with strong,
slightly curved, laterally compressed, sharp teeth, unequal in size. The
pre-orbital foramen is large, bordered above by the prefrontals, which are
raised into prominent knobs. The supratemporal foramina are extremely
small, the lateral foramina very large. The quadrate slants backwards. The
sacrum consists of five vertebrae. The caudal vertebrae carry long and
slender chevron-bones. The pubes and ischia are long and slender, each
forming a separate symphysis at their broadened ends. The three
{423}metatarsals are elongated and fused with each other. There seems to
have been some dermal armour in the shape of osseous plates, which extended
in one series from the occiput over the neck.
_Coelurus gracilis_, of the Upper Jurassic of Wyoming, and closely allied
forms in the Wealden of England, are remarkable for the pneumaticity of the
centra and processes of their vertebrae, the bony parts of which are
restricted to thin, hollowed-out shells, so that the whole skeleton must
have been very light. Computed length of these imperfectly preserved
creatures about five feet.
_Hallopus victor_, of the Upper Jurassic of Colorado. Anterior extremities
very short, with only four fingers; posterior limbs very long and slender,
especially the tibia; the much elongated metatarsals are separate, the
first absent, the fifth much reduced, so that the foot is tridactyle; the
calcaneum projects like a heel. The ilium is attached to two sacral
vertebrae only; the pubes are slender, forming a narrow symphysis, while
that of the ischia is broad. Most of the bones of this creature, which
probably progressed by hops, are hollow. Total length about three feet, the
length of the hind-limbs being about nine inches.
_Compsognathus longipes_, of the Upper Jurassic of Bavaria, is one of the
smallest of all the Dinosaurs. It is most remarkable on account of its
almost bird-like feet. The fibula is much thinner and somewhat shorter than
the tibia; the latter is closely attached to, although not fused with the
proximal tarsal bones, while the distal tarsals are fused with the united
and much elongated second, third, and fourth metatarsals; the fifth is
reduced to a short bone near the intertarsal joint; while the first is
represented by its distal portion only, which is stowed away on the hinder
aspect of the middle of the second metatarsal, and carries two phalanges.
The three middle toes consist of three, four, and four phalanges
respectively. Whilst the whole hind-limb is typically avian, the pelvis is
quite different; the pubic bones are simple, slender, and directed
forwards, forming a symphysis with their whole distal halves, and
broadening out distally into a horizontal process directed towards the
symphysis, which is likewise formed by the fusion of the inner surfaces of
the thin and rather flat ischia. The fore-limbs are only half the size of
the hind-limbs. The neck consists of about ten vertebrae, mostly with long
and {424}pointed ribs. Tail long with well-developed chevrons. The skull is
long and pointed, composed of thin bones, which have lost most of the
sutures; with large lateral, temporal, and pre-orbital, but without
supratemporal, foramina. Premaxillae, maxillae, and mandible with numerous
slender and rather long, conical, alveolar teeth.
ORDER III. ORTHOPODA
_Each pubic bone consists of an anterior or pre-pubic and a posterior or
post-pubic branch, neither of which forms a symphysis. Premaxillae
without teeth. With a premandibular predentary piece. Herbivorous._
The so-called pre-pubis is homologous with the pubis of most recent
reptiles, and with the pectineal process of birds, while the "post-pubis"
is homologous with the processus lateralis of Chelonians and Saurians, and
with the "pubis" of birds. The right and left halves of the pubis remain
widely asunder ventrally. In many cases the post-pubis, always directed
obliquely backwards, lies closely against the shaft of the ischium, which
always forms a distal syndesmosis, or a symphysis, with its fellow. The
fore-limbs are usually very short, provided with five or four short and
strong fingers. The hind-limbs are long and strong, mostly with three,
sometimes with four functional short toes, either plantigrade (STEGOSAURI)
or digitigrade (ORNITHOPODA). Femur with an inner distal, or fourth,
trochanter. The dentition is of the herbivorous type, restricted to the
dentaries of the mandible and to the maxillary bones, leaving the whole or
the greater part of the premaxillaries free. The additional "predentary"
piece of the mandible is possibly a calcified, but originally horny, pad.
The teeth are greatly compressed laterally, and finely serrated, but are
much ground down by use; several rows of successional teeth lie on the
inner or lingual side. The skull is strongly built, with large anterior
nasal openings; pre-orbital foramina very small or absent; orbits
completely encircled by bones; supratemporal foramina small, lateral
foramina large. Quadrate large, vertical or slanting slightly forwards. The
vertebrae are solid, not hollow; sacrum consisting of four, five, or more
vertebrae; ribs bifurcated, the capitula carried either by the centra, or
moved up to the diapophyses of the neural arches; chevron-bones
{425}numerous, and frequently long, especially on the anterior half of the
long and heavy tail.
Orthopoda occur from the Lias to the Upper Cretaceous, both in Europe and
in North America. The name Orthopoda, invented by Cope in 1866, is
appropriate for obvious reasons; it comprises the Stegosauri and
Ornithopoda of Marsh (1881). The latter term is not very fortunately
chosen, considering that the whole hind-limb of the Theropodous
_Compsognathus_ is far more ornithic than that of any three-toed
Ornithopoda, in which the tarsalia rarely fuse with the tibia and never
with the metatarsals. To apply the term Ornithopoda to the whole order is
quite unjustifiable, unless it is meant to apply to the strikingly
bird-like configuration of the pelvis.
SUB-ORDER 1. STEGOSAURI.–The fore- and hind-feet are plantigrade, or nearly
so, the metapodials being but little elongated, with more than three
functional digits. The bones of the limbs are solid. The ribs of the trunk
are bifurcated, and are carried by the diapophyses of the neural arches.
The body, especially the back, is protected by dermal bony plates, which
are not connected with the internal skeleton.
_Scelidosaurus harrisoni._ One nearly complete skeleton, about 11 feet in
length, from the Lias of Lyme Regis. About twenty-four pre-sacral
vertebrae, of which six or seven belong to the neck, four sacral and about
forty caudal vertebrae. Four fingers, four toes, with 2, 3, 4, 5 phalanges,
the fifth metapodials being quite vestigial; the hallux and pollex are very
short, so that the foot at least is functionally tridactyle. The tarsal
bones remain separate. The head is very small. Two rows of ridged bony
plates extend from the neck over the back, and converge into one row upon
the long tail; smaller plates, arranged in many rows, seem to have
protected the sides and under parts. _Hylaeosaurus_ and _Polacanthus_ of
the English Wealden are allied forms.
_Stegosaurus_, with several species from the Upper Jurassic of Colorado and
Wyoming, and others, e.g. _S. armatus_ (= _Omosaurus_), from the Kimmeridge
Clay of Wiltshire in England. The head is relatively very small, and the
brain is surpassed several times in thickness by the huge sacral swelling
of the spinal cord. Teeth numerous and small. All the cervical and
trunk-vertebrae carry bifurcated ribs, those of the trunk being carried
entirely by the very high neural arches. The fore-limbs are only about half
{426}the length of that of the hind-limbs, so that these creatures, which
were undoubtedly quadrupedal, must have had a very peculiar gait, standing
with the head, neck, and shoulders much lower than the arched back and
pelvic region. The ulna has a strong olecranon; the hand has four
functional fingers. The pre-acetabular portion of the ilium is much
elongated; the pre-pubic branch stands horizontally, while the post-pubis
is closely adpressed to the ischium. The astragalus is fused with the
tibia, the calcaneum with the fibula. The foot has only three short toes,
protected, like the fingers, by hoofs. The dorsal dermal armature consists
of very high, crest-like plates. _S. ungulatus_ of North America has a
computed length of 28 feet, with the hind-limbs about 7 feet long. This
creature was nearly 10 feet high, when measured from the ground to the tips
of the dermal crests on the middle of the back. These bony, laterally
compressed plates are themselves nearly 3 feet high, and are replaced, on
the hinder portion of the tail, by several pairs of pointed spikes about 2
feet in length.
[Illustration: FIG. 100.–Skeleton and dermal armour of _Stegosaurus
ungulatus_. × 1/60. (After Marsh.)]
SUB-ORDER 2. ORNITHOPODA.–The hind-limbs are distinctly digitigrade,
usually with only three functional toes, protected by claws. The long bones
are hollow. Femur with a long fourth trochanter. Without dermal
armour-plates.
_Camptosaurus._–Several species, up to 10 feet in length, from {427}the
Upper Jurassic and the Wealden of North America and England. Five fingers,
with 2, 3, 3, 3, 2 phalanges and four toes, with 2, 3, 4, 5 phalanges, but
the hallux is much shortened and does not touch the hard ground; astragalus
and calcaneum separate.
_Laosaurus_ of Colorado is a smaller form, intermediate in structure
between the former genus and _Hypsilophodon foxi_ from the Wealden of the
Isle of Wight. A small creature, less than 5 feet in length. Four fingers,
with 2, 3, 4, 2 phalanges; fifth metacarpal vestigial. Four toes with 2, 3,
4, 5 phalanges and long claws. Astragalus and calcaneum separate.
Post-pubis very slender. Each premaxillary with five pointed alveolar
teeth, leaving a wide median diastema; maxillaries with eleven, dentaries
with ten laterally compressed blade-like teeth.
_Iguanodon_ from the Wealden of England, Belgium, and Germany. Apparently
two species, _I. mantelli_, about 16 feet, _I. bernissartensis_ nearly 30
feet long. The premaxilla is quite toothless; the teeth of the maxillae and
mandibles stand in close series, implanted in alveolae; they are spatulate,
laterally compressed, with finely serrated edges, and slightly curved, the
lower outwards, the upper inwards, and bear a general resemblance to those
of _Iguana_, hence the generic name. There is only one functional set of
teeth, and these are much worn down by use, but in such a way that, owing
to the different curvature of the opposed teeth, the worn-down crowns form
cutting, and at the same time crushing, almost triturating surfaces,
indicating that these animals lived upon herbs. The gait of these creatures
was upright, as shown by their spoors; the long almost vertical ischia,
which form a padded symphysis, only slightly raised above the ground,
suggest that this symphysis was used as a true sitting support, the animal
resting upon it, the hind-limbs and the long tail. The latter, to judge
from the long chevrons and the high neural spinous processes, must have
been furnished with strong muscles. The whole tail was undoubtedly used as
a balance during the upright position. Many of the tendons of the dorsal
spinal muscles on the back and upper half of the tail are ossified. The
post-pubic branches are very slender, distally much reduced, and, except at
the obturator-foramen, separated from the ischia; the pre-pubes are very
strong and broad. The femur has a fourth trochanter, a feature which
{428}induced the unfortunate late Paul Albrecht to declare that _Iguanodon_
was a reptilian Duck! The tarsal bones are separate. The metatarsals and
toes are reduced to three, with 3, 4, 5 phalanges respectively, the first
being a mere styliform vestige. The anterior limbs are likewise very
powerful, but are much shorter; the hands are adapted for grasping,
possibly for defence and offence, as indicated by the pollex, which,
although short, is transformed into a formidable spur-like weapon, firmly
fixed at a right angle to the other four fingers, the phalanges of which
number 3, 3, 3, 4; the second and third fingers were protected by hoof-like
nails, the fifth finger is feeble, and stands somewhat apart. The whole
vertebral column consists of more than eighty vertebrae, of which ten are
cervical, eighteen thoracic and lumbar, while five or six are fused into
the sacrum. The cervical vertebrae are opisthocoelous, and carry short
ribs, except the atlas, which possesses two separate supra-dorsal pieces,
which fill the gap between it and the occiput.
[Illustration: FIG. 101.–Skeleton of _Iguanodon bernissartensis_. × 1/80.
(After Marsh.)]
Many specimens of _I. bernissartensis_, which is now completely known,
including even the hyoid bones, were discovered in 1878, in the Belgian
colliery of Bernissart, between Mons and Tournai, close to the French
frontier. The bones were in a fault or crack, filled with clay of Wealden
age, about one thousand feet below the present sea-level, and there about
thirty Iguanodons, all {429}apparently adult, had become embedded. Five of
them are now mounted in one of the public galleries of the Brussels Museum,
of which these perfect monsters form one of the chief attractions. Having
proved to be such a valuable find, they were claimed by the Government, on
the ground that Iguanodons were not included in the license of the Coal
Mining Company. The fact that not only _I. bernissartensis_, but also a few
specimens of _I. mantelli_, already known from England, where the large
form likewise occurs, were found in the same place, makes the specific
differences somewhat doubtful; they are perhaps sexual.
_Claosaurus_ of the uppermost Cretaceous strata of Wyoming, is one of the
latest of Dinosaurs. It is nearly allied to _Iguanodon_, but has only three
functional fingers, the fifth being absent, whilst the pollex is very
short.
_Hadrosaurus_ s. _Diclonius_ of the same level as the preceding genus in
North America, apparently also in the Middle and Upper Chalk of England and
Belgium, has a most peculiar spoon-shaped bill, the premaxilla and the
predental bone being spatulate and quite toothless. The teeth in the upper
and lower jaws are numerous and small, and whilst one set of teeth is being
ground down, the several successional series are already functional. _H.
mirabilis_ has in all about 2000 teeth; the total length of the skeleton is
38 feet, of which nearly 4 feet are taken up by the skull; in other
respects this genus is allied to _Iguanodon_.
_Ornithomimus_, of the Upper Cretaceous of Colorado, is known only from its
fore- and hind-limbs. The fore-limbs are short, with three fingers. The
hind-limbs are very long and strikingly bird-like. The metatarsals, of
which only the second, third, and fourth are developed, are much elongated;
the proximal half of the third is pushed back between the second and
fourth, and imperfectly fused with them, exactly as in young birds. The
astragalus has a long ascending process, and is fused with the tibia. The
fibula is very slender, distally much reduced; the calcaneum is represented
by a tiny nodule; the terminal phalanges end in pointed claws. _O. grandis_
must have reached a considerable size, to judge from its middle metatarsal,
which is 60 cm. or 2 feet long. Until more is known of these extraordinary
creatures, nothing definite can be said about their affinities. They may
perhaps belong to the Theropoda.
{430}ORDER IV. CERATOPSIA.
_Pubic bones simple, forming a symphysis, post-pubic branches being
absent. The mandible carries a toothless "pre-dental," and the fused
premaxillaries carry a similar, toothless, "rostral" bone._
The teeth of the upper and lower jaws are alveolar, and have two roots. The
fore-limbs are little shorter than the hind-limbs; pentadactyle and
plantigrade, with broad hoofs. Femur without a fourth trochanter.
Limb-bones solid. The skull is large, and remarkable for a pair of long
frontal bony cores, which probably carried large, pointed horns; the
parietal bones form a huge, horizontally broadened out crest, which extends
backwards over the neck. Upon this cranial neck-shield follow small dermal
bony plates. These miraculous creatures flourished during the Cretaceous
epoch in Europe and in North America. Some, for instance, the American
_Triceratops flabellatus_, reached a huge size, its skull alone measuring
more than 5 feet in length, while that of _T. prorsus_ is, including the
neck-shield, about 7 feet long. The total length of this monster, the back
of which stands about 8 feet high, is more than 20 feet. Other genera seem
to have a well-developed dermal armour, _e.g._ _Nodosaurus_ of the Middle
Cretaceous period of Wyoming.
[Illustration: FIG. 102.–Skeleton of _Triceratops prorsus_. × 1/70. (After
Marsh.)]
The Ceratopsia combine characters of the Sauropoda and of the Stegosaurian
Orthopoda; in their pelvis they agree with the former, in the development
of dermal armour and a predental bone they agree with the latter, while
they differ from either by the possession of a rostral element.
{431}_SUB-CLASS VI.–CROCODILIA._
If we had to deal only with the recent Crocodilia the following would be an
all sufficient diagnosis:–_Four footed, long-tailed reptiles, with fixed
quadrate bones, with teeth separately implanted in alveolae and restricted
to the upper and lower jaws._
[Illustration: FIG. 103.–1, Atlas and axis of _Crocodilus_. 2, Atlas and
axis of _Metriorhynchus_, a Jurassic Crocodile, see p. 439. 3, Analysis of
the first two cervical vertebrae of a Crocodile. 4, Diagram of the
fundamental composition of a Reptilian or other Amniotic, typically
gastrocentrous vertebra. _Az_, Anterior zygapophysis; _B.D_, basidorsal;
_B.V_, basiventral; _C_{1}_, _C_{2}_, first and second centra, formed by
the interventralia; _Cp^1_, _Cp^2_, articular facets of the capitular
portions of the first and second ribs; _I.V_, interventral; _N_{1}_,
_N_{2}_, first and second neural arch, formed by the basidorsalia (_B.D_ in
4); _Od_, odontoid process = first centrum; _Pz_, posterior zygapophysis;
_R_{1}_, _R_{2}_, ribs; _Sp_, detached spinous process of the first neural
arch; _t_{1}_, _t_{2}_, facets of the tubercular portions of the first and
second ribs; 1, 2, intercentra = basiventralia; ^2 (in 3), second
basiventral "complex or intercentrum," continued upwards as a meniscus or
intervertebral pad; _I_, _II_, _III_, position of the exit of the first,
second, and third spinal nerves.]
To define Crocodilia in general and to distinguish them from various
extinct groups we have to resort to additional characters. The vertebrae
are solid; the ribs of the neck and thorax possess a distinct capitulum and
tuberculum; there is a series of loose, compound abdominal ribs; the
humerus is devoid of an entepicondylar foramen; the iliac bones are
broadened out and attached to two sacral vertebrae; the pubic bones are
simple, not bifurcated, and neither they nor the ischia are ventrally
united. The skull always has a strong, bony, quadrato-jugal arch. The
possession of a longitudinal cloacal opening and of {432}an anterior or
ventral single copulatory organ can of course be asserted of recent forms
only.
In spite of these many characters common to all Crocodilia, it is very
difficult to separate the latter from the Dinosauria, the only absolute
difference lying in the ventral pelvic bones. It is therefore most
suggestive that the fore-limbs of the Mesozoic Crocodilia are so much
shorter and weaker than their hind-limbs, a discrepancy which is not
lessened before the Tertiary epoch. The Mesozoic Crocodilia were almost
entirely marine; the strongly-developed ankle-joint (indicated already by
such early forms as _Aetosaurus_ and _Mystriosaurus_) must have been
inherited from some terrestrial group with digitigrade tendencies and
shortened hind-limbs. All this points to some Theropodous Dinosaurian stock
of which the Crocodilia may well form an aquatic, further-developed branch.
Loss of the pubic and ischiadic ventral symphysis is not a serious
modification. So far as modern reptiles are concerned only the Chelonia and
_Sphenodon_ are related to the Crocodilia, whilst Monitors and other
lizards resemble them only superficially. We divide them into three Orders.
ORDER I. PSEUDOSUCHIA.
The few members of this peculiar group of reptiles are all restricted to
the Keuper or variegated marls, although they seem to have had a wide
distribution, some having been found in Germany, others in New Mexico. They
perhaps form an early side-branch of the generalised Crocodilian stock,
which died out with the Jurassic age.
The skull is distinctly short and pointed. The premaxillaries are very
small and are dorsally separated from each other by the large nasals, which
also keep the maxillae widely asunder. The nostrils are latero-terminal,
bordered chiefly by the nasals, below by the premaxillae and part of the
maxillae. The orbit is bordered below by the strong jugals, in front by the
prefrontal, above by a supra-orbital and a small postfrontal, behind by a
postorbital, which, firmly connected with the jugal and squamosal, shuts
off a supratemporal foramen. There is also a lateral temporal fossa, and a
large hole enclosed by the lacrymal and the maxillary bones. The teeth are
restricted to the anterior {433}half of the jaws. The neck, back, and tail
are covered by two rows of large and broad, closely-jointed bony plates;
smaller plates protect the sides and the ventral surface. The vertebrae are
still unknown.
_Aëtosaurus ferratus_ of the Upper Keuper near Stuttgart is the best known.
One of the greatest treasures of the Stuttgart Museum is a slab of
sandstone, about 2 square yards in size, upon which lie huddled together
twenty-four individuals of various sizes, the largest measuring 86 cm. or 2
feet 10 inches. They are in a beautiful state of preservation, and many of
them are in the most life-like attitudes, just as if a mass of sand had
fallen upon them and crushed them down, and as if they were struggling to
get out.
_Erpetosuchus_ and _Ornithosuchus_ of the Elgin sandstone seem to be allied
forms.
ORDER II. PARASUCHIA.
As the name implies, a collateral branch of the true Crocodilia. They are,
like the Pseudosuchia, restricted to the Keuper formation. The vertebrae
are mostly biconcave, sometimes with nearly plain, scarcely concave,
central joints. The premaxillae are very long and powerful. The nostrils
lie far back, rather near the orbits, on the top of the snout, within the
anterior half of each nasal and almost above the choanae. The latter are
situated in front of the palatine bones and are divided by a backwardly
directed process of the vomer, which is plainly visible on the roof of the
mouth. The palatines and pterygoids leave a wide median space between them.
The pterygoids are narrow and have three processes, the antero-lateral of
which joins the palatines and the maxillary bones (there being no separate
ectopterygoid), the inner joins the basi-occipital, and the postero-lateral
the quadrate.
The orbit is surrounded by the frontal, prefrontal, lacrymal, postorbital
and postfrontal, while the strong jugal is excluded. The temporal region
shows a lateral and a dorsal foramen; the latter opens backwards and above
the occiput, being bordered in front by the parietal, laterally by the
squamoso-occipital bridge.
The vertebrae are amphicoelous. The first and second {434}vertebrae are
devoid of ribs; the cervicals and first thoracics carry separate capitular
and tubercular processes for the attachment of the ribs, while the ribs of
the rest of the trunk are carried entirely by the long diapophyses, as in
the modern Crocodiles. The dermal armour consists of two rows of broad,
dorsal, and several rows of smaller, lateral, bony plates.
_Belodon_ is by far the best-known genus, with several species in South
Germany and North America, some of which reached a length of 10 feet,
without ventral armour. The closely allied _Stagonolepis_ of the Elgin
sandstone in Scotland had dorsal and ventral armour. Other genera in the
Triassic formations of India and North America.
ORDER III. EUSUCHIA.
Crocodilia in the stricter sense. The premaxillae are short and always
enclose the nostrils. The choanae lie behind the palatines, in recent forms
even within the pterygoids. They occur from the Liassic or Lower Jurassic
period to the present time.
The direct ancestors of the Eusuchia are still unknown. They cannot have
been developed from the Pseudosuchia, nor do we know intermediate stages
which connect them with the Parasuchia. The nostrils, situated within the
premaxillaries, always lie in front of the nasals, although these sometimes
extend forwards and form a bony internasal septum fusing with the usual
cartilaginous septum. The choanae, instead of opening immediately behind
the vomer, are carried far back, owing to the formation of a secondary bony
palate. In the Jurassic Crocodiles this roof is formed by the meeting of
the palatine bones in the medio-ventral line, and the choanae open
immediately behind. From Cretaceous times onwards this roofing is continued
by the pterygoids, which likewise form a median suture; and the united
choanae (which may, or may not, be divided by a thin bony septum) are
pushed towards the posterior end of the pterygoids. Since the Jurassic
times there exists also a tendency to enclose the Eustachian passages (the
remnants of the first gill-clefts) by bone. In the earlier members they
were still wide slits or open grooves on the ventral side of the
basi-occipital bone. Since the Cretaceous epoch they have been transformed
into bony canals and open through one median hole, situated between the
basi-occipital and the {435}basisphenoid, immediately behind the posterior
symphysis of the dorsal portion of the pterygoids, which latter almost
completely cover the basisphenoid. The vomer is not visible (except in
_Caiman niger_), being covered by the ventral junction of the palatines and
maxillaries. The broad, lateral wings of the pterygoids are connected by
separate bones, the ectopterygoids = transpalatines = transverse bones,
with the maxillaries, and in recent forms also with the jugals. Thus an
extensive, very firm bony palate is produced; and the large palatal
foramina, between the palatines, maxillaries, ectopterygoids and
pterygoids, are closed by the same dense mucous membrane which cover the
whole roof of the mouth.
The opisthotic and epi-otic bones fuse early with the lateral and with the
supra-occipital bones; only the pro-otic remains longer as a separate
element, perforated anteriorly by a large hole for the exit of the third
branch of the trigeminal nerve. The basisphenoid is scarcely visible, being
covered by the pterygoids. The presphenoid is large, continued forwards and
upwards into the usually cartilaginous interorbital septum. Near the
anterior and upper margin of the presphenoid is a large notch on either
side for the passage of the optic nerve, the three eye-muscle nerves and
the first branch of the trigeminal nerve. There are no separate
orbito-sphenoids, their place being taken by membrane or cartilage in
continuation with the interorbital septum, but the alisphenoids are large,
abutting upwards against the frontals. Each prefrontal sends down a
vertical process which joins the palatine of its side.
The configuration of the snout varies much. There are two parallel lines of
development since the Jurassic epoch, namely, long-snouted creatures, of
which two still survive as _Gavialis_ and _Tomistoma_, and more broad and
short-snouted members like the rest of the Crocodiles and Alligators. In
opposition to the Parasuchia the elongation of the snout is effected by the
maxillaries. The length of the nasals varies much, mostly in conformity
with that of the maxillaries. As a rule they reach the premaxillaries but
not always the nasal groove. In _Gavialis_ they are short, far separated
from the premaxillaries by the maxillaries, which meet in the dorso-median
line. The orbit is bordered by the frontals, which at an early age fuse
into an unpaired piece, and by the prefrontal, lacrymal, jugal, and
postfrontal. {436}At a deeper level the orbit is partly divided from the
lateral temporal fossa by a strong column which is formed by the meeting of
a downward process of the postfrontal with an inner process of the jugal,
and an ascending process of the ectopterygoid (cf. Fig. 108, p. 458). This
arrangement adds considerably to the strength of the skull. The lateral
temporal fossa is bordered in front by the column just described; below by
the jugal and the quadrato-jugal, which is firmly wedged in between the
jugal and quadrate; behind by the quadrate; above by the postfrontal, which
forms a strong superficial bridge with the squamosal. This rests upon and
often fuses with the quadrate and an intervening transverse wing-like
extension of the lateral occipital bone. By this squamoso-postfrontal
bridge part of the original temporal fossa is divided into the lateral one
just described, and a dorsal fossa. The latter is bordered by the
postfrontal, squamosal, and united parietals. This dorsal temporal fossa is
consequently not homologous with that of the Parasuchia, a vestige of which
is however present in many, especially in young skulls of Crocodiles, in
the shape of a narrow passage which extends backwards from the dorsal
fossa, bridged over by the junction of the parietal with the squamosal, and
bordered below by the occipitals.
The size of the upper temporal fossae stands in an inverse ratio to that of
the lateral fossae. In the older Eusuchia the upper were the larger of the
two. The temporo-mandibular muscle which lifts or shuts the lower jaw
arises from the walls of the upper fossa, passes beneath the jugal arch,
and is inserted into the supra-angular portion of the lower jaw. In the
more recent Crocodiles this muscle is more and more superseded by the
pterygo-mandibular muscle, which, arising chiefly from the dorsal surface
of the much broadened-out pterygoid bone, fills the widened space between
the latter and the quadrate, and is inserted into the outer surface of the
os angulare of the lower jaw. This muscle, owing to its general
disposition, is capable of much more powerful development and leverage than
the temporo-maxillary muscle, which latter, being more reduced, allows the
dorsal fossae to be more and more closed up by the surrounding bones.
The fossae are still comparatively large in the long-snouted genera
_Gavialis_ and _Tomistoma_, which live entirely upon fish and scarcely chew
their food, whilst these holes almost completely {437}disappear in some of
the Alligators, namely in the broad- and short-snouted members, which,
having a varied diet, taken from every available group of the animal
kingdom, chew their prey.
The quadrate extends obliquely backwards, and is immovably wedged in and
partly fused with the quadrato-jugal, the squamosal, and the lateral
occipital wings. Between the latter and the quadrate remains a slit-like
canal, well visible from behind, through which passes the continuation into
the mandible of the columellar or ossicular chain of the auditory
apparatus. Intricate passages, used as additional enlargements of the space
of the middle ear, pervade the proximal portions of the quadrate and the
roof of the cranium beneath the parietal bridges mentioned above, the two
sides communicating with each other. The supra-occipital bone is visible
from behind; its top is covered and partly fused with a continuation of the
parietals, which are, like the frontals, fused into an unpaired mass. The
occipital condyle is formed entirely by the basi-occipital bone, so far as
the articulating facet is concerned, but it is supported on either side by
a lamella from the lateral occipitals.
The two halves of the lower jaw form a symphysis of very variable length.
Each half is composed of six bones. (1) The articulare, perforated in its
upper, posterior, inner corner by a canal for the reception of the
siphonium, a narrow tube of connective tissue, which connects the cavities
of the middle ear with the large empty space enclosed within the lower jaw;
(2) the angulare; (3) the dentary, which alone carries the teeth; (4) the
splenial, a long splint-like bone on the surface of the inner or median
side of the jaw, of variable length; (5) the operculare, the counterpart of
the splenial on the outer side; (6) the supra-angulare, which forms the
dorsal border of the lower jaw between the dentary and the angulare.
The teeth, which are more or less conical or compressed laterally, are
deeply implanted in separate sockets. They are often shed throughout life,
the successors lying on the median side, and with their caps partly fitting
into the wide, open roots of the teeth to be expelled. The number of teeth
in the premaxilla is universally five on either side in recent forms, but
in a few species, e.g. _Crocodilus niloticus_ and _C. porosus_, the second
pair is lost with maturity and is not replaced. In the broad-snouted
{438}kinds, especially in the Alligators, most of the upper teeth overlap
laterally those of the lower jaw. In most species of _Crocodilus_ the
overlapping is less marked and the teeth partly interlock, but the fourth
mandibular tooth, generally the strongest and longest, is received into a
lateral notch at the junction of the premaxillary and maxillary. Frequently
those of the longer lower teeth which fit into pits of the upper jaw,
gradually transform the pits into holes by continued pressure upon the
bone, and in old specimens the tip of the lower tooth may even perforate
and stand out above the skin of the snout.
The vertebrae are solid, but remnants of the notochord persist for a long
time in the middle of the centra. These are still amphicoelous in the
Jurassic Eusuchia, and there were probably considerable intervertebral
portions of the notochord. From the Lower Chalk onwards the vertebrae are
procoelous, with the exception of the first caudal vertebra, which has a
knob at either end, so that naturally the posterior of the two sacral
vertebrae is opisthocoelous. This peculiar formation of the first caudal is
probably correlated with the flexibility of the tail.
Cartilaginous intercentral rings, pads or menisci, occur regularly
throughout the vertebral column, unless they are abolished by fusion of
adjoining vertebrae. It is most instructive to follow the attachment of the
ribs in one and the same individual. The position of the capitulum,
vertically below the tuberculum in the neck, changes in the thorax into one
in which the capitulum lies anterior to the tuberculum and in the same
horizontal plane with it. Moreover, whilst on the cervical vertebrae the
capitulum is carried by the centrum (enclosing with the tuberculum a
typical transverse canal for the vertebral artery, etc.), further back it
moves its point of attachment upwards, lying right upon the neuro-central
suture on the tenth and eleventh vertebrae. From the twelfth vertebra
backwards both capitulum and tuberculum are carried by the transverse
process or diapophysis of the neural arch. The ribs of the five or six
lumbar vertebrae are merely vestigial or absent. The ribs of the two sacral
vertebrae are very stout, fusing in the adult with both centrum and neural
arch. Some of the anterior caudal vertebrae also carry ribs, attached
across the neuro-central suture; long before maturity they fuse with their
vertebrae, and then look like transverse processes. Most of the caudal
vertebrae carry also a {439}pair of chevron-bones, and these are continuous
with the intercentral rings of cartilage.
The atlas and the epistropheus or axis are of supreme interest. Crocodiles
are, in fact, the only animals in which these two vertebrae retain all
their constituent hard parts in an almost undisturbed primitive condition
(Fig. 103, 1-4). The basal piece of the atlas-ring, the first basiventral
or intercentrum, carries a pair of long ribs attached by their capitular
portions. A small knob near the dorsal edge of the rib occurs in many
specimens, and is the last remnant of the tubercular portion. The latter
was still complete in Jurassic Crocodiles, for instance in _Metriorhynchus_
(Fig. 103, 2, _t_{1}_). The first centrum joins that of the second vertebra
as its so-called odontoid process, not directly, however, but by the
intercalation of the complete second basiventral, represented by a
cartilaginous disc, and by a large unpaired pyramidal piece (Fig. 103, 3,
^2). This, serially homologous with the ventral half of the atlas-ring, is
the second basiventral intercentrum, wedged in from below between the
odontoid process and the second centrum, with which it soon fuses.
Moreover, it carries the capitulum of the second rib (2, _Cp^2_), the
tuberculum of which is articulated with a facet of the second neural arch
in Jurassic Eusuchia (_t_{2}_). In recent Crocodiles this tubercular
portion is much reduced, and, curiously enough, is attached to a knob which
belongs to the odontoid piece or first centrum. This shifting explains the
apparently anomalous condition that "the atlas of the Crocodiles carries
two pairs of ribs, the second vertebra none." To complete the account of
the atlas we have to mention the separate unpaired piece which lies upon
the two neural arches. It is the detached neural spine, and not the remnant
of a "pro-atlas."
The first and second ribs (_R_{1}_ and _R_{2}_), at least in the recent
forms, are very long and are quite movable. Those of the next five cervical
vertebrae are firmly fixed, short, and adze-shaped. The eighth and ninth
are again long, and make the transition to the thoracic ribs, which are
mostly eight in number, some with uncinate processes. Then follow several
shorter or floating ribs, mostly two or three pairs. The next following
three presacral vertebrae carry no ribs. The two sacral and the caudal ribs
have already been mentioned.
As a rule the vertebral column of recent Crocodiles, Alligators, {440}and
Gavials is composed of twenty-six precaudal vertebrae (namely, nine
cervical, fifteen thoracic and lumbar, two sacral), and about thirty-four
to forty or more caudal vertebrae. Individual variations, including
lop-sided attachment of the iliac bones, are by no means uncommon.
The sternum remains cartilaginous. It consists of an anterior rhomboid
portion, which carries the coracoids and two pairs of ribs, and a posterior
longer and narrower portion formed by the median fusion of the next
following five or six ribs. Posteriorly the sternum bifurcates, each half
carrying two or three ribs, of which the last sometimes loses its proximal
connexion, and thus appears as a xiphisternal process. Ventrally, upon the
anterior part of the sternum lies the longitudinal, originally paired,
episternum. The shoulder-girdle consists of the coracoids and the scapulae,
which fuse with each other into one bony piece on each side. A pre-coracoid
is indicated in fossil forms by a notch in the coracoid.
The space between the posterior end of the sternum and the pubic bones is
occupied by the so-called abdominal sternum, composed of seven pairs of
ossifications, resting upon the ventral side of the rectus abdominis
muscle. Each pair consists of two closely apposed pieces, while the right
and left remain separate in the median line. The last pair is much stronger
than the rest, is more deeply imbedded in the rectus muscle, and is loosely
connected with the anterior margin of the two "pubic" bones.
The limbs are built upon the typical terrestrial pentadactyle type, but
were in the Jurassic species undoubtedly more adapted to swimming
locomotion. The fore-limbs were conspicuously shorter and smaller than the
hind-limbs, and it is only since Tertiary times that the difference has
decreased to a great extent. Ulna and radius remain separate. The proximal
row of carpal bones consists now of the ulnare and radiale, both strong and
distinctly elongated. On the outer side, between ulna and ulnare, lies a
pisiform bone. Upon the radiale follows a compound bone, often imperfectly
ossified towards the median side, and consisting of the first distal
carpal, the centrale, and the intermedium. The third, fourth, and fifth
carpals are fused into one mass. The second distal carpal remains separate.
All five fingers are present and well developed. The number of phalanges of
the pollex is two, of {441}the others three, four, four and three
respectively. During the embryonic development the number of phalanges of
the fourth and fifth finger increases temporarily, to as many as seven on
the fourth, to five or six on the fifth finger. Before the young animal is
hatched the numbers are reduced again, chiefly by fusion of adjoining
phalanges. This hyperphalangeal condition, typical of Plesiosauri,
Ichthyosauri, Cetacea, and several other absolutely aquatic animals,
naturally suggests the descent of the present Crocodiles from more
essentially aquatic ancestors, but hitherto no trace of supernumerary
phalanges has been found in any Jurassic Eusuchia, nor in the Parasuchia
and Pseudosuchia.
The composition of the pelvis is difficult to understand. It consists in
the adult stage of three separate bones, of which two only partake in the
formation of the acetabulum. The broad ilium sends out two processes; the
posterior and stronger articulates with the ischium, which sends out a
short and stout process towards the anterior process of the ilium,
enclosing a foramen. This process contains a separate centre of
ossification, possibly homologous with the true pubis, while each
club-shaped bone, loosely attached to it and directed forwards, generally
called the pubis of the Crocodiles, would then be equivalent to an
epipubis. Neither the "pubes" nor the ischia form a ventral median
symphysis.
The femur is devoid of a prominent inner trochanter. Tibia and fibula are
of almost equal strength. The tarsal elements are, in the adult, reduced by
fusion to five bones. The fibulare is transformed into a typically
projecting, heel-shaped calcaneum, while the intermedium is fused with the
tibiale into a broad astragalus. The first, second, and third distal
tarsalia are much reduced towards the inner side, and form one
wedge-shaped, partly cartilaginous mass. The fourth tarsale lies between
the fibulare and the fourth metatarsal, while the fifth tarsale is
hook-shaped and loosely attached to the outer side of the fourth. It has
lost its metatarsal and the rest of the fifth finger. Embryos are
hyperphalangeal, the fourth toe developing six phalanges, and there are
traces of the fifth toe. The numbers are ultimately reduced to 2, 3, 4, 4,
0 on the five toes. The fourth toe remains without a claw.
SKIN.–The epidermal horny layer is not shed periodically nor in pieces; the
wear and tear is made good imperceptibly. The {442}scales, which cover the
whole body, have a hard, horny, waterproof covering, but between them the
skin is soft. Each scale of the sides, belly, and tail, and especially
those of the lower jaw, shows a little dot or pit. At this spot the
epidermis is not cornified or thickened, and a nerve with sensory
corpuscles ends beneath the bottom of the pit. Sometimes these pits are
filled with débris of cells, and on the lower jaw, especially on the chin,
these organs, instead of forming pits, are raised into little wartlike
prominences.
The scutes or dermal portions of the scales consist of thickened, cutaneous
connective tissue, and are more or less extensively ossified, thus forming
a proper dermal armour. In most recent Crocodilia the armour is restricted
to the back, with occasional osseous plates on the throat, as in
_Osteolaemus_; regular although thin ossifications in the ventral scutes
occur in the Caimans only. The Crocodile and Alligator skins of commerce
consist entirely of the tanned cutis, minus the epidermis and the horny
coverings of the scutes. In some fossil genera the ventral armour was
extensively developed, especially in _Teleosaurus_, in some genera to the
exclusion of dorsal ossifications. The armour of the recent forms consists,
so far as the large scutes are concerned, of a considerable number of
scutes, which are arranged in transverse rows, each row corresponding with
one skeletal segment of the trunk proper. Mostly there is a detached
cluster of scutes on the back of the neck. On the trunk some of the scutes
are larger and more crested than others, and form in their totality a
variable number of longitudinal rows. The median pair is generally the most
conspicuous on the back. Some of the more lateral rows of keeled scutes
converge more and more towards the tail, the inner rows drop out
imperceptibly, and two lateral rows combine on the middle of the tail into
an unpaired series of vertical blades. These are no longer bony, but show
more strongly developed horny sheaths; they are very flexible, and
transform the tail into an effective propelling organ.
Most of the larger scutes and the upper surface of the bones of the skull
have a peculiar gnawed-out, almost honeycombed appearance, as is usual
wherever most of the cutis itself is transformed into bone or co-ossifies
with underlying bone, while the uppermost layers and the horny layer of the
epidermis are much reduced and thinned out.
{443}All the recent Crocodilia possess two pairs of skin-glands, both
secreting musk. One pair is situated on the throat, on the inner side of
the right and left half of the lower jaw. The opening of the gland, visible
from below (see the figure of _Crocodilus niloticus_, p. 461), is
slit-like, and leads into a pocket, which in large specimens is of the size
of a walnut; the bag is filled with a smeary pale brownish substance, a
concentrated essence of musk, much prized by natives. The secretion is most
active during the rutting time, when the glands are partly everted. My
young Crocodiles and Alligators often turned them inside out, like the
finger of a glove, when they were taken up and held by force. The other
pair lies within the lips of the cloacal slit, and is not visible from the
outside. The use of these strongly scented organs, which are possessed by
both sexes, is obviously hedonic. The sexes are probably able to follow and
find each other, thanks to the streak of scented water left behind each
individual.
The TONGUE is flat and thick, attached by its whole under-surface, so that
it can be elevated but not protruded. It fills the whole space between the
two halves of the lower jaw behind their symphysis. The dorsal surface
shows numerous irregular polygonal fields, in the middle of most of which
opens the duct of a large mucous gland. Tactile and gustatory corpuscles
are scattered over the surface in the shape of tiny wartlike elevations.
The hinder margin of the tongue is raised into a transverse fold, which, by
meeting a similar fold from the palate, the velum palatinum, can shut off
the mouth completely from the deep and wide cavity of the throat, which
leads of course into the gullet. Dorsally the choanae open into this
cavity; and since the narial passages are transformed into long tubes,
completely surrounded by bone, Crocodiles can lie submerged in the water,
with only the nostrils exposed and with the mouth open, and breathe without
water entering the windpipe. The opening of the latter, the glottis, is a
longitudinal slit, protected by the laryngeal cartilages, opened and closed
by muscles. There is also a pair of membranous folds within the glottis,
which serve as vocal cords. Ventrally below the larynx lies the
cartilaginous, broad, shield-shaped hyoid; on the sides are attached the
short hyoid horns. The TRACHEA is long, consists of about sixty or more
complete cartilaginous rings, and divides into two short bronchi, likewise
protected by complete rings. The trachea is depressed; its transverse
diameter decreases {444}from the glottis backwards. The LUNGS have attained
a high degree of efficiency. Each lung is an oval sac, and is transformed
into a complicated system of tubes, at the end of which are the countless
honeycomb-like respiratory cells, the whole lung being spongy. The main
bronchus is continued straight down to the posterior end of the lung, and
sends off during its course regular secondary bronchi, and these send off
tertiary bronchi. The whole arrangement is very regular, the tubes coming
off like rows of organ-pipes. Each lung hangs freely in the thoracic
cavity. Besides its ventral attachment by its arteries, veins, and the
bronchus, it is connected by loose tissue with the liver and the
pericardial septum. Each half of the thoracic cavity is partitioned off
from the abdominal cavity by a strong transverse mesenteric lamella. The
partition between the lungs and the stomach is at first simple, it then
divides, to enclose the liver; the anterior partition passing between liver
and lung to the inner surface of the sternum; the posterior lamella between
the liver and the stomach. Both meet on the ventral surface of the liver,
and are continued into or attached to the peculiar "diaphragmatic" muscle.
This is covered by the internal rectus muscle of the abdomen, arising from
the last pair of abdominal ribs near the pubic bones; it is innervated by a
branch of the last precrural nerve, and extends as a broad but thin
muscular sheath (always within and unconnected with the abdominal wall) to
the ventral posterior vein of the liver; thence it is continued as an
aponeurosis, together with the peritoneal lamella mentioned above, to the
inner surface of the sternum. Contraction of this singular muscle
indirectly widens the pulmonary cavity, and thereby directly aids
inspiration. It acts consequently like the diaphragm or midriff of Mammals,
although it is morphologically an entirely different muscle.
The STOMACH is smaller than one might expect from the fact that large
Crocodiles can eat up nearly a whole man; but a great deal of their prey is
stowed away preliminarily in the wide gullet until the rapid, powerful
digestion, which dissolves every bone, makes room in the stomach. This
consists of a wide, somewhat globular gizzard, rather muscular, with a pair
of tendinous centres like those of birds, and a much smaller pyloric,
globular, more glandular compartment. It leads into the duodenum, which is
coiled up into a double loop, and receives at its end the {445}hepatic and
pancreatic ducts. The small intestine is narrow, and is stowed away in a
few irregular coils; the rectum is wide; a caecum is absent.
The CLOACA is peculiar. The coprodaeum and urodaeum, cf. p. 498, are
confluent, and form a wide, oval bag, closed in front and behind by strong
sphincters, and it acts normally as a urinary receptacle. In the dorsal
wall open the two ureters; a little towards the sides, and ventrally, open
the two oviducts, on the right and left, near the base of the clitoris.
Then follows a transverse, soft, muscular fold, which shuts off this cavity
from the proctodaeum or outermost chamber. In the latter is stowed away the
rather large copulatory organ. It arises out of the medio-ventral wall of
the cloaca, and has a deep, longitudinal groove on its morphologically
dorsal side for the conduction of the sperma, the vasa deferentia opening
near its basal end. On either side of the root of this organ, in both sexes
alike, opens a peritoneal canal, wide enough in large specimens to pass a
goose-quill. The outer opening of the cloaca forms a longitudinal slit;
within it, dorso-laterally, are the openings of the two anal musk-glands.
The KIDNEYS are much lobed. The testes are long and oval; the ovaries are
much elongated and flat; and the eggs contained therein in great numbers
are extremely small, except those which ripen during the time of
propagation.
The VASCULAR SYSTEM has attained the highest state of development of all
reptiles. The heart is practically quadrilocular, the partition between the
right and left ventricle being complete; but there is still a small
communication, the foramen Panizzae, which lies in the middle of the wall
common to both aortae, where they leave their respective ventricles. The
left aortic arch conveys all the arterialised blood out of the left
ventricle, and supplies head, neck, trunk, and tail. The right aortic arch,
coming from the right ventricle, supplies venous blood, mixed with what
little arterial blood it receives through the foramen Panizzae, to most of
the viscera. On a level with the stomach both descending aortic arches are
still connected with each other; the left aorta supplies most of the gut;
the right, the trunk and the kidneys.
The outer EAR lies in a recess, dorsally overhung by the lateral edge of
the bony squamoso-postfrontal bridge; and this {446}carries a flap of skin,
provided with muscles, to close the ear tightly. The tympanic membrane is
visible at the bottom of the recess; shining through it is part of that
cartilage which is homologous with the malleus of the auditory ossicular
chain; the outward extension of the latter on its way to the mandible,
behind the joint, passes as a partly cartilaginous string through the
slit-like hole which is visible at the back of the skull, between the
quadrate and the latero-occipital wing.
The EYES have, besides the lower and upper lid, a third, the nictitating
membrane, which can be drawn over the front of the eyeball. In the upper
lid lies a cup-shaped bony plate of variable size. The pupil contracts into
a vertical slit. The iris is greenish.
[Illustration: FIG. 104.–Map to illustrate the present distribution of
Crocodilia.]
The recent GEOGRAPHICAL DISTRIBUTION of the various kinds of Crocodilia
loses its mystery when we recollect that during the Tertiary period
Alligators, Crocodiles, and long-snouted Gavials existed in Europe. The
solitary species of Alligator in China is the last living reminder of their
former Periarctic distribution. The group, taken as a whole, is otherwise
now intertropical, Crocodiles alone inhabiting the Palaeo-tropical region,
together with long-snouted forms in the Oriental sub-region, while
Alligators and Caimans, with a few Crocodiles, live in America.
They are all rapacious, doing much damage by their predatory habits, and
are fierce and sulky in temper. But the danger to man differs much in
different countries. While Crocodiles are dreaded in some localities, they
are in others considered almost harmless, and men swim through the haunted
waters without hesitation. It seems as if certain old and wily individuals
turn into man-eaters, just like tigers and lions.
{447}Their home is the water, in which they pass the night, their time of
hunting. The prey is either patiently watched or stalked, and nothing falls
amiss. Water-birds are seized by the beast, which rises imperceptibly from
below. Some species are said to make use of their powerful tails for
hitting the victim and even jerking it into the mouth. The strength of
their jaws is enormous, and they do not let go what they have seized,
unless, in the case of a man, he has the presence of mind and the
opportunity to dig his fingers into the monster's eyes whilst being dragged
down.
In the morning they crawl on to sandbanks, or on to logs of wood, which
they closely resemble, in order to bask, mostly in such a position that on
the slightest alarm they can plunge into the water. For this reason they
frequently make a half circle before they settle down to rest, with the
heads turned towards the river. There they bask all day long, apparently
fast asleep, often with gaping mouths. But their sense of hearing and of
sight is sharp, and they learn from experience, old individuals being by
far the most wary. Commercially the skins are now of considerable value.
The flesh is white, and is tolerable eating but for the combination of
fishy and musky odour, which, although faint, is not to everybody's liking.
All the species have a voice, a kind of loud, short bark or croak, heard at
night and when angered. The female lays several dozen or even three score
white, oval, hard-shelled eggs in the sand, well out of the reach of
moisture; and some species construct an elaborate kind of nest. The mother
watches it, takes care of and fights for her offspring, numbers of which
fall an easy prey to large storks, fishes, and to the stronger members of
their own kind.
In the cooler countries they hibernate in the ground; and in hot countries,
which are subject to drought, some kinds aestivate in the hardened mud; or
they migrate. When during a prolonged drought on the island of Marajó, at
the mouth of the Amazon, the swamps and lakes were dried up, the Alligators
migrated towards the nearest rivers, and many perished in the attempt. On
one farm were found 8500 dead, and at the end of Lake Arary more than 4000.
Such occurrences in bygone times may perhaps explain the masses of bones
found here and there in a fossil state.
{448}The age to which Crocodiles can live is quite beyond calculation. They
are capable of propagation long before they are anything like half-grown,
maybe at an age of little more than ten years; then they continue to grow
perhaps for more than one hundred years, until they die.
It is customary to divide the Eusuchia, most of which are extinct, into a
longirostral and a brevirostral section. In the former the snout is much
elongated and narrow, and the nasal bones, although they are sometimes very
long, do not reach the nasal groove. The mandibular symphysis is very long,
and is formed not only by the dentary but also by the splenial bones. In
the brevirostral section the snout is shorter, sometimes broad and rounded
off, and the nasal bones are supposed to reach the nasal groove, or at
least to approach it very nearly; the mandibular symphysis is formed by the
dentaries only. But these distinctions are quite arbitrary, and there exist
all kinds of intermediate forms. For instance, in _Goniopholis_ and
_Diplocynodon_, which are both undoubtedly near allies of the recent
Crocodiles and Alligators, the nasal bones are considerably removed from
the nasal groove; and in _Crocodilus cataphractus_ they are separated even
from the premaxilla by the medio-dorsal suture of the maxillaries. Again,
in _Goniopholis_ the mandibular symphysis is so long that it comprises part
of the splenial bones. Both typically long- and short-snouted forms occur
already in the Upper Oolite, but in the Lower Jurassic age only
long-snouted kinds seem to have existed. The latter cannot easily be
connected with _Belodon_, one of the Parasuchia, on account of the position
of the nostrils; the mere shortening of the long premaxillaries of
_Belodon_ would not transfer its distinctly paired nostrils to the anterior
end of the premaxilla. To account for the position of the nasal groove in
the Eusuchia, we have to go back to a primitive condition, such as that of
the Pseudosuchian _Aëtosaurus_, and this consideration shows that the
Parasuchia and Eusuchia are collateral branches.
The Eusuchia have been split into many families. Zittel, for instance,
divides them into ten, some of them on insufficient grounds, since there
are too many intermediate forms; and more, sometimes quite unexpected,
modifications are still being found. Several of the accepted families
represent collateral or convergent lines of development.
{449}[Illustration: FIG. 105.–Group of Crocodiles. A long-snouted Gharial
or Gavial (_Gavialis gangeticus_) on the top of _Crocodilus acutus_; a Nile
Crocodile (_C. vulgaris_) in the foreground; _C. palustris_, a "Mugger," in
the right upper corner. Observe the peculiar floating attitude of the young
specimen.]
{450}There is the same tendency to transfer the choanae further back, owing
to the formation of a solid secondary roofing in of the mouth, to transform
the amphicoelous into procoelous vertebrae, to reduce the supratemporal
foramina, and to obtain a better development of the dorsal armour, whilst
that on the ventral side is gradually reduced. Lastly, there is a tendency
towards a shortening and broadening of the snout, a condition which has
reached its culmination in the Alligators, while the Gavials are survivals
of another branch. The notches in the premaxilla, for the reception of some
of the lower teeth, have also been acquired independently. Although the
recent Crocodilia cannot now, as has been pointed out by Boulenger, be
separated into different families, no valid diagnoses being possible owing
to the existence of _Tomistoma_, their phylogeny shows them to belong to at
least two heterogeneous groups.
KEY TO THE GENERA OF RECENT CROCODILIA.
I. Snout very long and slender. The mandibular symphysis extends at least
to the fifteenth tooth, and is partly formed by the splenial bones.
_a._ Nasal bones very small, and widely separated from the
premaxillaries .......... _Gavialis gangeticus_, p. 451.
_b._ Nasal bones long, in contact with the premaxillaries ..........
_Tomistoma schlegeli_, p. 453.
II. Snout not slender, but triangular or rounded off. The mandibular
symphysis does not reach beyond the eighth tooth, and does not reach the
splenial bones.
_a._ Fourth mandibular tooth fitting into a notch in the upper jaw.
1. Without a bony nasal septum .......... _Crocodilus_, p. 454.
2. Nasal bones dividing the nasal groove .......... _Osteolaemus_,
p. 466.
_b._ Fourth mandibular tooth fitting into a pit in the upper jaw.
1. Without a bony nasal septum .......... _Caiman_, p. 471.
2. Nasal bones dividing the nasal groove .......... _Alligator_,
p. 466.
FAM. 1. TELEOSAURIDAE, in the Lias and Oolite of Europe; marine.–Snout very
long and slender. Nasals widely separated from the premaxillae by the
maxillaries. Choanae at the posterior end of the palatines. In front of the
eye a small sub-lacrymal foramen. Supratemporal foramina large. Vertebrae
amphicoelous. Anterior limbs scarcely half as long as the posterior pair.
The dermal armour consists of two rows of broad scutes on the back, while
the belly is protected by a shield of numerous bony scutes, which are
connected with each other by sutures. Teeth numerous and rather slender.
General appearance like that of Gavials.
{451}_Teleosaurus_ of the Middle and Upper Oolite in England and France.
Snout very slender. Nasals narrow and short. The under side is protected by
a beautifully finished armour, consisting of a square breast-shield of four
rows of bony scutes, and a larger, long, oval shield on the belly, with
about six longitudinal and seventeen transverse rows of scutes.
_Mystriosaurus_, of the Upper Lias in France and Germany, reached a length
of 15 feet, and is characterised by an additional series of keeled but
smaller caudal plates running parallel with the middle pairs, which are
neatly sutured together.
FAM. 2. METRIORHYNCHIDAE, in the Upper Oolite of Europe; marine.–Nasals
broad posteriorly, sometimes extending with a pointed wedge very near the
premaxillae. Without sub-lacrymal foramina. Eyes with a ring of
ossifications in the sclerotic. Dermal armour unknown. Vertebrae and
choanae like those of the previous family. _Metriorhynchus_ and
_Geosaurus_.
FAM. 3. MACRORHYNCHIDAE, in the freshwater deposits of the Purbeck,
Wealden, and Greensand of Europe. Snout long and slender. The nasals are
narrow, and so elongated that they meet a similar long extension of the
premaxillaries. Choanae between the palatines and pterygoids. Vertebrae
amphicoelous. Dermal armour consisting of two imbricating dorsal and eight
ventral rows, e.g. _Pholidosaurus_ of the English Wealden.
FAM. 4. GAVIALIDAE.–Snout long and slender. The choanae are situated
entirely within the pterygoids. Vertebrae procoelous. Members of this
family make their first appearance in the littoral marine deposits of the
Upper Chalk of Europe and North America; others are common in tertiary,
marine, and freshwater deposits, whilst only two genera and species occur
now in the Oriental sub-region.
_Thoracosaurus_ in the Upper Chalk of New Jersey and France and Belgium is
intermediate between _Gavialis_ and _Tomistoma_. The prefrontal bones are
very small, while the lacrymals are very long and surround the nasals
posteriorly. The nasals themselves are slender, and reach the posterior
likewise long and narrow prolongations of the premaxillaries.
_Gavialis._–The snout is extremely long and slender. The mandibular
symphysis is so long that it comprises a great portion of the splenial
bones, and extends backwards almost to the level of the last teeth and to
the palatal foramina. The nasal {452}bones are very short, and are
separated from the premaxillaries by the long suture of the maxillaries.
About twenty-eight upper and twenty-five lower teeth on each side.
_G. gangeticus_, the only recent species, is essentially Indian, inhabiting
chiefly the basins of the Ganges, Brahmaputra, and Indus; it occurs also in
the Mahanadi of Orissa and in Arakan, but does not live in the Irrawaddy,
nor in the Narbada, Kistna, and farther south. In spite of its great size,
which reaches 20 feet or even more, it is harmless, and lives entirely upon
fish; hence its Hindustani name, _gharial_, meaning fish-eater, of which
the generic name is a corruption.
The nuchal and dorsal scutes form a continuous shield, but there are two
small postoccipital scutes. General colour, dark olive-brown above; the
young are paler, with dark markings. The male is remarkable for several
peculiarities. The nose is very much swollen, and can be inflated like a
bag when the nostrils are closed. In connexion herewith, probably produced
by the recoil of the air in the long narial passages towards the choanae or
posterior nares, there is a pair of hollow globular swellings, in large
specimens of the size of a goose's egg. The shell of these globes is formed
by the dorsal wings of the palatine bones above the floor of the choanae,
and they extend forwards to the right and left of the ethmoid almost to the
vertical downward process of the prefrontals.
[Illustration: FIG. 106.–Skull of _Gavialis gangeticus_ (the Gharial). × ⅛.
_F_, frontal; _J_, jugal; _L_, lacrymal; _Mand_, mandible; _Mx_, maxillary;
_Na_, nasal; _Par_, parietal; _Pm.c_, premaxillary; _Prf_, prefrontal;
_Ptf_, postfrontal; _Qj_, quadrato-jugal; _Sq_, squamosal.]
Although the Gharial is common enough, we know next to nothing about its
habits, and in zoological gardens it is rather rare. A. Anderson[139] has,
however, made the following observations. Forty eggs were dug out of the
sand, where they were {453}lying in two tiers, twenty below and twenty
above, with a foot of sand between. The young ran with amazing rapidity the
moment they were hatched. Some of them actually bit his fingers before he
had time to remove the shell from their bodies! The length of these
new-born creatures was 15 to 16 inches, 9 of which belonged to the long and
slender tail.
Several fossil species have been described from the Pliocene deposits of
the Sivalik Hills of India; and in the same district occurred the closely
allied _Rhamphosuchus crassidens_, which reached the gigantic length of
about 50 feet!
_Tomistoma._–The general configuration of the skull and snout is that of
_Gavialis_, but the nasal bones are long and reach the premaxillaries,
although not the nasal groove, thereby separating the maxillaries. The
first and fourth mandibular teeth fit into notches of the upper jaw, while
most of the others fit into pits between the teeth of the upper jaw. About
twenty upper and eighteen lower teeth on each side.
_T. schlegeli_, the only species, reaches a length of 15 feet; it inhabits
the rivers and swamps of Borneo, Malacca, and Sumatra. Fossil specimens of
_Tomistoma_ have been found in the Miocene of Malta and Sardinia.
_Gavialosuchus_ of the Miocene of Hungary is closely allied.
FAM. 5. ATOPOSAURIDAE.–The few members of this family, _Atoposaurus_,
_Alligatorium_, and _Alligatorellus_, lived in the Upper Oolitic period of
France, and were small, about one foot in length. The vertebrae are
amphicoelous. The nasal groove is divided by a prolongation of the nasal
bones. The head is short, and in its general shape rather like that of a
lizard.
FAM. 6. GONIOPHOLIDAE, in the Purbeck and Wealden of Europe and the
corresponding level of North America. The vertebrae are amphicoelous. The
choanae are still elongated but are situated between the palatines and
pterygoids. The premaxillaries are rather large, and each sends a broad
triangular process between the nasal and maxillary. The nasals are broad
and are well separated from the nasal groove. The splenials help to form
the mandibular symphysis.
_Goniopholis._–The general configuration of the skull is rather like that
of _Crocodilus vulgaris_. There is a pair of deep notches in the upper jaw
for the reception of the lower canine teeth. _G. simus_ and _G. crassidens_
in England and continental Europe, and {454}others in Colorado, were
large-sized Crocodiles, some with a skull 2 feet in length. The dermal
armour consisted of a pair of dorsal rows, a thoracic and an abdominal
shield, composed as in the Teleosauridae of six to eight longitudinal
sutured rows.
FAM. 7. CROCODILIDAE.–Beginning in the Upper Cretaceous period of Europe
and North America, many forms of Crocodiles, Alligators, and Caimans
existed in the Tertiary period in America, Europe, and India; persisting in
Europe until the Plistocene. The vertebrae are procoelous. The choanae are
completely surrounded by the pterygoids. The nasals reach the nasal groove,
except in _Crocodilus cataphractus_. The orbits are larger than the small
supratemporal fossae, and always continuous superficially with the lateral
temporal fossae, the postfronto-jugal bridge not reaching the surface. The
dorsal armour consists of more than one pair of longitudinal rows, while
the ventral armour is much reduced in thickness or absent.
_Diplocynodon._–Common in the Oligocene and Miocene of Europe, e.g. _D.
hastingsiae_. The skull resembles that of the Alligators, but has a pair of
lateral notches in the premaxilla for the reception of the third, and
sometimes also of the fourth mandibular tooth. The ventral armour is still
rather strong.
_Crocodilus._–The fourth mandibular tooth fits, as a rule, into a notch in
the upper jaw. The other teeth are more or less interlocked with those of
the other jaw. The fifth upper tooth is the largest. The nasal bones form
the posterior border of the nasal groove, but do not extend into it as a
septum. The bony scutes of the dorsal shield are keeled, and stand closely
together, being rarely united by suture; and they form from four to six
principal rows.
Crocodiles have occurred since the Upper Chalk in Europe; many species
existed in the Tertiary epoch in Europe and North America, decreasing in
numbers in the Pliocene and disappearing with the beginning of the
Plistocene. About ten recent species are known, and these have now a
somewhat scattered distribution; namely, three species in Africa, one of
them extending into Syria; three in tropical America and the West Indian
Islands; the rest in the Malay, Indian, and North Australian countries.
_C. palustris._–The "Mugger" of India. The premaxillo-maxillary suture is
transverse, as in the Alligators. The adults {455}retain the five teeth in
each half of the premaxilla. The mandibular symphysis is short, extending
only to the level of the fourth or fifth tooth. The snout is stout, rather
broad; the top of the head is rough but without any ridges. The upper and
lower jaw each contain nineteen teeth on either side. The nuchal scutes,
six in number, are packed closely together, the four biggest forming a
square. Four smaller scutes are arranged in a curved line on the occiput.
The dorsal shield is composed of four, sometimes of six rows of larger
scutes, of which the central pair is the broadest. The fingers are webbed
at the base; the outer toes are broadly webbed, and the outer edge of the
hind-limbs is turned into a serrated fringe. The general colour of the
upper parts is dark olive-brown; the young are pale, with black spots. The
length of twelve feet is considered a fair average size for a large
specimen.
[Illustration: FIG. 107.–Dorsal view of the skull of _Crocodilus
palustris_. × ⅛. The arrangement of the nuchal scutes is shown in the upper
left-hand corner; _E_, position of the ear-flap.]
This, the "Marsh Crocodile," has a wide distribution. It inhabits the
rivers, ponds, tanks, and marshes of India and Ceylon, extending eastwards
through Burma and Malacca into most of the Malay islands, westwards into
Beluchistan. This species is frequently venerated by the Hindoos, and is
kept in a kind of domesticated condition, attended by fakirs. One of the
most famous crocodile ponds, the so-called "mugger-peer," lies in an oasis
of the sandy stretches to the north-west of Karachi. A. L. Adams has
described a visit to this pond.[140]
"The greater pond is about 300 yards in circumference, and contains many
little grassy islands, on which the majority of the Crocodiles were then
basking; some were asleep on its slimy sides, others half submerged in the
muddy water, while now and then a huge monster would raise himself upon his
diminutive legs, and waddling for a few paces, fall flat on his belly.
Young ones, {456}from a foot in length and upwards, ran nimbly along the
margin of the pond, disappearing suddenly in the turbid waters as soon as
we approached. The largest crocodile lives in a long narrow tank separated
from the others. The fakirs, and natives who worship in the neighbouring
temples, have painted his forehead red; they venerate the old monster,
making a salaam to his majesty whenever he shows himself above water. A
handsome young Beloochee, whose occupation it was to feed the animals,
informed us that this specimen was upwards of 200 years old, and that by
way of a 'tit-bit' he was in the habit of devouring the young crocodiles.
During our visit this enormous brute was asleep on the bank of his
dwelling-place, and seemed quite indifferent to our presence, although we
came within a foot of him, and even attempted to arouse him by rubbing his
nose with a leg of goat's flesh, which, however, a young one greedily
seized. Our attendant tried in vain to excite their ferocity, but beyond a
feeble attempt to snap their trenchant teeth, the animals showed no
disposition to attack us.
"A pony was wading about in the pond and feeding on the grassy hillocks,
but the crocodiles took no notice of him.
"The crocodiles dig deep in the sand, under the neighbouring date-trees,
and there deposit their eggs. Quantities of deciduous teeth, of various
sizes, were strewn along the slimy sides of the pond.
"Strangers are expected to stand treat, not only by the fakirs and natives,
who gain a livelihood by hanging about the pond and showing the monsters,
but even the crocodiles themselves seem to anticipate a feast, and on the
arrival of a party come out in unusual numbers. Accordingly, we had a goat
slaughtered, during which operation the brutes seemed to rouse themselves,
as if preparing for a rush. Then our guide, taking piece after piece of the
flesh, dashed it on the bank, uttering a low growling sound, at which the
whole tank became in motion, and crocodiles, of whose existence we had been
before ignorant, splashed through the shallow water, struggling which would
seize the prize. The shore was literally covered with scaly monsters,
snapping their jaws at one another."
Sir J. Emerson Tennent[141] has had many opportunities of studying the
habits of the Marsh Crocodile. According to him {457}it is essentially
cowardly in its instincts, and hastens to conceal itself on the approach of
man. One of these creatures, which was overtaken in the jungle by a
gentleman riding on horseback, fled to a shallow pool, and thrusting its
head into the mud till it covered up its eyes, remained motionless, in
profound confidence of perfect concealment.
"There is a popular belief that the crocodile is exceedingly sensitive to
tickling, and that it will relax its hold of a man if he can only contrive
to reach and rub with his hand the softer parts of its under side. An
incident of some reality in this piece of folk-lore came under my own
observation. One morning ... we came suddenly upon a crocodile asleep under
some bushes of the buffalo-thorn, several hundred yards from the water. The
terror of the poor wretch was extreme when it awoke and found itself
discovered and completely surrounded. It was a hideous creature, upwards of
10 feet long.... It started to its feet and turned round in a circle,
hissing and clanking its bony jaws, with its ugly green eye intently fixed
upon us. On being struck with a stick, it lay perfectly quiet and
apparently dead. Presently it looked cunningly round, and made a rush
towards the water, but on a second blow it lay again motionless and
feigning death. We tried to rouse it, but without effect; pulled its tail,
slapped its back, struck its hard scales, and teased it in every way, but
all in vain; nothing would induce it to move till, accidentally, my son,
then a boy of twelve years old, tickled it gently under the arm, and in an
instant it drew the limb close to its side and turned to avoid a repetition
of the experiment. Again it was touched under the other arm, and the same
emotion was exhibited, the great monster twisting about like an infant to
avoid being tickled."
In the dry season, when the tanks become exhausted, the Marsh Crocodiles
have occasionally been encountered in the jungle, wandering in search of
water. During a severe drought, in 1844, they deserted a tank near
Kornegalle, and traversed the town during the night, on their way to
another reservoir in the suburb; two or three fell into the wells; others,
in their trepidation, laid eggs in the street, and some were found
entangled in garden fences and killed.
Generally, however, during the extreme drought, when unable to procure
their ordinary food from the drying up of the {458}watercourses, they bury
themselves in the mud and remain in a state of torpor till released by the
recurrence of rains.
[Illustration: FIG. 108.–Dorsal view of the skull of _Crocodilus porosus_.
× about ⅙. _Col_, buttress connecting the postfrontal with the jugal and
ectopterygoid; _F_, frontal; _Jg_, jugal; _Mx_, maxillary; _Na_, nasal;
_P_, parietal; _Pm_, premaxilla; _Pof_, postfrontal; _Pr.f_, prefrontal;
_Q_, quadrate; _Qj_, quadrato-jugal; _R_, the characteristic ridge on the
prefrontal bone; _Sq_, squamosal; _T_, perforations in the premaxilla
caused by a pair of lower incisor teeth.]
_C. porosus_ s. _biporcatus_.–The premaxillo-maxillary suture on the palate
does not form a transverse line, but is W-shaped, and extends backwards as
in the rest of the species of Crocodiles to be described. This Indian
species is easily recognised by the prominent longitudinal ridge which
extends in front of each eye, over the prefrontal bones, and by the absence
of sub-occipital scutes. The nuchal scutes consist of four large ones,
which form a square, and one or two smaller scutes on each side. The dorsal
shield contains four to eight principal longitudinal rows. The digits,
webs, and the serrated fringe of the legs are like those of _C. palustris_.
The head and snout, however, are distinctly longer, and more slender in
proportion, and the adult has only four teeth in each premaxilla. The
general colour is dark olive-brown. Young specimens, as usual, are much
paler and are spotted with black.
This species attains a much larger size than the Marsh Crocodile. Specimens
of 15 to 20 feet in length are not uncommon, and there is a record of one
monster of 33 feet. Consequently this is, both in bulk and length,
undoubtedly the largest species of recent reptiles. It is essentially an
inhabitant of tidal waters or estuaries, frequently entering salt water and
going out to sea. Herewith corresponds its wide distribution, namely, the
whole coast of the Gulf of Bengal, extending to {459}Southern China, and
across the Malay Archipelago to the northern coasts of Australia. Eastwards
it ranges to the Solomon Islands and even to Fiji. Curiously enough, it
does not seem to occur on the west coast of India.
According to Tennent it is ready to assail man when pressed by hunger, and
the same authority mentions the following serio-comic incident. A man was
fishing, seated on the branch of a tree overhanging the water, and to
shelter himself from the drizzling rain he covered his head and shoulders
with a bag folded into a shape common with the natives. While in this
attitude, a leopard sprang upon him from the jungle, but missing its aim,
seized the bag and not the man, and fell with it into the river. Here a
crocodile, which had been eyeing the angler in despair, seized the leopard
as it fell, and sank with it to the bottom.
I have had some personal experience in the bringing up of the young of this
species. Two dozen of them had come from Ceylon when quite young, only one
foot long. At first they were very shy, and huddled together in their tank,
but they took food greedily–strips of fish and, later on, sheep's heart.
When frightened they emitted peculiar, high-pitched, half-croaking sounds.
Some of them snapped at the finger when touched; others were of a more
gentle disposition; the shy ones were undoubtedly the most vicious. Within
one year they grew to 18 or 20 inches, and added much to their bulk. Then
they were transferred to a deeper and larger tank in a greenhouse, in which
they could roam about at liberty. In the daytime they dozed on the margins
of their pond, mostly in such a position that, at the slightest alarm, they
could plunge back into the water. The strongest specimen left the tank
entirely, and took up its favourite place for basking on the stump of a
tree, to reach which it had to climb up a rough wall of stones. After three
years, several had grown to the length of three and a half, and even four
feet, and had by this time become formidable pets. Although handled
frequently, they never became tame, the only change in their behaviour
being that, instead of rushing off in a fright, and hiding for half an hour
at the bottom of the tank, they became more vicious and confident, making
for and snapping at the hand which fed them. The nights were spent
regularly in the water, either floating {460}with just the nostrils
exposed, or in search of food, frogs being their favourite prey, while
their main sustenance consisted of "lights," with an occasional mouse, or a
piece of solid meat by way of an _entrée_. Small pieces were bolted. The
tough "lights," namely lungs with the windpipe and blood-vessels, were
causes of great quarrels. Two or three would get hold of a lump of this
kind, tearing at it, and twisting and rolling over in opposite directions.
The supply of warm water came through a stout pipe of red india-rubber, and
this was an irresistible attraction to the crocodiles. On many a morning
the tube was found twisted into a knot, one of the creatures having spent
hours in chewing it and in trying to wrench it off. In order to aid
digestion they swallowed pebbles. The most favourable temperature of the
water was 85° F.; if below 75° F. they refused to eat, but a continued
exposure to 60° F. did not hurt them. When the temperature rose above 95°
F. they left the water, although means had to be taken to prevent them from
lying on the hot-water pipes.
[Illustration: FIG. 109.–Dorsal view of the skull of a very old specimen of
_Crocodilus niloticus_, in which most of the bony sutures are obliterated,
× about ⅒.]
_C. niloticus_ s. _vulgaris_.–The premaxillo-maxillary suture on the palate
is W-shaped. The nasal bones form only a small part of the posterior border
of the nasal groove. There are eighteen or nineteen upper and fifteen lower
teeth on each side. In old specimens some of the anterior mandibular teeth
perforate the premaxillae, as indicated in Fig. 109, and they even pierce
through the integument so as to be visible from above. The nuchals are
composed of four large scutes, with a smaller one on each side and
sometimes one behind, and there is a row of smaller pieces across the
occiput. The dorsal shield contains six to eight principal longitudinal
rows. The fingers are webbed at the base; the outer toes are very broadly
webbed; and there is a serrated fringe on the outer side of the leg. The
general colour of the adult is dark olive-brown; the young are paler, with
black spots and vermiculations. The under parts are yellowish white.
{461}The Nile Crocodile is essentially African, ranging from the Senegal to
the Cape and to Egypt. It is also very common in Madagascar. Nothing is
known about its occurrence in Arabia, but a few specimens of rather small
size seem still to exist in Syria, in the Wadi Zerka, an eastern tributary
of the Jordan.
Even in historical times the Crocodile must have been very common in lower
Egypt, to judge from the number of mummies preserved by the old Egyptians.
Now it is practically exterminated, and there are scarcely any left below
Wadi Halfa.
[Illustration: FIG. 110.–Ventral view of a young _Crocodilus niloticus_,
showing the arrangement of the bony scutes and the two openings of the
musk-glands on the lower jaw. The upper right-hand figure shows on a larger
scale the disposition of the nuchal scutes and the first row of dorsal
scutes.]
Such a conspicuous and dangerous creature has naturally always enjoyed
notoriety. It is well described in one of the oldest writings of the world,
the Book of Job. "Canst thou draw out leviathan with an hook? or his tongue
with a cord which thou lettest down?... His scales are his pride, shut up
together as with a close seal. One is so near to another, that no air can
come between them. They are joined one to another, they stick together,
that they cannot be sundered.... Lay thine hand upon him, remember the
battle, do no more." Bows and arrows, spears and clubs, are of little avail
against such a {462}monster; the dragging out of a hooked, full-grown
specimen requires many men and is a formidable task. Of course firearms
have changed all this, and its invulnerability to bullets is nonsense. It
is true that a bullet sent into the head is generally ineffective, since it
is a hundred to one that the bullet does not hit the small brain, and even
if it does, the creature sinks to the bottom and is lost to view until
decomposition sets in and the gases developing in the body cause it to
float.
Herodotus has quaint stories about these crocodiles and their worship.
Amongst other stories he mentions that the bird _Trochilus_, supposed to be
the _Pluvianus aegyptius_, a kind of Plover, slips into the gaping mouth to
pick off the leeches which infest the reptile's gums. "In Egypt it is
called Champsa, but the Ionians call them κοκοδρίλοι on account of the
resemblance to the lizards which live on their garden walls." This is in
fact the origin of the name crocodile, κόρδυλος being the ancient Greek for
lizard and newt. With reduplication κορκόρδυλος and by metathesis
ultimately κροκόδειλος. The Arabic name is _ledschun_.
The story about the Plover seems to be true. These birds are sometimes seen
sitting upon basking crocodiles, and since the latter are in the habit of
resting, perhaps half asleep, with the mouth wide open, it is possible that
these agile birds do pick their teeth, and that they, being also very
watchful, by their own cry of warning and by fluttering off on the approach
of danger, give the alarm to the crocodiles and thus benefit them in more
than one way.
But the equally old story about the Ichneumon or Mongoose is an idle
invention. Mongooses are partial to eggs, but they certainly prefer those
of hens and other birds to those of the crocodile, which are far too hard
and strong to be broken by such a little animal. Moreover, as we shall see
presently, the eggs are far too well concealed.
The best account of the habits of these crocodiles is the one given
recently by Voeltzkow,[142] who has spent a long time in Madagascar to
collect material for the study of their development.
He says that _C. niloticus_ is not only the most common reptile, but
perhaps the most common vertebrate in Madagascar. {463}It occurs in every
pool and river in great numbers, especially upon the sandbanks of the
Betsiboka River, where one may see more than one hundred within one hour's
paddling down stream. The largest specimen measured by Voeltzkow was 13
feet long; the largest in the National Collection is a little less than 15
feet.
The crocodiles are caught in various ways. The simplest apparatus consists
of two pointed sticks, which are fastened cross-wise within the bait to
which is attached a rope, and this is made fast on the bank of the river or
lake. The animal, when it has once swallowed this spiked bait, keeps its
jaws firmly closed, so that it can be dragged out of the water. Another
method is more reliable. A long and strong rope is made into an easily
slipping noose, with an opening of about 18 inches. The bait is attached to
the upper part of the noose, while the lower portion is kept open by a
springy branch, the whole thing being so balanced that it will float
upright. When a crocodile seizes the bait, which it does with a side jerk
of the head, the branch falls out of the noose and the latter closes around
the upper or lower jaw.
These crocodiles dig long subterranean passages of 30 to 40 feet in length;
the passage opens in the bank below the level of the water, and gradually
ascending ends in a somewhat wider compartment, which allows the creature
to turn round. Two or three air-holes are pierced through the ceiling of
the burrow, in which bones and other remains of food are often found, so
that the natives' belief, that the crocodiles retire into these chambers in
order to devour their prey in undisturbed secrecy, appears very probable.
When suddenly disturbed or frightened they take to these lairs, and since
their position is clearly marked by the air-holes, the natives block the
passage and then dig the animal out from above.
Eggs are laid, in Madagascar, from the end of August to the end of
September; the number of one set varies from twenty to thirty. They are
deposited in a nest. This is in the ground, mostly in white sand, and
consists of a hollow 18 inches to 2 feet deep. The walls are rather
vertical, but near the bottom they are undermined, and here the eggs are
placed. The centre of the pit being somewhat higher, the eggs roll by
themselves into the undermined peripheral region. The laying takes place
{464}during the night, mostly a little before daybreak. After one half of
the eggs has been laid, they are covered up with sand, whereupon the other
half is deposited. Then the hole is completely filled up and no visible
traces are left behind; but the mother sleeps upon the nest and thus leads
to its discovery. The position of the nest is so chosen that it cannot be
reached by moisture from below; the eggs are most susceptible to moisture,
a very slight amount of which causes them to turn bad.
The shape of the eggs of one and the same clutch varies much, some being
elliptical, others cylindrical with rounded off ends. Their size varies
from 5.5 to 9 cm. in length, and 4 to 5 cm. in width. The shell is white
and glossy, thick and hard, either roughly granular or smooth. They are
hatched in about twelve weeks.
Voeltzkow feels certain that the mother returns to the nest at the proper
time in order to dig the young ones out and to conduct them to the water.
To test this story he had a nest surrounded with a fence; the mother
returned several times and partly destroyed the fence, which was then
replaced by a stronger one. One day, when the young had been hatched, the
nest was found to be filled with sand, the shells and one dead little
crocodile being at the bottom of the hole. The mother had dug a deep ditch
below the fence, but had not succeeded in reaching the nest, although she
had received and conducted her offspring away. As a rule, when the young
are hatched, the sand and the shells are found to be scraped out of the
nest. The mother is probably warned by the hiccough-like sound which the
young emit while still within the unbroken shell. Voeltzkow heard them
piping from the other end of his room, the eggs being covered with a layer
of sand two feet high. The sounds were heard when he walked past the nest,
or knocked against the box. Possibly the young hear the mother when she
retires to the nest to sleep on it, and give her warning to remove the eggs
out of the groove. However, they do not break the shell until several days
later.
The hatching is not caused by the rainy season, since it took place a
fortnight before the first showers. The "egg-tooth" of the newly hatched
young is 0.5 to 0.75 mm. high, bicuspid, and acts like a borer or auger. It
is still visible on the tip of the upper jaw, in front of the nose, when
the creature is two weeks old. The {465}newly hatched crocodile is of an
astonishing size, so that it is rather puzzling to understand how it was
stowed away in the egg. For instance, an egg of 8 cm. length and 5 cm.
width, sends forth a crocodile 28 cm. or 11 inches in length. Even at this
early age they snap at the finger.
The egg is covered by a hard shell, within which is a thicker outer and a
thinner inner membrane. The "white" is jelly-like, sometimes of a greenish
tinge, and is so consistent that it will not flow. The yolk is round, and
so large that it nearly reaches the shell-membrane in the short diameter.
The yolk itself is surrounded by a very thin but strong membrane.
The embryo begins to develop long before the egg is laid. When laid the
germ is about 4 mm. long and shows about twelve somites. The cephalic bend
begins at the end of the second week, the tail grows longer and the embryo
becomes curled up. At the end of the third week it measures 10 mm. in a
straight line from brain to vent. The limbs begin to bud in the fourth
week. With the sixth week the final shape begins to reveal itself, and is
completed at the age of eight weeks; but a third month is necessary to
ripen the embryo.
_C. cataphractus_ is the Common Crocodile of West Africa, from the Senegal
to the Congo. In opposition to _C. niloticus_ it does not enter brackish
water. It is easily recognised by the very slender snout, which rather
resembles that of the Gavial; but the mandibular symphysis, although
extending to the level of the eighth tooth, does not reach the splenial
bones. The premaxillo-maxillary suture on the palate is not transverse, but
extends backwards. In conformity with the length of the snout the
maxillaries meet in the dorso-medial line behind the nasal opening, thus
excluding the nasals from the latter. The nuchal scutes consist of two
large pairs, almost in contact with the dorsals, six of which form the
principal longitudinal rows. The gular and ventral scutes ossify in the
adult, hence the specific name. The fingers and toes are slightly webbed.
General colour above, dark olive-brown; yellowish below. The young are
olive with large black spots.
The natives of the Lower Congo catch the crocodiles with two pointed sticks
tied together cross-wise, surrounded with entrails by way of a bait. The
whole is fastened to a pole or a strong rope and thrown into the river; and
a narrow line, with a float {466}attached to the cross-sticks, indicates
the whereabouts of the crocodile when it has taken the bait and has sunk to
the bottom.
_C. johnstoni_, of Northern Australia and Northern Queensland, and _C.
intermedius_, of the Orinoko, are allied to _C. cataphractus_, at least so
far as the configuration of the bones of the slender and long snout is
concerned. The former is small, scarcely reaching the length of 7 feet,
while the South American species grows to 13 feet.
_C. americanus_ s. _acutus_.–This species, which inhabits the West Indian
Islands, being there the only representative of the order, occurs also in
Florida, and extends through the warmer parts of Central America into
Venezuela, Colombia, and Ecuador. Its characteristic feature is a median
ridge or swelling on the snout. The length and relative width of the latter
varies considerably. The maxillaries sometimes meet dorsally, or they
remain separated by the narrow nasals, which in this case reach the
posterior corner of the nasal groove. The nuchal scutes vary likewise;
there being often a smaller pair on the side of and another behind the four
principal scutes, which, as usual, form a square. A transverse row of
little suboccipital scutes is also common. Largest size about 12 feet long.
[Illustration: FIG. 111.–Dorsal view of the skull of _Crocodilus
americanus_. × ⅙. _F_, Frontal; _Jg_, jugal; _L_, lacrymal; _Mx_,
maxillary; _Na_, nasal; _P_, parietal; _Pmx_, premaxillary; _Prf_,
prefrontal; _Ptf_, postfrontal; _Qj_, quadrato-jugal; _Sq_, squamosal; _T_,
tooth-perforation.]
_Osteolaemus tetraspis_ s. _frontatus_.–The only species of this genus
inhabits the rivers of the west coast of Africa, from Sierra Leone to the
Ogowai. It differs from _Crocodilus_ chiefly by the bony septum of the
nasal groove, produced by forward extension of the nasal bones. The snout
is rather short and stout; the upper surface very rugose and deeply pitted,
but without ridges. The gular and ventral scutes are ossified, hence the
generic name. Total length about 5 feet.
_Alligator._–The fourth mandibular tooth fits into a pit in {467}the upper
jaw, and this pit is in some adult specimens transformed into a hole, the
tip of the tooth appearing on the upper surface through the perforation.
Most of the other teeth of the lower jaw are overlapped by those of the
upper jaw. The number of teeth on either side amounts to seventeen to
twenty in the upper and eighteen to twenty in the lower jaw. The nasal
bones form not only the posterior border of the nasal groove, but they
divide the latter by a median bony septum. The dorsal shield is formed by
six or eight longitudinal series of keeled bony scutes, which, although
standing close together, do not articulate with each other. Ossification of
the gular and ventral scutes is absent or very slight.
Alligators occur in the fluviatile deposits of the age of the Upper Chalk
in Europe, where they did not die out until the Pliocene age; they are now
restricted to two species, one in the Southern States of North America, the
other in China.
_A. mississippiensis._–The much-depressed and broadly rounded snout bears
some resemblance to that of a pike, hence the now discarded specific name
of _lucius_. The neck is protected by two pairs of large scutes, which form
a square, interrupted in the middle line, with a pair of small scutes in
front and another behind. Of the eighteen transverse dorsal rows of scutes
eight are broad and prominent. The fingers are about half webbed, the outer
toes about two-thirds webbed. The general colour is greenish black or dark
brown above, yellowish below. Young specimens have yellowish cross-bands on
a darker brown ground.
The Alligator's northern limit is the mouth of the river Neuss in North
Carolina, 35° N. lat. From this point they abound near the mouths of all
the creeks and rivers as far south as the Rio Grande, ascending the
Mississippi to the entrance of the Red River in 33° 50' N. lat.
The habits and the embryology of the American Alligator have been described
by S. F. Clarke,[143] who gives the following vivid and minute account:–
"Usually one finds them in the waters of the smaller streams and ponds,
lying with only the tip of the nose and the eyes exposed, or lying on an
exposed place on the bank where the grass and other plants are beaten down,
and the black, rich mud of the river bank is smoothed by the repeated
movements of the {468}alligators in climbing up and down. There they bask
in the sunlight until disturbed by the hunter or the desire for food. When
aroused they make for the bottom, and I have never waited long enough to
see one return unless he were vigorously stimulated with a long pole. They
frequently dig a cave for themselves in the bottom of the pond or stream,
or in the bank beneath the water. Oftentimes one can start them out of the
cave by using a pole, but if very obstinate, the hunters dig them out with
spades.
[Illustration: FIG. 112.–Skull of _Alligator mississippiensis_. A, Dorsal;
B, ventral; C, lateral view. _Ag_, Angular bone of mandible; _Cd_,
occipital condyle; _Ch_, choanae or posterior narial openings–the median
small hole behind them indicates the position of the opening of the
Eustachian tubes; _Jg_, jugal; _L_, lacrymal; _Mx_, maxillary; _No_,
nostrils; _Pa_, palatine; _Pm_, premaxillary; _Pt_, pterygoid; _Q_,
quadrate; _T_, _Tr_, transverse bone or ectopterygoid.]
"As the water decreases in the streams and ponds with the summer heat, the
alligators travel to the larger bodies of water. {469}During the breeding
season, from the end of May to the beginning of July, the males are very
active, wandering about to various ponds and rivers in search of the
females. Fierce battles are said to take place during this time between the
excited males; and the mutilated specimens that one sees are weighty
evidence for the truth of this assertion.... It is in the breeding season
also that their bellowing is mostly heard, and more in the night than
during the day. I have frequently heard them, while lying in the swamps at
night, when they were in ponds fully a mile distant.
"The largest specimen I saw measured 12 feet in length; and none of the
many hunters and other natives of Florida I have met have seen any longer
than 13 feet. All the hunters agree that it is only the males that acquire
the great size; no one had ever seen a female that measured over 8 feet,
and the majority are not over seven.
"The male has a heavier, more powerful head, and during the breeding season
especially is more brilliantly coloured. The more brilliant colour occurs
in patches and streaks on the sides of the head and body; it is generally a
light yellow, or even whitish, and on one large male I saw a fairly bright
red spot over each eye.
"The alligators are rapidly diminishing in numbers under the stimulus of
the high prices offered to the hunters for their hides. Both Whites and
Indians make increasing war upon them. Several thousand skins were brought
into the little station of Fort Pierce in 1890. The pioneers and settlers
always destroy the nests and eggs, because the alligators eat their pigs;
and the cleaned eggs and young alligators are sold by hundreds in the curio
shops farther north. As their numbers diminish in Florida it is noticed
that the Moccasin snakes increase. In Louisiana also the alligators are
disappearing; and there the musk-rats are at the same time increasing, and
are doing much damage by burrowing in the levees along the Mississippi.
While the alligator can make a very stout fight, I have never seen one
offer fight if there was any chance of retreat. They never offered to
molest us, even when we waded through the ponds where they were.
"The nest of the alligator is very large, and is built by the female. A
great quantity of dead leaves and twigs, together with {470}much of the
finely divided humus underlying them, is scraped together into a low mound
about 3 feet high; this varies considerably in its other dimensions, being
in some instances 8 feet in diameter at the base. The nests are built on
the bank of a stream or pool, and the female digs a cave under water in the
bank close to the nest. Careful examination, of the largest nest found
showed a root of a neighbouring palmetto-tree, nearly an inch in diameter,
running through it at about a foot above the ground; there were also roots
of a grape vine growing near, which extended nearly through the nest. This
furnishes strong support to the statement of many of the hunters, that the
nests are used for more than one season. I could get no evidence whatever
that the nests are used more than once a year.
"The eggs are laid near the top of the nest, within 8 inches of the
surface, are four or five layers deep, and have no regular arrangement or
uniform position of their axes in relation to the nest. The number of eggs
to a nest varies from twenty to thirty, and averages twenty-eight; the
maximum found was forty-seven.
The eggs are white, elliptical, and vary in length from 50 to 90 mm. or 2
to 3½ inches, and in the shorter diameter from 28 to 45 mm. Generally there
is only slight variation in the eggs of one nest, but occasionally a nest
is found in which most of the eggs are about the average size, while from
two to five are very much smaller.
"The shell is much rougher than that of a hen's egg, and much thicker. The
shell membrane consists of an outer and an inner layer, in both of which
the fibres are arranged spirally about the egg, but at right angles to one
another.
"The white of the egg has the consistency of a very thick jelly, is very
clear and transparent, and is so firm that the whole egg, when perfectly
fresh, may be turned out of the shell and shell membrane, and transferred
from one hand to the other without breaking, and with but slight change of
form. The white lies mostly at either end of the shell, but extends also in
a thin layer between the yolk and the sides of the shell. The yolk holds a
median position in the egg, is spherical, of a very light pale yellow, and
so large that it almost touches the shell membrane about the midline."
According to Holbrook the young as soon as they are disengaged from the
shell seek the water and shift for themselves, {471}the parents taking no
care of them, though they may remain for some weeks in the same locality.
In the spring and early summer months, and during the time of incubation,
and especially on cloudy days or in the evening, alligators make a great
noise; their croak is not unlike that of the bullfrog, but louder and less
prolonged. On the approach of winter they select holes in the ground, where
they remain torpid until spring. In this state of hibernation many are dug
out by the negroes, who esteem the tail as an article of food.
_A. sinensis_.–The first intimation of the existence of a Crocodilian in
the Yang-tse-kiang was made by Swinhoe in 1870, but it was not until nine
years later that Fauvel[144] described the creature as _A. sinensis_. The
same gentleman gave also an exhaustive account of the former records of
this species in Chinese literature. According to Boulenger its nearest ally
is _A. mississippiensis_, but it approaches the Caimans by the presence of
ossifications in the ventral shields, which ossifications are, however,
wide apart from each other. There are three pairs of large nuchal scutes in
contact in the median line, besides smaller scutes in front of the nuchals
and behind the occiput. The dorsal shield contains six rows of larger
scutes. The fingers are not webbed. The general colour is greenish black
above, speckled with yellow; greyish below. Total length only about six
feet.
_Caiman_.–The five species of this genus, confined to Central America or to
the East Andesian parts of South America, resemble the Alligators in most
features, but differ from them in the following points. The nasals,
although bordering the nasal groove, do not form a bony nasal septum. The
supratemporal fossae are very small; or closed up, as in _C. trigonatus_
and _C. palpebrosus_ of Guiana. The ventral armour is composed of
overlapping bony scutes, each of which is formed of two parts united by a
suture.
_C. sclerops_ has the widest distribution, from Southern Mexico to the
northern half of Argentina. The upper eyelid is rugose, although only
incompletely ossified, and is often more or less produced into a small
horn. _C. niger_ has flat upper eyelids.
According to Bates, Caimans exist in myriads in the waters of the Upper
Amazons. One species, _C. trigonatus_, the _Jacaré-tinga_ {472}of the
natives, reaches only six feet in length and has a slender muzzle and a
black-banded tail. Another species, _C. niger_, the _Jacaré-nassu_ or large
Caiman, attains an enormous bulk and a length of 20 feet. They migrate
annually, retreating to the flooded forests in the wet season and
descending to the main rivers in the dry season.
{473}CHAPTER XI
PLESIOSAURIA–ICHTHYOSAURIA–PTEROSAURIA–PYTHONOMORPHA
_SUB-CLASS VII.–PLESIOSAURIA._
_Mesozoic aquatic reptiles, with two pairs of pentadactyle limbs, firmly
fixed quadrate bones, single temporal arches, numerous alveolar teeth,
and ribs which articulate only with the centra of the biconcave
vertebrae._
The Plesiosauria comprise the Mesosauri, Nothosauri, and Plesiosauri in an
ascending order of development, which concerns especially the changes from
a semi-terrestrial to an absolutely aquatic life;–elongation of the neck
with corresponding shortening of the tail, and the gradual transformation
of the limbs into hyperphalangeal paddles.
The skull varies considerably in length. Seen from above it shows the
nostrils, orbits, very large supratemporal foramina, and the interparietal
hole. The nostrils lie rather far back, in front of the orbits, between the
elongated premaxillaries, short nasals, and the usually large maxillaries.
The orbits are rather small, bordered behind by the postfrontals and
postorbitals, which two bones fuse together in the Plesiosauri. The
temporal bridge is long, and is formed by the junction of the two bones
just mentioned with the squamosal mass, which overlaps the greater portion
of the quadrate, and perhaps contains the quadrato-jugal. The dorsal branch
of the squamosal joins a corresponding diverging branch of the parietal,
and completely shuts off the posterior region of the supratemporal foramen.
The interparietal hole is small and placed far back. The palate possesses a
row of teeth on the pterygoids in _Lariosaurus_. The choanae open
separately between the vomers and maxillaries. The pterygoids are very
long; posteriorly they join the quadrates, anteriorly they extend
{474}right up to the vomers, separating the palatines from each other
thereby. Palatal vacuities are absent in _Nothosaurus_; small and oval,
between the palatines, pterygoids, ectopterygoids and maxillaries in
_Lariosaurus_; still smaller in the Plesiosauri.
The vertebrae are mostly biconcave, in the Triassic genera still perforated
by the chorda, while in many Plesiosauri the centra are solid, with almost
plane articulating surfaces. The neural arches are usually firmly sutured,
or quite fused with the centra. Intercentra are absent, except as chevrons
in the tail. Although the cervical and some of the thoracic ribs of the
Triassic genera have typical capitula and tubercula, they articulate
exclusively upon the centra, and not upon the neural arches also. The
number of cervical vertebrae amounts to nine in _Mesosaurus_; in
_Lariosaurus_ it is increased to about twenty; and in some Plesiosauri to
between thirty and forty. The cervical ribs are very short, but they
increase gradually towards the thorax, which is well protected by long and
strong ribs, which decrease again very gradually, being still long in the
lumbar region. There is, properly speaking, no sacrum, because the one to
four sacral ribs remain quite separate. The tail is still long in
_Lariosaurus_, consisting of about forty much shortened vertebrae;
considerably shorter than the neck in most of the Plesiosauri. A sternum is
absent, but the belly is protected by many strong abdominal ribs, crowded
together, and consisting each of a median and two pairs of lateral pieces.
The shoulder-girdle is very strong, composed of scapulae, very strong
coracoids, clavicles, and an interclavicle. The precoracoids are indicated
by a process and a notch in the Triassic genera; in the later forms they
are abolished. The coracoids always meet in the median line, and often
produce a strong symphysis. The scapulae possess a very prominent and large
acromial process, upon which rest the dorsal or lateral ends of the
clavicles. In some Plesiosauri the shoulder-girdle has undergone an
absolutely unique modification. The correct interpretation has been given
by C. W. Andrews after the examination of exquisitely preserved specimens
of _Cryptoclidus_ from the Oxford clay of the Middle Oolite, near
Peterborough. The dorsal portion or main shaft of the scapula is reduced to
what now looks like a dorso-lateral process, while the broad acromial
process is much elongated, and lies in _Plesiosaurus_ upon the {475}ventral
surface of the clavicle; the latter and the irregularly T-shaped
interclavicle being, however, still visible from below. In _Cryptoclidus_
the two acromial processes meet each other and form a long ventral
symphysis, which meets that of the much-enlarged coracoids, the latter
enclosing with the scapulae a pair of roundish foramina. The clavicles are
not visible from below; they rest upon the dorsal surface of the scapular
symphysis, and the interclavicle seems to be suppressed. Young
_Cryptoclidus_ (Fig. 113, B) and various species of _Plesiosaurus_ show
intermediate conditions.
[Illustration: FIG. 113.–A, Restored outlines of a _Plesiosaurus_, × 1/50;
B, dorsal view of the pectoral arch of an immature _Cryptoclidus_, from the
middle Oolite; C, fore-limb of a _Plesiosaurus_, from the Lias. _A_,
Acromial process of scapula; _Cl_, clavicle; _Co_, coracoid; _H_, humerus;
_i_, carpale intermedium; _M_{1}_ to _m_{5}_ first to fifth metacarpals;
_p_, pisiform bone; _R_, radius; _r_, radial carpal; _S_, scapula; _U_,
ulna; _u_, ulnar carpal.]
This unique arrangement is correlated with the enormous development of the
fore-limbs, although nothing of the kind has taken place in the
Ichthyosauri, which have similar large paddles. The limbs exhibit
considerable differences in the various groups of Plesiosauria, but they
are all pentadactyle. In the oldest, the Mesosauri and Nothosauri, the
limbs are still of the terrestrial type, although fitted for swimming; the
chief bones are still slender and elongated, and none of the five fingers
and toes have more than five phalanges, the usual number of which seems to
be 2, 3, 4, 5, 3 for the first to fifth digits respectively. In the
Plesiosauri the limbs are transformed into long hyperphalangeal paddles,
unfit for progression on land, rather like those of the Ichthyosauria, with
much {476}shortened radius and ulna, tibia and fibula; but the phalanges,
which increase to about ten, are always longer than broad, and there is no
indication of an increase of the number of fingers, or of additional,
lateral, phalanx-like nodules. The pelvis is very strong; the broad pubes
and ischia meet in the middle line, and they either enclose one wide
undivided foramen, or the two symphysial portions meet, and there are then
two obturator-foramina. The pubes are generally much larger, especially
broader, than the ischia; and although partaking in the formation of the
acetabulum, they do not articulate with the ilia, at least not in
Plesiosauri. The ilia are always small; in Plesiosauri attached to only one
or two sacral ribs; to three or four in the Triassic genera.
Ichthyosauri and Plesiosauri were combined as "Enaliosauria" by Conybeare.
Owen recognised their fundamental differences, and separated them as
"Ichthyopterygia" and "Sauropterygia," according to the structure of the
limbs. We now know that the paddles of the Ichthyosauri bear but a
superficial resemblance to the fins of fishes, and are fundamentally
referable to the pentadactyle type, as are the paddles of the Plesiosauri,
although the latter retain more of the typical features of reptilian limbs.
It was soon recognised that the Nothosauri are allied to the Plesiosauri,
but the Mesosauri (until then vaguely grouped with the Rhynchocephalia, or
linked with Protorosauri as Proganosauria) have only recently[145] received
their proper place in the system as members of the Plesiosauria, which we
divide into two main groups.
ORDER I. NOTHOSAURI.[146]
The limbs are of the terrestrial type; the five digits have the usual
number of phalanges, which do not exceed five. The bones of the limbs are
slender; the humerus has an entepicondylar foramen.
FAM. 1. MESOSAURIDAE.–The neck contains about ten vertebrae. The vertebrae
are deeply biconcave, perforated by the chorda dorsalis. Sacral vertebrae
four in number. Clavicles strong; interclavicle very small. _Mesosaurus_,
the only genus, with one species, _M. tenuidens_, about one foot in length,
was found in {477}South Africa, probably in Triassic sandstone. Very
similar specimens are known from São Paolo in Brazil.
FAM. 2. NOTHOSAURIDAE.–With sixteen to twenty-one cervical and three to
five sacral vertebrae. The vertebrae are biconcave. The clavicles are
strong; the interclavicle is much reduced. Coracoids with distinct acromial
processes.
_Nothosaurus mirabilis_, of the Muschelkalk of Germany. Total length about
ten feet. Length of head about one foot. The teeth are very irregular.
About five slender, long teeth are implanted in each side of the
premaxilla, with wide spaces between them, similar to those of the
symphysial portion of the lower jaw. Those of the maxillaries are numerous
and small, except two large pairs in the anterior portion, on a level
between the orbits and nostrils. The upper and lower teeth overlap, or
cross each other. The palate of the long and slender skull is quite bony,
without anterior palatal or infra-orbital vacuities.
_Lariosaurus balsami_, about one foot in length, from the fresh-water
deposits of the Upper Trias in Lombardy. Neck with about twenty, tail with
about forty vertebrae. Head comparatively shorter; more triangular than in
_Nothosaurus_; palate with small infra-orbital vacuities. The number of the
phalanges of the fingers and toes is apparently 2, 3, 4, 4, 3 and 2, 3, 4,
5, 4.
_Anarosaurus pumilio_, of the Muschelkalk, near Magdeburg, and
_Neusticosaurus_ and _Simosaurus_ of the same geological age, are allied
forms.
ORDER II. PLESIOSAURI.
The limbs are transformed into hyperphalangeal paddles. The clavicles are
small, and are overlapped ventrally by the strongly developed acromial
processes of the scapulae. The vertebrae are slightly biconcave or plane.
The neck consists of at least twenty vertebrae; those of the thoracic
region have long transverse processes; the sacral vertebrae are mostly
reduced to two or one. Very large, massive animals.
FAM. 1. PLIOSAURIDAE.–About twenty cervical vertebrae, with proximally
bifurcated ribs. The scapulae do not meet ventrally; they enclose with the
coracoids a single large foramen, and are fused with the clavicles.
_Pliosaurus_, the principal genus, contains several species of gigantic
size; for instance, _P. grandis_, of the Kimmeridge clay, Upper Oolite, of
England, has a skull {478}nearly 5 feet long and 2 feet broad, armed with
many enormous conical teeth, some of which reach one foot in length,
inclusive of the long collar and root-portion. The neck is rather short,
owing to the much condensed, disc-shaped centra of the vertebrae. Total
length of this species about 30 feet. Other species in England and
continental Europe as far as Russia.
FAM. 2. PLESIOSAURIDAE.–The neck is very long, and consists of from
twenty-eight to forty vertebrae. The scapulae do not meet ventrally, but
the symphysial portion of the coracoids meets the clavicles and the
interclavicle, the pectoral arch thus enclosing two foramina. Chief genus
_Plesiosaurus_, with many species. The head is comparatively small, the
neck very long, the tail short, although consisting of from thirty to forty
vertebrae. The third digit (Fig. 113, C) is the longest, and possesses nine
or ten phalanges. The abdominal ribs are very strong, and reach from the
pectoral to the pelvic girdle. Range from the Lower Trias to the Lower
Oolite, chiefly European. _P. dolichodirus_ and _P. conybeari_, the latter
reaching a total length of more than 15 feet, from the Lower Lias,
especially at Lyme Regis.
FAM. 3. ELASMOSAURIDAE.–The neck is extremely long, possessing from
thirty-five to seventy-two vertebrae, with single-headed, not bifurcated,
ribs. The scapulae meet ventrally, and enclose with the very broad
coracoids two foramina. The tail is short. The pisiform bone articulates
with the humerus. Otherwise much resembling the Plesiosauridae. Principal
genus _Cimoliasaurus_, with many synonyms, and many species from the Middle
Oolite to the Upper Chalk; cosmopolitan distribution, e.g. _C.
cantabrigiensis_, of the Greensand and Upper Chalk; _C. trochantericus_, of
the Kimmeridge clay; _C. haasti_ in New Zealand; _C. australis_, _C.
chilensis_; others in North America. _Cryptoclidus_ of the Middle and Upper
Oolite of Europe. _Elasmosaurus_, of the Upper Cretaceous formation in
Kansas, with a computed total length of 45 feet, of which 22 belong to the
neck, with its seventy-two vertebrae.
_SUB-CLASS VIII.–ICHTHYOSAURIA._
_Marine, whale-shaped reptiles, with the anterior and posterior limbs
transformed into hyperphalangeal paddles. Restricted to the Mesozoic age
from the Trias to the Upper Chalk._
The skull is long, owing to the elongated slender snout, which {479}is
formed mainly by the premaxillary bones. The nostrils lie far back, in
front of the orbits, and are bordered by the long nasals, the
premaxillaries, a small part of the maxillaries, and posteriorly by the
large lacrymal bones. The eyes are large, and are strengthened by a
sclerotic ring composed of many closely overlapping bones. The orbits are
very large, and are directed sideways so as to be scarcely visible from
above. They are formed above by the long prefrontals, which join the
postfrontals; behind by the long postorbitals; below by the long and
slender jugals; in front by the lacrymals and prefrontals. The
postorbito-temporal region of the skull is short but high, and, with the
exception of the supratemporal foramen, is entirely closed in by bones,
namely, the quadrato-jugals, supratemporals, and squamosals. The latter,
with the parietals and large postfrontals, surround the supratemporal
foramina. The parietals and the small frontals enclose the parietal
foramen. The whole temporal arch consequently recalls much that of the
Pareiasauri and Stegocephali, chiefly owing to the presence of conspicuous
supratemporal and postorbital bones, which, together with the
quadrato-jugal, close in the whole side without any indication of a lateral
or infratemporal foramen. The postorbital completely separates the jugal
from the quadrato-jugal, and this almost hides the quadrate. The occipital
condyle is single. The lateral occipitals and the supra-occipital bones
retain their sutures. The pro-otic and opisthotic bones remain separate.
The latter lie between the basi- and lateral occipitals, the squamosal,
quadrate, and pterygoid. The pterygoids, which posteriorly touch the
quadrato-jugals, basi-occipitals, opisthotics, and basisphenoid, are very
long and remain widely separated from each other; in the space between them
appears the long ensiform presphenoid. Anteriorly they are connected
through the ectopterygoids with the maxillae, and touch the palatines.
These are likewise narrow and slender, but touch each other in the middle
line, and contain the well-separated, slit-like choanae, laterally to which
lie the elongated, rather narrow, palatal vacuities. The vomers are mostly
not visible; when they appear on the surface they are long and narrow, and
enclose the choanae between them and the palatines.
The teeth are pointed, conical and thickly covered with enamel, which in
transverse sections forms vertical ridges, recalling {480}the folds of the
Labyrinthodonts. The teeth have open roots, and are not implanted in
separate alveoli, but lie in long grooves of the premaxillaries,
maxillaries, and dentals.
The vertebrae are numerous, up to 150, two-thirds of which belong to the
tail. The centra are deeply biconcave and short, not co-ossified with the
neural arches, which have therefore often broken loose. The atlas much
resembles the other cervical vertebrae in so far as its centrum is concave
in front and scarcely ankylosed with that of the second. Its basiventrals,
equivalent to the ventral half of the atlas-ring of other reptiles, thus
become an unpaired intercentral wedge, between the first centrum and the
basis of the cranium; the neural arches rest upon the centrum, but remain
separate from each other, or at least diverge dorsally. The atlas carries
no ribs. Intercentra occur also between the second and third vertebrae;
they reappear in the tail as chevron-bones. All the other vertebrae carry
ribs, which gradually increase in length towards the trunk and decrease
again equally gradually on the tail. In the neck and trunk they have
separate capitula and tubercula, which articulate upon short knobs of the
centra; towards the tail these shift farther and farther towards the
ventral side, and ultimately unite. Although the ribs of the trunk are so
long, there is no trace of a sternum, but there are many "abdominal ribs"
crowded together, each consisting of a middle and a pair of lateral pieces.
The shoulder-girdle is very complete, but the pieces remain separate, or at
least do not co-ossify; it consists of a T-shaped interclavicle, clavicles,
broad coracoids touching each other in the middle line, and short scapulae.
The existence of small separate precoracoids is doubtful. The pelvis is
much reduced; the small ilium is quite unconnected with any vertebrae; the
small pubes and ischia form no symphyses. The fore- and hind-limbs are very
similar to each other; the posterior are, however, much smaller. Both are
transformed into highly specialised paddles. It is of the greatest
importance, as an indication that the Ichthyosauri are descendants of a
terrestrial stock, and have been modified into what they are owing to
having taken to marine life, that in the oldest members known, the
paddle-like structure of the limbs was less advanced than in the later
species. In _Mixosaurus_ of the Muschelkalk of Europe the ulna and radius
are still distinctly longer than broad, and they enclose a space
{481}between them. They articulate with three carpal bones, the ulnare,
intermedium, and radiale, while a small pisiform bone lies on the outer
side, between the ulnare and the outer distal carpal bone. In
_Ichthyosaurus_, from the Liassic period onwards, the ulna and radius are
much shortened, broader than long, and touch each other without any
intervening space; the pisiform element is enlarged. Lastly, in
_Ophthalmosaurus_ of the Middle Oolite (but not in contemporary species of
_Ichthyosaurus_) the ulna and radius are still more reduced, and the
pisiform has moved up to the humerus, so that the latter articulates with
three bones.
[Illustration: FIG. 114.–A, Ventral view of the shoulder-girdle and right
fore-limb of an _Ichthyosaurus_, from the Lias; B, part of the fore-limb of
a _Mixosaurus_, from the Trias; C, part of the fore-limb of an
_Ophthalmosaurus_, from the Chalk. _c_{1}_, _c_{2}_, first and second
centrale carpi; _Cl_, clavicle; _Co_, coracoid; _H_, humerus; _I_,
interclavicle; _i_, intermedium carpi; _p_, pisiform; _R_, radius; _r_,
radial carpal; _Sc_, scapula; _U_, ulna; _u_, ulnar carpal.]
Other important features of these paddles are not only the much-increased
number of phalanges (sometimes up to twenty or more), but also the increase
of digits to six or more, produced apparently by a splitting of the third
finger into two series, and by the development of additional rows of
phalanx-like bones on the outer and inner margins of the paddle. This
increase of fingers exists, for instance, in _Ichthyosaurus communis_, but
not in _I. tenuirostris_. Owing to this peculiar development of paddles the
constituent bones are extremely numerous, and from the radius and ulna
downwards they are all closely packed, and have assumed a polygonal, often
hexagonal, shape, dwindling to more or {482}less flattened nodules towards
the ends of the digits. These carpal and phalangeal bones are common
objects in amateurs' collections; they fit together by the short angular
facets, while the two flat and broader surfaces are those of the dorsal and
ventral sides.
The Ichthyosaurs lived upon fishes and cuttlefish, as is indicated by their
dentition and the shape of the snout, and proved by the coprolites, most of
which are full of fragments of bones and ganoid scales of fishes, and of
the beaks and shells of cuttlefish; the larger of these true coprolites
(literally "petrified dung"), in coprolite-beds, contain also an abundance
of other fossils, such as Ammonites, Terebratulae, molluscs and
fish-remains; they are several inches long, and many of them show on the
outside ring-like impressions, undoubtedly caused by a spiral valve of the
intestinal canal. In conformity with their absolutely aquatic life the
Ichthyosaurs were viviparous. Several well-preserved adult specimens have
been found, which contain the skeletons of one or more rather large young
within the body, in exactly the position in which such foetal creatures
would lie, namely, with the head in the pelvic region of the mother, while
the rest of the body stretches along the vertebral column towards the
chest. The suggestion that these young Ichthyosaurs have been swallowed by
their cannibal elders is too idle to require serious refutation.
Until within a few years Ichthyosaurs were always restored with a smooth
and even back, but several well-preserved specimens have come to light in
Würtemberg which show the complete contour of the animals, with a long,
somewhat jagged fin on the middle of the back. Since then not a few
specimens in various collections have on closer examination revealed the
same feature, except, of course, those in which the outlines of the fin had
been chiselled away in order to "improve" the look of the slab. The fins
were undoubtedly of the "adipose" kind;–raised folds of the skin. The
latter is now known to have been covered, at least at the bases of the
dorsal fins, with hard little scales, probably osteoderms.
Many specimens are beautifully preserved, others present a very peculiar
appearance. They look, namely, like long rolls of clay, and nobody but an
expert would suspect an _Ichthyosaurus_ within such a log. The explanation
is simple. The dead {483}creature was rolled about by the waves of the surf
on the Liassic muddy beach until it was wrapped in a mantle of clay and
then imbedded on the shore.
The distribution of Ichthyosaurs in time and space is wide. The earliest
are found in the Middle Trias; in the Lias they are very common, fairly
frequent in the Oolites, dying out with the Cretaceous epoch. They have
left no descendants, being far too specialised, and their origin is quite
unknown. _Mixosaurus_, the oldest genus, occurred in Europe, and has also
been found in the Triassic strata of Spitsbergen. _Ichthyosaurus_, the
chief genus, is known from the Liassic, Oolite, and Cretaceous strata of
Europe, a famous place being Lyme Regis; and also from the Cretaceous
strata of Queensland and New Zealand. The Jurassic of Wyoming has yielded
_Baptanodon_.
[Illustration: FIG. 115.–Restored outlines of _Ichthyosaurus
quadriscissus_. (After Fraas.)]
ORDER ICHTHYOSAURI.
The few genera are easily recognised.
_Mixosaurus_, Triassic, with radius and ulna still elongated, a
longitudinal space occurring between them. Both jaws with numerous uniform
teeth.
_Ichthyosaurus_, with much shortened radius and ulna; both jaws with
uniform series of teeth. Many species are known, some with four to five,
others with several additional and incomplete rows of fingers and toes. _I.
trigonodon_ of the Lias in Würtemberg seems to have reached the size of 30
feet, the vertebrae showing a diameter of 9 inches, while the skull is 6
feet long. _I. communis_ and _I. tenuirostris_ are common in the English
Lias. The long-snouted _I. campylodon_, with large, spaced teeth, occurs in
the Gault of Cambridge, Dover, and France; and {484}there are many others.
_Ophthalmosaurus_, of the Upper Oolitic and Cretaceous formations of
England, had very small vestigial teeth.
_Baptanodon_, of the Upper Jurassic epoch of Wyoming, was toothless, and
was one of the six-toed forms.
_SUB-CLASS IX.–PTEROSAURIA._
_Mesozoic reptiles with fixed quadrate bones and with the anterior limbs
transformed into wings, the enormously elongated ulnar finger carrying a
patagium._
The skull bears a superficial resemblance to that of Birds. It articulates
with the neck by a single condyle, at nearly a right angle. The
interparietal foramen is absent, but there are five pairs of foramina on
the surface of the skull, namely, the nostrils, orbits, supra- and
infra-temporal and pre-orbital foramina. Most of the constituent bones of
the cranium fuse with each other, and the composition of the various arches
is therefore difficult to make out with certainty. The premaxillaries are
fused together, and extend dorsally backwards between the nasals, which
themselves diverge towards the prefrontals. The nostrils are bordered
chiefly by the maxillaries, nasals, and prefrontals. The orbits are very
large, mostly shut off in front from the pre-orbital foramina by a bridge,
which is formed by descending processes of the prefrontals and ascending
processes of the jugal. Above and behind, the orbits are bordered by the
frontals, postfrontals, and possibly the quadrato-jugals. The whole
temporal region is shortened from before backwards, but heightened
dorso-ventrally, and the whole temporal fossa is divided into a supra- and
infra-temporal portion by the junction of the postfrontal with the
squamosal, the latter joining the parietal, thus closing the supratemporal
fossa behind. This is conspicuous only in the older forms, e.g.
_Dimorphodon_, but is very small in _Pterodactylus_, and quite abolished in
_Pteranodon_. The infratemporal fossa is a narrow slit, slanting obliquely
upwards and backwards, between the quadrate and the quadrato-jugal. A
foramen of this kind occurs elsewhere only in the Rhynchocephalia. The
quadrate is long, firmly fixed, and slants so far forwards that the
mandibular joint lies on a level below the middle of the orbit. The
pterygoids articulate with strong and long processes of the basisphenoid,
touch the quadrate posteriorly, enclose an interpterygoid vacuity, {485}and
extend forwards as slender bones to the vomer, separating the palatines.
The choanae are enclosed by the vomer, palatines, and maxillaries, and they
lie in dorsal recesses above the level of the roof of the mouth. The teeth
are alveolar, pointed, of variable size, and restricted to the jaws; in the
Pteranodonts they are absent.
The brain is known from the natural cast of _Scaphognathus_, and shows some
remarkably bird-like features, especially the width of the hemispheres,
which touch the well-developed cerebellum, while the optic lobes lie on the
sides of the cerebellum, with a pair of appendices, the so-called flocculi,
elsewhere known in birds only.
The caudal vertebrae are still amphicoelous, while the presacral vertebrae
are procoelous. Abdominal ribs are few in number and are very thin. The
true ribs possess capitula and tubercula; those of the neck are very short
and directed backwards; in the thoracic region they are long, and some are
attached to a broad sternum with a keel and a median anterior process, on
the sides of which latter articulate the coracoids. Precoracoids and
clavicles are absent. The scapulae are long, sabre-shaped, and turned back
as in birds; in _Pteranodon_ they show the unique modification of
articulating with special processes of the neural arches of several
ankylosed thoracic vertebrae.
[Illustration: FIG. 116.–_Pterodactylus crassirostris._ × ⅓. (From
Geikie.)]
The hand possesses only four fingers; the four phalanges of the ulnar
finger are very much elongated for the support of the patagium; the other
fingers remain short and are provided with little claws. The ilia are
expanded horizontally, and are firmly attached to from three to six
vertebrae, which mostly fuse together into a sacrum. The ventral half of
the pelvis consists of a pair of broad bones, which contain a small
obturator-foramen; they form a ventral symphysis, and are usually fused
with the ilium. These bones represent the conjoint ischia and pubes, while
the so-called pubes, a pair of flat and club-shaped bones, are excluded
{486}from the acetabulum. The whole arrangement resembles that of the
Crocodilian pelvis. The hind-limbs are bird-like in so far as the fibulae
are reduced to splints, and attached to the proximal halves of the long and
slender tibiae. The feet contain five separate toes with rather long
metatarsals and short claws. Many of the bones are hollow.
The Pterosauria have no relationship with the birds, in spite of the number
of apparently striking resemblances (_e.g._ choanae, pre-orbital foramina,
brain, scapula, fibula, cervical vertebrae), which are, however,
coincidences, cases of convergence, in conformity with the aerial life. The
totally different plan of the wings is sufficient to show this. On the
other hand, the real affinities of this group of flying reptiles are
unknown. They turn up "fully fledged" in the Lower Lias, and they reach
their highest specialisation in the Upper Cretaceous epoch, with which they
have died out. In fact we do not know any forms through which to connect
them with other extinct reptiles. The skull shows some Rhynchocephalian
features; the pelvis, Crocodilian features; and this combination points
back a long way.
ORDER PTEROSAURI.
SUB-ORDER 1. PTERODACTYLI, with alveolar teeth in the upper and lower jaws.
Imperfect remains, impressions of phalanges of the long patagial finger,
are known from the Rhaetic of Würtemberg. The oldest well-known genus is
_Dimorphodon_, Lower Lias of Lyme Regis. _D. macronyx._–Total length
between 3 and 4 feet, of which the large light skull takes up about 9
inches, and the long thin tail about 2 feet. The patagial finger is about
20 inches, the whole wing about 28 inches long. _Rhamphorhynchus
longicaudatus_ of the Upper Oolite of Germany is remarkable for the long
slender teeth, which are directed forwards and separated by wide spaces
from each other. The nine or ten cervical vertebrae are elongated. _R.
phyllurus_ of the same geological age has left impressions of the flying
membranes. They extend from the whole length of the wing and the sides of
the trunk to the thigh as far as the knee, and from the inside of the
hind-limbs to the tail. The end of the tail carries a spatulate membrane.
Allied is _Ornithocheirus_, with many species in the English Wealden and
Greensand. {487}_Pterodactylus_, with many species from the Upper Oolite,
chiefly of Germany.–The tail is very short, consisting of a few vertebrae
only. The seven neck-vertebrae are so much elongated that the neck is as
long as the trunk with the tail. _P. longirostris_ measures about 1 foot in
total length, while _P. spectabilis_ is one of the smallest, only of the
size of a lark. The wings, however, measure 10 inches from tip to tip. The
largest is _P. giganteus_, with a "spread" of more than 5 feet.
SUB-ORDER 2. PTERANODONTES.–The beak is long, pointed, toothless, and
laterally compressed; mandibular symphysis very long. _Pteranodon
longiceps._–The skull has a long parieto-supraoccipital crest, which
extends far back. The supratemporal foramina are abolished. The pre-orbital
and orbital foramina are confluent. The scapulae are attached to several
thoracic vertebrae. The skull of this gigantic species has a length of two
feet and a half, and the spread of the wings measures nearly 20 feet. This,
and several much smaller species, are from the Middle Cretaceous formation
of Kansas.
[Illustration: FIG. 117.–_Rhamphorhynchus muensteri_, × ⅐, as restored by
Marsh. (From Geikie.)]
_SUB-CLASS X.–PYTHONOMORPHA._
_Very long-necked and long-bodied marine Cretaceous reptiles, with
movable quadrates, single lateral temporal arches and procoelous
vertebrae; with paddle-shaped, pentadactyle limbs; and with the teeth
ankylosed to the jaws._
The skull possesses many of the essential features of the typical lizards.
The premaxillaries, frontals, and parietals are fused into unpaired bones.
There is an interparietal foramen. {488}The nostrils are dorsal, bordered
by the premaxillae, nasals, prefrontals, and maxillaries. The
quadrato-jugal arch is incomplete, and the orbit is posteriorly confluent
with the infratemporal fossa, but a supratemporal space is shut off by the
single arch, which is composed of the postfrontal, squamosal, and
supratemporal. The latter is interposed between, and connects the squamosal
and quadrate with the latero-posterior branch of the parietal. There is a
space between this parieto-squamosal arcade and the epi-otic, which is
fused with the lateral wing of the lateral occipital bone. The foramen
magnum is bordered by the two supra-occipital, lateral occipital, and the
unpaired basioccipital bones; the condyle is triple. The quadrate is
movable, articulating with the squamosal and laterally expanded epi-otic.
There is no bony connexion of the quadrate with the jugal, which is
restricted to its anterior half, and attached to the maxillary and
lacrymal. The quadrato-jugal is absent as a separate bone; it is probably
fused with the anterior surface of the quadrate, as indicated by a
perforation of the quadrate, resembling in this respect the
Rhynchocephalia. The vomers are long, and separate the elongated choanae
from each other. The palatines separate the vomers from the pterygoids,
which enclose a long median vacuity and are not connected with the
quadrates. The teeth are conical, and stand near the inner margin of the
jaws upon little prominences, with which they fuse. Some genera have teeth
upon the pterygoids also.
The vertebrae are very numerous and are mostly procoelous. They are
noteworthy for the possession of an additional anterior and a posterior
pair of articulating processes on the neural arches, homologous with the
zygosphenes and zygantra of Snakes and Iguanidae (see p. 582). Intercentra
are absent, except in the tail. The ribs have no tubercula, and articulate
with the centra of the vertebrae to which they belong.
The pectoral arch is strong. The scapulae are short and broad; the
coracoids, fused with the precoracoids, except for a notch, are flat and
broad, and meet ventrally; posteriorly they articulate upon the anterior
margin of the flat sternum, to the lateral margin of which are attached
several ribs. Clavicles and interclavicle seem to be absent. Abdominal ribs
are likewise absent. The pelvic girdle is feeble; the ilia, ischia, and
pubes are loosely connected with each other, the pairs of ventral elements
{489}meeting also in the middle line. The ilia are loosely attached to two
vertebrae in the Dolichosauri; in the Mosasauri they have lost this
connexion. Both anterior and posterior limbs are transformed into
pentadactyle paddles, with much shortened and broadened bones of the arms
and legs. The digits are to a certain extent hyperphalangeal, since several
of them possess five phalanges.
The Pythonomorpha are undoubtedly allied to the Sauria, but they are
certainly not their ancestors, since typical Autosauri occur in the Lower
Chalk; nor are the Snakes their descendants, in spite of many convergent
resemblances. We consider them to be the marine collateral branch of the
Sauria, which rapidly developed highly specialised, often very large forms,
restricted to the Cretaceous epoch, with a wide, cosmopolitan distribution.
ORDER I. DOLICHOSAURI.
This older group is characterised by the sutural symphysial connexion of
the two mandibles and by the possession of two sacral vertebrae. The body
is snake-like. Pleurodont. _Dolichosaurus longicollis_ of the Lower Chalk
of Kent and Sussex; total length about 3 feet, with about seventeen
cervical vertebrae and pleurodont teeth. _Acteosaurus_ of Istria; anterior
extremities distinctly shorter than the posterior pair; tail long.
Vertebrae, like those of _Dolichosaurus_, with zygosphenes.
_Plioplatecarpus_ of the Upper Chalk of Holland has a slender
interclavicle; the vertebrae are without zygosphenes, but those of the
cervical region possess a downwardly directed long hypapophysial process
with a separately ossified epiphysis.
ORDER II. MOSASAURI.
The two halves of the lower jaw are connected by ligament and are therefore
movable as in Snakes. There are no sacral vertebrae, the pelvis having lost
its connexion with the vertebral column. The formation of the limbs into
paddles is more pronounced than in the Dolichosauri.
_Mosasaurus_, the chief genus, so called from Mosa, the Latin name of the
river Maas, with several species from the Upper Cretaceous strata of the
Netherlands, England, and North {490}America. _M. camperi_, from Belgium,
with a skull about 4 feet in length, armed with many large, curved,
acrodont teeth. The vertebral column consists of about one hundred caudal
and thirty-four precaudal vertebrae, of which seven are cervical, without
zygosphenes. The total length of the type-specimen is estimated at 25 feet.
_Platecarpus_ of North America and New Zealand, and various other North
American genera, also contained species of large size.
_Liodon._–Premaxilla without teeth, the others nearly smooth instead of
being ridged. With a very wide distribution in the Chalk of Europe, North
America, and New Zealand. _L. haumuriensis_ of New Zealand seems to have
been the giant amongst these monstrous marine creatures; its total length
has been computed from imperfect fragments at 100 feet.
_Clidastes_, of the Upper Cretaceous of North America and Europe, although
not so massive, comprises the most elongated forms. The cervical vertebrae
possess long median hypapophyses with separate epiphyses; most of the
vertebrae are much elongated and have well-developed zygosphenes. _C.
tortor_ had a skull nearly two feet and a half long.
{491}CHAPTER XII
SAURIA–AUTOSAURI OR LACERTILIA–LIZARDS
_SUB-CLASS XI.–SAURIA._
_Reptiles with movable quadrate bones, with a transverse, external,
cloacal opening, near the posterior lateral corners of which open the
eversible, paired (right and left) copulatory organs._
The Sauria, which comprise the AUTOSAURI or Lacertilia in the wider sense
and the OPHIDIA or Snakes, are the most recently developed groups of
Reptiles. No fossils are known from strata earlier than those of the
Cretaceous epoch. Their origin has probably to be looked for among the
Prosauria, of which _Sphenodon_, cf. p. 294, is the only surviving member.
The Sauria have attained their great development within the Tertiary
period. They, both Autosauri and Ophidia, are now the two dominant
Reptilian groups, and they have, so to speak, a future before them, being
apparently still on the increase in numbers and species, but certainly not
in size.
ORDER I. AUTOSAURI OR LACERTILIA–_LIZARDS_.
_Saurians which have the right and left halves of the mandibles connected
by a sutural symphysis._
The overwhelming majority possess well-developed limbs, movable eyelids and
cutaneous scales, covered by the mostly thin and horny epidermis. But there
are many kinds of Autosauri, especially those belonging to the degraded,
burrowing families, which have lost not only one or both pairs of limbs,
but even the limb-girdles, while the eyes have become concealed beneath the
skin, and in some cases the scales have been lost, or reduced {492}to mere
vestiges. Moreover in some of these burrowing and limbless forms the
quadrate bones have become more or less immovable.
We divide the Autosauri into three sub-orders:–I. GECKONES, p. 502; II.
LACERTAE, p. 513; III. CHAMAELEONTES, p. 567, with about 270, 1500, and 50
species respectively.
The Autosauri are of great interest, since they exhibit a great, almost
endless variety in shape, size, and structure in direct adaptation to their
surroundings. Most of these modifications are restricted to the external
organs, or rather to those which come into direct contact with the outer
world, namely the skin, the limbs, the tail, or the tongue. The majority of
the Autosauri are terrestrial, but there are also semi-aquatic forms. There
are climbing, swiftly running, and even flying forms, while others lead a
subterranean life like earthworms. Most of them live on animal food,
varying from tiny insects and worms to Birds and Mammals, while others live
upon vegetable diet. According to this diet, the teeth and the whole
digestive tract are modified. The intestine is relatively short in the
carnivorous, long in the herbivorous species. But swiftness, the apparatus
necessary for climbing, running, and digging, the mechanism of the tongue,
the armament and the muscles of the jaws (hence modifications of the
cranial arches, etc.), stand also in correlation with the kind of food and
with the way in which it has to be procured.
A very interesting study of the influence of the climate and the nature of
the country upon Reptiles has been made by Boettger[147] with especial
reference to the Transcaspian desert-region. The winter is there short, but
very severe, and there is a considerable amount of snowfall, while the
summer is intolerably hot. The spring arrives suddenly. Lilies and tulips,
which have been asleep for nine or ten months, sprout towards the end of
February, and a carpet of flowers covers the ground for a short time. Then
everything shrivels up during the rainless and fierce heat of the summer,
and the autumnal storms of dust and sand kill off the last remnants of
vegetation. There are no trees, and even prickly shrubs are rare. Instead
of broad leaves the plants have grass-like blades or needles. The little
shrubs do not form coherent patches, but they are scattered {493}about, and
around the roots of each shrub the wind accumulates little mounds of sand
and dust, a place of retreat for rodents, lizards, snakes, and even for the
female tortoises. G. Kadde's "law of the steppe" is in full force;–there is
little change of forms in a wide district, but all these forms are
peculiar, and they congregate socially in great numbers. Most
characteristic are those kinds of Geckos which, like _Teratoscincus_, cf.
p. 507, have become inhabitants of sand instead of climbers of rocks and
trees; various kinds of _Phrynocephalus_, cf. p. 521, and _Varanus
griseus_; the four desert-species of Lacertidae are brownish-grey or sandy
yellow, with conspicuous stripes or spots. Of snakes are to be mentioned
_Eryx jaculus_, digging in the sand, and about ten other non-poisonous
snakes. _Tropidonotus_ is, of course, restricted to permanently watery
places, where they can get frogs and fishes. Of poisonous snakes there is
the Cobra and _Echis arenicola_. Of Amphibia only _Bufo viridis_ and _Rana
esculenta_ var. _ridibunda_ exist in suitable places, but there are neither
Tree-frogs nor Newts.
Characteristic features of these inhabitants of the desert are the
following:–
1. Velocity. The Lizards are slender. The Sand-snake, _Tephrometopon_, is
whip-like; even the Cobra has a relatively narrower and longer tail than
the Indian specimens, although the number of the vertebrae and of the
scales is the same. All the desert-snakes are remarkable for the great
number of their ventral shields, two hundred and more.
2. Hard, scaly covering, for instance in _Agama_, _Echis_, _Gymnodactylus_,
_Teratoscincus_; the latter with its fish-like scales is exceptional among
Geckos, resembling the likewise deserticolous _Geckolepis_ and _Homopholis_
of Africa.
3. Capacity for digging in the sand in order to escape great cold, or
burning heat. All the Lizards and the Tortoise, _Testudo horsfieldi_, have
strong claws. The snakes _Typhlops_ and _Eryx_ dig with their specially
modified snouts, and their tails are very short and blunt. The Sand-viper,
_Echis_, has the scales of the back arranged in very oblique rows, so that
it can heap sand upon its body by wriggling, shaking, and up-and-down
motions of the body. The Agamoid _Phrynocephalus_ does this by means of
lateral folds of the skin.
4. Arrangements for running on sand. The lizard _Eremias_ {494}has very
large crural shields; _Scapteira_ has the digits broadened out into
shovels; others, e.g. _Phrynocephalus_ and _Teratoscincus_, have long
lateral fringes on the digits, a very rare arrangement among Geckos,
occurring elsewhere among them only in _Ptenopus_ and _Stenodactylus_,
which are likewise inhabitants of the desert.
5. Protection against the everlasting, ubiquitous sand. In the digging
species the nostrils are directed upwards instead of forwards; in most of
the snakes they are protected by complicated valves, or they are reduced to
small pin-holes. The eyes of _Typhlops_ are overhung by the head-shields.
In _Agama_ and _Phrynocephalus_ the margins of the lids are broadened into
plates and are furnished with peculiar scales. In _Teratoscincus_ the upper
lid is enlarged. The lizard _Mabuia_ has the lower lid much enlarged, with
a transparent window in it, so that the eye can be closed without impeding
sight, an arrangement carried to the extreme in _Ablepharus_, cf. p. 560.
The ear-opening is either small, or protected by fringes of scales, or it
is abolished, _e.g._ in _Phrynocephalus_.
6. Coloration. Pure green is quite absent, even in _Bufo viridis_ and in
_Rana esculenta_, since there is no green in that country, at least not of
long duration. White, with grey and black spots, occurs only in the
nocturnal Geckos. Yellow, brownish, reddish colours are common, in
adaptation to the sand. The advantages of the carmine-red, and of the blue
spots of _Phrynocephalus_, and the yellow or bright red under surface of
its tail, are unknown. Striation is of frequent occurrence among the
lizards and snakes, probably in adaptation to the dry grass heaped up
around the scattered shrubs.
Concerning the various organic systems of the Autosauri only some of the
more important features may here be mentioned.
SKELETON.–The vertebrae are procoelous, with the exception of most of the
Geckones, in which they are amphicoelous. So-called intercentra, in the
shape of unpaired nodules or wedges, persist between most of the cervical
vertebrae. In the tail these wedges, the remnants of the basiventralia, are
generally present, frequently in the shape of chevron-bones. Sometimes they
fuse with the centra of the vertebrae; occasionally the axial or central
portion of these basiventrals persists as a sort of fibrous disc, which may
calcify separately, and is interposed between the caudal end of the centrum
and the articulating {495}knob. The caudal vertebrae of the Geckones and of
most Lacertae are liable to break across, like those of _Sphenodon_. They
are enabled to do this owing to a transverse split, which makes its
appearance with the ossification of the vertebral bodies and extends later
into and across the neural arch and the various lateral processes. The
split is ultimately referable to a transverse septum of cartilage, wrongly
called chordal cartilage, which develops in the shell of the body of the
vertebra, destroys the chorda, and extends peripherally. The cells of this
septum retain throughout life their juvenile quasi-embryonic character.
When the tail is broken off–and this always happens at such a septum–the
cells of the remaining half reproduce a new tail. The latter is, however,
in reality a sham tail, since neither new centra nor arches, but only a
non-segmented rod or tube of fibro-cartilage is produced by this process of
regeneration. Reproduction of centra is precluded by the previous normal
reduction of the chorda, around which alone proper bony centra could be
formed. The regenerated tail is, however, invested with new muscles, and
with skin, but the scales often differ considerably from those of the
normal organ. Boulenger[148] has found that the new or aberrant scaling is
in some cases a reversion to an ancestral form. This is, for instance, the
case in _Pseudopus_, and in the Tejoid genus _Gymnophthalmus_; to a certain
extent also in Geckos and Skinks. On the other hand, Lacertidae,
Gerrhosauridae, and also Anguidae reproduce a caudal scaling true to their
type. Injured or broken-off tails are often reproduced double, or even
trifid; sometimes an additional little tail grows out from an injured spot,
anywhere on the side of the old remaining but mended tail.
The ribs of the trunk articulate by their capitula only, while the reduced
tubercula are attached to their vertebrae by ligaments. In the tail the
capitular portion is much reduced, while the tuberculum is much stronger
and lies behind, no longer above, the capitulum, fusing sometimes directly
with the centrum. The ribs of the poststernal region of Geckos and
Chameleons are very long, and meet each other in the middle line, forming
thin cartilaginous hoops.
The limbs are of the typical pentadactyloid type. The distal tarsalia are
often fused with the metatarsals, so that the chief {496}bending of the
foot is effected by truly intertarsal joints. The greatest modification
occurs in the foot of the Chameleons, in which the proximal tarsalia are
reduced in number, and form a globe for the articulation with the tibia and
fibula.
The shoulder-girdle and sternum much resemble that of _Sphenodon_ in their
completeness. The coracoids articulate with the sternum; the precoracoids
and the basal parts of the scapulae often send out several processes
towards those of the other side, so that several fenestrae are formed. The
clavicles are complete, but are absent in the Chameleons. The interclavicle
is mostly T-shaped. A presternum is absent, but the sternum proper is well
developed, often forming a rhomboid plate, usually cartilaginous, often
diverging backwards into xiphisternal processes.
The pelvis is attached to two vertebrae by means of several ribs. The
ischium and pubis form symphyses. The pubis carries a well-developed
lateral process, and the obturator-nerve pierces the shaft of the pubis.
Epipubic and hypo-ischial cartilages are of frequent occurrence.
The hyoid apparatus consists of a median, styliform rod, which extends
forwards into the tongue; it is often bifid behind. The unpaired piece
carries two pairs of horns. The posterior of these, the first pair of
branchial arches, extends backwards along the gullet, and is very long if
the tongue is very slender and protractile. The anterior pair, the hyoid
arches, consists of two pieces on either side, one short and directed
forwards, the other long, connected with the former at a sharp angle and
continued upwards to the sides of the skull, often in direct continuity
with the columellar chain of the ear.
The modifications of the skull concern chiefly the composition of the
temporal arches, see Figs. 55, M, N, O, p. 281. The quadrate bone is
movable, but it has become fixed in various degraded families, where the
skull shows a great reduction and concentration; the postorbital and
temporal arches, the interorbital septum, and with it the columellae cranii
are lost. The columella cranii of the Chameleons, which is generally stated
to be absent, is really present, although in a much reduced state, and is
partly imbedded in the interorbital septum. The occipital condyle has
become bifid in Amphisbaenidae.
Burrowing and living in sand are often correlated with partial or complete
reduction or loss of the limbs and their {497}girdles. This loss of limbs
is as a rule correlated with an elongation of the trunk, not always at the
expense of the tail, which in such cases is much shortened. The vestiges of
the hind-limbs come to lie as near the vent as possible. This reduction of
the limbs occurred in several families which are not directly related to
each other. Moreover, it does not occur in all the members of the family,
not always in those of the same genus, and there is a considerable amount
of individual variation. In most cases of reduction the fore-limbs
disappear before, or are smaller than, the hind-limbs. In the
Amphisbaenidae (cf. _Chirotes_, p. 566), and in the Tejidae the reverse
takes place. In extreme cases the reduction is so complete that even the
pectoral girdle has disappeared, leaving scarcely any trace, _e.g._ in
_Dibamus_, p. 564.
The SKIN is normally covered with scales, which are formed by the cutis and
have a horny epidermal coating. The latter, thin and transparent, is shed
periodically, peeling off in flakes, except in _Anguis_ and perhaps other
snake-shaped creatures, which shed the skin in one piece. In the
Amphisbaenidae the scales have practically disappeared. When well developed
the scales are prominent, and imbricate or overlap with their free
posterior edges; but in many cases the scales are not "scale-like" at all,
only like little tubercles, which give the skin a granular appearance.
Frequently, for instance in the Scincidae and Anguidae, all the scales
contain "osteoderms," or ossified portions of the cutis, and encase the
whole body and tail. In other families, _e.g._ Lacertidae, such osteoderms
are restricted to the scales or shields on the head, where they come into
contact and fuse with the underlying cranial bones, and moreover roof in
the supratemporal fossa.
The skin of the Autosauri is entirely devoid of glands. The femoral and
pre-anal pores of many families, occurring especially in the males, are
probably not glands. They are arranged in rows on the under surface of the
thighs and in front of the anal opening. Each of these organs perforates a
scale and leads into a tubular invagination, which is lined with epidermal
cells, the proliferation of which produces a horny yellowish débris, and
this fills the tube and appears above the surface in the shape of a little
cone. The use of this "excretion" is unknown; it is possibly hedonic.
{498}Most Autosauri are capable of changing colour. In most of them this
faculty is restricted to the assumption of paler or darker tints owing to
the shifting of the colouring matter contained in the chromatophores. In
others new, often vivid colours are the result. The mechanism is described
in detail in the Chameleon on pp. 570 and 574.
Pigment is deposited either directly in the upper strata of the cutis, just
below the Malpighian layer, or it is contained in chromatophores. The
latter are imbedded in the deeper layers of the cutis, and send out movable
contractile processes, in which their pigmented protoplasm is conveyed
towards or away from the surface. The only colours available are black,
red, yellow, and white, with their combinations of grey and brown. The
white pigment consists of guanin-salts. Blue and green are structural
colours, not due to pigment. The same can no longer be said of the Ophidia,
since Boulenger has observed accidentally that green Tree-snakes (e.g.
_Dryophis_) give the alcohol in which they are kept the colour of green
Chartreuse.
DIGESTIVE ORGANS.–The tongue is very variably developed, and affords good
taxonomic characters. It is always furnished with many tactile, or with
gustatory, corpuscles. When the tongue is very long and narrow it is
generally forked, and in these cases, for instance in the Varanidae, is
almost entirely used as a sensory organ. In others, especially where it is
broad, it assists in catching the food, and in the Chameleons it has
attained a most elaborate development (see p. 569).
Salivary glands are restricted to labial glands. In _Heloderma_ those of
the lower jaw are transformed into poison-glands, an analogy to what
prevails in the poisonous snakes. The intestinal canal is longest in the
herbivorous forms; the rectum sometimes possesses a short blind sac or
caecum.
The CLOACA of the Sauria is somewhat modified; instead of the Coprodaeum,
Urodaeum, and Proctodaeum forming three successive chambers, the urodaeum
is practically reduced to its dorsal half, forming a dorsal recess between
the two other chambers. The Coprodaeum is constricted into several
successive chambers, and is always well shut off from the urodaeum by a
strong sphincter. The urodaeum receives the urinary excretions, which are
mostly chalky white and are rather consistent instead of being fluid. The
right and left oviducts also open into it. The vasa {499}deferentia open
into the dorso-lateral portions of the walls of the urodaeum, but the
sperma is conducted by folds of the lining of this chamber towards the
bases of the copulatory organs, which, although arising from the lateral
and posterior corners of the cloaca, where uro- and procto-daeum meet, are
stowed away outside the cloaca. These organs are always paired. The
proctodaeum or outermost cloacal chamber is shallow. Its inner opening is
round and is furnished with a sphincter, but it is surrounded and covered
by lips of the outer skin, which form a transverse slit. This is due to the
peculiar arrangement of the copulatory organs.
Each organ consists of a tube of erectile tissue, and can be everted like
the finger of a glove. To the apex of the tube is attached a long retractor
muscle, which arises from the ventro-lateral surfaces of the caudal
vertebrae and extends a considerable distance back. When at rest and
withdrawn the organs form slight conical, longitudinal swellings on either
side of the root of the tail, an external feature by which male specimens
can generally be distinguished. Only one organ is inserted at one time.
The majority of Autosauri lay EGGS, surrounded by a white or yellowish
shell, which is either hard, for instance in Geckos, or parchment-like,
_e.g._ in Chameleons, in _Lacerta viridis_ and _L. agilis_, and in _L.
vivipara_. Eggs with a thin and soft shell sometimes exhibit the
paradoxical feature of increasing in size after they have been laid. This
is explained by the growth of the embryo, which stretches the shell and
does not merely live upon the white and yellow contents of the egg itself,
but also takes in air and moisture. Many Lizards do not lay their eggs
until they contain ripe embryos, which burst the shell shortly after
deposition. Some, for instance _Lacerta vivipara_, _Anguis fragilis_, and
_Chamaeleo pumilus_, are practically viviparous. The embryos, especially
those which are enclosed in hard-shelled eggs, are provided with a sharp,
calcareous "egg-tooth" on the top of the snout.
The LUNGS are thin-walled sacs, sometimes provided with lateral
ex-sacculations, and these reach their greatest development in the
Chameleons. The breathing is effected by the motion of the ribs. Inflatable
sacs on the throat, or on the sides of the neck, for ornamental or sexual
purposes, occur in various families. The lungs of much-elongated,
snake-shaped Lizards are generally {500}asymmetrical; the right being
reduced in Amphisbaenidae; the left in other cases.
Several Autosauri, for instance the Geckos, _Psammodromus_, and various
other Lacertidae have a weak voice.
The FAT-BODIES are mysterious organs which are situated beneath the skin,
and extend from the inguinal region forwards along the ventral sides of the
belly. They are often of considerable dimensions; largest in the spring, in
both sexes, at the time of propagation. Their colour is greyish-white or
yellow, owing to the great accumulation of fat in the meshes of the
connective tissue which composes the frame-work of these organs. An artery
enters them, breaks up into capillaries, and these combine to form an
efferent vein. After the time of propagation these organs are reduced to
grey or reddish flaps, consisting mainly of very vascular connective
tissue. G. W. Butler[149] has written a long paper on their morphology. The
same author[150] has investigated the "sub-divisions of the body-cavity in
Lizards, Crocodiles, and Birds," with reference to peritoneal diaphragmatic
structures.
The GEOGRAPHICAL DISTRIBUTION OF THE AUTOSAURI teaches few, but important
lessons. We have to restrict ourselves to the principal families, leaving
out those which are small and have a limited distribution; also those
which, like the few Anelytropidae in Africa and in Mexico, are not natural
groups.
The Geckones, which are probably the oldest of modern Autosauri, are
practically cosmopolitan, being absent only in the cold and in the cooler
temperate regions. They are common even in Oceanic Islands, for instance in
New Zealand and in the Sandwich Islands. Although not at all aquatic, they
are particularly fit to be transported accidentally on or in the trunks of
floating trees, to which they cling firmly, and they can exist without food
for months. I once received a little South American Gecko in perfect health
from a grocer, who found it in a well-closed wooden box containing canned
meat, two months after delivery of the box in Cambridge.
The Scincidae, likewise an old family, are equally cosmopolitan, but
although many exist in the islands of the Pacific a few only occur in New
Zealand. Many of the genera have a very wide distribution; for instance,
_Lygosoma_, with its one hundred and sixty or more species, occurs in the
Australian and {501}Palaeotropical regions, and also in North and Central
America, not extending, however, into South America. _Mabuia_, with more
than sixty species, occurs in the Palaeotropical and the Neotropical
regions. Whether these and other widely-distributed genera are all natural
is another question.
The Agamidae, Varanidae, Lacertidae, and the Chamaeleontes are restricted
to the Old World. The Agamidae and Varanidae have the widest distribution,
occurring in the whole of the Old World with the notable exception of
Madagascar and New Zealand. The Lacertidae are Palaearctic and
Palaeotropical, being however absent in Madagascar, and, broadly speaking,
not extending eastwards beyond Wallace's line. It is a most suggestive fact
that most of those families of Reptiles, and even of other Vertebrates
which have a wide distribution and are apparently debarred from
transgressing Wallace's line, are also absent from Madagascar.
The Chameleons are essentially African, with their centre of greatest
abundance and development in Madagascar, only one or two species occurring
in Socotra, Southern Arabia, and in Ceylon and Southern India. Since they
also exist, _Ch. sechellensis_, on various islands in the Indian Ocean, for
instance in Mauritius and the Seychelles, the Chameleons are perhaps an
indication of the former existence of a direct land-connexion between
Southern India and Southern Africa.
The Iguanidae are essentially American, with the remarkable exceptions of
_Chalarodon_ and _Hoplurus_ in Madagascar, and _Brachylophus_ in the Fiji
and Friendly Islands. This peculiar distribution finds some analogies in
that of Dendrobatinae (p. 272), certain Boinae (p. 601), and _Centetes_ and
_Solenodon_ among Insectivora. An Iguana (_I. europaea_) has, however, been
described from the Eocene of France and England. The supposed relationship
of the Iguanidae with the Agamidae makes the problem only more puzzling,
since Agamidae are absent in Madagascar. If we have recourse to the
Zonuridae, which are confined to Africa and Madagascar, and are supposed to
be intermediate between Anguidae and Iguanidae, then we may have ultimately
to conclude that the Malagasy Iguanoid genera and the American Iguanidae
are a case of convergent evolution.
The Amphisbaenidae are distributed over America, including the West Indies,
Africa exclusive of Madagascar, and the {502}Mediterranean countries. This
is very puzzling, considering that these subterranean, helpless creatures
positively cannot travel. Boulenger regards them "as a degraded type of the
Tejidae, with which they are to some extent connected by _Chalcides_ and
its allies," _i.e._ genera with reduced limbs, cf. p. 562.
However, this supposed relationship with a strictly American family does
not explain the occurrence of Amphisbaenidae in Africa. Either they are not
a natural group, or they had, as already degraded, limbless creatures, a
much wider range; and this would imply their being a very old family,
perhaps as old as we suppose the Coecilians to be.
Anguidae occur in North and South America, in Europe and the Mediterranean
parts of North Africa, and in Trans-Gangetic India. Their older relations,
the Zonuridae, inhabit Africa and Madagascar.
Madagascar is consequently devoid of Agamidae, Varanidae, Lacertidae,
Anguidae, and Amphisbaenidae, while it possesses, besides the cosmopolitan
Scincidae and Geckones, only Chameleons, Gerrhosauridae, and Zonuridae,–all
three essentially African families,–and a few Iguanidae. This means that
the Autosaurian fauna of Madagascar is intimately related to that of
Africa, and that it possesses only old families so far as Sauria are
concerned. But since this great island was separated from its continent not
earlier than in Mid-Tertiary times, it follows that most of these "old"
families are comparatively recent.
Australia possesses only Agamidae and Varanidae besides the ubiquitous
Geckos and Skinks. Besides the latter two families it has nothing in common
either with Madagascar (an analogy with the Anura) or with America. The
Autosauri consequently do not support the idea of a Notogaea, cf. p. 74.
This again indicates the comparatively recent age of Autosaurian families.
The marked difference which exists between the Old and the New World points
to the same conclusion. On the other hand, the Autosauri support the idea
that the Palaeotropical region is but the tropical and therefore richer
continuation of the now impoverished Palaearctic sub-region.
SUB-ORDER 1. GECKONES.–The typical Geckos are characterised as follows.
_Four-footed Autosauri with amphicoelous vertebrae; skull without bony
temporal arches; clavicles dilated and with a perforation near the ventral
end; parietal bones {503}separate; eyes (with few exceptions) without
movable lids; pleurodont; tongue fleshy and broad, slightly nicked
anteriorly, and capable of protrusion._
This definition does not apply to a few forms. In the _Eublepharinae_ the
vertebrae have advanced to the procoelous condition, and the parietals are
fused together, while the eyes are provided with typical, movable lids. In
the _Uroplatinae_ the clavicles are not dilated, and the nasals are fused
into one bone. The Geckos seem to be not only a very independent but also a
very old branch of Saurians. Although fossil representatives are unknown,
the resemblance of their vertebrae to those of the Palaeozoic Microsauri is
at least remarkable. They are now practically cosmopolitan within the
warmer zones, being found in abundance in all intertropical countries and
islands, even in New Zealand. About two hundred and seventy species are
known, which have been subdivided into about fifty genera. The generic
differences are trivial with few exceptions, and refer mostly to the
structure of the digits.
[Illustration: FIG. 118.–Map showing the distribution of Geckonidae.]
The more important features of the vertebral column are the absence of
axial joints and the persistence and life-long growth of the chorda
dorsalis. Each vertebral centrum consists of a cartilaginous tube, more or
less calcified or ossified, with a narrow waist and a cartilaginous septum
in the middle. In the tail this septum, which is only slightly invaded by
ossification, coincides exactly with the line of transverse division of the
vertebrae into an anterior and a posterior half. This is the level where
the tail breaks off and whence it is renewed. Between every two successive
centra lies an intercentrum, broadest ventrally, crescent- {504}or
wedge-shaped. Dorsally it is continued as fibro-cartilage, and the whole
ring acts as an articular pad instead of the joint. Chevron-bones are
common in the tail.
The ribs are bifurcated, but the tubercular portion is frequently reduced.
The post-thoracic ribs are usually very slender, and so long that they meet
each other in the middle line, in this case bearing an extraordinary
resemblance to the so-called "abdominal ribs" of other reptiles.
The bony frame of the skull is slender. There is a complete absence of bony
arches spanning over the temporal fossae, or bordering the orbit, which is
open posteriorly. The upper jaw, owing to the slender and flexible nature
of the respective bones, is movable upon the rest of the skull; in this
respect not unlike the upper jaw of a duck. The dentition is pleurodont and
the teeth are minute. The eyes of the typical Geckos are peculiar. They are
covered with an absolutely transparent skin, shaped like a watch-glass,
beneath which the eye moves freely, while the true upper and lower lids are
reduced to tiny folds. The covering "watch-glass" is probably a
modification of the nictitating membrane. In the Eublepharinae, however,
and in the few species of the Geckonine genera _Aelurosaurus_ of Borneo and
Australia, and _Ptenopus_ of South Africa, the upper and lower lids are
present and movable. The pupil contracts mostly into a vertical slit,
except in the few diurnal kinds, e.g. _Phelsuma_, of the islands in the
Indian Ocean, and the African _Lygodactylus_.
Another peculiarity of at least many Geckos is the extraordinary
development of the endo-lymphatic sacs of the ear, which, being filled with
the chalk-like otoconia or otolithic crystals, perforate the skull, and are
stowed away in the shape of a pair of large bags behind the ears, or on the
sides of the neck.
The skin exhibits considerable variety. It is mostly soft above, with
little granular tubercles, sometimes containing small dermal ossifications
or calcifications. The latter are most developed on the head, where they
occasionally fuse with the underlying bones. A few species of _Tarentola_
possess supra-orbital bones, independent remnants of such osteoderms. The
ventral surface is generally covered with small imbricating scales, but in
some genera, e.g. _Homopholis_, such scales occur also on the dorsal
surface, reaching their highest development in _Teratoscincus_ (p. 507). In
a few forms, notably in _Ptychozoon_ {505}(p. 512), the skin of the sides
of the body and tail is produced into a series of lobes and flaps, the
object of which seems to assist adhesion. Many, perhaps the majority of
Geckos, have adhesive digits, by means of which some kinds are enabled to
climb absolutely smooth and vertical surfaces, for instance a window-pane;
or, what is more startling, they run along the smooth, white-washed
ceiling, back downwards. The apparatus is complicated in its minute detail,
but is very simple in principle. The adhesion is effected neither by sticky
matter, nor in the way described in the Anura (p. 187), but by small and
numerous vacua. The under surface of each digit is furnished with many
transverse lamellae. The pressing down of the foot upon a smooth surface
causes the lamellae to spread asunder and to drive out the air; partial
retraction lets them return to their original position by virtue of their
elasticity; and little vacua are produced. Each lamella is further beset
with tiny hair-like excrescences, which secure adpression to even the
slightest irregularity of surface and at the same time enhance the
elasticity of the pads. The arrangement of the lamellae and pads differs
much in the various genera. For instance, the lamellae are either broad and
entire, or they are divided into two parallel rows, with or without lateral
hairy fringes; or the under surface of the digits is granular, but strongly
fringed; or the lamellae are restricted to the dilated tips of the digits,
etc. The fingers and toes are mostly furnished with sharp, curved claws,
and these are in many cases retractile between some of the lamellae, or
into a special sheath. Those Geckos which live on sandy, barren ground are
as a rule devoid of adhesive pads, the digits being narrow. The typically
padded, adhesive digits cause a peculiar sensation when a Gecko hangs on to
one's finger, and this feeling has perhaps given rise to the erroneous
notion of stickiness.
[Illustration: FIG. 119.–_Ptychozoon homalocephalum._ A, Ventral view of
the right hand. × 2. B, Side view of a finger to show the peculiar
arrangement of the claw-bearing joint.]
The tail exhibits many kinds of shape and size. Mostly {506}cylindrical and
tapering to a point, it is leaf-like in _Gymnodactylus platurus_ of
Australia; provided with many lobes, and used as a parachute in the Malay
_Ptychozoon_. In _Nephrurus asper_ of Eastern Australia the tail is quite
short, much shorter than the limbs, much swollen at the base, and very thin
towards the end, which carries a round knob. The tail of all Geckos is very
brittle and can be quickly regenerated, except the long rat-like tail of
the Persian _Agamura_. In many other desert-forms the tail is long,
slender, and laterally compressed, acting in such cases like that of
desert-forms among the Lizards.
Many Geckos have a voice, mostly rather feeble, and sounding like a soft
"click" or "chick" produced by our tongue. Repetition of this sound
resembles in some species the word "gecko." They lay eggs, rather globular,
or but slightly oval, hard-shelled, and white, mostly two in number.
_Naultinus elegans_ of New Zealand is said to be viviparous. The males are
generally larger than the females, and they are further distinguished by
the possession of femoral or pre-anal pores.
All Geckos feed upon animals, chiefly upon insects, but the larger forms
take anything they can master. With few exceptions they are nocturnal,
which, however, does not prevent them from occasionally baking themselves
in the sun. They are capable of changing colour, but since their
ground-colour is almost universally grey, yellow, or brown, the range of
the colour-changes is restricted to the adoption of darker or lighter hues.
The skin is shed in flakes and eaten.
Geckos are absolutely harmless; they cannot even inflict painful bites.
However, in many countries they are feared as much or even more than the
most poisonous snakes. In the south of Spain and Portugal, for instance,
where Geckos are plentiful in and outside the houses, and are consequently
objects of daily observation, the "_osga_" is considered a dreadfully
poisonous creature. They become very tame, or rather confiding in their
regular habits, provided they are not molested. If caught–and they have
many enemies among other lizards and snakes–the only safety of these
defenceless and mostly small creatures lies in their tail, which, being
extremely brittle, is left in the claws or jaws of the pursuer. The
remaining stump soon produces a new tail, in shape and size like the old
one, but with a different and simpler scaling. I knew of several specimens
of {507}the Portuguese _Platydactylus facetanus_, which, having lost their
tails in the act of being caught, were kept in a box for six weeks without
food. On their arrival in England they had each grown a new stump nearly
half an inch long!
FAM. GECKONIDAE. SUB-FAM. 1. GECKONINAE.–Vertebrae amphicoelous; parietal
bones separate; clavicles dilated and perforated. Hereto belong the
overwhelming majority of Geckos, only a few of which can be mentioned.
_Teratoscincus scincus._–This most peculiar creature, about six inches in
length, inhabits the steppes of Turkestan and neighbouring desert-regions
of Persia. It is a thorough desert-form. The digits are devoid of adhesive
lamellae, but are granular inferiorly and strongly fringed laterally, an
arrangement which is rare among Geckos, practically restricted to it with
_Ptenopus_ and _Stenodactylus_, which are likewise deserticolous. This is a
beautiful illustration of adaptation to the surroundings. A Gecko, instead
of climbing rocks and trees, has lost the climbing apparatus, or has
transformed parts of it for running upon loose sand. The body is covered
with imbricating, rather large and smooth scales. The tail is round at the
base, compressed in its posterior half, covered below and on the sides with
scales like those of the body, but on the upper side with a series of
large, transverse, nail-like plates. By rubbing these plates upon each
other, this Gecko produces a shrill, cricket-like noise, sitting at night
in front of his house, perhaps in order to attract grasshoppers. The noise
is made by both sexes.
_Ptenopus_, a Gecko of Damara Land, likewise adapted to desert-life,
produces a similar chirping noise by its throat.
_Phyllodactylus_ is a genus of world-wide distribution, occurring in
tropical America, Africa, Madagascar, and Australia, extending to the
Norfolk Islands and to Lord Howe's Island. One species, _Ph. europaeus_,
occurs on the islands in the Western Mediterranean. The digits are
furnished with transverse lamellae, the greater number of which are broken
up into small scales forming three longitudinal series. The ends of the
digits are dilated, with two large plates inferiorly, separated by a
longitudinal groove into which the claw is retracted. The upper parts of
the body are covered with juxtaposed scales intermixed with larger
tubercles. The abdominal scales are small and imbricating. The cylindrical,
tapering tail is slightly prehensile, covered with {508}small scales
arranged in verticils. This species is devoid of femoral or anal pores.
General colour above grey-brown, with darker and lighter markings; a dark
streak on the side of the head, passing through the eye. Under parts
whitish. Total length up to 3 inches. The eggs are almost round, measuring
8.7 by 7 mm.
[Illustration: FIG. 120.–_Hemidactylus turcicus_ (left), and _Tarentola
mauritanica_ (right). × 1.]
_Hemidactylus_, likewise a widely distributed genus, with many species. The
digits are dilated, inferiorly with two rows of lamellae; the clawed joints
are slender, bent at an angle, and rising from within the extremity of the
dilated portion. _H. turcicus_, between 3 and 4 inches long.–The upper
parts of the body are covered with minute granules, mixed with larger
tubercles. The abdominal scales are small and slightly imbricating. The
male has several pre-anal pores. The tail is covered above with minute
scales and tubercles, below with a series of large transversely dilated
plates. The general colour is white below, brown above, with darker spots,
and with white specks on many of the tubercles. This species extends from
{509}Southern Portugal and Spain to Karachi. Like _Phyllodactylus_ and
various other kinds of Geckos, the body is semi-transparent; so much so
indeed that the white eggs shimmer through the body in certain lights.
_Tarentola mauritanica_ s. _Platydactylus facetanus_.–The digits are
strongly dilated, with undivided lamellae below, and a flat, nail-like
scute on their upper surface near the tip. Only the third and fourth digits
are clawed. Femoral or pre-anal pores are absent. The upper parts are
covered with scales and granules, and bear several longitudinal rows of
strongly keeled, large tubercles; the under parts have hexagonal scales.
General colour above greyish-brown, with darker or lighter markings; with a
dark streak through the eye. Total length of large males about 6 inches.
This species is one of the commonest Geckos in the Southern Mediterranean
countries. In Portugal it extends northwards to the Douro. It has been
introduced by ships into the ports of Cette, Toulon, and Marseilles. It is
easily kept in captivity, like most Geckos indeed, provided they are
supplied with a variety of insect-food, water in the shape of drops, and
suitable places to hide in. A female, which I had received from Algiers in
a little tin box, with a lump of meat (presumably its food!), laid two eggs
six weeks after its arrival. This was towards the end of April. Towards the
end of June in the same year it again laid two eggs, measuring 13 × 10 mm.
Another specimen laid in June in two successive years. These and other
Geckos live very well in a greenhouse, or in a large glass cage. They
change colour most adaptively. They hunt preferably at night for insects,
which are stalked and then suddenly rushed at. Drops of water are taken by
a lapping motion of the tongue. For sleeping-places they selected bits of
hollow bamboo, but these had to be vacated when some tree-frogs crept into
them for the daytime, and the Geckos took to some curved pieces of bark, on
the under side of which they slept, with their backs downwards. This is, by
the way, a favourite position of rest of most Geckos. But _Stenodactylus
guttatus_ of Egypt lies flat on its belly, tucks the fore-feet under and
inwards like a cat, rests the head upon them, and stretches the hind-limbs
out backwards. The little Geckos are rather intelligent. They take no
notice of a finger put against the other side of the glass to which they
happen to cling; but {510}when the hand is put inside their cage and
approaches them too near, they dart off suddenly. When driven into a corner
they wriggle and wag their tails, or even raise the latter, perhaps as an
invitation to grasp it, in which case it would of course break off. When
caught, they emit feeble sounds, and attempt to bite with the mouth widely
open. During the moulting, which takes place at least twice a year, in the
spring and in the autumn, the skin peels off in flakes; if, as happens
sometimes, the skin upon the lamellae is not stripped off neatly, these
refuse to act, and the creature cannot climb until all the old skin has
been rubbed off.
In their native haunts they are very regular in their habits. Favourite
resorts of theirs are old olive trees or oak trees, the rough and cracked
bark of which affords excellent places for hiding in. Hollow trees are of
course preferred. Not a single specimen is seen during the early hours of
the morning or in the forenoon; but when the sun has become broiling hot,
and our own shadow passes over the stem of a tree, we become aware of
flitting little shadows which jerk over its surface. These are Geckos which
had been basking, motionless; very dark grey, almost blackish, just like
the colour of the grey bark upon which the last wet season's moss has been
scorched to a black cinder. It is difficult to espy a Gecko whilst it is
glued on to such a tree. Only the little beady eyes betray it, watching you
carefully. Nothing appears more easy than to catch that motionless thing.
You put out your hand and it is gone; like a flash it has moved a foot
higher up, or down, to the right or to the left, just where you least
expected it to go, and there it clings on motionless as before. It does not
seem to run; it glides along, dodging over to the other side of the stem
and back again. There is system in its motions, since, taking a last
leisurely look around, it gently disappears in a rent or hole. Towards the
evening, or when the shadows become longer, the Geckos become lively. One
after another appears on the surface, upon the tree, or at the entrance of
the cave, and they all move about in their peculiar rushing jerks. Spiders,
flies, mosquitoes, moths, form the principal diet, and the hunting goes on
well into the night. Where a gecko has been seen once it is sure to
reappear the next day at the same hour. Those which take up their abode
inside a house become almost domesticated. They are strange sights when
hunting for flies, {511}running up and down the papered walls; but we
fairly gasp when they come to the upper corner, calmly bend over, and with
the next jerk slide along the white-washed ceiling. We are accustomed to
flies performing such feats, but at animals five inches long, supple and
fat, we are inclined to draw the line. However, that is the way of Geckos,
and–be it confessed–the more we ponder over the mechanism of their fingers
and toes, the less we comprehend how such little vacua can support or
suspend such heavy creatures from a dry and often porous surface.
_Gecko._–The digits are strongly dilated with undivided lamellae. All,
except the pollex and hallux, have a very short compressed terminal phalanx
with a retractile claw. Males with femoral or pre-anal pores. This Eastern
genus includes some of the largest of all Geckos.
_G. stentor_ of the Malay countries reaches a length of 15 inches. _G.
verticillatus_ s. _verus_ s. _guttatus_ ranges from Eastern Bengal to China
and through the Indian archipelago. It grows to about one foot in length.
The head is large; the back is covered with small granules and about a
dozen rows of large tubercles. The tail, when intact, and the belly are
covered with scales, those of the tail being arranged in transverse rows,
several of which make up distinct rings. The upper parts of the body are
grey or yellowish with red spots and vermiculations. According to
Theobald[151] it lays about eight hard-shelled white eggs as big as a
musket-ball, cementing them to trees, rocks, or secluded buildings. The cry
is "touk-tay," several times repeated, and ending in a long-drawn out,
diminuendo, guttural rumble. This animal does not confine itself to
insects, but eats young rats also. Dr. Mason has seen it devour smaller
species of house-lizards, and Theobald has seen it seize a bat flying round
the room, and devour it.
Tennent[152] tells the following story about one of these creatures: "In an
officer's quarter in the fort of Colombo, a Gecko had been taught to come
daily to the dinner-table, and always made its appearance along with the
dessert. The family were absent for some months, during which the house
underwent extensive repairs, the roof having been raised, the walls
stuccoed, and the {512}ceilings whitened. It was naturally surmised that so
long a suspension of its accustomed habits would have led to the
disappearance of the little lizard; but on the return of its old friends,
it made its entrance as usual at their first dinner the instant the cloth
was removed."
_Ptychozoon._–The digits have the same structure as described in the genus
_Gecko_, but they are entirely webbed. The extraordinary feature of
_Ptychozoon_ is the membranous expansions on the sides of the head, body,
limbs, and tail, which are said to act as parachutes. _P. homalocephalum_,
the only species, inhabits the Malay Islands and the Malay Peninsula. It
reaches a length of 8 inches. A specimen obtained by F. H. Bauer in Java,
in the month of November, laid two eggs a few days after its capture. One
young was hatched in the middle of the following May, and two days later
another came out of the second egg. The characteristic folds of the skin
were already clearly discernible.
SUB-FAM. 2. EUBLEPHARINAE.–Differing from the true Geckos by their
procoelous vertebrae and the fusion of the two parietal bones into one. The
eyelids are not reduced, but remain functional. This sub-family is
undoubtedly a heterogeneous assembly, as indicated by the very scattered
distribution of its few species (about seven), in India, West Africa, and
Central America.
[Illustration: FIG. 121.–_Ptychozoon homalocephalum._ × ⅔.]
SUB-FAM. 3. UROPLATINAE, composed of a few species of the genus _Uroplates_
in Madagascar. The distinctive characters of {513}these otherwise typical
Geckos are the fusion of the nasal bones into one, the small size of the
interclavicle, and the non-dilated shape of the clavicles.
Neither the Eublepharinae nor the Uroplatinae are more nearly related to
other Autosauri than are the other Geckos. They are modifications within
the sub-order of the Geckones.
SUB-ORDER 2. LACERTAE.–_Autosauri with procoelous, solid vertebrae, and
with the ventral portions of the clavicles not dilated._
Cope,[153] discarding outer appearances as deceptive in the classification
of the Lacertae, laid stress upon internal characters, notably the presence
or absence of osteoderms, the formation of the skull, and the structure of
the tongue. Boulenger[154] has followed and improved upon Cope's
arrangement, and has elaborated the classification, which, being used by
himself in the three volumes of the Catalogue of Lizards in the British
Museum, has also been followed in the present work, with slight alterations
in the order of treatment of the families. For our present purpose we
diagnose the families as follows, giving preference to such characters as
are most easily ascertained:–
SYNOPSIS OF THE FAMILIES OF LACERTAE.
Fam. 1. Agamidae. Acrodont. Tongue broad and thick. No
osteoderms. Old World, p. 515.
Fam. 2. Iguanidae. Pleurodont. Tongue short and thick. No
osteoderms. America, Madagascar, Fiji
Islands, p. 528.
Fam. 3. Xenosauridae. Pleurodont, solid teeth. Anterior part of
tongue retractile. No osteoderms on the body.
Mexico, p. 536.
Fam. 4. Zonuridae. Pleurodont. Tongue short, not retractile. With
osteoderms at least upon the skull, where
they roof in the supratemporal fossae.
African sub-region, p. 536.
Fam. 5. Anguidae. Pleurodont, solid teeth. Anterior part of
tongue emarginate, retractile into the
posterior portion. Osteoderms on body and
head, roofing over the supratemporal fossae.
Limbs mostly reduced. America, Europe, India,
p. 537.
Fam. 6. Helodermatidae. Pleurodont, lower teeth grooved, with poison-
glands. Tongue bifid. Osteoderms tiny.
Postfronto-squamosal arch absent, p. 540.
Fam. 7. Lanthanotidae. Pleurodont. Tongue short and bifid. {514}
Postfronto-squamosal arch absent. No
osteoderms. Borneo, p. 541.
Fam. 8. Varanidae. Pleurodont. Tongue very long, bifid, smooth,
very protractile. No osteoderms. Postorbital
and temporal arches incomplete. Old World,
p. 542.
Fam. 9. Xantusiidae. Pleurodont. Tongue very short and scaly. No
osteoderms. Supratemporal fossa roofed over
by the cranial bones. No movable eyelids.
Central America and Cuba, p. 547.
Fam. 10. Tejidae. Teeth solid, almost acrodont. Tongue long,
deeply bifid, with papillae. No osteoderms.
Limbs sometimes reduced. America, p. 547.
Fam. 11. Lacertidae. Pleurodont. Tongue long, bifid, with papillae
or folds. With osteoderms on the head.
Supratemporal fossae roofed over by the
cranial bones. Old World, p. 549.
Fam. 12. Gerrhosauridae. Pleurodont. Tongue long, with papillae, but
feebly nicked. With osteoderms on the head
and body, roofing over the supratemporal
fossae. African sub-region, p. 559.
Fam. 13. Scincidae. Pleurodont. Tongue scaly, feebly nicked.
Osteoderms on the head and body. Limbs
often reduced. Cosmopolitan, p. 559.
The following five "families" are much degraded in conformity with their
usually subterranean life, see p. 496:–
Fam. 14. Anelytropidae. Without limbs. Body covered with scales.
Mexico and Africa, p. 564.
Fam. 15. Dibamidae. Vermiform, limbless body covered with scales,
without osteoderms. Australasia and Nicobar
Islands, p. 564.
Fam. 16. Aniellidae. Without limbs; body covered with scales,
without osteoderms. California, p. 564.
Fam. 17. Amphisbaenidae. The body is covered with soft skin, forming
numerous rings with mere vestiges of scales.
Without limbs, except _Chirotes_ with four-
clawed fore-limbs, p. 565.
Fam. 18. Pygopodidae. Snake-shaped, with scales. Fore-limbs absent,
hind-limbs appearing as a pair of scaly
flaps. Australia, p. 567.
These eighteen "families" of the Lacertae fall into four main groups. We
naturally assume that the presence of osteoderms and of complete cranial
arches indicate more archaic conditions than their absence, just as we
conclude that limbless forms have been evolved from creatures with fully
developed limbs. We arrange the four groups with their families as
follows:–
{515}Group I. Zonuridae and Anguidae assume a central position, with
Iguanidae and Agamidae as two parallel families of highest development.
Aniellidae as the most degraded forms. Helodermatidae and Lanthanotidae
as rather primitive and solitary survivals.
Agamidae Iguanidae
| |
| Xenosauridae
| |
Zonuridae–Anguidae–Helodermatidae.
|
V
Aniellidae.
Group II. Xantusiidae–Tejidae–Amphisbaenidae.
Group III. Scincidae–Gerrhosauridae–Lacertidae.–Here also Anelytropidae
and perhaps also Dibamidae as degraded Scincoids.
Group IV. Varanidae, which are in many respects the most highly developed
of all.
Pygopodidae are of obscure relationship.
[Illustration: FIG. 122.–Map showing the distribution of the Agamidae.]
FAM. 1. AGAMIDAE.–Acrodont, Old-World Lizards, with a broad and short
tongue. The teeth are usually differentiated into incisors, canines, and
molars. The orbit is closed posteriorly; the temporal fossa is bridged over
by an arch which is formed chiefly by the squamosal and the well-developed
jugal; the postorbital mostly remaining small, and the postfrontal and
supratemporal bones being either absent or not present as separate
elements. The limbs are well developed. The eye, provided with complete
eyelids, is distinctly small and has a round pupil. The skin is devoid of
osteoderms, although large and numerous spines are often present,
especially on the head and on the tail. The Agamidae, of which about two
hundred species, arranged {516}in about thirty genera, are known, exhibit a
great diversity of mostly flat-bodied, terrestrial and more laterally
compressed, arboreal forms. The majority are insectivorous, a few Agamas
have a mixed diet, while _Uromastix_ and some others are chiefly, if not
entirely, frugivorous and herbivorous. They are an exclusively Old-World
family, avoiding the cooler parts of the Palaearctic sub-region, and also,
a very curious fact, Madagascar. The majority live in Australia and in the
Indian and Malay countries, comparatively few in Africa, chiefly the genus
_Agama_.
[Illustration: FIG. 123.–_Draco volans._ × ⅔.]
_Draco_ ("Flying Dragon").–The body is much depressed and the sides extend
as a pair of large wing-like membranes, which are supported by five or six
of the much-elongated posterior ribs, and can be folded up like a fan. On
the throat are three pointed appendages, a short one on either side and a
long one in the middle. The tail is very long and slender, but not brittle.
About twenty species of this extraordinary genus inhabit the various
Indo-Malayan countries; one, _D. dussumieri_, occurs in Madras. _D. volans_
of the Malay Peninsula, Sumatra, Java, and Borneo is about 10 inches long,
5 of which are taken up by the tail. The {517}male has a small nuchal
crest. The upper parts of this pretty creature have a metallic sheen, with
small dark spots and undulating cross-bands upon the rich brown
ground-colour. The wings are orange with black markings. The gular sac of
the male is orange, that of the female is blue.
The "Flying Dragons" use their wings as parachutes, but their sailing
powers are said to be very moderate. Certainly they do not fly by moving
the wings, but when at rest upon a branch, amidst the luxurious vegetation
and in the immediate neighbourhood of gorgeously coloured flowers, which
partly conceal them by their likeness, they greatly resemble butterflies,
especially since they have the habit of opening and folding their pretty
wings.
_Ceratophora._–This exclusively Ceylonese genus is remarkable for a
flexible, erect, and pointed appendage which arises from the top of the
snout; it is best developed in the males, vestigial or absent in the
females. Gular appendages are absent. The trunk is crestless, slightly
compressed, and covered with partly keeled scales. The tail is slender and
very long, about two-thirds of the total length of the animal. The general
colour is olive-brown, with irregular darker markings and with light
streaks on the head and thighs. _C. stoddarti_ and _C. tennenti_ are about
10 inches long, the former without, the latter with, little scales upon the
rostral appendage.
_Lyriocephalus_, with _L. scutatus_ (Fig. 124) of Ceylon as the only
species, is remarkable for its Chameleon-like appearance. A splendid case
of convergent evolution, but most improbably of mimicry. The tympanum is
quite hidden. The head is raised into a pair of sharp bony edges. On the
top of the nose is a thick globular lump, recalling the genus
_Ceratophora_, and also various Malagasy Chameleons. The back and sides are
covered with very small granular scales, intermixed with several rows of
enlarged scales as in _Chameleo pumilus_, and there is a serrated crest
along the back from neck to tail. The under parts are covered with large
keeled scales with sharp points directed backwards, especially on the tail.
The whole body is laterally compressed. The pollex and the fifth toe are
strongly opposed to the other digits. The general colour is greenish above,
whitish below. Total length about one foot.
_Calotes_, with many species in India and in the Malay Islands, is
distinguished by a crest on the neck and back. Many of the males have a
gular sac. The tail is extremely long. These lizards are remarkable for
their changes of colour.
{518}[Illustration: FIG. 124.–_Lyriocephalus scutatus._ × ⅔.]
_C. versicolor_ ranges from Afghanistan through the whole of India to
Southern China, and attains a length of 14 inches, 11 of which are taken up
by the tail. It possesses no gular sac, but has a well-developed crest. The
whole body and tail are covered with strongly keeled scales. When the
lizard is irritated, or swallowing its food, the head and neck become
brilliant red, whilst the usually brownish tint of the body is converted
into pale yellow. Mr. Annandale has favoured me with the following
observations on _C. emma_:–"In the Malay Peninsula the Europeans misname
this lizard Chameleon. The colour-changes appear to be brought about by
emotions, although the lizard is often darker towards {519}evening than it
is at mid-day. The males are very pugnacious, and change colour as they
fight. At the time of courtship a curious performance is gone through by
the male, the female remaining concealed in the foliage hard by. He chooses
some convenient station, such as a banana leaf or the top of a fence, and
advances slowly towards the female. His colour is then pale yellowish
flesh-colour, with a conspicuous dark spot on each of the gular pouches,
which are extended to their utmost. He stands upright, raising the fore
part of the body as high as possible, and nodding his head solemnly up and
down. As he does so, the mouth is rapidly and repeatedly opened and shut,
but no sound is emitted. When he is driven away, caught or killed, the dark
spot disappears entirely from the neck. If one male is captured, another
takes his place within a few hours."
_C. ophiomachus_ of Southern India and Ceylon reaches 2 feet in length, has
a fold of skin in front of each shoulder, and is generally known as the
"blood-sucker" on account of the red colour displayed during excitement on
the head and neck.
_C. mystaceus_, chiefly in Burma and Siam, but also in the Nicobar Islands
and in Ceylon, has a small gular sac and an oblique fold in front of each
shoulder. The specific name seems to refer to the yellowish lips.
Mason[155] gives the following vivid account of it:–
"This is a very common species in gardens in Toung-ngoo. A pair made their
home in the mango trees near my study window. The female blundered into the
house a few days ago, but I found her a very unattractive animal of a
uniform earth-brown colour. The male, however, is sometimes a beauty. He
may be often seen jerking his head up and down, with the head, pouch, and
whole front of the body a glowing ultramarine blue, contrasting beautifully
with the reddish-brown of the hinder part of the body and tail. From the
nose to the shoulders, below the eye, is a broad white band, which is
interrupted by three reddish-brown patches, in line with the white band,
before reaching the uniform reddish brown of the hinder part of the body.
Occasionally the white band below the eye assumes a brownish colour, and
the animal appears to have a brown band down each side. He does not always,
however, appear in this gay dress. While I am writing, I see him coming
down the trunk of one of the trees {520}in a very faded garment. His skin
suggests a bright calico after it has been washed, whose colours succumb to
soap. The blue is there, but it is no longer the bright blue of yesterday.
It has changed to a dull light indigo colour. He runs across the grass to
the foot of another tree, and stops on the bare ground at its base, where
for a minute or more he bites with great energy at a struggling
grasshopper, and while thus exercising himself the blue fades out from his
body altogether, and his whole body takes the colour of the brown earth on
which he stands. After tarrying a minute or two he ran up the other tree,
and the dull light blue colour seemed to return to him."
_Agama_ with many species in Africa and Asia; some in South-Eastern Europe.
The body is somewhat depressed. There is a fold across the throat and a pit
on either side; the presence of a gular sac is variable. A dorsal crest is
absent or but feebly developed. The males have pre-anal pores.
_A. sanguinolenta._–The body is covered with strongly keeled and pointed
scales. On the sides of the head are a few spine-like scales. The
ear-opening is partly concealed by a fringe of spinous scales. The males
have a gular pouch. This is a typical inhabitant of the deserts and steppes
of Turkestan. Zander[156] has observed the habits and many changes of
colour of this lizard. The usual garb is earthy brown above, with somewhat
darker and rather indistinct markings. The under parts are whitish.
Sometimes the creature changes to dirty white, at other times into blackish
or grey brown. Bluish-red stripes may appear on the sides of the body; blue
lines begin to show on the throat, and ultimately the whole belly,
originally white, may become ultramarine blue. When the general tone
happens to be sulphurous yellow, blue often appears on the tail and limbs.
Brick red appears on four longitudinal rows of patches on the sides of the
body. Sometimes the whole animal assumes a vinous tinge, or it is at first
greenish before turning into blue. The change begins on the tail and limbs,
extends over the head, and at length reaches the back. Red appears in both
sexes, more frequently in the female; blue almost entirely in the male.
Sunlight and warmth only intensify the colours. Adaptive coloration,
besides the usual sandy garb, has not been observed. The lizards live on
soil which is baked as hard as bricks, or in {521}cavities of old walls,
provided there is vegetation. They require vegetable food, besides insects,
grazing on grass, and having a fondness also for _Mesembryanthemum
cardiforme_. Very large males reach a total length of one foot. They are
pugnacious, especially during the time of breeding. The male inflates its
gular sac into the size of a walnut, stands up upon its four limbs, with
its head slightly lowered and turned to one side. Then it darts upon the
foe which it has been eyeing for some time.
[Illustration: FIG. 125.–_Agama stellio._ × ½.]
_A. stellio_ is the commonest Agama in Egypt, Asia Minor, and in some of
the Grecian Islands, where the Greeks still call it _korkordilos_, just as
they did in the time of old Herodotus. The Arabic name is _hardun_. This
lizard is easily recognised by the irregular folds on the neck, which are
beset with spinous horny scales. It grows to a length of 15 inches. The
general colour is brown, with dark patches on the back. When basking they
become almost black; in the breeding season the male assumes red tints on
the head and neck.
_Phrynocephalus._–This is a typical Agamoid of the steppes and deserts of
Asia. The head is short and thick, the ear is {522}hidden. The body is
depressed, devoid of a dorsal crest; on the throat is a transverse fold but
no sac.
A. Zander[157] has made interesting observations upon the habits of several
species.
_Ph. helioscopus_ lives on hard stretches of soil, which are absolutely
bare of vegetation, the soil being baked as hard as a paved road. The
lizards live on any insects they can get hold of, chiefly, however, upon
mining ants. When chased they run with short jerks, carrying the tail high
or rolled up.
_Ph. interscapularis_ occurs, in Transcaspia, on the shifting, loose sand.
It runs so fast that one scarcely sees anything but its shadow. The tail is
rolled upwards. With short jerks it suddenly changes its direction, stops
behind a few blades of grass, or in the open, makes a few shaking, wavy
movements, and covers itself lightly with sand. Shortly after that the top
of the head appears, the grains of sand rolling off between the strong
supraciliary ridges, and the little creature, only about 3 inches long,
peeps out of its temporary hiding-place.
_Ph. mystaceus_, which inhabits Transcaspia and parts of Southern Russia,
often faces its aggressor, raising itself upon its fore-limbs, curling and
uncurling its tail in its excitement, and holding its mouth widely open.
The creature, which attains a length of 9 inches, inclusive of the long
tail, then assumes a markedly changed aspect. The flaps of skin at the
corners of the mouth swell up into a half-moon-shaped transverse plate, the
hinder surface of which is covered by the outer skin, while the front is a
continuation of the rosy lining of the mouth, which thereby appears hugely
enlarged. When biting it hangs firmly on to the finger. This frightening
attitude is interesting, since it occurs in a much more developed condition
in the following genus.
_Chlamydosaurus kingi._–This peculiar Agamoid, which inhabits Queensland
and Northern and North-Western Australia, is easily recognised by the large
frill-shaped dermal expansion on either side of the neck. The two halves
are confluent on the throat. The whole frill can be erected, and is worked
by the much-elongated arches or horns of the hyoid apparatus, which extend
into the flaps of skin, somewhat like the ribs of an umbrella. The
specially modified hyoidean muscles spread out {523}and fold the frill.
When this curious creature is pursued it folds the frill and runs in a
semi-erect position upon its hind-limbs, with its fore-limbs hanging down.
However, it cannot keep up this peculiar gait for long, and it then
suddenly turns to bay, frequently at the root of a tree, which it can climb
with ease. When standing at bay it spreads out the shield to its full
extent, in the middle of which appears the widely opened mouth, which is
red inside and armed with powerful teeth. Altogether this lizard presents a
formidable aspect, and is an enemy not to be despised, considering that it
is strongly built and grows to nearly 3 feet in length. For a further
account of the habits and of the mechanism of the frill see De Vis.[158]
[Illustration: FIG. 126.–_Chlamydosaurus kingi._ × ¼.]
_Physignathus._–This is a water-loving genus, inhabiting well-watered
districts with luxuriant vegetation in Australia, Papuasia, Siam, and
Cochin China. The body and the very long tail are laterally compressed and
furnished with a low, serrated crest. _Ph. lesueuri_ of Queensland reaches
a length of about 18 inches. The general colour is dark olive above, with
darker and lighter {524}cross-bands, and with a broad black band reaching
from the eye to the shoulder. The under parts are pale olive, with small
black dots. The throat, although devoid of a special sac, is frequently
bulged out by the hyoid apparatus, as shown in Fig. 127, taken from a
specimen in the Zoological Gardens in London.
_Uromastix_ is a typical desert-form, inhabiting the dry and sandy tracts
of North Africa, Arabia, Syria, Persia, and North-Western India. The genus
is easily recognised by the short and thick tail, which is covered with
whorls of large spinous scales, while the much-depressed body and head are
almost smooth, being covered with very small scales. The tympanum of the
ear is quite exposed. The incisors are large, uniting in the adult into one
or two pairs of large cutting teeth, separated from the molars by a
toothless space. There is a transverse fold on the throat. Pre-anal and
femoral pores are well developed.
[Illustration: FIG. 127.–_Physignathus lesueuri._ × ⅓.]
These "Spiny-tailed Lizards" live chiefly upon vegetable food, leaves,
grass and fruit, but they vary this diet with insects, at least in
captivity, where they become rather partial to meal-worms. They are
absolutely terrestrial and diurnal, preferring sandy places, where they
bask or rather roast themselves in the sun; for the night, at the approach
of rain, or on dull and chilly days, they retire into their burrows, which
they dig in {525}the sand or in the hard ground, unless they hide in the
cracks of rocks. They have a regular mania for digging with their strong
limbs and short, curved claws. Although they love a great amount of heat,
and become stiff when cooled down to about 16° C. = 60 F., they can stand
several degrees of dry frost without injury. During the cold season they
hibernate. The spiny tail is used for defence. The lizard lies as a rule in
such a position in its hole that the tail blocks the narrow passage; when
touched with the hand it deals out jerky side-blows with the tail. The bite
is deliberate and very painful.
_U. hardwicki_ is a native of North-Western India and Beluchistan,
occurring especially in Sindh and Rajputana, for instance near Delhi and
Agra. This species is of a delicate sandy colour, with dark dots or
vermiculations, interspersed, occasionally, with pale blue specks. The
under parts are whitish on the tail with a greenish hue. A distinctive and
obvious mark is a large blackish patch on the anterior side of the thigh.
Total length up to one foot.
I have several times received consignments of the Indian Spiny-tailed
Lizard through the kindness of friends, but I must confess that they are
far less easily kept than one is led to believe from certain exaggerated
accounts. They are lovely, most interesting, and surprisingly tame
creatures. I received one lot in the month of June. They made burrows in
the dry soil, basked in the sun and on the grassy sods of their roomy cage,
and showed great curiosity. When approached, they at first scrambled off or
sank down flat, shut their eyes and feigned death. They then opened their
tiny yellow eyes a little, while others peeped out of their retreats to see
if all was safe, or attracted by some noise. Soon they became so tame that
they crawled over my hand. But the difficulty consisted in feeding them.
They greedily lapped up drops of water. Their dung consisted of the
indigestible parts of some species of _Equisetum_ or Mare's tail, mixed
with fragments of beetles and ants. Lettuce, cabbage, cauliflower, grass,
the flowers of red and white clover, Mare's tail, wheat, rice, and Indian
corn were offered, but they only took a few blades of grass and the hard
Indian corn, besides meal-worms. This is all the more astonishing since
other specimens are known to partake freely of herbaceous food. None of
them survived the late autumn, and most of them succumbed to a disease
{526}known as intussusception of the gut. They certainly could not complain
of the want of heat, since the bottom of their cage was kept permanently
warm by a lamp, and in the autumn they invariably slept in the warmest part
of the soil, avoiding the cool regions which would have given them a chance
of hibernating.
Another consignment arrived in the month of February. None of them ate
anything or survived the early summer.
[Illustration: FIG. 128.–_Uromastix acanthinurus._ × ¼.]
_U. acanthinurus_ and _U. spinipes_ are common in Algeria, Tunis, and
Egypt, where they prefer sandy and rocky localities. Their Arabic name is
_Dab_. In Algeria they are sometimes called "lézards des palmiers," perhaps
because they eat dates, besides berries, grass, and various flowers. Very
large specimens attain a length of 18 inches. Like the other species of
_Uromastix_ they have no voice. The African species can change colour to a
great extent. At a low temperature they are mostly grey or brownish black
above, dirty white below. When it is warmer they change to lighter shades
of brown or even to orange yellow and to green, with black or brown specks
and vermiculations. {527}A young specimen of _U. acanthinurus_ has been
observed to grow within twelve months from 90 to 150 mm. in length.
_Moloch._–The mouth of this peculiar-looking creature is very small; the
lateral teeth of the upper-jaw are implanted horizontally and directed
inwards. The body is much depressed, and, like the short tail and head, is
covered with small scales or tubercles intermixed with large spines. _M.
horridus_, the only species, inhabits the sandy districts of Western and
Southern Australia. Nothing is known about its habits except that it seems
to live upon ants. Its extremely rough skin is, according to an accidental
observation by Dr. Willey, highly hygroscopic. He happened to put a live
specimen into a shallow dish with water, when, to his surprise, the water
was sucked up as by blotting-paper.
[Illustration: FIG. 129.–_Moloch horridus._ × ⅔.]
_Liolepis._–The body is depressed, without a crest, and is covered with
minute granular scales. The tail is long, and has small keeled scales.
There is a strong transverse gular fold, and a fold along the side of the
body. The tympanum is distinct. Femoral, but no pre-anal, pores are
present.
_L. belli_, the only species, about 18 inches long when full grown, is a
native of South-Eastern Asia. The general colour is brownish, with pale
black-edged spots along the back; the sides are marked with black and
orange vertical bars; the under parts are orange, variegated with blue.
Annandale remarks that this is perhaps the commonest lizard on the barren
stretches of sand in Lower Siam, especially near the coast. It is
exceedingly active and timid. Though its colour is brilliant, the green and
{528}grey eye-like spots which ornament its back, and the orange and purple
stripes on its sides, are not conspicuous amidst the natural surroundings,
the former harmonising with the shadows cast upon the sand by the scanty
vegetation which it supports, and the latter being more or less concealed
by the folds into which the skin that covers the ribs naturally falls. When
the male is roughly handled and is unable to use its powerful jaws, it
flattens its body in such a way that the stripes become most conspicuous.
The female is unable to do this with such effect, as her ribs do not seem
to be so mobile and her colours are less bright. _Liolepis_ lives in holes
in the ground, which often go down vertically for more than 2 feet before
there is a bend in their course. Each burrow generally contains a pair of
these lizards, which, according to the natives, are strictly monogamous.
FAM. 2. IGUANIDAE.–Pleurodont lizards with a short and thick,
non-protractile tongue; almost entirely American, with the remarkable
exception of two genera, _Hoplurus_ and _Chalarodon_ in Madagascar, and
one, _Brachylophus_, in the Fiji Islands. Most of the Iguanidae are
insectivorous, but some of the most striking forms are herbivorous, e.g.
_Iguana_, _Amblyrhynchus_, and _Basiliscus_. In their general structure the
Iguanidae closely resemble the Agamidae, from which they differ chiefly by
the pleurodont dentition. The orbit is surrounded by bone, and the temporal
fossa is bridged over by an arch which is formed by the junction of the
squamosal chiefly with the postorbital, the jugal taking as a rule less
share in the arch. Dermal ossifications are absent on the body.
There are about three hundred different species, which have been grouped
into about fifty genera, representing arboreal, terrestrial, burrowing,
semi-aquatic forms, and even one semi-marine species. Their external
appearance varies consequently within wide limits.
_Anolis_ is distinguished by the partial dilatation on the middle
phalanges, which carry a series of transverse adhesive lamellae. In its
general shape _Anolis_ resembles slenderly built and long-tailed
Lacertidae, which it may be said to represent in tropical and sub-tropical
America, inclusive of the West Indian Islands. The males have a large gular
appendage, which can be distended by the hyoid bones. _Anolis_ is an expert
climber, living in trees, or rushing about on fences or walls of houses in
search of insects; {529}most species can change colour to a great extent.
More than a hundred species are known, of which we mention only one, very
common in the Southern United States.
_A. carolinensis_ of the South-Eastern United States and of Cuba is
beautiful golden green on the whole upper surface; the gular sac becomes
vermilion when stretched; when flaccid, it is white with occasional red
lines and spots. The under parts are white. In cold weather and in
confinement this little lizard, which is scarcely 6 inches in length,
appears dark brown, sometimes with a white line along the back. The changes
of colour are very sudden. They are thoroughly arboreal, leaping from leaf
to leaf like Tree-frogs.
[Illustration: FIG. 130.–Map showing the distribution of Anguidae,
Iguanidae, and Zonuridae.]
In _Anolis_, _Polychrus_, _Hoplurus_, _Chalarodon_, _Liosaurus_, and a few
others, the posterior ribs are much elongated and imbedded in the abdominal
muscles, often reaching the medioventral line, a feature elsewhere known in
the Geckos only.
_Polychrus._–The body is laterally compressed, covered with small scales,
but devoid of crests. The digits are likewise compressed, with keeled
lamellae on the under surface and with four large scales at the base of
each claw. Both sexes have femoral pores. The male possesses a small gular
sac. A few species in Tropical America.
_P. marmoratus_ in South America, where it is often called the Chameleon on
account of its power of changing colour. The tail is nearly three times as
long as the head and body, and is covered with keeled scales. The general
colour of this arboreal creature, {530}which reaches a length of 18 inches,
is green, but the hues are very variable, and within a short time the
creature can change into dull brown, with or without blackish spots and
bands, or with whitish spots and black lines on the head and other parts of
the body.
_Basiliscus_ is remarkable for the high and erectile crests which are
developed on the back and tail of the males. The toes are bordered on the
outer side with small lobes. The limbs are long, the hind-limbs when
stretched forwards reaching the tip of the snout. Several species in
Central America and the adjoining countries to the south.
[Illustration: FIG. 131.–_Basiliscus americanus_ (male). × ¼.]
_B. americanus_ reaches the considerable length of nearly 3 feet. The male
has a crest on the top of the head, and this is produced backwards into a
leathery lobe. The back is adorned with a very high crest; the folds and
dark-coloured marks in which give, in the accompanying illustration, the
impression that the crest is supported by spines. The long tail carries a
similar crest. The general colour of the "Basilisc" is green and brown with
dark cross-bars on the back. The crest of the male is said to be red. These
creatures are very common amidst the {531}luxuriant vegetation on the banks
of the rivers of the Tierra Caliente of Mexico and in Guatemala. They lie
upon the branches of trees, preferring those which overhang the water, into
which they plunge at the slightest alarm. The high crests, being restricted
to the male sex, are not essential to their swimming; they propel
themselves by rapid strokes of the fore-limbs, letting the long rudder-like
tail drag behind. The eggs, measuring 20 by 13 mm., are laid in April or
May, and are hidden in a hole at the base of a tree. About one dozen make a
set, and they are said to be hatched within a very short time. Owing to
their being strictly herbivorous, these pretty and striking-looking
creatures do not endure captivity in Europe, unless indeed their particular
food can be procured.
_Iguana._–The body and tail are laterally compressed and are covered with
very small scales, while those on the top of the head are large. The neck
and back carry a high crest, which is composed of separate, laterally
compressed, soft spines. A similar but lower crest borders the anterior
edge of the large gular sac, which is not dilatable. The lateral teeth are
remarkable for their finely serrated or denticulated anterior and posterior
edges. Both sexes have long rows of femoral pores. Only two species in
Tropical America, absolutely herbivorous. Their delicate flesh is much
esteemed as food.
_I. tuberculata_ (Fig. 132), of South and Central America and the West
Indies, reaches a length of 5 to 6 feet. The general colour of the upper
parts is a mixture of green and blackish, frequently speckled with white or
yellow, and there is usually a pale band in front of each arm. The flanks
are marked with dark, light-edged bars. The under parts are pale greenish
or whitish. The Iguanas live in the trees, and when there is danger they
jump into the water whatever the height of the tree, coming down with
violence. In going up some of the narrow, unfrequented creeks in the
Mosquito country, according to Napier Bell,[159] the voyager often
encounters quite a shower of falling Iguanas, and runs some risk of getting
his neck broken. Large specimens, 6 feet long, weigh perhaps 30 lbs. They
burrow deep horizontal holes in the sloping side of a bank. About two dozen
eggs, nearly 2 inches long, are laid in a hole, where they are hatched in
the month of May.
{532}Iguanas are often brought to the markets, either lashed lengthwise to
a branch of the tree on which the specimen happened to be surprised, or
tied up with the long tendons of their own toes.
[Illustration: FIG. 132.–_Iguana tuberculata._ × ⅕.]
_Metopoceros cornutus_ of Hayti is closely allied to _Iguana_, but the male
has three conical horn-like scales on its head. The general colour of the
whole animal, which grows to more than one yard in length, is dull black.
The following two genera, each containing one species only, are restricted
to the Galapagos Islands. Darwin[160] gives a long and vividly written
account of their habits.
_Conolophus subcristatus._–Fully grown specimens are a yard long. Their
shape is stout, the head and fore part of the body appearing especially
heavy. The head is covered, or rather paved, with large cobble-stone-like
scales. On the neck is a low crest of recurved spines, while the median
line of the back appears simply serrated. All the teeth are trilobate. A
gular sac is absent. The coloration is striking. The head is lemon-yellow;
{533}the back is red, merging into dark brown on the flanks. The belly is
dark yellow with a tinge of reddish brown.
This lizard was found by Darwin on some of the Galapagos Islands. On James'
Island it was so common that the party found it difficult to pitch their
tent, on account of the ground being undermined by the many burrows of the
reptiles. They feed during the daytime upon the succulent cactus and the
leaves of various trees. The perfectly harmless creatures are, or were,
eaten by the inhabitants.
_Amblyrhynchus cristatus_ is closely allied to _Conolophus_, of which it
may be said to be an aquatic modification. The top of the blunt head is
covered with low, conical, broad-based scales. Over the neck, back, and
tail extends a continuous crest of low, recurved, spiny scales. All the
teeth are trilobate. The body and even more so the tail are laterally
compressed. The general colour is dark brown above, paler and inclining to
whitish below. Younger specimens have pale grey spots and blackish
cross-bands on the back and sides. Total length up to 4 feet. The
remarkable feature of this Iguanoid is its semi-marine life. It inhabits
the rocky and sandy strips of coast of most of the Galapagos Islands,
feeding upon certain kinds of algae, which it has to dive for, since these
plants grow below tide-marks.
_Phrynosoma_ ("Horned Toads").–The body of these little creatures is much
flattened and broadened, devoid of a dorsal crest, but covered with larger
and smaller, strongly keeled scales. The head is bordered posteriorly by
conspicuous osseous spines. The under parts are covered with small, very
regular scales. Both sexes have a long row of pores on the under surface of
the thighs. The general colour of the upper parts is a mixture of yellow,
grey, brown, and black, the larger spiny scales causing the animal to look
as if it were sprinkled with the dried husks of seeds, for instance those
of Buckwheat. The object is concealment, by close adaptation to the arid,
sandy localities which are the home of "Horned Toads." About one dozen
species inhabit the western half of the United States and Central America.
All the species are viviparous, almost the only instance among Iguanidae.
_Ph. cornutum_ has five spikes on each side of the head: one postorbital,
three temporal, and one occipital, the latter being by far the largest. The
sides of the lower jaw project in the shape {534}of prominent ledges, and
are protected by a series of small spines. The ventral scales are keeled.
The under parts are yellowish, frequently with a few brown spots. This
species, which grows to a length of 5 inches, ranges from Illinois through
Kansas and Texas to Northern Mexico.
[Illustration: FIG. 133.–_Phrynosoma cornutum_ ("Horned Toad"). × 1.]
_Ph. coronatum_, an inhabitant of California, has an additional smaller
spine between the two large occipitals. The scales of the belly are quite
smooth.
These peculiar-looking and interesting creatures recall some of the extinct
Dinosaurs in the curious configuration of their head: small miniatures
indeed. In order to be kept in good health, and to be observed properly,
they require, above all, warmth, sunshine to bask in, sand to burrow in,
and proper food. The latter consists of all kinds of small insects, the
necessary variety of which is best procured by making sweepings with a
butterfly-net in a meadow. They take green-flies, house-flies, ants, smooth
caterpillars, small moths, meal-worms, wood-lice, etc. The food is snapped
up very quickly by a flash of the tongue, which can be turned out, almost
like that of a frog, but only to the extent of half an inch. Water in the
shape of dew, or drops, is absolutely necessary. When in good condition,
they defaecate regularly every alternate day.
{535}[Illustration: FIG. 134.–_Phrynosoma coronatum_ ("Horned Toad"). × 1.]
They love to bask in the broiling sun, heating themselves well through; and
in the afternoon, long before sunset, when the sand is warmed up to 40° C.,
or fever-heat, they prepare to go to bed. For this they select a dry and
soft spot, and within a few minutes manage to dig themselves in flat,
literally sinking into the sand by pushing themselves forwards, and by
shovelling the sand upon their backs with peculiar motions of the fringed
sides of their flat bodies. Sometimes the spines of the head remain
sticking out, looking like dry thorns scattered over the sand. To prevent
the latter from getting into the nostrils, these are provided with
closely-fitting valves. Thus they remain concealed during the night, and
not until the sun is well up do they leave their hiding-place, first
peeping out, and then raising their head and neck, letting the sand roll
off between the spines. Still half concealed, the back covered with little
pebbles, seeds, or bits of dry leaves, they wait for a long time before
they feel lively enough to sally forth. Although mostly slow and deliberate
in their movements, stalking about with arched back, and raised upon the
fore-limbs, they can run fast enough for a few yards before they stop again
and nod in a ridiculous way. When they see themselves observed, they shut
their eyes and slowly sink {536}down. On cool and dull days they do not
appear at all, and during part of the cooler season they require artificial
heat until they are ready to hibernate. Unless they are allowed to
hibernate, they will keep on feeding through the winter, but in that case
are sure to die in the following spring.
FAM. 3. XENOSAURIDAE, with _Xenosaurus grandis_ in Southern Mexico as the
sole species, seems to connect the Iguanidae with the Anguidae. According
to Boulenger, its affinity to the former is shown by the T-shaped
interclavicle, the absence of symmetrical bony shields on the head and of
osteodermal plates on the body. Affinity to the Anguidae is indicated first
by the short tongue, which has a narrow, feebly incised, retractile
anterior part, covered with flat papillae; secondly, by the teeth, which,
instead of being hollow at the base, are solid; lastly, by the palatine
bones, which are widely separated.
_X. grandis_, scarcely one foot in length. The body is depressed, covered
above with minute granules and tubercles, below with smooth scales. A
distinct fold of skin extends from the axilla to the groin, recalling the
more strongly developed lateral fold of some of the Anguidae.
FAM. 4. ZONURIDAE.–This family, comprising four genera with about one dozen
species in South and Tropical Africa, and in Madagascar, likewise seems to
connect Iguanidae and Anguidae. It is distinguished from the former by
dermal ossifications, which roof over the supratemporal fossa; from the
latter by the tongue, the hollow teeth, and, in _Zonurus_ at least, by the
occurrence of dermal ossifications on the trunk and tail. The tongue is
short, villose, scarcely protractile, entire, or but feebly nicked at the
tip. The Zonuridae may therefore be defined as _pleurodont African lizards
with a short tongue, and with a bony roof to the supratemporal fossae_.
_Zonurus._–The whole head, back, and tail are covered with bony scales, the
horny covering of which forms very sharp spikes, especially on the tail.
The body is depressed. The ear-opening is large. South Africa, in dry and
rocky localities; one species, _Z. tropidosternum_, in Madagascar.
_Z. giganteus_ s. _derbianus_, with strong spikes on the occiput, neck, and
tail. General colour yellowish brown. Total length about 15 inches.
_Chamaesaura_ of South Africa closely approaches the {537}Anguidae by its
snake-shaped body, extremely long tail, and vestigial limbs. In _Ch. aenea_
both pairs of limbs are still present and pentadactyle, but are very small;
in _Ch. anguina_ the limbs are reduced to little styliform stumps; and in
_Ch. macrolepis_ they are altogether absent. The scales of the body and
tail are strongly keeled and imbricating, but are devoid of dermal
ossifications. Total length up to 2 feet.
[Illustration: FIG. 135.–_Zonurus giganteus._ × ¼.]
FAM. 5. ANGUIDAE.–Pleurodont lizards with osteoderms, and with the tongue
composed of two distinct portions, of which the anterior is thin,
emarginate, extensible, and retractile into the posterior thicker portion.
The supratemporal fossa is roofed in by dermal bones. The whole body is
protected by bony plates underlying the imbricating scales. The teeth vary
much in shape, but they are always solid, the new teeth not growing into
the base of the old ones, but between them. The limbs are in a very
unstable condition, there being in the family a general tendency to reduce
and lose the limbs. The shoulder- and pelvic-girdle however remain,
although sometimes merely vestigial. The tail is long, very brittle, and
easily reproduced. All the Anguidae are strictly terrestrial, and live on
animal diet. {538}Some _Anguis_, at least, are viviparous. The distribution
of the seven genera, with some forty species, is very scattered. The
majority, chiefly _Gerrhonotus_, inhabit Central America, a few occur
farther north and south–two, _Anguis fragilis_ and _Pseudopus pallasi_, in
Europe, and one in the Himalayas and in Burmah.
_Gerrhonotus_ has a pair of deep longitudinal folds, each of which extends
from the region of the neck along the side of the body towards the tail.
The four limbs are well developed and pentadactyle. The teeth are conical.
Many species, mostly in Central America. _G. coeruleus_ has the widest
range, extending from Costa Rica to Vancouver. It is also one of the
largest species, reaching a length of more than one foot. The tail is
nearly twice as long as the rest of the body. General colour above brown
with blackish bars and spots, especially on the more yellowish flanks;
under parts whitish with a greenish tinge, often with brown spots arranged
in longitudinal rows.
_Ophisaurus_ s. _Pseudopus_ is closely allied to the previous genus, being
possessed of the same kind of deep lateral folds; the limbs are, however,
reduced to a pair of tiny spikes, half concealed at the sides of the anal
cleft. The teeth are conical, and in the adult have somewhat flattened
crowns. The body and tail are very long and snake-like, but the head is
that of a typical Lizard.
_O. apus_ s. _Pseudopus pallasi_, the Glass-Snake of the Balkan Peninsula,
South Russia, Asia Minor, and Morocco, grows to more than one yard in
length, of which about two-thirds belong to the tail. The general colour is
brown above, paler below. Young specimens are olive-grey with dark brown
cross-bands on the back. _O. gracilis_ inhabits the Eastern Himalayas and
Burmah, the others live in North America.
The "Glass-Snake" inhabits bushy localities, where it can hide under the
fallen leaves and in the sand; it cannot climb, and avoids the water. Its
movements resemble those of a snake, but are far less graceful, owing to
the stiff armour in which the whole body is encased. The food consists
chiefly of snails, the shells of which are crushed, and of mice, but
nothing comes amiss which can be mastered, namely insects, worms, small
lizards, young birds, and vipers. The prey, when caught, is rapidly twisted
round and round, or shaken until it is giddy or stunned, whereupon the
Glass-Snake proceeds to chew it with its powerful jaws, and then to swallow
it in pieces. {539}Although it can bite so well, it never does so when
caught, but resorts to the much more disagreeable defence of twisting
itself around one's hand and arm, and besmearing them with its disgustingly
stinking excrements. Those who have observed Glass-snakes praise their
tameness, and the intelligent way in which they hunt about in search of
their food. They lay eggs under moss and leaves, and the young seem to
require many years to grow up.
[Illustration: FIG. 136.–_Anguis fragilis_ (the Slow-worm). × ½.]
_Anguis_, with only one species, _A. fragilis_, the "Slow-worm" or
"Blind-worm," is devoid of a lateral fold. Limbs are entirely absent. The
whole body is covered with smooth roundish scales, with a substratum of
dermal ossifications. The teeth are curved backwards, fang-shaped, and have
a very faint longitudinal groove on their anterior surface. The ear-opening
is very minute, more or less hidden by surrounding scales. The eyes are
perfectly well developed, provided with movable lids, and it does not speak
well for the power of observation of most people that this creature should
generally be known as the "Blind-worm." The whole skin is shiny, metallic,
quite smooth, brown above, blackish below. But the coloration is subject to
much individual variation. Old specimens are sometimes adorned with blue
specks. The very young are exquisitely beautiful, the upper surface being
silvery white, with a median and two more lateral lines of deep black; the
under parts are black. The iris is yellowish red. Very large specimens
measure more than one {540}foot in length, more than half of which belongs
to the tail. One in the British Museum is 425 mm. = 17 inches long.
The Slow-worm is viviparous, _i.e._ the young are fully developed, and
burst the transparent, soft, yellowish eggs immediately after these are
laid. This takes place in the months of August or September, about one
dozen making a litter. The little creatures are at first about one inch and
a half long, and as thin as an ordinary match. They eat the smallest of
spiders and delicate insects; later on earth-worms, which they bite into
and then suck out before devouring them. When six weeks old and well fed
they are about 3 inches long, but it is at least four or five years before
they are mature. The little ones carefully avoid the hot sunshine, and the
adults are likewise rather partial to the shade, although strictly diurnal.
Their chief food consists of earth-worms and slugs. For the night they
retire under moss, leaves, stones, or into the ground. In the autumn the
Slow-worms dig passages or burrows, which often serve as the
winter-quarters of many specimens, as if there were no other place
available, or rather as if the spot selected were by far the best with
regard to safety, dryness, and warmth.
FAM. 6. HELODERMATIDAE.–Pleurodont, _poisonous_ lizards of North America.
The teeth are fang-like, recurved, with slightly swollen bases, rather
loosely attached to the inner edge of the jaws. Each tooth has a groove on
its anterior and posterior surface, and a series of labial glands which
secrete the poison open near the bases of the teeth of the lower jaw. The
skull has strong postorbital but no postfronto-squamosal arches. The pre-
and post-frontals are in contact, separating the frontal from the orbit;
the premaxillaries are fused into one; the nasals and frontals remain
separate. The limbs are short, but strong and well developed. The tongue is
villose, with an anterior smooth portion, which is bifid and protractile,
resembling the tongue of the Anguidae and of _Aniella_. The skin of the
upper surface is granular, with many irregular bony tubercles, which give
it an ugly warty look. The under parts are covered with flat scales.[161]
_Heloderma_, the only genus, with _H. horridum_ in Mexico and _H.
suspectum_ in New Mexico and Arizona, reaches about 2 feet {541}in length.
The animal, stout, depressed, thick-tailed, looks rather repulsive when it
squats down in its usual lethargic way. The whole skin is blackish brown
and yellow or orange, these two "warning" colours being distributed
unevenly, except on the thick, peculiarly-shaped tail, where they are
arranged in alternate rings. The specific differences are rather imaginary.
The New Mexican form is supposed to be more orange and yellow than black,
with a somewhat smoother skin and with shorter toes and tail.
[Illustration: FIG. 137.–_Heloderma suspectum_ (the Gila Monster). × ⅕.]
The "Gila Monster" inhabits dry localities, spends most of the daytime in
concealment between the roots of trees, and crawls about in the evening in
search of worms, centipedes, frogs, and the eggs of large lizards. Frogs
are probably paralysed or killed by the bite which, although not so
dangerous as that of poisonous snakes, is effective enough to produce
severe symptoms even on man, and a few cases of death of people who had
been bitten are on record. In captivity they are very partial to eggs,
which they break and then lap up. During the dry and hot season they
aestivate.
FAM. 7. LANTHANOTIDAE.–_Lanthanotus borneensis_, of which only two
specimens are known, one in the Vienna Museum, the {542}other in the
Sarawak Museum, was described by Steindachner as the type of a distinct
family, near the Helodermatidae. Boulenger,[162] after examination of the
Sarawak specimen by means of a sciagraph, has come to the conclusion "that
the affinity of _Lanthanotus_ to the Helodermatidae is fully confirmed."
The teeth of _Lanthanotus_ show, however, no traces of grooves;
poison-glands are probably absent, and there are no osteoderms. The skin is
covered with wart-like tubercles, each with a horny, peeled scale. The eyes
are very small, the ears are concealed. The general colour is reddish brown
above, yellowish, with brownish bands, below. Total length about one foot,
a little more than half of which belongs to the roundish tail.
[Illustration: FIG. 138.–A, Ventral, B, dorsal view of the skull of
_Varanus griseus_. × 1. _B.O_, Basi-occipital; _B.S_, basisphenoid; _Col_,
columella auris or stapedial rod; _E.P_, ectopterygoid; _Fr_, frontal;
_Jug_, jugal; _Lac_, lacrymal; _N_, nasals; _Pal_, palatine; _Par_,
parietals; _Pr.f_, prefrontal; _Pt.f_, postfrontal, fused with postorbital;
_Ptg_, pterygoid (endopterygoid); _Q_, quadrate; _Tb_, turbinal; _Vo_,
vomer.]
FAM. 8. VARANIDAE.–_Pleurodont Old-World Lizards, with a long, deeply bifid
and protractile smooth tongue._ They reach a large size, and the neck is
relatively much longer than that of other lizards. The limbs are well
developed. The skin is {543}covered with very small juxtaposed scales and
tubercles above, while the ventral scales are squarish and arranged in
transverse rows. Osteoderms are entirely absent. The tail is very long,
often laterally compressed. The teeth are large and pointed, dilated at the
base. The premaxilla is unpaired and dorsally extends backwards to the
likewise unpaired nasal. There is a pair of small supra-orbital bones,
easily lost during maceration. The orbit is open behind, the jugal being
short and not meeting the postfrontal; the postorbital forms a slender arch
with the supratemporal. The vomers are long and diverge posteriorly. The
palatines, pterygoids, and ectopterygoids enclose on either side an oval
infra-orbital foramen. The Varanidae contain only one genus, _Varanus_,
with nearly thirty species in Africa, Southern Asia, and Australia, but not
in Madagascar.
[Illustration: FIG. 139.–Map showing the distribution of the Varanidae.]
_Varanus._–The name of "Monitor" bestowed upon these creatures has a
curious origin, owing to a ridiculous etymological mistake. The Arabic term
for Lizard is "Ouaran"; this has been wrongly taken to mean warning lizard,
hence the Latin _Monitor_, one of the many synonyms of this genus, e.g.
_Hydrosaurus_ and _Psammosaurus_. Many of the "Monitors" are semi-aquatic,
others inhabit dry, sandy districts, while others are at home in
well-wooded localities. They are all rapacious, taking whatever animals
they can master according to their size, which in some species amounts to 6
or 7 feet.
_V. niloticus_ inhabits the whole of Africa, except the north-western part.
It reaches a length of more than 5 feet. The colour of the adult is
brownish or greenish grey above, with darker reticulations and yellowish
ocellated spots on the back and limbs. The under parts are yellowish with
blackish cross-bands. The ground-colour of the young is black above with
yellow lines on the head and neck, and with yellow spots on the back and
limbs; the tail has black and yellow bars.
_V. salvator_ ranges from Nepal to Ceylon, Cape York, and {544}Southern
China, inclusive of the Malay Islands and the Philippines. This is the
largest species, specimens of 7 feet in length being on record. The general
colour is dark brown or blackish above, with yellow spots or ocelli. The
snout and chin have transverse black lines on a lighter ground. A black
band, bordered with yellow, extends from the eye along the side of the
neck. The under parts are yellow.
Mr. Annandale has favoured me with the following observations:–"_Varanus
salvator_ is common in Lower Siam, where it is equally at home on land, in
water, and among the branches of trees. The eggs are laid in hollow
tree-trunks. When in the water the lizard swims beneath the surface, the
legs being closely applied to the sides, and the tail functioning both as
oar and as rudder. Their food is very varied. In the states of Patalung and
Singora, in which the Siamese practise a form of tree-burial, these great
lizards are accused, probably with justice, of eating the flesh of the
corpses in the aërial coffins. I have disturbed a large Monitor devouring
the body of one of its own species, which had evidently been dead for some
days. Another, which was chased by some men, dropped from its mouth a small
flying squirrel (_Sciuropterus_); a third, which I dissected, had lately
swallowed a small tortoise, the hard shell of which had been broken into
innumerable fragments. The stomachs of several others contained nothing but
dung-beetles, for which Varanus may often be seen hunting, turning over the
dung of elephants and buffaloes with its fore-feet. The Malay name of these
lizards is Biawak."
According to Mason and Theobald[163] all the Varanidae and their eggs are
highly esteemed for food, and are sought for in hollow trees with the aid
of dogs. If not wanted at once, the wretched creature has its fore-feet
bent over its back, a few of its toes are broken and the sinews drawn out
and tied into a knot, rendering the animal helpless. The Karens, who are
extravagantly fond of the flesh, steal up the tree with a noose at the end
of a bamboo, and often noose them while leaping for the water, or catch
them in a boat which is brought under the tree. The head, the natives say,
is venomous, and they discard it altogether, but the flesh of the other
parts, which smells most odiously, is deemed preferable to that of fowls.
{545}Sir J. G. Tennent[164] gives the following account of _V. salvator_:–
"The 'Kabara-goya' of the Singhalese is partial to marshy ground, and when
disturbed upon land will take refuge in the nearest water. From the
somewhat eruptive appearance of the yellow blotches on its scales, a
closely allied species, similarly spotted, obtained the name of _Monitor
exanthematicus_, and it is curious that the native appellation of this one,
_Kabara_, is suggestive of the same idea. The Singhalese, on a strictly
homoeopathic principle, believe that its fat, externally applied, is a cure
for cutaneous disorders, but that taken inwardly it is poisonous. The
skilfulness of the Singhalese in their preparation of poisons and their
addiction to using them are unfortunately notorious traits in the character
of the rural population. Amongst these preparations the one which above all
others excites the utmost dread, from the number of murders attributed to
its agency, is the potent _kabara-tel_, a term which Europeans sometimes
corrupt into _cobra-tel_, implying that the venom is obtained from the
hooded-snake; whereas it professes to be extracted from the Kabara-goya.
"In the preparation of this mysterious compound, the unfortunate
Kabara-goya is forced to take a painfully prominent part. The receipt, as
written down by a Kandyan, was sent to me from Kornegalle by Mr. Morris,
the civil officer of that district; and in dramatic arrangement it far
outdoes the cauldron of Macbeth's witches. The ingredients are extracted
from venomous snakes by making incisions in the head of these reptiles and
suspending them over a basin to collect the poison as it flows. To this,
arsenic and other drugs are added, and the whole is boiled in a human
skull, with the aid of three Kabara-goyas, which are tied on three sides of
the fire, with their heads directed towards it, and tormented by whips to
make them hiss so that the fire may blaze. The froth from their lips is
then added to the boiling mixture, and so soon as an oily scum rises to the
surface, the kabara-tel is complete. Before commencing the operation of
preparing the poison, a cock has to be sacrificed to the demons.
"This ugly lizard is itself regarded with such aversion by the Singhalese
that if one enter a house or walk over the roof, it is regarded as an omen
of ill-fortune, sickness, or death; and in {546}order to avert the evil, a
priest is employed to go through a rhythmical incantation."
Captain Robinson, renowned as a hunter of tigers on foot in the old days of
muzzle-loading rifles, has told me the following unique use to which these
large lizards are put by ingenious thieves in India. In order to be able to
get over a wall too high for climbing without assistance, the thief
provides himself with a strong lizard, ties a rope round its waist and lets
the animal go, when it at once scales the mud wall by its strong and sharp
claws, and jumps down on the other side. The weight of the lizard, which,
moreover, holds vigorously on to the ground, and the friction of the rope
on the top of the wall, are sufficient to help the man over!
[Illustration: FIG. 140.–_Varanus salvator_ swallowing a Fowl's egg. × ⅛.]
It is a sight, never failing in its attraction to the visitors of the
Zoological Gardens in London, to see one of the big Monitors fed with an
egg. The lizard knows the treat well that is in store for it. It raises
itself up high in expectation, then examines the egg with the long tongue,
takes it up gingerly and swallows it entire, crushing it by the contraction
of the muscles of its gullet. On one occasion it was given a rotten egg
which burst in its mouth, and the lizard refused for a long time to take
another.
_V. gouldi_ is common in Australia and in New Guinea. It reaches a length
of about 4 feet. Its colour is brown above {547}with yellow spots on the
back and limbs, and with yellow rings on the tail. Two yellow streaks
separated by a black band extend from the temples along the side of the
neck. The under parts are yellowish, sometimes with black spots.
FAM. 9. XANTUSIIDAE.–Three Californian, or West-Indian genera, with less
than half-a-dozen species. _Pleurodont with a short tongue and with the
supratemporal fossa roofed over by bone._ The tongue is scarcely
extensible, with oblique overlapping folds which converge towards the
median line, and with scale-like imbricate papillae towards the tip. The
skull possesses complete postorbital and postfronto-squamosal arches, the
latter meeting the parietals and roofing over the supratemporal fossa. The
palatines are in contact with each other, and there are no infra-orbital
fossae. There are no osteoderms; the body is covered above with small
granular scales, below with larger scales. The eyes are devoid of movable
lids. The tympanum is exposed. Femoral pores are present. Limbs and tail
well developed. _Xantusia_ and _Lepidophyma_.
FAM. 10. TEJIDAE.–American Lizards with a long and bifid tongue. The
greater portion of the tongue is covered with scale-like papillae; the
anterior forked and pointed ends are smooth. The teeth are solid and
implanted almost upon the edge of the jaw, being therefore intermediate
between the acrodont and pleurodont condition. The shape of the posterior
teeth shows several modifications; they are conical or tricuspid, or
molar-like in the adult Tejus; in _Dracaena_ they are transformed into
large, oval crushers. The palatines are in contact anteriorly. The
infra-orbital fossae are surrounded by the palatine, pterygoid, and
ectopterygoid bones, the maxillary being excluded from the fossa, as in
_Varanus_ (see Fig. 138, p. 542). The skull has no supra-temporal arch.
Osteoderms are absent; the body is covered with small scales, or the skin
is simply granular above; the under surface is covered with larger scales,
generally arranged in transverse rows.
This large family, which comprises nearly forty genera with more than a
hundred species, exhibits great diversity of form. Some are inhabitants of
forests and are arboreal, while others are strictly terrestrial, preferring
hot and sandy plains, or they dwell below the surface and are transformed
into almost limbless and blind-worm-shaped creatures. The range of the
family extends over the whole of the South American continent, over the
West {548}Indian Islands, and through Central America into the warmer parts
of the United States.
_Tupinambis_ ("Teju").–The skin of the back is smooth, covered with small
scales; with large scales on the top of the head. The skin on the neck is
generally thrown into two irregular transverse folds. The long and narrow
tongue is capable of being telescoped into a sheath at its base. The
lateral teeth are compressed and tricuspid in the young, but the later
generations of teeth have obtuse crowns in the adult. _T. teguixin_ is the
largest member of the whole family; it reaches a length of a yard, most of
which, however, belongs to the tail. The general colour is bluish black,
with pale or whitish-yellow spots on the back, flanks, and tail, combining
into more or less transversely arranged bands. The limbs are black, with
many and tiny yellow dots. The ground-colour of the under parts is reddish
yellow, with irregular black bars. This species inhabits the greater part
of South America, east of the Andes, from Uruguay to the West Indies. _T.
nigropunctatus_ is confined to the Continent, and lacks the dark
cross-bands on the belly, which is uniformly yellowish or speckled with
black.
[Illustration: FIG. 141.–_Tupinambis nigropunctatus._ × ⅙.]
{549}The "Tejus" frequent forests and plantations, and are carnivorous.
Their strength and swiftness enable them to catch all kinds of animals,
from insects and worms to frogs, snakes, mice, and birds. As they take
chickens and eggs from the farms they are considered noxious, and they are
frequently hunted down with dogs for the sake of their flesh, which is
regarded as good to eat. They defend themselves with lashing strokes of
their long tail and with their powerful jaws. They retire into burrows, and
they deposit their hard-shelled eggs in the ground. In captivity they can
easily be kept on meat.
_Dracaena guianensis_ of the Guianas and the basin of the Amazon has the
lateral teeth transformed into regular large molars, with broad and rounded
crowns. The tail is strongly compressed, with a double, denticulated keel.
It seems to be semi-aquatic, and, to judge from the teeth, herbivorous.
_Ameiva_ and _Cnemidophorus_, with many species chiefly in tropical
America, have laterally compressed bi- or tri-cuspid teeth. The skin forms
a double fold on the neck, and is covered on the upper surface of the body
with very small scales; those on the ventral surface are large, and
arranged in regular rows. Most of the species are small, under one foot in
length, and are extremely pretty, very active, timid, and mainly
insectivorous.
_C. sexlineatus_ is one of the few species of _Cnemidophorus_ which
inhabits the southern half of North America. Like all its relations it has
the appearance of an ordinary lizard (_Lacerta_). The head is dark brown. A
purple or brownish band extends over the back and tail, bordered on either
side with three golden-yellow longitudinal lines. The flanks are brown, the
under parts bluish white. The iris is golden, and the inner margins of the
lids are bordered with a narrow band of bright yellow. This species is a
very fast runner, and frequents dry and sandy places. Its total length
amounts to about 10 inches.
FAM. 11. LACERTIDAE.–_Pleurodont Old-World Lizards, without osteoderms on
the body, and with the supratemporal regions roofed over by osteoderms._
The limbs are always well developed, and have five fingers and five toes,
always provided with sharp claws. The skin covering the head forms large
shields, mixed with small scales; most of which, especially the shields,
contain dermal ossifications. These frequently fuse with the underlying
bones of the top of the skull.
{550}[Illustration: FIG. 142.–Skull and lower jaw of _Lacerta viridis_. A,
Dorsal view; B, ventral view; C, from the left side; D, right half of the
lower jaw, from the inner side, with some of the pleurodont teeth. _E.P_,
Ectopterygoid; _F_, _Fr_, frontal; _jug_, jugal; _Lac_, lacrymal; _Max_,
maxillary; _N_, _Na_, nasal; _N_{1}_, in B, inner narial opening; _Pal_,
palatine; _Par_, parietal; _Pmx_, premaxillary; _Pr.f_, prefrontal; _Pt.f_,
postorbital; _Pt.f_{2}_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate;
_S.ang_, supra-angular; _Sq_, squamosal; _Vo_, vomer.]
The latter is always well marked off from the neck. The postorbital arch is
complete. The temporal region is completely roofed over by bones dorsally,
chiefly owing to the size of the postfrontal (Fig. 142, _pt.f_{2}_) which
fills the space between the parietal and the squamoso-postorbital bridge,
thus abolishing the supra-temporal fossa. The squamosal is very small,
placed {551}between the postfrontal (_pt.f_{2}_), the lateral occipital and
the supratemporal. The large jugal and the quadrate are not connected with
each other. The columella cranii is well developed. The infra-orbital
fossae are surrounded by the palatines, pterygoids, ectopterygoids, and
maxillaries. The palatines and pterygoids remain separated in the middle
line. The pterygoids frequently carry little teeth. The other teeth are
typically pleurodont, hollow, slightly curved, and bi- or tri-cuspid.
The skin covering the body, the legs, and the tail is devoid of osteoderms.
The scales on the dorsal surface vary much in size, from large, strongly
keeled scales to tiny granulations. Those of the ventral surface are large,
broader than long, and are frequently arranged in regular transverse and
longitudinal rows. The tail, generally long and pointed, is very brittle.
All the sense-organs are well developed. The tympanum is exposed. The
tongue is deeply bifurcated, narrow, flat, and covered with scale-like
papillae.
Various Lacertidae, especially some of those genera which live and dig in
the sand, have a transparent disc in the middle of the lower eyelid, so
that they can see while the eye itself is protected. This is for instance
the case in some specimens of the Indian and African _Eremias_. In the
Indian genus _Cabrita_ the transparent disc is very large, and in
_Ophiops_, which inhabits sandy stretches from North Africa to India, the
lower eyelid is fused with the rim of the much-reduced upper lid, and forms
a large transparent window.
The Lacertidae or True Lizards comprise nearly twenty genera, with about
one hundred species, and are typical of the Old World, being found in
Europe, Asia, and Africa, but not in Madagascar nor in the Australian
region. They are most abundant in Africa. Their northern limit coincides
fairly closely with the limit of the permanently frozen under-ground. This
is indicated in the map (Fig. 143) by the dotted line. All the Lacertidae
live upon animal food, chiefly insects, and after them worms and snails;
but the larger lizards take what they can master, frequently other lizards,
and even younger members of their own kind. Many of them love sugar, which
they lick, and all require water. They are all terrestrial, preferring,
according to their kind, such localities as yield them their particular
food.
{552}[Illustration: FIG. 143.–Map showing the distribution of the
Lacertidae.]
Sunshine and warmth make a marvellous change in the same individual, which
on dull, rainy, or cold days lies in its hole, or shows only sluggish
movements. Their sense of locality is great, or rather each individual
inhabits one place, of which it knows every nook and corner, cranny, tree,
and bush. It has its favourite hole to sleep in, a stone, the branch of a
tree, or a wall to bask upon, and when disturbed or chased it makes with
unerring swiftness for a safe spot to retire into. The same lizard, when
once driven away from its own locality, seems to lose all its presence of
mind, flounders about, and is comparatively easily caught. Most lizards are
extremely curious, although shy, and this state of their mind can be made
use of by those who want to catch them without injury, and above all
without getting the animal minus the brittle tail. This safe way of
catching lizards consists in taking a thin rod with a running noose of
thread at the end, in drawing the latter over the lizard's head, and then
raising it. The little creature does not mind the rod in the least; on the
contrary, it watches it carefully, and often makes for the thread. The boys
in Southern Italy have improved upon and simplified this mode of catching
lizards by bending the end of a wisp of grass into a noose, and covering
the latter over with a thin film of saliva. The shiny film, like a
soap-bubble, is sure to excite the curiosity of the creature. The late
Professor Eimer[165] refers to this practice {553}as carried out by the
children of two thousand years ago, and he sagaciously explains that the
beautiful statue of the so-called Apollo Sauroctonos represents a boy who
is in the act of noosing the little lizard on the tree.
_Lacerta._–A row of enlarged scales forms a distinct collar across the
ventral half of the neck, in front of the chest. The scales on the back are
much smaller than those on the tail, which is long, round, and pointed. The
digits have smooth, tubercular lamellae on the under surface. Femoral pores
are well marked. This genus, with about twenty species, ranges through
Europe, Northern and Western Asia, and Africa north of the Equator.
_L. vivipara_, the Common English Lizard, has a very wide range, through
Northern and Central Europe and Siberia to the Amoor country and the Island
of Saghalien. It occurs throughout Great Britain, even in Ireland, where it
is the only species of reptile, occurring, for instance, in the County of
Meath and in the south-eastern counties, _e.g._ Waterford. It does not
occur south of the Pyrenees or south of the Alps. The supra-ocular and the
supraciliary scales are in contact with each other, not being separated by
a series of little granules. Normally there is a single postnasal and a
single anterior loreal shield. The ventral scales are arranged in six or
eight longitudinal series, of which the second series on each side from the
median ventral line is the largest. The coloration of this species is
subject to much variation. The general colour of the adult is brown or
reddish above, with small darker and lighter spots; many specimens have a
blackish vertebral streak and a dark lateral band edged with yellow. The
under parts are orange to red in the male, with conspicuous black spots;
yellow or pale orange in the female, either without or with scanty black
spots. The newly-born specimens are almost black. The males are slightly
smaller than the females; males of a total length of 6 inches, and females
7 inches long, may be considered rather large specimens.
This lizard is, as the specific name implies, viviparous, i.e. the six to
twelve young burst the eggs immediately after they have been laid;
sometimes the mother has to retard the laying, in which case the young are
born free. The female does not make a nest, but simply deposits her
offspring on the ground and leaves the young to their fate. For the first
few days the little ones, which scarcely measure three-quarters of an inch
in {554}length, remain almost motionless between leaves or in cracks of the
ground, and they do not take any food. They grow, however, quickly, living
upon the remains of the yolk which has slipped into their body. Their first
food consists of Aphides and similar tiny insects.
The Common Lizard prefers moist localities and is very hardy. It extends
northwards to Archangel, and in the Alps it ascends to nearly 10,000 feet
above the level of the sea. However, on the approach of the cold season, in
the month of October, it withdraws into its winter quarters, frequently in
company with many of its own kind.
_L. agilis_, the Sand-Lizard, has nearly the same wide range as _L.
vivipara_, except that it does not go so far north and does not extend
eastwards beyond Central Siberia. It is absent in Ireland and Scotland,
while in England it is restricted to the southern half.
The characters which distinguish the Sand-Lizard from _L. vivipara_ are
few, although the majority of the specimens of either kind are very
distinct in their coloration, and _L. agilis_ is strictly oviparous,
depositing its eggs in the ground, under leaves, in heaps of weeds and
similar places. The Sand-Lizard has usually a single postnasal and two
superposed anterior loreals, the three shields forming a triangle. The
temples are covered with flat scales, two or three of which are enlarged
and in contact with the parietals, but there is no tympanic scale.
The coloration is subject to much variation, local as well as individual.
As a rule the Sand-Lizard gives the impression of being striped
longitudinally, the striation being caused by rows of dark and white spots
and patches along the sides of the back, flanks, and tail. In the male a
more or less pronounced green, in the female brown and grey are the
prevailing ground-colours. A typically coloured male during the breeding
season is grass-green on the sides and suffused with green on the yellow
under parts; the sides are dotted with black, with whitish eye-spots. The
under parts are spotted with black. The adult female is brown or grey
above, with large dark brown, white-centred spots, which are arranged in
three rows on each side. The under parts are cream-coloured, with or
without black specks. The young are grey-brown above with white,
black-edged spots; the under parts are whitish. Total length of the adult
up to 8 inches. {555}The male is a little smaller than the female but has a
relatively longer tail, a little less than half the total length.
The Sand-Lizard is easily kept in captivity, and lives for years if allowed
a variety of food and proper places to hibernate in. It pairs in the
spring, in England in May or June; the white, parchment-like eggs,
numbering five to eight, are hatched in the following July or August.
_L. viridis_, the Green Lizard, inhabits Southern and Middle Europe and
South-Western Asia. The general colour of this beautiful lizard is
emerald-green above, changing into greenish yellow on the flanks and into
yellow on the belly. The throat, especially in the males during the
breeding season, is blue. The upper parts are frequently speckled with
black. The young are brown or green above with one or two yellowish lateral
stripes, which persist in some adult females. There are usually two
superposed postnasal shields. The semilunar collar on the neck is well
pronounced, and there is usually a distinct gular fold. The tail is often
very long, especially in the males, sometimes nearly three-quarters of the
total length, which in very large males reaches 16 or 17 inches. The
females do not quite reach this length.
The Green or Emerald-Lizard prefers rocky localities, from the sea-level,
as for instance in Jersey, up to a height of several thousand feet. It is
extremely swift and can climb trees, which it sometimes resorts to when
chased. When hard pressed it takes tremendous leaps down to the ground,
marvellously enough without injury to body or tail, which latter is
otherwise very brittle. They pair in the spring or early summer after much
fighting between the males; the eggs, to the number of about ten, are
whitish and are deposited a month later. The young are hatched after
another four weeks.
This beautiful lizard does not keep well in captivity, although it becomes
very tame; it eats meal-worms, snails, earth-worms, and insects, especially
butterflies, but it sickens after the first winter even if it has been
allowed to hibernate.
In Portugal and Spain _L. viridis_ is represented by a slightly different
kind, _L. schreiberi_, the chief interest of which lies in the fact that it
approaches _L. ocellata_ in several respects. The occipital shield is large
and is usually broader than the interparietal. The dorsal scales are
smaller, and there are eight {556}well-developed rows of ventral scales.
Instead of being uniformly green, the upper parts are usually spotted and
vermiculated with black; sometimes, especially in the females, the black
spots have a white ocellus in the centre. The under parts are yellowish,
with or without black spots. The throat is blue. The young look very
different. They are olive-brown above with large yellow, or bluish-white,
black-edged ocelli on the side of the head and body.
Other forms, perhaps of sub-specific rank, approaching _L. ocellata_, occur
in the Balkan Peninsula, where, for instance in Dalmatia, the typical _L.
viridis_ attains its most beautiful development.
[Illustration: FIG. 144.–_Lacerta ocellata_ (the Eyed Lizard). × ⅓.]
_L. ocellata_, the Eyed Lizard, inhabits Spain and Portugal, extending
northwards into the South of France and into the Riviera, southwards into
Morocco and Algeria; these southern forms (_L. pater_ and _L. tangitana_)
approach _L. viridis_. The Eyed Lizard is green or dark olive above, with
black or yellowish dots, which are sometimes combined into a kind of
network pattern. The under parts are uniformly greenish yellow. The sides
of the body are adorned with about two dozen blue, black-edged spots or
"eyes." The intensity of the blue and the depth of the green ground-colour
vary much according to sex, time of the year, and state of health. Males
during the breeding season are most beautiful and brilliant. The occipital
shield is broad; there are two superposed nasal but no tympanic shields.
The supraoculars are separated from the supraciliaries by a series of
granules. The collar is well marked, but not the gular fold. {557}The
dorsal scales are minute and granular; the ventral shields are arranged in
eight or ten longitudinal rows.
The "Eyed Lizard" reaches a considerable size, especially the males, which
develop a very strong and thick head, and are much more robust and powerful
than the more slender females. Old males reach a length of 2 feet,
two-thirds of which length belong to the tail; but the latter varies much,
even if it has never been broken and renewed.
The Eyed Lizard keeps extremely well in captivity, and in this respect is
unlike the Green Lizard. A case has been recorded of its living thirteen
years. This species is very intelligent. Although at first ferociously wild
and biting furiously, these lizards soon become tame and take food
regularly. One of my own, a half-grown male from Northern Spain, about one
foot in length, made its home in a little niche of the greenhouse-wall,
whence it emerged regularly to take the offered food from my hand. It soon
knew the whole place thoroughly, making use of the creepers whilst scaling
up to its retreat, jumping over certain gaps, descending to the ground at
certain spots, basking on certain stones, invariably in the same methodical
way. In the month of October it retires into the ground on the coolest side
of the greenhouse, and although the latter is well warmed, the lizard
remains invisible until the next February or March, when on some fine day
it is rediscovered basking upon exactly the same stone where it had been
seen five months before. The only drawback in connexion with keeping this
kind of lizard in company with other creatures is their voraciousness;
since large, fully adult specimens attack and eat any other small lizard,
slow-worm, or snake they can find. They also take mice. The eggs are often
deposited in hollow trees.
_L. muralis_, the Wall-Lizard, is very common in Southern Europe, Asia
Minor, and Northern Africa. Northward it extends into Belgium and into
South Germany. In the Iberian Peninsula it ascends up to 5000 or 6000 feet
above the level of the sea. This graceful little creature, with an average
length of 6 to 8 inches, is easily recognised by the series of granules
between the supraocular and supraciliary scales and usually by having only
six rows of ventral scales. The great variety in coloration has given rise
to the establishment of many races, varieties, and sub-species. In the
typical forms the upper parts are brown or {558}greyish, with blackish
spots or streaks, sometimes with a bronzy greenish sheen. The under parts
are white, yellow, pink, or red, either uniform or, especially in the
males, with large black spots. The lateral rows of ventral shields are
frequently blue. The colour-varieties are almost endless. One of the most
noteworthy is that described as var. _coerulea_ by Eimer; this, confined to
the Faraglione Rocks near Cápri, is blackish above, like the rock, and
sapphire-blue below. Similarly coloured specimens, var. _lilfordi_, occur
on some of the rocky islets of the Balearic Isles.
The Wall-Lizard deserves its name, since in the Mediterranean countries
there is scarcely a wall on which these active lizards do not bask or run
up and down, often head downwards, in search of insects. They are
oviparous. The hibernation is short and not very deep, since these lizards
can sometimes be seen basking on sunny winter days before their regular
appearance in the early spring.
_Psammodromus_, with a few species in South-Western Europe, notably in the
Iberian Peninsula and in North-Western Africa, has no distinct semilunar
collar, but has a short fold in front of each arm. The back is covered with
large, rhombic, strongly keeled and imbricating scales. The lateral scales
pass gradually into the ventrals, which are smooth and arranged in six
longitudinal rows.
_P. hispanicus_ is bronzy brown above, with small black and white specks,
and with one or two longitudinal streaks on each side. The under parts are
white. Total length about 5 inches. Although also found inland, this
species prefers sandy dunes, studded with prickly and scanty vegetation. It
runs very fast and digs itself rapidly into the sand when pursued. When
caught it either utters a faint cry like "tsi-tsi," or it feigns death. The
pairing takes place in June; half-a-dozen eggs are laid about eighteen days
later, deeply imbedded in the warm sand, and they are hatched in eight
weeks. The eggs are said to grow[166] after they have been laid from 13 by
7 mm. to 17-20 by 10-11 mm. The newly hatched little creatures measure
about 2 inches in length, more than half of which belongs to the tail.
_P._ (_Tropidosaura_) _algirus_ has the same range as _P. hispanicus_, but
grows to 10 inches in length, and is much more {559}beautifully coloured.
The upper parts are bronzy brown with one or two golden, dark-edged,
lateral streaks; the under parts are whitish; the male has one or more
blue-eyed spots above each shoulder.
_Acanthodactylus_ is distinguished by the laterally fringed digits. This
genus ranges throughout Northern Africa to the Punjab. One species, _A.
vulgaris_, extends into Spain and Portugal. The dorsal scales are small and
almost smooth, but those on the tail are strongly keeled; the ventrals are
much broader than long, and are arranged in eight to ten rows. The fringes
on the digits are but feebly developed in the shape of lateral
denticulations. The adults are grey-brown with faint longitudinal stripes,
and with more conspicuous black and pale spots; in the breeding season
larger blue-eyed spots appear on the sides near the limbs. The tail is
often pink, especially on the under surface. Total length about 7 inches.
FAM. 12. GERRHOSAURIDAE.–Pleurodont African Lacertidae with osteoderms on
the head and body.
This family is intermediate between the Lacertidae and the Scincidae. The
tongue is constructed like that of the Lacertidae, but is only feebly
nicked anteriorly. Dermal ossifications roof over the temporal region, and
femoral pores are present. On the other hand, the osteoderms, which cover
the whole body, are in their structure and arrangement typically Scincoid.
The tail is long and fragile. A lateral fold is usually present. The limbs
are sometimes reduced to useless stumps. The few genera and species of this
family are strictly confined to the African sub-region, being found in the
whole of Africa south of the Sahara, and in Madagascar.
_Gerrhosaurus_, with a strongly developed lateral fold and complete limbs,
occurs in Africa. _G. flavigularis_, of South Africa, has a total length
about one foot.
_Tetradactylus_, of South Africa, has also a strong lateral fold, but the
limbs are either very short and pentadactyle (_T. seps_), or tetradactyle,
or they are minute pointed stumps, as in _T. africanus_.
FAM. 13. SCINCIDAE.–Pleurodont lizards with strongly developed osteoderms
on head and body, with very feebly nicked, scaly tongue, with complete
cranial arches, and with separated premaxillaries.
{560}The temporal region is covered over, as in the Lacertidae, with
strongly developed, bony, dermal ossifications. Similar osteoderms underlie
the scales which cover the body and tail. The tongue is relatively short,
not forked behind, and but very feebly nicked at the tip; it is covered
with scale-like papillae. Femoral pores are absent.
All the Skinks prefer dry, sandy ground, in which they not only burrow, but
move quickly about, either for protection or in search of their animal
food. In connexion with this sand-loving and at least temporary
subterranean life stands the frequent reduction of the limbs. Every stage
from the fully developed and functional pentadactyle limb to complete
absence of limbs is represented. There are species within the same genus
with five, four, three, or two fingers or toes. There are Skinks without
fore-limbs, but with vestigial hind-limbs, and _vice versa_. The
interesting point is that these reductions do not indicate relationship
within the family, but have happened independently. They are impressive
illustrations of convergent retrogressive evolution.
_Ablepharus_, widely distributed in the Old World, has the lower eyelid
transformed into a transparent cover, which is fused with the rim of the
reduced upper lid, exactly as in the Lacertine genus _Ophiops_.
All the Scincidae seem to be viviparous, some of them, e.g. _Trachysaurus_,
in the strict sense of the word, since the hard or parchment-like egg-shell
has been dispensed with.
The family contains about four hundred species, which have been arranged in
nearly thirty genera, many of them on fanciful grounds. The family is
cosmopolitan, but reaches its greatest diversity in numbers and forms in
the tropical parts of the Old World, especially in the Australian region,
inclusive of the islands of the Pacific. America, notably South America,
has the smallest number.
_Trachysaurus_, with one species, _T. rugosus_, inhabits the whole of the
Australian continent. It is easily recognised by the large and rough
scales, and the short and broad stump-like tail. It is dark brown above
with yellowish irregular markings; the under parts are yellowish, marked
with brown. Embryos of this species have yellow transverse bands on the
back, but these often fade away before birth. The creature is strictly
{561}viviparous, the egg-membrane being very thin, and the two or three
embryos are ripened in uterus-like dilatations of the oviducts. The period
of gestation is about three months, and the birth takes place, in South
Australia, about April. According to Fischer[167] this species, which is
often in the market, is easily kept. It requires warmth, sand and stones
for basking, and water, in which it soaks itself preparatory to the
shedding of the skin, which takes place half-a-dozen times in the year, and
is a slow process, requiring eight to ten days. The food consists chiefly
of worms, lizards, and snakes, but meat, cabbage, and lettuce are also
taken. The total length is about one foot.
[Illustration: FIG. 145.–_Trachysaurus rugosus._ × ⅓.]
_Cyclodus_ s. _Tiliqua_, of Australia, Tasmania, and the Malay Islands, has
stout lateral teeth with spherical crowns. The imbricating, cycloid scales
of the body and the rather short but pointed tail are quite smooth and
shiny. _C. gigas_, of New Guinea and the Moluccas, reaches a length of
nearly 2 feet. The general colour is brownish yellow, with broad, dark
bands across the body and tail.
_Scincus_, of North Africa, Arabia, Persia, and Sindh, has pentadactyle
limbs, with laterally serrated digits. The eyelids are well developed, but
the ear is hidden under scaly flaps. _S. officinalis_, of the Sahara and of
Egypt, grows to about 8 inches in length. The snout is peculiarly shaped,
cuneiform. The eyes are very small. The scales of the body are perfectly
smooth; the sides of the belly are somewhat angular. The {562}whole shape
of the creature, the scales, and the digits are adapted to burrowing and
moving quickly through the loose sand. The general colour is yellowish or
brownish above, each scale with small brown and whitish spots; the under
parts are uniform whitish. The young are quite beautiful, being uniform
pale salmon-coloured above, silvery white below. When a little older,
yellow spots appear on the flanks and grey bands across the back. These
Skinks live in the absolutely dry reddish-yellow sand of the desert, in
which they may almost be said to swim about, so swift and easy are their
movements. They live on insects, while in their turn they are eaten by
snakes, and above all by the _Varanus_ lizards.
[Illustration: FIG. 146.–_Cyclodus gigas._ × ¼.]
Of _Mabuia_ with about forty species, in the whole of Africa, Southern
Asia, and in Tropical America, we mention only _M._ (_Euprepes_) _vittata_,
on account of its partly semi-aquatic life, a very rare condition among
Scincidae. This creature, about 7 inches long when full grown, frequents
damp localities in Tunis and Algeria, where the French call it "Poisson de
sable." It often sits on the floating leaves of _Nymphaea alba_, and dives
into the water in order to escape. Its proper element is, however, the
sand, and for the night it retires under stones. The general colour is
olive brown with a lighter vertebral band and two narrow whitish lines on
each side, sometimes edged with black. The under parts are yellowish or
greenish white.
_Chalcides_ s. _Seps_ s. _Gongylus_, of the Mediterranean countries
{563}also occurs in South-Western Asia. The lower eyelid has a transparent
disc. The body is much elongated, and is covered with smooth shiny scales.
The limbs are very short, or reduced to mere vestiges.
_Ch. ocellatus_, of the Southern Mediterranean countries, occurring also in
Malta and Sardinia, reaches about 10 inches in length. The snout is
conical, the ear-opening a small slit or hole. The limbs have five fingers
and toes. The under parts are uniform silvery white, but the colour of the
upper parts is very variable, mostly olive brown with black spots and
irregular cross-bars, or with dark and light spots; sometimes uniform
bronzy brown with a light upper and a black lateral band. This Skink seems
to have no fixed abode, but digs itself into the sand wherever it wants to
hide. The skin is not shed in flakes, but, as in most Skinks, it peels off
by a process of gradual desquamation. Fischer's specimens paired towards
the end of December. The gestation lasted 56 days, when nine young were
born, which measured about 75 mm. or 3 inches; when three weeks old they
had increased to nearly double this length.
_Ch. lineatus_, of Spain and Portugal, and of the South of France, like
_Ch. tridactylus_ of Italy and North-West Africa, has only three fingers
and toes. The fore-limbs are only about one quarter of an inch in length in
large specimens of 10 inches total length; the hind-limbs are a little
longer. The general colour is bronzy olive or brown above, in the former
species with nine or eleven darker longitudinal streaks; uniform, and with
an even number of streaks in the latter species. _Ch. bedriagae_, of Spain
and Portugal, has mostly five fingers and toes, and the limbs are
relatively longer in this smaller species; but it is a question if these
and other species of this genus are not to a great extent simply individual
variations, since the reduction of the limbs and toes seems to be a very
recent feature. _Ch. guentheri_, of Palestine, otherwise in every respect
like _Ch. tridactylus_, but reaching a length of more than 14 inches, has
the limbs reduced to tiny conical stumps without a trace of separate
digits.
I have caught _Seps_ accidentally under stones or pieces of bark in sandy
districts. On the western coast of Galicia and Portugal, close to the sea,
they frequent the gorse-bushes, on which they can be seen basking, provided
they are approached {564}stealthily. They disappear on the slightest alarm,
almost swimming, as it were, with great agility through the prickly cover,
and then hiding and wriggling through the loose sand between the roots.
The following five "families" are composed of degraded forms of various
descent. Most of them lead a burrowing, subterranean life, in adaptation to
which the body has become snake-shaped or worm-like. The fore-limbs are
entirely absent, except in _Chirotes_; the hind-limbs are absent, or
reduced to small flaps; the girdles are reduced correspondingly. The skull
is devoid of postorbital, postfronto-squamosal, supratemporal, and jugal
arches. The quadrate bone is mostly immovable. The eyes and ears are
concealed, except in the Pygopodidae.
FAM. 14. ANELYTROPIDAE.–An artificial assembly of a few degraded Scincoids.
The worm-shaped, limbless body is devoid of osteoderms. The tongue is
short, slightly nicked anteriorly, and covered with imbricating papillae.
Columellae cranii are present. _Anelytropsis papillosus_ in Mexico.
_Typhlosaurus_ and _Feylinia_ in South and West Africa.
FAM. 15. DIBAMIDAE, consisting of the genus _Dibamus_, with _D.
novae-guineae_, in New Guinea, the Moluccas, Celebes, and the Nicobar
Islands. The tongue is arrow-shaped, undivided in front, covered with
curved papillae. Columellae cranii are absent. The vermiform body is
covered with cycloid imbricating scales without osteoderms. The limbs and
even their arches are absent, but in the males the hind-limbs are
represented by a pair of flaps. Total length of the animal about 6 inches.
FAM. 16. ANIELLIDAE.–The genus _Aniella_ comprises a few small worm- or
snake-shaped species in California, which seem to be degraded forms of
Anguidae. The eyes and ears are concealed, limbs are entirely absent, the
body and tail are covered with soft, imbricating, more or less hexagonal
scales. The tongue is villose, smooth, and bifid anteriorly. The teeth are
relatively large, few in numbers, recurved, with short swollen bases. The
skull, by reduction, approaches the Ophidian type; there is no columella
cranii, the postorbital arch is ligamentous, the premaxillary is single,
the nasals and frontals remain separate, the pre- and post-orbitals are in
contact with each other, excluding the frontal from the orbit.
_A. pulchra._–Silvery, the scales edged with brown; back and {565}tail with
a narrow, brown, median line. Total length, 7 to 8 inches.
FAM. 17. AMPHISBAENIDAE.–Worm-shaped lizards with the soft skin forming
numerous rings, each of which is divided into many little squares, the
vestiges of scales which are otherwise restricted to the head. The eyes and
ears are concealed. Limbs are absent except in _Chirotes_, which has short
four-clawed fore-limbs. The pectoral arch, and still more so the pelvic
arch, are reduced to minute vestiges. The tail is very short. The skull is
small, compact, and strongly ossified, in adaptation to the burrowing life,
and is devoid of postorbital and postfronto-squamosal arches and of
columellae. The teeth are either acrodont or pleurodont. The tongue is
slightly elongated, covered with scale-like papillae, and bifurcates into
two long and narrow smooth points.
[Illustration: FIG. 147.–Map showing the distribution of Amphisbaenidae.]
The Amphisbaenas lead an entirely subterranean, burrowing life, like
earth-worms. They are frequently found in ants' nests or in manure-heaps.
Their progression is very worm-like, their annulated soft skin enabling
them to make almost peristaltic motions and to move backwards as well as
forwards. They crawl in a straight line, with slight vertical waves, not,
like other limbless lizards or snakes, by lateral undulations. The food
consists of worms and small insects. About one dozen genera with more than
sixty species are known, most of which inhabit the warmer parts of America,
the West Indies, and Africa. Four inhabit Mediterranean countries.
{566}If the tongue and the dentition be taken as indications of
relationship, the Amphisbaenidae may perhaps be considered as degraded
descendants of Iguanidae, a family which contains various limbless,
burrowing, worm-shaped forms. But it is also possible that the
Amphisbaenidae are not a natural group. This consideration applies with
most force to the genera _Amphisbaena_ and _Anops_, the various species of
which occur in America and in Africa.
_Chirotes canaliculatus_, the only species of the genus, is the only
Amphisbaenid which still possesses fore-limbs. These are short, stout,
placed close behind the head, and are provided with four-clawed digits.
This species occurs in Mexico and California, is brownish or
flesh-coloured, and reaches a length of about 8 inches.
_Amphisbaena_, with nearly thirty species, in Tropical America and Africa.
On account of the short rounded-off head and the almost equally blunt tail
these creatures are called by the natives "cobras de dous cabezas," _i.e._
snakes with two heads, or they are known as "maes das formigas," _i.e._
mothers of ants, because of their predilection for taking up their quarters
in the nests of ants or termites. The scientific name refers of course to
their capability of moving forwards and backwards (ἀμφίς, at both ends, and
βαίνω, walk).
_A. fuliginosa_, one of the commonest species in South America and in the
West Indies, is chequered black and white. The skin of the body has about
two hundred rings, the tail about thirty. Total length between one and two
feet. A more or less distinct fold extends along each side of the body from
the neck to the tail, at the level where the dorsal scales originally
joined the ventral scales.
_Blanus_ is the only genus of the Mediterranean province. _B. cinereus_, of
Portugal, Spain south of the Cantabrian range, Morocco, and Algeria,
reaches a length of 10 inches, but such large specimens are rather rare.
The general colour of the living animal is pink with a brownish tinge and
with minute grey specks. The lateral lines or folds are well marked, and a
stronger transverse fold is placed behind the head. The body shows from one
hundred and ten to one hundred and twenty-five rings, the tail from twenty
to twenty-two; each body-ring contains about thirty little squares or
remnants of scales. There are a few pre-anal pores.
{567}I have sometimes found this species in Portugal whilst digging for
earth-worms in manure-heaps and similar moist places, where they lead the
same life as the worms except that they live upon them and upon insects.
When kept dry they become very thin and shrunken, but when put back into
moist soil they again become turgid and supple within a short time. Those
which I have kept in glass jars filled with rich mould throve very well,
living upon the tiny insects and worms which infest such compost soil; they
dug long tortuous channels, in which they moved forwards and sometimes
backwards, but they never came to the surface.
FAM. 18. PYGOPODIDAE.–Pleurodont, snake-shaped lizards, without fore-limbs,
but with the hind-limbs appearing as a pair of scaly flaps.
The shoulder-girdle is much reduced. The hind-limbs, although very small
and hidden within the scaly, almost fin-like flaps, still possess five
toes. The ischium appears externally as a small spur on either side of the
anal cleft. The eyes are devoid of movable lids, remaining open and
unprotected; the pupil is vertical. The ear is either concealed or exposed.
The tongue is fleshy, slightly forked and extensible. The body is covered
with roundish imbricating scales. The tail is very long and brittle. The
few genera of this undoubtedly natural family of unknown relationship
contain in all about ten species, restricted entirely to Australia,
Tasmania, and perhaps New Guinea. Next to nothing is known about their
habits, except that some of them eat other lizards.
_Pygopus lepidopus_ is distributed over the whole of Australia. It reaches
a total length of about 2 feet, 16 inches of which belong to the tail.
General colour coppery grey above, sometimes with several longitudinal
series of dark spots.
_Lialis burtoni_ of nearly the same size and equally wide distribution has
the hind-limbs reduced to extremely small, scarcely visible, narrow
appendages.
SUB-ORDER 3. CHAMAELEONTES.–_Acrodont Old-World Saurians with a laterally
compressed body, prehensile tail, and well-developed limbs with the digits
arranged in opposing, grasping, bundles of two and three respectively._
The Chameleons are an essentially African family. About half of the fifty
species known inhabit Madagascar, the others {568}the African continent.
One, the common Chameleon, is North African, extending into Andalucia; two
others occur in South Arabia and Socotra, and only one in Southern India
and Ceylon.
This sub-order is well distinguished from all other Saurians by several,
mostly unique, characters. The tongue is club-shaped and extremely
projectile, to a length equal to that of the body. The head is usually
described as forming a casque, with prominent crests and tubercles. There
is no tympanum and no tympanic cavity. The parietal bones, united into one,
extend backwards far beyond the occiput, and the tip of this projection is
met by a much-elongated supratemporal bone, which, partly fused with the
squamosal, helps to enclose a huge supratemporal fossa. The latter is
widely open behind. The postfronto-squamosal arch and the postorbital arch
are strong. The jugal is widely separated from the quadrate; the latter
stands vertically and is not reached by the pterygoid. There is no
columella cranii. The pre- and post-frontals often join to form a
supra-orbital roof. The nasals are very small and are excluded from the
nares, which are bordered entirely by the enlarged prefrontals and by the
maxillaries. The premaxillaries are small and carry no teeth. The latter
are acrodont, compressed and tricuspid, and are restricted to the
maxillaries and mandibles.
[Illustration: FIG. 148.–Map showing the distribution of Chameleons.]
The limbs are peculiar. Not only are they relatively long and very slender,
but two digits are permanently opposed to the other three. On the hand the
first three fingers form an inner bundle opposed to the outer, or fourth
and fifth fingers. On the foot the inner bundle is formed by the first and
second, the outer by the other toes. The shoulder-girdle is of the ordinary
Saurian type, but there are no clavicles and no interclavicle. The costal
sternum is well developed; the ribs posterior to those which meet the
sternum are very thin and elongated: they meet and fuse with their fellows
in the medio-ventral line. These hoops are not connected with their
neighbours in front or behind. The tail is prehensile by being rolled
downwards; it is not brittle and is incapable of being renewed. The skin is
not covered with scales, but with {569}granules. The eyes are very
remarkable. The eyeballs themselves are large, but the eyelids are united
into one fold with a small central opening. However, when the Chameleon is
asleep the margins of this opening sometimes become more slit-like. The
right and left eye can be, and are incessantly, moved separately from each
other, and the creature squints terribly. Each eyeball, together with the
pin-hole eyelid, is rolled up and down, backwards and forwards,
independently of the other eye. This is a unique feature, but it also
occurs in people who squint badly. The question "What, and how, do these
creatures see?" is therefore quite idle, especially since in reptiles
binocular vision does not exist at all and, consequently, cannot be
disturbed by squinting.
The tongue has attained an extraordinary development. The tongue proper
(Fig. 152) is club-shaped, and is covered with a sticky secretion. The base
or root of the tongue is very narrow, composed of extremely elastic fibres,
and is supported by a much-elongated copular piece of the hyoid. The
elastic part of the tongue is, so to speak, telescoped over the
style-shaped copula, and the whole apparatus is kept in a contracted state
like a spring in a tube.
[Illustration: FIG. 149.–A, Dorsal, B, ventral, and C, lateral view of the
skull of _Chamaeleon vulgaris_. × 1. _Cond_, occipital condyle; _EP_,
ectopterygoid; _Jug_, jugal; _Lac_, lacrymal; _Pal_, palatine; _Par_,
parietal; _Prf_, prefrontal; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_,
quadrate; _Sq_, squamosal; _Vo_, vomer.]
A pair of wide, very elastic blood-vessels and special elastic bands extend
from the base into the thick end of the tongue. {570}By rapidly filling the
apparatus with blood, and by the action of certain hyoid muscles, the
spring is, so to speak, released, and the momentum gained by the thick and
heavy club-shaped tongue proper projects it far out of the mouth. The
sticky end of the club shapes itself into an upper and a lower flap, which
partly envelop the prey, and the elastic bands of the far-stretched stalk
withdraw the whole. The detailed working of this ingenious shooting
apparatus is not easy to follow. An ordinary full-grown Chameleon can shoot
a fly at the distance of 7 or 8 inches. The whole performance is very
quick, lasting less than one second. When the desired object is very near,
only 2 or 3 inches off, the Chameleon has a certain difficulty in shooting
its prey. The tongue is at first put out slowly, tentatively, the following
jerk is feeble, and it seems as if the apparatus refuses to work unless it
is allowed to shoot out with full force.
Another remarkable and quite proverbial feature of Chameleons is their
changing of colour. This is by no means restricted to Chameleons, which
indeed are rivalled in this respect by various other lizards, for instance
by the Indian Agamoid _Calotes_ and by the American _Ameiva_.
The microscopical structure and mechanism of the colour-changing apparatus
is, in _Chamaeleon vulgaris_, as follows:–
The epidermis is colourless, and the Malpighian layer is not particularly
modified except that in it are imbedded some iridescent cells, with very
minute wavy striation on their surface. The cutis contains in its leathery
tissue a great number of small and closely packed cells, filled with
strongly refractive granules, chiefly guanine-crystals. These cause the
white colour by diffuse reflection of direct light. The cells nearer the
surface are charged with oil-drops and appear yellow. Large chromatophores
are imbedded in the white granular mass, most of them with blackish-brown,
others with reddish pigment, the granules of which are shifted up and down,
towards and away from the surface of the cutis, in ramified branches of the
chromatophores. When these branches are contracted the pigment is conveyed
back into the bulbous basal portion of the chromatophores and the skin
appears yellow or white. When all the pigment is shifted towards the
surface of the cutis, the animal looks dark, sometimes black. In
intermediate conditions the light is changed into green by diffraction
through the yellowish upper strata and by the finely {571}striated
iridescent cells of the Malpighian layer. Those parts into which the
chromatophores do not send pigment appear as yellow spots. The
chromatophores are to a great extent under control of the will of the
Chameleon, but external stimuli, as heat and cold and other reflex actions,
also play a great part in their movements.
For further information on this subject see Brücke,[168] P. Bert,[169]
Pouchet,[170] Thilenius,[171] and lastly Keller,[172] who has written a
very long but rather confused account.
The process of moulting is curious. When the Chameleon is in good health
the whole process is accomplished within a few hours. The skin to be cast
off becomes loose and assumes a blistered appearance. Sometimes the
creature looks as if it were wrapped up in white, semi-transparent tissue
paper. By rubbing against stones, or between the twigs of trees, the skin
comes off in large flakes, first on the lips, then on the contorted body,
and last on the under surface of the hands and feet. During a rapid and
successful moult the changes of colour go on as usual in the new skin.
Sometimes large flakes of the old skin remain adherent for days, especially
on the top of the head. The moulting takes place several times in one year.
One of my _Ch. vulgaris_ moulted in January and September, and then not
until June of the next following year. A _Ch. pumilus_ moulted in the
months of May, October, and March.
[Illustration: FIG. 150.–Diagrammatic section through the skin of a
Chameleon. Highly magnified. _C_, deeper portion of the cutis; _Ch_, three
chromatophores, in various stages of contraction, filled with black, brown,
or reddish pigment; _E_, epidermis; _W_, white layer of granules; _Y_,
yellow layer of cells.]
When they know themselves to be discovered, Chameleons make themselves as
thin as possible by compressing the body or rather the belly. This is done
by means of the peculiarly elongated abdominal ribs described above. The
whole body is then put into such a position that, by presenting only its
narrow edge to the enemy, it has become as little visible as {572}possible.
At the same time the Chameleon turns round upon its twig, so that the
latter comes to stand between the observer and its own body, which may
thereby be completely hidden. When angry, the creature either presents its
broadest surface, swaying to the right and left, or it blows itself up and
hisses. The lungs are very capacious, and, instead of being bag-shaped, end
in several narrow blind sacs which extend far down into the body-cavity, so
that not only the chest but the whole body can be blown up.
The usual mode of propagation is by means of eggs, but a few species allied
to _Ch. pumilus_ are viviparous. The time of incubation and of gestation is
long. For instance, the pairing of _Ch. vulgaris_ takes place in the month
of August. The eggs are laid in the last week of October, about fifty to
sixty days later. Sometimes, however, the eggs are retained much longer,
since I have received specimens with ripening eggs in July which did not
lay until the end of October. The eggs are deposited in the ground and are
not hatched until the following February or March, _i.e._ about 130 days
later. The new-born little creatures are snowy white, and cannot change or
rather assume colour until after the second week.
All Chameleons are insectivorous and require enormous quantities of food,
which must be alive to be taken. Most of them prefer Orthoptera, _e.g._
Locusts and Grasshoppers, and Lepidoptera. They also eat flies, meal-worms,
and cockroaches, but their tastes differ not only individually but also
temporarily. They require change of diet. One individual will take
cockroaches greedily, whilst another of the same kind will rather starve
itself than touch one. The same applies to meal-worms. It is a great but
common mistake to suppose that Chameleons do not require water. On the
contrary they drink regularly and often, generally by licking up drops of
water or by scooping them up with their lips, shoving the snout along the
edges of wet leaves. It is not too much to say that most Chameleons are
short-lived in captivity on account of the want of water. Those which are
sold by the dealers are generally in a parched condition. Sprinkling the
twigs or leaves of their cage with water works a wonderful change in them;
the dull, apathetic-looking creatures drink and drink, revive, assume
brighter colours, and will soon take food, which they have until then
refused {573}obstinately. Once I have even seen a Chameleon, when put into
the greenhouse, make straight for a tank and actually drink in gulps.
After they have fattened themselves in the autumn, Chameleons, at least
those of North Africa, withdraw to hibernate in the ground. But nothing is
known about how, when, and where they do this, nor is it known if tropical
species aestivate during the dry season.
Chameleons are notoriously difficult to keep successfully, whereby we do
not mean the keeping for three to six months. This is easy enough, since it
takes them several months to die of starvation. The difficulty is to keep
them through the winter. To enable them to do this, it is absolutely
necessary to fatten them up during the summer and autumn. Otherwise,
although kept in a warm place, they are liable to lose their appetite in
the autumn, when they become restless, probably with the desire to
hibernate. Those few individuals which get over this critical period, say
during the month of October, and do not refuse food, are probably safe. But
those are doomed which refuse to eat meal-worms or cockroaches or such food
as can be procured easily during the winter.
The origin of the Chameleons is unknown. They form only one family,
CHAMAELEONTIDAE, with between fifty and sixty species, which, with a few
exceptions, belong to the genus _Chamaeleon_.
_Ch. vulgaris_ is the Common Chameleon of North Africa, Syria, and Asia
Minor. It occurs also in a few parts of Southern Andalucia, for instance
near Jerez, and near Nerja, to the east of Malaga, where it has possibly
been introduced. A series of conical, slightly enlarged granules forms a
little crest on the median line of the throat. A whitish line, which does
not change colour, extends from the chin to the vent. The rest of the skin,
with the exception of a median dorsal series of slightly enlarged tubercles
on part of the back, is composed of small granules. A small but distinct
lobe of leathery skin extends along either side of the occiput towards the
posterior end of the median parietal crest. Dead or spirit-specimens are
usually pale yellow; living ones are greenish, usually with differently
coloured patches on the sides. Exceptionally large males reach a total
length of about 9 inches, females reach the length of perhaps a foot, but
about half of the total length belongs to the tail.
{574}It is impossible to say what is the colour of this Chameleon, since
the same specimen may within a few days appear in half-a-dozen different
garbs, not counting minor combinations of colour. After it has been watched
for several months, when all its possibilities seem to be exhausted, it
will probably surprise us by a totally new combination. Not every specimen
changes alike: some keep the same appearance for a long time, others change
often; some are partial to specks, others to large patches. In the group of
Chameleons shown in Fig. 152 several of the more usual arrangements of
colour have been indicated by stippling and various kinds of
cross-hatching.
[Illustration: FIG. 151.–_Chamaeleon vulgaris._ × ⅔.]
A represents the usual coloration at night. The whole animal, which has
just been stirred up from its sleep in the dark, is cream-coloured, with
irregular patches of yellow on the head, the back, the sides of the body,
the legs, and the tail.
B has the usual coloration: grey-green, with innumerable small darker
specks, with two series of pale brown patches on the sides of the body, and
with one patch on the region of the ear.
{575}[Illustration: FIG. 152.–Showing changes of colour in Chameleons. A to
D, _Chamaeleon vulgaris_ (see p. 574). _Chamaeleon pumilus_ in the right
upper corner.]
{576}C is the same specimen in an excited frame of mind; it is represented
in the act of shooting a fly. The light brown patches have changed to
maroon brown; and many round golden yellow spots have appeared on the green
parts.
D shows a specimen, coloured like C, within a few seconds after it has been
put into an angry mood, in the present case by having its tail squeezed.
The whole body is blown out, the thick tongue causes the throat to bulge
out, and all the yellow spots have become blackish green.
Many small spots scattered over the body are usually a sign of anger. One
of the specimens described above was, when fast asleep in a dark room,
dirty white, with about two dozen large and small round spots of a rich
yellow on each side of its body. Then a lighted lamp was brought into the
room without in any way disturbing the animal. Within sixteen minutes the
yellow spots had vanished completely; the whole body and tail had become
suffused with greenish yellow, which gradually turned to pale yellowish
green, and those parts which in Fig. B are pale brown, were just
distinguishable as pale yellowish-white regions. The Chameleon was found to
be fast asleep, and it kept this coloration during the rest of the evening.
Other specimens behaved on similar occasions in the same way, but the
greatest interest is attached to the fact that frequently only that side of
the body "greened up" which happened to be exposed to the light, whilst the
opposite side remained whitish. These changes are not absolutely
unconscious; they are, after all, under the control of the creature. In
order to test the possibility of direct action of the light, I have taken
the precaution of throwing the light of a candle only upon the body, whilst
the head was kept in darkness. No changes of colour took place whilst the
animal was asleep, but when a little light was allowed to sweep across the
closed eye, this soon began to twitch, and although the creature did not
open the eye, the usual changes of colour began to take place. When the
light was removed, the animal soon re-assumed its whitish appearance.
Artificially coloured light, for instance green, red, or blue glass or
paper, has apparently no influence upon the changes of colour. The
Chameleons behave as they would behave under ordinary conditions. Direct
and hot sunshine however causes them to darken, sometimes to turn uniform
dull black, except for the white median ventral {577}line. Occasionally I
found one of the specimens described above deep maroon brown, with dozens
of round orange spots. Blue and red do not seem to be within the range of
_Ch. vulgaris_, but the combinations of green, yellow, brown, black, and
white, with their various shades, are almost endless. Sometimes the
Chameleons do not turn pale during the night, but remain more or less dull
green, with or without brownish patches. Adaptation to their immediate
surroundings takes place to a very moderate degree only, but as a rule they
are brightest, especially in their green tints, when they are allowed to
sit amongst green foliage. The introduction of a branch with fresh leaves
generally has a brightening effect upon those which have previously been
confined in a cage with dry twigs only. Cold does not necessarily make them
pale, but they appear duller, and the changes take place more slowly. After
all, Linnaeus has summed up the little we really know about the causes of
these changes, in the following terse sentence: "Vivus varios colores
assumit secundum animi passiones, calorem et frigus."
Chameleons are not very amiable. When taken up they blow themselves out or
they bite painfully, and it is a long time before they are tame enough not
to go through various antics of anger when one approaches them. When taken
in the hand they produce a peculiar faint grunting noise, which, however,
can be better felt than heard. They quarrel much amongst each other; and
the males, during the pairing season, are particularly ill-tempered. Each
individual selects its own particular branch to sleep on, if possible a
horizontal one, upon which it crouches down lengthwise, with the head and
belly resting upon the branch. The tail generally makes a turn round
another branch, and the four legs, grasping some supporting branch, are put
into any, sometimes into an almost incredibly, awkward position. Although
they climb about a good deal during the daytime, they generally resort to
their accustomed sleeping branch, and they defend this vigorously against
would-be intruders.
Chameleons are most deliberate in their movements, sometimes provokingly
slow. Each arm and foot leaves the firmly grasped branch with great
hesitation, and makes with equal deliberation for some other foothold. It
does not matter if the thigh appears almost twisted out of its joint. The
creature will {578}remain in the most uncomfortable position, forgetting,
one might think, to put one or more of its limbs down, but keeping them
instead in the air.
It is most interesting to watch them stalking their prey. Suppose we have
introduced some butterflies into their roomy cage, which is furnished with
living plants and with plenty of twigs. The Chameleons, hitherto quite
motionless, perhaps basking with flattened-out bodies so as to catch as
many of the sun's rays as possible, become at once lively. One of them
makes for a butterfly which has settled in the farther upper corner of the
cage. With unusually fast motions the Chameleon stilts along and across the
branches and all seems to go well, until he discovers that the end of the
branch is still 8 inches from the prey, and he knows perfectly well that 7
inches are the utmost limit to a shot with his tongue. He pauses to think,
perhaps with two limbs in the air, but stability is secured by a judicious
turn of the tail. After he has solved the puzzle, he retraces his steps to
the base of the branch, climbs up the main stem, creeps along the next
branch above, and when arrived at the 7 inch distance, he shoots the
butterfly with unerring aim. The capacity of the mouth and throat is
astonishing. A full-grown Chameleon will catch, chew, and swallow the
largest moth, for instance a _Sphinx ligustri_. When large, the prey is
chewed, but the wings and legs are swallowed with the rest. Occasionally
these parts are bitten off, especially the prickly long legs of large
locusts.
In water Chameleons are quite helpless. Sometimes they inflate themselves,
but they always topple over on to the side, and the movements of their
limbs are absolutely without any definite purpose.
When the eggs are ripe, and this happens with the Common Chameleon about
the end of October, the female refuses to take food, and becomes restless.
One of my specimens searched about probing the ground for about a week
before she dug a hole in some more solid soil. This took two days. In the
evening I found her sitting in the hole to the middle of her body. On the
following morning she was still there, but busy filling the hole with soil
and covering it with dry leaves. A few eggs were lying about outside, two
of which at least I saw her taking up by the hand and putting them on the
{579}nest, which was found to contain some thirty soft-shelled eggs closely
packed upon each other. During the whole process she was very snappy, and
hissed much when approached. After that she crept into the twigs as usual,
but refused to eat, vomited at once the artificially introduced food,
became restless on the sixth day, crawling about at the bottom of the cage,
and died on the following day. This is the usual fate, almost without
exception, of females after they have deposited their eggs in captivity.
The great number of eggs and their deposition naturally exhausts them, and
they probably want to hibernate at once. The eggs, which are yellowish,
long-oval, about half an inch long and covered with a parchment-like shell,
are very difficult to rear, chiefly on account of the difficulty of
regulating the moisture. They shrink up when too dry, and they are very
liable to become mouldy. According to Fischer[173] the eggs can be hatched
in a large flower-pot with a layer of horse-droppings at the bottom, then a
layer of 6 inches of slightly moist soil, then the eggs, then another 6
inches of loose soil, with a glass plate covering the top, securing at the
same time ventilation. In this way he succeeded in hatching several sets of
eggs after 125 and 133 days respectively.
_Ch. calcaratus_, the Indian Chameleon, is found in the southern half of
the Peninsula and in Ceylon, but it is far from common. It much resembles
_Ch. vulgaris_, but the male is distinguished by a tarsal process or
"spur," covered with skin, on the inner side of the foot.
_Ch. pumilus_, the Dwarf Chameleon of South Africa, reaches a total length
of 5 to 6 inches. It has a well-marked, serrated gular crest, which extends
from the chin to the end of the neck. The chest and belly are without a
toothed line, but a strongly serrated series extends from the occiput over
the back and tail (see the right upper corner of Fig. 152 on p. 575). A row
of enlarged tubercles or scales extends along the sides of the body. The
general colour is green, with a large and long patch of brick-red on the
sides; small dots and spots of intense red are scattered over various parts
of the body. The changes of colour are rather limited. At night the Dwarf
Chameleon does not turn pale, but generally keeps its colour. When they are
very well the green is quite saturated, and the large red patch on the side
is {580}interrupted by several blue spots. When they are angry or unhappy
the red turns into dirty brown, and the green becomes quite dull. Sometimes
the whole animal turns dull black.
This pretty little species is relatively hardy, being, as a native of South
Africa, accustomed to cold nights. It does well in an ordinary temperate
greenhouse, where it will live for several years, provided it has an ample
supply of flies and meal-worms. It is viviparous, the young being probably
born in the month of March or April.
_Ch. bifidus_, of Madagascar, shows an extraordinary difference between the
sexes. The male reaches the great length of 16 inches, and develops two
long rostral processes, which extend forwards beyond the snout; these
processes are formed of dense connective tissue, which ossifies in the
adult, and they are covered with scaly skin.
_Ch. parsoni_, likewise of Madagascar, is the giant amongst Chameleons,
reaching a total length of 2 feet. The male has two large rostral processes
which diverge upwards and outwards.
_Brookesia_, with several species in Madagascar, may be mentioned on
account of its stunted appearance. The tail is much shorter than the body
and scarcely prehensile; the scales on the soles are spinous. Total length
only about 3 inches.
_Rhampholeon_, of tropical continental Africa, with several species, is
likewise remarkable for the stunted and dwarfed appearance, and for the
peculiar claws, each of which is furnished with a second cusp which is
directed downwards. The tail is much shorter than the body. The total
length of _Rh. spectrum_ of the Camaroons is about 3 inches.
{581}CHAPTER XIII
SAURIA, _continued_–OPHIDIA–SNAKES
ORDER II. OPHIDIA–_SNAKES_.
_Saurians which have the right and left halves of the lower jaw connected
by an elastic band._
The Snakes are the most highly specialised branch of the Sauria, from which
they do not differ in any fundamental characters. The chief modifications
consist in the absence of the limbs and limb-girdles (a feature intimately
correlated with the much-elongated body), and in the swallowing apparatus.
The reduction of the limbs and the elongation of the body also occurs in
many Lacertilia; in several of the older families of Snakes (_e.g._
Typhlopidae and Boidae) vestiges of the hind-limbs and even of the pelvis
are still in existence. Even the peculiar suspensorial apparatus of the
lower jaw approaches that of the Lacertilia in the burrowing Ilysiidae and
in _Xenopeltis_.
In the majority of the Snakes the quadrate is very loosely suspended from
the squamosal (by some authorities homologised with the supratemporal bone
of other reptiles), and this again is loosely attached to the lateral
parietal region of the skull, placed horizontally, and elongated so far
backwards that the vertically placed quadrate lies in a plane behind the
skull. In most Snakes the elongated pterygoids are loosely attached to the
inner side of the distal end of the quadrates, and they also often touch
the mandibles. The whole palatal apparatus is movably attached to the
skull, except in some burrowing families. The right and left pterygoids and
palatines are widely separated from each other. The pterygoids and
maxillaries, connected by the ectopterygoids, are absent, owing to
reduction, in the {582}Typhlopidae and Glauconiidae only. The premaxilla is
unpaired and small, and is rarely furnished with teeth. The latter are
always sharp and recurved, and are lodged in sockets upon the edge of the
supporting bone, with which they become firmly ankylosed. There is a
perpetual succession of teeth. In the majority of Snakes teeth are carried
by the maxillaries, palatines, pterygoids, and dentaries, rarely by the
premaxillaries. The palatal teeth are restricted to the palatines in
_Oligodon_, _Dasypeltis_, and _Atractaspis_ only.
Peculiar modifications prevail in the poisonous Snakes. Those maxillary
teeth which are at their base in connexion with the openings of
poison-glands (modified upper labial glands), either have a furrow on the
anterior side (Proteroglypha if the anterior teeth are grooved, _e.g._ the
Cobras; Opisthoglypha if some of the posterior teeth are grooved), or the
groove is converted into a canal, as in the Solenoglypha or Viperidae. The
special modification of the maxillaries of the vipers with their long
poison-fangs is described on pp. 587 and 637.
The orbit is generally closed behind by the postfrontal. Quadrato-jugal,
postfronto-squamosal, and other arches are absent, so that the temporal
fossa is quite open (see Fig. 156, p. 597, and Fig. 155, p. 596). The
occipital condyle is distinctly triple. The mandibles are composed of
several bones, but the coronoid is absent in the Xenopeltidae, Colubridae,
Amblycephalidae, and Viperidae; it is large in the Boidae, reduced to a
nodule in the Ilysiidae.
The parietals are always fused into a large unpaired bone, which generally
forms a sharp crest and partly overlaps the occipitals; there is no
interparietal or pineal foramen.
The vertebral column consists of many, often nearly three hundred
vertebrae, and these skeletal segments correspond in number with those of
the ventral and transverse scales of the skin. The vertebrae are
procoelous; in addition to the anterior and posterior zygapophyses they
have a pair of accessory articulations on the neural arches, dorsally to
the zygapophyses;–the "zygantrum" carried by the posterior end of the
neural arches, its articular surfaces looking upwards; and the "zygosphene"
carried by the anterior end and looking downwards. Such accessory
articulations occur also in a few Lizards, _e.g._ Iguanidae. The vertebrae
of many Snakes have unpaired vertical, blade-like {583}haemapophyses on
their centra for the more effective attachment of the muscles. All the
vertebrae, except the atlas, carry ribs. These articulate by their
capitular portions only, and are very movable in a head- and tail-ward
direction. The ribs being long, and fitting with their ventral ends into
the connective tissue of the sides of the ventral transverse scales, are
the principal agents in pushing the body forwards, the posterior edges of
these scales being sharp and imbricating.
The skin is covered with scales, absolutely devoid of osteoderms. When the
scales are enlarged they are called shields. The keel, a common feature, is
caused by a slight ridge of the cutaneous part of the scale. The whole skin
is covered with a thin layer of horny epidermis, which is shed frequently,
at least several times in one year; the shedding begins at the lips, and
the whole outer skin is turned inside out from head to tail, retaining
every minute detail of the cutaneous scales; even the watch-glass-like
covering of the eyes is preserved.
The eyes are peculiar in so far as they possess no lids. The latter are
still present in a vestigial condition in the embryo, but their place is
taken by what is probably a modification of the nictitating membrane, which
is drawn over the eye and covered with a single transparent scale of the
horny skin, like a watch-glass. The eyes themselves are quite movable. The
"tears," which of course cannot appear on the outside, are drained off into
the nasal cavities by the naso-lacrymal ducts.
The ear is likewise peculiar. There is a long columellar rod with a fibrous
or cartilaginous pad at the outer end, which plays against the middle of
the shaft of the quadrate, an arrangement which, we must assume, produces a
thundering noise in the internal ear, since every motion of the quadrate
during the act of swallowing conveys the vibrations directly to the
fenestra ovalis. The tympanic cavity, the Eustachian tubes, and the
tympanum are abolished, and no external traces of the ear are visible.
However, in spite of all this, Snakes can hear very well.
The nose is well developed, and many Snakes, for instance the Grass-Snake,
are guided to their prey as much by the sense of smell as by the eyes and
ears. The tongue is slender, very protractile and bifid, always moist, and
furnished with many sensory corpuscles. It acts entirely as an additional
sense-organ, hence the incessant play of the tongue of a snake which wants
{584}to investigate anything. In spite of the protractility of the tongue,
the hyoid apparatus is very small; the hyoid arches themselves are reduced
to mere vestiges near the base of the first and only branchial arches,
which are thread-like and extend backwards down the throat.
The trachea is very long, and opens far forwards in the mouth; it can be
slightly protruded between the two halves of the lower jaw so as not to be
blocked during the act of swallowing. This is a laborious process. The
snake, having got hold of its prey with its teeth, generally shifts it into
the most convenient position, in order to swallow the head first. One half
of the mandible is then pushed forwards, then the other half; the recurved
teeth afford the necessary hold, and the snake, little by little, draws its
mouth-cavity, and later on itself, over the prey. In fact, it literally
gets outside it. Sometimes with a large victim this process may last for
hours; the whole mouth and head become painfully distended and the veins
swollen almost to bursting. The snake pushes the prey against a stone or
other obstacle, rests awhile quite exhausted, and begins afresh. At last
the bulk of the prey has passed the mouth, the skin of the neck is
stretched to the utmost, the scales being separated by wide interstices,
the ribs work spasmodically, the victim is pressed into the shape of a
sausage, and the deed is done. In order to assist deglutition there is a
great amount of salivation, but the often-heard story that Snakes cover
their prey with saliva before they swallow it, is a fable, or based upon
faulty observation, snakes sometimes being forced to disgorge the
half-swallowed prey, which, in such a case, is covered with slime. One of
my tame snakes had swallowed a frog on my table when a friend entered the
room. The snake was frightened, jumped on to the ground, striking it with
its full belly, and thereby hurting the frog, which squeaked loudly,
whereupon the snake reversed its mechanism and the frog hopped away, none
the worse for its terrible experience.
In correlation with the elongated narrow space of the body-cavity the lungs
are not equally developed, the right being much smaller than the left. The
latter is a very thin-walled, hollow bag, and the posterior half or third
scarcely contains any of the honey-comb-like respiratory "cells," but acts
merely as a reservoir of air.
{585}The cloacal arrangement is essentially the same as that of the
Lacertilia, but Snakes possess no urinary bladder. The copulatory organs
are stowed away beneath the skin in recesses of the posterior lateral
corners of the shallow cloacal vestibulum. Each organ is generally
bifurcated at the free end, and furnished with little spike-shaped, but
scarcely horny, excrescences. On each side of the outer cloacal chamber, in
both sexes, lies a roundish gland with an offensive, strongly-scented
secretion; that of various Boas smells disagreeably sweet and musky. The
majority of Snakes lay eggs, but most of the Viperidae and the thoroughly
aquatic kinds, besides a few terrestrial forms, are viviparous. The
egg-shells are like parchment, with very little or no calcareous deposit,
so that they are always soft; many embryos are, however, provided with a
little "egg-tooth" on the tip of the snout.
[Illustration: FIG. 153.–Map showing the distribution of dangerously
poisonous snakes.]
Snakes are intelligent creatures; some become quite affectionate in
captivity, but most of them are of a morose disposition, and do not care
for company.
The GEOGRAPHICAL DISTRIBUTION of Snakes has been dealt with in detail in
connexion with the various families. Unfortunately very few fossils are
known. One of the oldest is _Palaeophis_, of the London clay (Lower
Eocene). Remains of Elapine and of innocuous Colubrine snakes have been
found in the Lower Miocene of Germany; Crotaline forms are known from the
Miocene of Turkey and North America. All the Plistocene {586}remains belong
to recent genera. There are indications that the Ophidia are a relatively
young branch of Reptilia, essentially of Tertiary date, but the foundations
of the distribution of most of the older families were laid in Miocene
times. The older families, notably those which still possess vestiges of
hind-limbs or of the pelvis, are circumtropical, _e.g._ Typhlopidae,
Boidae. The few survivors of the Glauconiidae are likewise circumtropical,
with the exception of Australia. The Ilysiidae occur in South-Eastern Asia
and in tropical South America; their offshoot the Uropeltidae are
restricted to India and Ceylon. The Colubridae and even many of their
sub-families are cosmopolitan. It is quite possible that the Opisthoglypha
and Proteroglypha are not natural groups, but that their respective
conditions have been developed on various occasions and in different
countries. The same applies more strongly to the Viperidae, a further
development of the Opisthoglyphous type. To judge from their distribution,
the Crotaline snakes were possibly developed in the Palaearctic sub-region;
they spread all over America, but they were debarred from entering either
Australia or Africa. The Viperidae, on the other hand, are restricted
entirely to the Palaeotropical region and to the Palaearctic sub-region.
The fact that no separating belt of water existed for them between Europe
and Africa, indicates their being the most recently developed of poisonous
snakes. Madagascar is the only large country which, besides snakeless New
Zealand, enjoys a total absence of poisonous snakes of any kind, while the
Oriental is the only sub-region which suffers from the presence of numerous
species of every sub-family of poisonous Elapine, Crotaline, and Viperine
snakes.
_Snake-Poison._–Many Snakes, belonging to different families, are
poisonous, and unfortunately there is no external character, easily
ascertained, by which every poisonous snake can be distinguished from a
harmless kind. If the head is very broad, this is probably due to the pair
of poison-glands on the sides of the head; but many harmless snakes can
flatten and broaden their heads in a suspicious way, and, what is much
worse, many of the most poisonous snakes, for instance the Cobras, have a
head as smooth and as sleek-looking as the Grass- or Ring-Snake, the most
harmless of species. It so happens that, with a few exceptions, for
instance among the Crotalines and Vipers, no {587}badly poisonous snake has
loreal shields, _i.e._ a pair of shields intercalated between the nasals
and the preoculars, but this character is obviously no good for any
practical purposes. Therefore, unless you know a snake well enough when you
see it, leave it alone, because a mistake may be fatal.
The poison is secreted in modified upper labial glands, or in a pair of
large glands which are the homologues of the parotid salivary glands of
other animals.[174] A duct passes from the gland forwards along the side of
the upper jaw. Just in front of the fang it doubles on itself, so as to
open by a small papilla on the anterior wall of the sheath of mucous
membrane which embraces the base of the tooth like a pocket. As mentioned
before (p. 582), the poison is conveyed either along a furrow on the
anterior side of the tooth, or the growing substance of the tooth partly
converts the furrow into a canal which opens only near the end of the
tooth. This is a perfectly devilish contrivance, ensuring the conveyance of
the poison into the very deepest part of the wound. The Elapinae have
relatively short fangs, while those of the Vipers, and especially those of
the Crotaline snakes, are much longer, sometimes measuring nearly an inch
in length. The most formidable apparatus is that of the Viperidae, since in
them the maxillaries, each provided with only one acting fang, and without
any other teeth behind, can be erected. The mechanism is explained in Fig.
154 and Fig. 179 (p. 647). The apparatus of the upper jaw is so constructed
that the pushing forwards of the horizontal pterygoid bar will, by acting
on the ectopterygoid, rotate and erect the short maxillary. The pulling
forwards is effected by contraction of the spheno-pterygoid muscle, which
arises far forwards from the basal orbito-sphenoid region, and is inserted
on to the inner dorsal surface of the pterygoid. The principal closing
muscles of the mouth are the temporo-masseteric muscles (Fig. 179, _T.a._
and _T.p._) and the inner and outer pterygoid muscles, which latter arise
from the outer surface of the pterygoid bone, or from the maxillary, and
are inserted on to the articular region of the mandible.
A strong ligament arises from the squamoso-quadrate junction, and spreads
fan-shaped upon the connective tissue {588}wall of the poison-gland; the
anterior and posterior ends of the gland are held by another strong band,
which stretches from the maxilla to the mandibular joint. The whole is so
arranged that the acts of opening the jaws (by the digastric muscles) and
the erection of the fang-bearing maxillaries are enough to mechanically
squeeze the contents out of the poison-gland. A portion of the anterior
temporal muscle is attached to the capsule of the poison-gland.
[Illustration: FIG. 154.–Explanation of the biting mechanism of a
rattlesnake. _Ia_ and _Ib_, position of the apparatus when the mouth is
shut. _IIa_ and _IIb_, position of the apparatus when the mouth is opened
widely; the spheno-pterygoid muscle (_P.e_) is contracted, the pterygoid
(_Pt_) is pulled forwards, the transverse bone or ectopterygoid (_Tr_)
pushes the maxillary (_M_), rotates it and thereby causes the poison-fang
(_J_) to assume an erect position. _Di_, Digastric muscle, contraction of
which lowers, or opens, the lower jaw; _G_, the groove or pit
characteristic of the Crotaline snakes; _J_, poison-fang; _M_, maxillary;
_P_, palatine; _P.e_, spheno-pterygoid muscle; _Pm_, premaxillary; _Pt_,
pterygoid; _Q_, quadrate; _Sq_, squamosal; _T.a_, insertion of the anterior
temporal muscle, by contraction of which the mouth is shut; cf. Fig. 179
(p. 647); _Tr_, transversum or ectopterygoid; X, origin and insertion of a
muscle and a strong ligament, contraction of which draws the maxillary and
its tooth back into the position of rest and assists in shutting the
mouth.]
An excellent account of the nature and of the effect of the venom of Snakes
has been written by Charles J. Martin.[175] The following condensed account
has been abstracted from it:–
"The poison is a clear, pale yellow, or straw-coloured fluid, {589}which
reacts acid, and contains about 30 per cent of solids, but this varies much
according to the state of concentration. Most venoms are tasteless, but
Cobra poison is said to be disagreeably bitter. Dried venom keeps
indefinitely, and dissolves readily in water. It keeps also in glycerine.
It contains albuminous bodies in solution. The venom is, in fact, a pure
solution of two or more poisonous proteids, which are the active agents,
with a small quantity of an organic acid or colouring matter. The venom is
destroyed by reagents which precipitate proteids in an insoluble form, or
which destroy them, _e.g._ silver nitrate or permanganate of potash.
Hypochlorites have the same effect. Carbolic acid and caustic potash
destroy it only after a day or two.
"The venom is generally introduced into the subcutaneous tissue, whence it
reaches the general circulation by absorption through the lymph and
blood-vessels. When introduced directly into a vein, the effects are
instantaneous. It is absorbed by the conjunctiva, but, excepting Cobra
poison, not by the mouth or alimentary canal, provided there be no hollow
teeth or no abrasions. The venom of the various kinds of Snakes acts
differently.
"The symptoms of Cobra poison. Burning pain, followed by sleepiness, and
weakness in the legs after half an hour. Then profuse salivation, paralysis
of the tongue and larynx, and inability to speak. Vomiting. Incapability of
movement. The patient seems to be conscious, but is unable to express
himself. The breathing becomes difficult. The heart's action is quickened.
The pupil remains contracted and reacts to light. At length breathing
ceases, with or without convulsions, and the heart slowly stops. Should the
patient survive, he returns rapidly to complete health.
"The symptoms of Rattle-snake poison. The painful wound is speedily
discoloured and swollen. Constitutional symptoms appear as a rule in less
than fifteen minutes: prostration, staggering, cold sweats, vomiting,
feeble and quick pulse, dilatation of the pupil, and slight mental
disturbance. In this state the patient may die in about twelve hours. If he
recovers from the depression, the local symptoms begin to play a much more
important part than in Cobra poisoning: great swelling and discoloration
extending up the limb and trunk, rise of {590}temperature and repeated
syncope, and laboured respiration. Death may occur in this stage. The local
haemorrhagic extravasation frequently suppurates, or becomes gangrenous,
and from this the patient may die even weeks afterwards. Recovery is
sudden, and within a few hours the patient becomes bright and intelligent.
"Symptoms of bite from the European Viper. Local burning pain; the bitten
limb soon swells and is discoloured. Great prostration, vomiting, and cold,
clammy perspiration follow within one to three hours. The pulse is very
feeble, with slight difficulty in breathing, and restlessness. In severe
cases the pulse may become imperceptible, the extremities may become cold,
and the patient may pass into coma. In from twelve to twenty-four hours
these severe constitutional symptoms usually pass off, but in the meantime
the swelling and discoloration have spread enormously. Within a few days
recovery usually occurs somewhat suddenly, but death may occur from the
severe depression, or from the secondary effects of suppuration.
"Symptoms of bite from the Daboia or _Vipera russelli_. These resemble the
effects of Rattle-snake poison, but sanious discharges from the rectum,
etc., are an additional and prominent feature. The recovering patient
suffers from haemorrhagic extravasations in various organs, besides from
the lungs, nose, mouth, and bowels. Kidney haemorrhage and albuminuria is a
constant symptom. The pupil is always dilated and insensitive to light.
"Symptoms of bite of Australian Elapine snakes. Pain and local swelling.
The first constitutional symptoms appear in fifteen minutes to two hours.
First faintness, and an irresistible desire to sleep. Then alarming
prostration and vomiting. The pulse is extremely feeble and thread-like,
and uncountable. The limbs are cold, and the skin is blanched. Respiration
becomes shallow with the increasing coma. Sensation is blunted. The pupil
is widely dilated, and insensible to light. There is sometimes passing of
blood. If the patient survives the coma, recovery is complete and as a rule
rapid, without secondary symptoms. The Australian venom and that of all
viperine snakes, perhaps also that of the Cobra, if introduced rapidly into
the circulation, occasions extensive intravascular clotting. If the venom
is slowly absorbed, the blood loses its coagulability, {591}owing to the
breaking down of the red blood-corpuscles, most so with vipers, less with
Australian snakes, least so with the Cobra. The Cobra venom is supposed to
extinguish the functions of the various nerve-centres of the cerebro-spinal
system, the paralysation extending from below upwards, and it has a special
affinity for the respiratory centre. The toxicity or relative strength of
the Cobra venom has been calculated to be sixteen times that of the
European Viper. Snakes can poison each other, even those of the same kind.
"_Treatment._–Apply a ligature above, not on the top of the situation of
the bite; twist the string tightly with a stick. Then make a free incision
into the wound. Sucking out is dangerous! Then bandage the limb downwards,
progressing towards the wound; repeat this several times. Direct
application into the widened wound of calcium hypochlorite, i.e. bleaching
powder, is very good, or of a 1 per cent solution of permanganate of
potash, or Condy's fluid. Amputation of the finger is the best remedy of
all if a large snake has bitten it. Do not keep the ligature longer than
half an hour. Then let the circulation return, and apply the ligature
again. In any case, do not keep the ligature on for more than one hour for
fear of gangrene.
"_Internal remedies._–The administration of enormous doses of alcohol is to
be condemned strongly; small stimulating doses are good, but stimulation
can be more effectively produced by ammonia or strychnia. Hypodermic
injection of strychnine, in some cases as much as one to two grains (but
not into a vein!) has in some cases had good results; but injection of
ammonia, instead of doing any good, has disastrous sloughing results. There
is only one fairly reliable treatment, that by serum therapeutics, the
injection of considerable quantities of serum of animals which have been
partially immunised by repeated doses of snake-venom. Unfortunately this
treatment will not often be available."
Several well-known Mammals and Birds are immune by nature against
snake-venom, but most of them avoid being bitten. Some birds induce the
snake to strike and bite frequently into their spread-out wings. Such more
or less immune creatures are the Mongoose, the Hedgehog, and the Pig, the
Secretary bird, the Honey Buzzard, the Stork and probably other
snake-eaters.
{592}CLASSIFICATION OF OPHIDIA.–Duméril and Bibron[176] divided Snakes
according to their teeth into Opotérodonts, Aglyphodonts, Solenoglypha,
Proteroglypha, and Opisthoglypha.
J. E. Gray[177] divided Snakes into two sub-orders: Viperina and
Colubrinia. Günther[178] distinguished between Ophidii colubriformes, O.
colubriformes venenosi (Elapidae and Hydrophidae) and O. viperiformes.
Cope[179] laid stress upon the modifications of the squamosal,
ectopterygoid, and ectopterygoid bones, and also upon the condition of the
vestigial limbs. He divided the snakes into Scolecophidia (Typhlopidae),
Catodonta, Tortricina, Asinea (the harmless snakes without limb-vestiges),
Proteroglypha, and Solenoglypha.
Boulenger[180] has accepted Cope's principles, and, mainly by combining the
Asinea with the Proteroglypha as Colubridae, has produced a logically
conceived system, by far the best hitherto proposed. It has been followed
in the present work. Boulenger's phylogenetic system stands as follows:–
9 Viperidae
5 Uropeltidae | 8 Amblycephalidae
| 7_a_ C. Opisthoglypha 7_b_ C. Proteroglypha |
| | | |
| +––––––––––––––––––––+––––––––––––+
| |
4 Ilysiidae 7 Colubridae Aglypha
| 6 Xenopeltidae |
| | |
+––––––––––––––––––+–––––––––-–––––––––––––+
|
1 Typhlopidae 3 Boidae 2 Glauconiidae
I. No ectopterygoid; pterygoid not extending to quadrate or to mandible;
no supratemporal (squamosal); prefrontal forming a suture with nasal;
coronoid present; vestiges of pelvis.
Maxillary vertical, loosely attached, toothed; mandible edentulous; a
single pelvic bone. .......... _Typhlopidae_, p. 593.
Maxillary bordering mouth, forming a suture with premaxillary,
prefrontal, and frontal, toothless; lower jaw toothed; pubis and
ischium present, latter forming a symphysis. .......... _Glauconiidae_,
p. 594.
II. Ectopterygoid present; both jaws toothed.
A. Coronoid present; prefrontal in contact with nasal.
1. Vestiges of hind-limbs; supratemporal (squamosal) present.
Squamosal large, suspending quadrate. .......... _Boidae_, p. 596.
Squamosal small, intercalated in the cranial wall. ..........
_Ilysiidae_, p. 594.
2. No vestiges of limbs; squamosal absent. .......... _Uropeltidae_,
p. 595.
{593}B. Coronoid absent; squamosal present.
1. Maxillary horizontal; pterygoid reaching quadrate or mandible.
Prefrontal bone in contact with nasal. .......... _Xenopeltidae_,
p. 605.
Prefrontal not in contact with nasal. .......... _Colubridae_,
p. 606.
2. Maxillary horizontal; pterygoid not reaching quadrate or mandible.
.......... _Amblycephalidae_, p. 637.
3. Maxillary vertically erectile, perpendicularly to ectopterygoid;
pterygoid reaching quadrate or mandible. .......... _Viperidae_,
p. 637.
For ordinary practical purposes this synopsis is useless, being based
entirely upon anatomical characters, not all easily ascertained. The
following characterisation of families may therefore be preferred:–
Eyes vestigial; no teeth in the lower jaw; without enlarged ventral
scales. .......... _Typhlopidae._
Eyes vestigial; teeth restricted to the lower jaw; without enlarged
ventral scales. .......... _Glauconiidae._
Eyes very small; head not distinct; ventral scales scarcely enlarged;
tail extremely short, ending obtusely and covered with peculiar scales.
.......... _Uropeltidae._
With vestiges of the hind-limbs appearing as claw-like spurs on each side
of the vent; ventral scales transversely enlarged; eyes functional, free.
Ventral scales scarcely enlarged. .......... _Ilysiidae._
Ventral scales transversely enlarged. .......... _Boidae._
With a pair of poison-fangs in the front part of the mouth, carried by
the otherwise toothless, much shortened, and vertically erectile
maxillaries; ventral scales transversely enlarged; eyes free. ..........
_Viperidae._
All the remaining Snakes combine the following characters: the
maxillaries are typical, not separately movable, horizontal, with a
series of teeth.[181] The mandible is toothed but has no coronoid bone.
There are no vestiges of limbs or of their girdles. The eyes are free.
Dentary movably attached to the tip of the articular bone of the
mandible; skin beautifully iridescent. .......... _Xenopeltidae._
Without a mental groove; the ends of the pterygoids are free, not
reaching the quadrates. .......... _Amblycephalidae._
With a median longitudinal groove between the shields of the chin; the
squamosal is horizontally elongated, movable; the pterygoid reaches the
quadrate. .......... _Colubridae._
FAM. 1. TYPHLOPIDAE.–Burrowing snakes which have the whole body covered
with uniform cycloid scales, and with the teeth restricted to the small and
transversely placed maxillary bones. The pterygoids do not extend backwards
to the quadrates, and there are no endopterygoids. The quadrates slant
obliquely forwards, and are attached directly to the pro-otics, {594}owing
to the absence of squamosal bones. The prefrontals are in lateral contact
with the nasals. There are vestiges of the pelvis, reduced to a single bone
on each side. The eyes are hidden by shields of the skin.
The Typhlopidae, mainly composed of the genus _Typhlops_, with about one
hundred species, are undoubtedly the last living descendants of formerly
cosmopolitan, rather archaic, snakes, which in adaptation to their
burrowing life and insectivorous diet have undergone degradation. They are
still widely distributed in all tropical and sub-tropical countries, some
on the solitary Christmas Island, but not in New Zealand. One species, _T.
vermicularis_, inhabits the Balkan Peninsula and South-West Asia. It is
brown above, yellowish below, and reaches a length of about 10 inches. The
tail is extremely short and ends in a horny spine. _T. braminus_ is widely
distributed in Southern Asia, the Malay Islands, the islands in the Indian
Ocean and in Southern Africa.
FAM. 2. GLAUCONIIDAE.–In most respects resembling the Typhlopidae, but the
maxillaries retain their normal position and are toothless, teeth being
restricted to the lower jaw, which is stout and short. The pelvic girdle
and the hind-limbs show the least reduction found in any recent Snakes; in
the pelvis the ilia, pubes, and ischia can still be distinguished, the last
even retaining their symphysis; there are also vestiges of femurs. About
thirty species, nearly all belonging to the genus _Glauconia_, are found in
South-Western Asia, Africa, and the warmer parts of America, including the
West Indies.
FAM. 3. ILYSIIDAE.–The scales of the cylindrical body are smooth and small,
those on the ventral side are scarcely larger. The tail is extremely short
and blunt. The head is very small, not distinct from the neck. The gape of
the mouth is very narrow. Teeth are carried by the mandibles, the
pterygoids, palatines, maxillaries, and one or two or more by the
premaxillae. The endopterygoids are short. An important cranial feature is
the short quadrates, which stand rather vertically and are connected with
the cranium by the squamosals; these are very small and are firmly wedged
in between the upper ends of the quadrates and the pro-otic, lateral, and
supra-occipital bones; now forming part of the cranial wall. Vestiges of
the pelvis and hind-limbs are very incomplete, and terminate in claw-like
spurs, {595}protruding between the scales on either side of the vent. The
eyes are very small, and are either free or covered by transparent shields.
The few, scarcely half-a-dozen, species are found in South America
(_Ilysia_) and in Ceylon, the Malay Islands, and Indo-China.
_Ilysia_ (_Tortrix_) _scytale_, the Coral-Snake of Tropical South America,
is a beautiful coral-red with black rings. On account of its beauty,
perfectly harmless nature, and for "cooling purposes," this snake, which
grows to nearly a yard in length, is sometimes worn as a necklace by native
ladies. All the Ilysiidae lead a partly burrowing life, live chiefly upon
worms, insects, and little Typhlopidae, and are viviparous.
FAM. 4. UROPELTIDAE.–Burrowing snakes of Ceylon and Southern India, with a
short and rigid cylindrical body and a very short tail, which ends in a
large peculiar shield, often obliquely truncated. The scales of the body
are smooth, and are little larger on the belly; the coloration is mostly
very beautiful. The eyes are very small.
The Uropeltidae are somewhat intermediate between the Ilysiidae,
Glauconiidae, and Boidae. The pterygoids do not reach the quadrates; but
ectopterygoids are present; the quadrates are very small and directly
attached to the skull, squamosals being absent. Teeth are carried by the
mandibles and by the maxillaries, which are normal in their position. There
are no vestiges of hind-limbs or of the pelvis. The Uropeltidae, of which
about forty species are known, are viviparous, burrow in the ground, and
frequent damp localities, preferring mountain-forests. The use of the
characteristic tail-shield is not clear; perhaps it assists these rather
rigid creatures in digging, by being pressed against the ground.
_Uropeltis._–The tail is obliquely truncated, ending in a roundish, flat
shield.
_U. grandis_ s. _philippinus_.–The latter name seems to have misled W.
Marshall[182] into including the Philippine Islands in the range of the
family, a mistake which is sure to be propagated. The species, the only one
of the genus, is confined to Ceylon; it is blackish above, yellow below,
frequently with small yellow spots above and brown spots on the under
surface. It grows to about 18 inches in length.
{596}_Rhinophis._–The tail-shield is convex and the snout is pointed. _Rh.
sanguineus_ of Southern India is black above with a bluish gloss, sometimes
with small pale specks; the belly and several of the lateral series of
scales are bright red, spotted with black. The tail-shield is black and
red.
[Illustration: FIG. 155.–Skull of _Eunectes murinus_. × 1. The teeth on the
maxillary, palatine, and pterygoid have been omitted. _Col_, Columella
auris; _Cond_, occipital condyle; _E.P._ and _E.Ptg_, ectopterygoid or
transverse bone; _F_, frontal; _Mand_, mandible; _Max_, maxillary; _Na_,
nasal; _Pal_, palatine; _Par_, parietal; _Pmx_, premaxillary; _Pr.f_,
prefrontal; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate; _Sq_,
squamosal; _Tb_, turbinal.]
FAM. 5. BOIDAE.–Typical Snakes, usually large, and with vestiges of pelvis
and hind-limbs, appearing externally as claw-like spurs on each side of the
vent. The scales of the upper surface are usually small and smooth, while
those of the ventral surface form one broad series on the belly, and one or
two rows on the tail. The quadrate is carried by the horizontally elongated
squamosal, which rests loosely upon the lateral occipital region. The
prefrontal is in contact with the nasal. Teeth are carried by the
mandibles, the pterygoids, palatines, maxillaries, and, in the Pythoninae,
by the premaxillaries also. For further details see Figs. 155, 156.
{597}[Illustration: FIG. 156.–A, Ventral, B, dorsal, view of the skull of
_Eunectes murinus_. Lettering as in Fig. 155. × 1.]
The Boidae comprise between sixty and seventy species, which have been
grouped into many genera, on unimportant characters, referring to the
scales and shields of the head. It is doubtful if they are natural groups,
a consideration which detracts much from their value in the study of
geographical distribution. Even the two sub-families are not free from this
reproach. The range of the family is world-wide, Boidae occurring in all
tropical and sub-tropical countries, including islands, except New Zealand.
A few species live in South-Eastern Europe (_Eryx_) and in North-Western
America. They mostly prefer wooded districts, especially forests; climbing
trees, assisted by the short and partly prehensile tail. Others are
semi-aquatic, and a few live in sandy localities. They are all rapacious,
and by preference feed on warm-blooded creatures, which they constrict by
coils of the body in order to hold, kill, and crush the victim before
swallowing it. Exaggerated notions are entertained about their swallowing
capacity. It is obvious that a large snake, 20 feet long, half a foot
thick, and weighing several hundred pounds, can crush a tiger, a stag, or
even a {598}cow; but common sense tells us where to draw the line when it
comes to the swallowing of the prey. Small game, although of a bulk
apparently far too big for the snake, is so crushed and mangled that it is
turned into the shape of a sausage preparatory to the long process of
swallowing. The Boidae lay eggs, and some species incubate them, or rather
the female coils herself round them for the sake of protection. No
appreciable amount of extra warmth is developed. Unfortunately the
observations of one of the best cases on record[183] were conducted so
imperfectly that they are of little value.
SUB-FAM. 1. PYTHONINAE.–With a pair of supra-orbital bones, intercalated
between the prefrontal, frontal, and postfrontal bones. The sub-caudal
scales are mostly in two rows. The premaxilla often carries a few small
teeth.
The Pythoninae, comprising about twenty species, are restricted to the
Palaeotropical and Australian regions, with the sole exception of
_Loxocemus bicolor_ in Southern Mexico.
_Python_, the principal genus, has teeth on the premaxilla. The rostral,
each of the anterior upper labials, and some of the lower labial shields,
contain a deep, probably sensory, pit. The maxillary and mandibular teeth
are long, but decrease from before backwards. The head is distinct from the
neck, and is covered with symmetrical shields or with small scales. The
scales of the body are small and smooth. The tail is short and prehensile;
below with two rows of scales. The pupil of the eye is vertical. The range
of the genus extends over the whole of the Palaeotropical and Australian
regions, excepting Madagascar and New Zealand.
_P. spilotes_, the "Carpet Snake" of Australia and New Guinea, is mostly
beautifully marked, but is subject to much variation in colour. The more
typical specimens are black above, each scale with a yellowish dot, with
yellow spots or combinations of dots, more or less arranged in rows. The
under parts are yellow. It reaches a length of about two yards, and spends
a great part of its time in trees.
_P. reticulatus_ is the commonest species in Indo-China and in the Malay
Islands. Four upper labial shields of each side are pitted. The specific
name refers to the bold, dark, lozenge-shaped markings upon the lighter
yellowish or brown ground. A black {599}line extends over the head from the
nose to the neck, and another on each side from the eye to the angle of the
mouth. The under parts are mostly yellowish, with small brown spots on the
sides.
This is one of the largest species of Python, some specimens being known
which measured about 30 feet in length.
[Illustration: FIG. 157.–_Python spilotes_ (the Carpet Snake). × ⅛.]
As a sample of folk-lore connected with this monstrous snake the following
Burmese fable has been recorded by Mason:–[184]
"According to a Karen legend all the poisonous serpents derive their
virulence from the Python, which, though innocuous now, was originally the
only one that was venomous. In those days he was perfectly white, but
having seduced away a man's wife, Aunt Eu (Eve), he made her, while she was
in his den, weave figures on his skin in the forms which are now seen. At
that time, if he bit the footstep of a man in the road, such was the
virulence of his poison that the man died, how far soever that man might
have passed from the bitten track. The Python had not, however, an ocular
demonstration of the fact, so he said to the Crow: 'Crow, go and see
whether people die or not when I bite the foot-track.' The Crow went to the
neighbourhood of a Karen cabin, and found the people, as is their custom at
funerals, laughing, singing, dancing, jumping, and beating drums. He
therefore returned to the Python, and told him that so far from {600}his
efforts producing death, on the contrary they produced joy. The Python was
so angry when he heard this that he ascended a tree and spit up all his
venom, but other creeping things came and swallowed it, and people die of
their malignancy to this day. The tree, therefore, from which the Python
spat up his venom became deadly, and its juice is used to this day for the
purpose of poisoning arrows. The Python made the other creatures promise
not to bite without provocation. The Cobra said: 'If there be transgression
so as to dazzle my eyes, to make my tears fall seven times in one day, I
will bite.' So said the Tiger (whose bite the Karens esteem as virulent as
a serpent's) and others, and they were allowed to retain their poison. But
the Water Snake and Frog said they would bite with or without cause as they
liked; so the Python drove them into the water, where their poison melted
away and their bite became harmless."
[Illustration: FIG. 158.–_Python molurus._ × ⅒.]
_P. molurus_ is the species of India and Ceylon, ranging, however, also
into Indo-China. Boulenger quotes W. Elliot[185] {601}as the authority for
the statement that this species grows to the length of 30 feet. Only two
pairs of upper labials are pitted. The general colour above is greyish or
yellowish brown with a dorsal series of large reddish-brown, black-edged
patches, and on the sides of the body with a series of smaller spots with
light centres. On the head is a lance-shaped marking; a brown stripe passes
from the eye backwards. The under parts are yellowish.
_P. sebae_ and _P. regius_ are African species. The former has two pairs of
upper labials pitted, the latter four pairs. _P. sebae_ is generally pale
brown above with dark brown, black-edged cross-bars, which are usually
connected by a sinuous dark stripe along each side of the back. The upper
surface of the tail has a light stripe between two black stripes. The belly
is spotted and dotted with dark brown. _P. sebae_ ranges over the whole of
Tropical and Southern Africa, perhaps with the exception of Eastern Africa.
_P. regius_ of West Africa is beautifully marked, and may be recognised by
the dark brown, black-edged band along the back, sending down triangular or
Y-shaped processes on the sides, which are pale brown. This dorsal band
encloses a light streak on the neck and another on the tail. The belly is
yellowish.
These African Pythons grow to a length of about 15 feet, but specimens so
large as this are not often met with. The negroes of certain parts of the
coast of Guinea are said to worship them and to keep them in special
temples, where they are regularly attended to. Their food consists chiefly
of small Mammals, notably rats, and of Birds. A couple of these snakes
paired in the Zoological Gardens of London in the month of June. The female
laid nearly one hundred eggs in the following January, and incubated them
until April, when the embryos were found to be still unripe.
SUB-FAM. 2. BOINAE.–Without supra-orbital bones. The premaxilla is
toothless. The subcaudal scales form mostly a single row.
The Boinae comprise between forty and fifty species. Most of them are
American, but the genus _Eryx_ inhabits North Africa, Greece, and
South-Western Asia; the genus _Enygrus_ inhabits New Guinea and many of the
Pacific Islands, for instance New Britain (Neu Pommern), the Solomon,
Loyalty and Fiji Islands, {602}and the New Hebrides. _Casarea dussumieri_
is found on Round Island near Mauritius; and two species of _Boa_ and one
of _Corallus_ represent the Boidae in Madagascar, while all the others live
in Central and South America.
_Boa._–The maxillary and mandibular teeth gradually decrease in size. The
scales of the upper parts of the body and tail are smooth and very small.
The rostral shield is enlarged. The nostrils are placed between two or
three nasals, and these are separated from those of the other side by small
scales. The tail is short and prehensile. The pupil is vertical.
_B. constrictor_, of South America, has the head covered with small scales,
one of the pre-oculars being enlarged. The eye is separated from the
labials by several series of tiny scales. The general colour is a delicate
"pale brown above, with fifteen to twenty dark brown cross-bars widening on
each side, and, if connected by a dark dorso-lateral streak, enclosing
large elongate oval spots.... On each side is a series of large dark brown
spots with light centres, most of which alternate with the cross-bars. On
the tail the markings become much larger, brick-red, edged with black, and
separated by narrow, yellowish interspaces." Under parts yellowish with
black dots. _Boa constrictor_, a name applied in popular parlance to many
species, reaches a length of more than 10 feet; the largest specimen in the
British Museum measures exactly 11 feet. A few other species inhabit
Central America and the West Indies. _B. dumerili_ and _B.
madagascariensis_, both of Madagascar, cannot be separated from the genus
_Boa_.
A. D. Bartlett[186] has described the following incident:–
"In the evening of 5th October 1892 two pigeons were put into the cage in
which two fine specimens of _Boa constrictor_ had been living on friendly
terms since the beginning of the year. The larger snake seized one of the
pigeons and the keeper left the house. The next morning only one of the
snakes, the larger specimen, was visible, and from its enormously extended
body it was evident that it had swallowed its companion, which was about 9
feet in length. It had no longer the power of curling itself round, but
remained extended nearly to its full length in a straight line, and
appeared to be at least three times its normal circumference. It was almost
painful to see the distended skin, {603}which had separated the scales all
over the middle of the body. By 2nd November, twenty-eight days later, the
snake had not only digested its companion but had regained its appetite as
well as its normal size, and it immediately swallowed a pigeon put into its
den."
This peculiar case is not one of ordinary cannibalism. It is rather an
unintentional accident. When two snakes happen to get hold of the same
animal (in the present case a pigeon) and begin to swallow it, the action
of swallowing becomes almost mechanical, the snakes continuing to push
their jaws over the prey–which in the case of a bird or mammal they cannot
taste, nor can they see it–so long as they feel something in the mouth.
After the original prey has been mastered, it is the turn of the opposite
snake's head, and if the weaker snake does not give way it is swallowed by
its stronger mate. Grass-Snakes will swallow several frogs if these are
tied together in a string, and other snakes do the same with mice. There
are instances on record in which a _Python_ swallowed its blanket, which,
being absolutely indigestible, caused its death.
[Illustration: FIG. 159.–Head of _Eunectes murinus_. × 1.]
_Casarea_, the "Round-Island Snake," differs from _Boa_ chiefly by the
rough and strongly keeled scales, and by the relatively much longer tail.
_Eunectes murinus_, the "Anaconda," is an aquatic _Boa_. It differs from
this genus mainly by the inner of the three nasal shields being in contact
with that of the other side (see Fig. 159), and by the absence of the
little scales between the eye and the labials; the snout is, moreover,
covered with shields instead of small scales. The pupil of the eye is
normally vertical, but it had contracted into a round pinhole in the dead
but still fresh {604}specimen from which the figure was drawn. The general
colour is dark olive-brown, with large oval black spots arranged in two
more or less alternating rows along the back, and with smaller black,
white-eyed spots along the sides. The under parts are whitish, spotted with
black. The upper parts of this and of many other dark-coloured species of
Boidae are often shiny, with an iridescent lustre.
The Anaconda combines an arboreal with an aquatic life, a kind of existence
eminently in harmony with the well-watered, dense forests of Tropical South
America, which are the home of this, the largest of all modern Snakes. It
is said to attain a length of as much as 33 feet. There is no inherent
impossibility in such statements, but the giant specimens seem to have a
knack of keeping out of the naturalist's way.
The Anaconda feeds chiefly upon Birds and Mammals, which it catches either
on land, mostly during the night-time, or in the water. For the latter
purpose it lies submerged in the rivers or floats about leisurely, only the
head being above the surface, and anything suitable is attacked. In other
localities the snake, if so inclined, establishes itself upon the branches
of a tree which overhangs the water, or the track of the game. These
aquatic Snakes seem to be viviparous.
_Eryx_ has the head not distinct from the neck and covered entirely with
small scales. Those of the body are likewise small, and are either smooth
or keeled. The tail is very short. The anterior maxillary and mandibular
teeth are longer than the posterior teeth. These snakes, most of which are
less than 3 feet in length, inhabit the sandy districts of North Africa,
Arabia, and South-Western Asia, extending into Central Asia. One species,
_E. jaculus_, extends into Greece and the Ionian Islands. Like the other
species it is an ugly creature, pale grey or yellowish above, with darker
patches and spots. The under parts are whitish. The scales are smooth on
the front half of the body, becoming keeled further back and on the tail.
Total length under 2 feet. The pupil is vertical.
According to Zander[187] and Werner[188] this snake lives in sandy
localities, digging itself into the sand, or covering the body lightly with
sand and leaving only the eyes and nostrils free. The whole body is very
flabby, and presses itself into any irregularity of the {605}ground over
which the snake creeps. Some specimens live on lizards, others prefer mice.
The prey is caught by the head, and further secured by several turns of the
body of the captor, whose tail is then turned forwards, round the head of
the victim, so as to form a kind of knot.
Not less striking than their agility is their jealousy, which is so strong
that a snake will occasionally leave the mouse which it has just strangled
in order to seize another snake's mouse. Sometimes several snakes fight for
the same mouse, coiled together into one inextricable lump so that the
mouse itself is quite invisible. The snakes poke their heads about in
search of the hidden prey, and every attempt of one of the snakes to free
itself, causes the others to squeeze it firmer and firmer, thinking
apparently that the motion was caused by the lost prey.
Occasionally one of Werner's captives caught several mice in succession.
With these it crawled into a corner, dropped the mice, and then proceeded
quietly to swallow one after another. After a fortnight the whole repast
was digested, and the snake was ready for more.
FAM. 6. XENOPELTIDAE.–The single species, _Xenopeltis unicolor_, of
South-Eastern Asia, including the Malay Islands, has been raised to the
dignity of family-rank on account of the following combination of
characters. The prefrontal bones are still in contact with the nasals as in
the previous families, but the coronoid bones of the mandibles are absent
as in the remaining families. The whole suspensorial apparatus and the
lower jaw itself are peculiar. The dentary bone is movably attached to the
end of the much-elongated articular bone, the movability being enhanced by
the absence of the coronoid element.[189] The quadrate is short and thick,
and is carried by the short and broad squamosal, which lies flat against
the skull, resembling in this respect that of some of the Ilysiidae.
Boulenger rightly considers _Xenopeltis_ to be in various ways intermediate
between this family, the Boidae and the Colubridae. The head is small and
not distinct from the neck. The eyes are small and have a vertical pupil.
The body is cylindrical, covered above with {606}smooth black or brown and
highly iridescent scales, hence the generic name. The ventral scales are
white and transversely enlarged as in the majority of snakes. The tail is
short, but not stunted, measuring about 4 inches in full-grown specimens of
a total length of 3 feet.
FAM. 7. COLUBRIDAE.–This family comprises those snakes (about nine-tenths
of all recent species) which combine the following
characters:–ectopterygoids are present: the squamosals are loosely attached
to the skull, and carry the quadrates, which are not reached by the
pterygoids: the prefrontals are not in contact with the nasals: the
maxillaries are horizontal and form the greater portion of the upper jaws:
the mandibles lack the coronoid process or element: both jaws are toothed.
The best arrangement of this enormous cosmopolitan family with terrestrial,
arboreal, and aquatic forms, is that by Boulenger, who, adopting Duméril's
terms, has divided them into three parallel series.
A. _Aglypha._–All the teeth are solid and not grooved.
B. _Opisthoglypha._–One or more of the posterior maxillary teeth are
grooved.
C. _Proteroglypha._–The anterior maxillary teeth are grooved or
"perforated."
The Aglypha are harmless, non-poisonous. Most of the Opisthoglypha are
poisonous, although few of them are dangerously so. The Proteroglypha,
which comprise the "Cobras" and their allies, are deadly poisonous.
SERIES A. AGLYPHA.
SUB-FAM. 1. ACROCHORDINAE.–The postfrontal bones, besides bordering the
orbits posteriorly, are extended forwards so as to form the upper border of
the orbits, separating the latter from the frontals. The few genera and
species of this sub-family are mostly aquatic, inhabiting rivers, or
estuaries with brackish water, and they have been known to swim far out
into the sea. The body is covered with small, frequently granular scales;
in the typically aquatic forms the body is slightly compressed laterally,
and the ventral scales are scarcely larger than the others. Most of these
ugly snakes inhabit the rivers of coasts of South-Eastern Asia and
Papuasia; one, _Stoliczkaia_, is found in the Khasia Hills {607}of
North-Eastern India; another, _Nothopsis_, lives far from its supposed
allies, on the Isthmus of Darien, Central America.
_Acrochordus javanicus_ has no ventral shields. The head is flat, covered
with small granules, with the eyes and nostrils on the upper surface. The
general colour is dull olive-brown, lighter and spotted beneath. The food
consists of fishes. Total length up to 4 feet.
_Chersydrus granulatus_ ranges from the coast of Madras to New Guinea. The
body and tail are compressed, and form a ventral fold, covered with tiny
scales like the rest of the body. General colour grey above, yellow below.
SUB-FAM. 2. COLUBRINAE.–The postfrontal bones are restricted to the
posterior border of the orbits. The maxillary and dentary bones carry teeth
on their whole length. The scales are usually imbricating. This sub-family
contains the overwhelming majority of snakes, about 1000 species, all of
them harmless so far as poison is concerned. None of them reach a great
size, species of 6 or 7 feet in length being rare, e.g. _Zamenis mucosus_,
but a few species of the Indian genus _Zaocys_ s. _Coryphodon_ grow to 10
feet. Most of the Colubrine snakes are oviparous, but some, e.g.
_Coronella_, are viviparous. Some are aquatic, or semi-aquatic, others are
absolutely arboreal, others again prefer dry, sandy, or rocky localities,
according to their food. The distribution of the sub-family is
cosmopolitan, finding its natural limits only in the permanently frozen
under-ground, a condition which makes hibernation impossible. Most of them
love warmth and like to bask, although many are not fond of the broiling
sun. In the temperate regions they hibernate. As a rule they are
intelligent and some of them become even affectionate.
_Tropidonotus._–The teeth form closely set series on the whole length of
the maxillaries, palatines, pterygoids, and the greater portion of the
dentaries. The premaxilla is toothless. The teeth of the maxillaries
gradually increase in length, the posterior teeth being the longest. The
pupil is round. There is a pair of internasal shields. The scales covering
the body have each an apical, sensory pit, are mostly keeled, and are
arranged in longitudinal series. The ventral shields are broad; the
sub-caudals form two rows. This genus, with more than seventy species, has
a wide range, practically over the whole world with the exception of New
Zealand and the southern half of Australia.
{608}_T. natrix_, the common Grass-Snake, has a divided, or double, anal
shield. The strongly keeled scales of the body form nineteen rows. There
are normally seven upper labials, the third and fourth of which border the
eye. The usual colour of the Grass-Snake is olive-grey or brown above, with
black spots and narrow cross-bands. The labials are white or yellowish,
with black sutures. The belly is checkered black and white, more or less
suffused with grey. There are several colour-varieties. The typical or
northern form has a white, yellow, or orange collar, bordered behind by a
black collar; the pale collar is sometimes faint or absent. The second
variety, rather common in Spain and Portugal, although not the only form in
the Peninsula, has no collar whatever, and these specimens are sometimes
almost uniformly grey-green above. The third variety, common in
South-Eastern Europe and in Asia Minor, has a well-marked collar and a
yellowish streak along each side of the back. But there are also almost
black specimens.
The usual length of an adult female Grass-Snake is about 3 feet, but very
exceptional cases of more than 6 feet are on record; the males are smaller
and more slenderly built. The range extends over the whole of Middle
Europe, Algeria, West and Central Asia. It does not, however, occur in
Ireland or Scotland. Its northern limit is the southern part of Sweden.
The Grass-Snake prefers moist, grassy localities, with the neighbourhood of
water, chiefly on account of the food, which consists entirely of fishes
and Amphibia, notably of frogs; tree-frogs are preferred to anything else;
toads are occasionally eaten, but mice are never taken.
The Grass-Snake can climb trees or rather shrubs and is an accomplished
swimmer, often spending much of its time in water for fishing purposes. The
fish is caught by the belly and then generally swallowed on land. The
Grass-Snakes appear in the spring and disappear in the autumn to hibernate
in the ground. They pair, in England, in the month of May or June, usually
on warm and sunny mornings. The eggs are laid from July to the end of
August, mostly in rich vegetable soil, in heaps of weeds or in
manure-heaps. Young snakes lay fewer eggs than old specimens, which
sometimes produce more than three dozen at a time. The eggs are soft,
whitish yellow, about one inch long, and soon stick together, so that the
whole clump {609}can be taken up at once. As a rule the new-laid eggs do
not contain any visible sign of the embryo, but it often happens that the
snake has to delay oviposition, and then the embryos are more or less
advanced. This is especially the case with recently caught specimens. The
young are hatched in the late summer or in the autumn, and seem to live at
first upon soft insects and worms. Curiously enough they are easily drowned
when they fall into the water, even in a shallow tank. My tame snakes have
often laid eggs between the stones in the greenhouse; the young throve well
upon unknown food, but most of them met their fate in the water. When they
are a few weeks old they are strong enough to take baby-frogs.
The Grass-Snake becomes very tame, learns to distinguish between different
people, allows itself to be handled without hissing or without voiding the
obnoxiously smelling contents of its cloaca and anal glands, will in time
take the offered food from the hand, and will even crawl up the arm or
sleeve and coil itself up contentedly. One of the finest specimens, quite
green, without a trace of a collar, and with brownish-red eyes, I caught in
the Guadiana, where it had been fishing in midstream. It swam towards the
bank, dived, and hid itself at the bottom between rocks. This snake, a
female, became very tame. It never hibernated, shed its skin regularly
every few months, and grew within nine years from 35 inches to 42 inches in
length.
The Grass-Snake is perfectly harmless: although hissing, and striking out
furiously with its head, it never bites, not even when it is severely
handled. Its only defence consists of the awful contents of the cloaca and
the anal glands, the secretion of which smells of concentrated essence of
garlic mixed with other indescribable odours. The wildest specimens I have
ever met with inhabited a swamp with a little stream to the north of Oporto
close to the coast. To my utter surprise some of them actually made for me,
swimming along rapidly with the head erect, about 6 inches above the water,
and darting forwards with widely opened jaws, but they did not bite. These
and other kinds of allied snakes require to drink much and often.
Occasionally they drink milk when this is offered them, but that they suck
the udders of cows or the breasts of women is an idle fable.
{610}_T. viperinus._–The scales are strongly keeled and form twenty-one to
twenty-three longitudinal rows. The third and fourth labials border the
eye. The anal shield is divided. The eyes and nostrils are directed upwards
instead of sidewards, in adaptation to the essentially aquatic habits of
this species, which lives upon fishes and Amphibia. The general colour is
grey to reddish brown, with a black zigzag band along the back and a
lateral series of black, yellow-eyed spots. The belly is yellow or red,
checkered with black.
[Illustration: FIG. 160.–_Tropidonotus sirtalis._ × ½.]
The Viperine Snake bears a general resemblance to the common viper. It
inhabits France, Italy, Spain and Portugal, and Morocco. Very large
specimens attain a length of nearly 3 feet, but the ordinary size of adults
is 2 feet. This snake spends most of its time in the water, but it is often
found on land, basking on the top of a low wall or on a low shrub. It is
exceedingly common in Spain and Portugal, where it inhabits almost every
ditch, any standing water or slow river. In the Alemtejo, when during the
rainless and hot summer the small {611}rivers have nearly dried up, these
snakes collect in great quantities in the remaining stagnant and muddy
pools, and as the stock of suitable fish gets exhausted, are often reduced
to a deplorably emaciated condition. By the month of August they have
become so thoroughly aquatic that they cannot be kept alive in dry
surroundings for twenty-four hours. Those which I collected generally died,
apparently from some kind of cutaneous suffocation, during the night
following their capture. Taken under other conditions they are very easily
kept and tamed.
I once caught a Viperine Snake in a ditch whilst it was swallowing an eel
of nearly its own length. Both were separated, and then put into a small
bag together with other creatures, and no more attention was paid to them
for several hours. When I opened the bag again, the snake, undisturbed by
my incessant walking about, was again busily engaged in trying to get
outside that same eel!
_T. sirtalis_ (Fig. 160) is one of the almost endless varieties of what is
now known by the name _T. ordinatus_, of North and Central America.
_T. tesselatus_ is closely allied to _T. viperinus_, which it represents in
South Germany, Italy, South-Eastern Europe, and Asia; but the scales form
only nineteen rows, and the fourth, or fourth and fifth labials, border the
eye. The usual colour is olive-grey with dark little spots, and with a dark
chevron-shaped band behind the occiput. The lower parts are yellow or red
checkered with black, hence the specific name.
_Zamenis._–The maxillary teeth are not closely packed; they increase
slightly in size backwards, and the last two are often a little larger and
separated from the rest by a diastema. The mandibular teeth rather decrease
in size from before backwards, inversely with the upper teeth. The scales
are smooth with apical pits; the sub-caudals form two rows. The eye is
large, and has a round pupil. The range of this genus, with about thirty
species, extends over the whole of the Periarctic region.
_Z._ (_Ptyas_) _mucosus_ (Fig. 161), the Rat Snake of India, extending from
Transcaspia to Java, is a very common species, often seen in menageries.
Its general colour is brown above, often with black cross-bands on the
hinder part of the body and tail. The under parts are yellowish. The fourth
and fifth labials border the eye. {612}The scales on the body form only
seventeen rows. Another feature of this species is the prominent ridge of
the back-bone, not only in half-starved but in well-conditioned specimens.
The Rat Snake grows to a length of more than 7 feet, and is as ill-tempered
as most species of this genus.
[Illustration: FIG. 161.–_Zamenis mucosus_ (Rat Snake). × ⅕.]
_Z. gemonensis_ s. _viridiflavus_ inhabits France, Italy, the Balkan
Peninsula, and Asia Minor. Its coloration is very variable. In general it
is either green above and yellow below, hence the appropriate name
_viridiflavus_, or the ground-colour of the back is greyish or olive-yellow
with brownish spots, which form more or less longitudinal rows on the
trunk, but gradually pass into blackish continuous lines on the tail; the
under parts are yellow or greenish white, often with many very small, dark
specks. The scales form seventeen or nineteen rows; the anal shield is
divided. There are two small postocular scales and one subocular; of the
eight labials, the fourth and fifth border the eye. This species is very
lively, attacks {613}and bites furiously, climbs well, and when suspended
from branches can protrude half of its length in a horizontal direction. It
eats any kind of Reptile, Bird, or Mammal it can master; small animals are
swallowed directly, rats and moles are first killed by constrictions. Large
specimens reach perhaps 6 feet in length.
_Z. hippocrepis_ is the representative species in the Iberian Peninsula and
in North-Western Africa. It is rarely more than 4 feet long, and is very
pretty, the ground-colour being reddish or olive-yellow with a row of
large, dark brown, yellow-edged spots along the back. Two rows of smaller
spots adorn the sides; where the dark spots are large, the pale
ground-colour is restricted to forming rings around the spots, producing a
pretty appearance. The under parts are yellow or orange, with black spots.
On the head is a dark, pale-edged patch in the shape of a horse-shoe, a
feature alluded to by the specific name. Structural characters are the
possession of a row of little subocular scales, which completely separate
the eye from the labials, the double anal shield, and the small and smooth
scales on the body, which form generally as many as twenty-seven rows.
_Z. constrictor._–The American Black Snake. The scales are smooth, and
arranged in seventeen rows; the anal shield is divided. The general colour
above is uniform bluish-black; below slaty, tinged with blue; the chin and
throat are silvery white, sometimes with a black spot. Large specimens
attain a total length of 6 feet.
Holbrook gives the following exhaustive account of this species, about
which many sensational stories are current even in would-be scientific
periodicals:–
The "Black Snake" is one of the commonest of North American species. It is
extremely active, climbing with facility, and running with great rapidity,
whence it is not uncommonly called the "Racer." It frequents shady places,
covered with thick shrubs, on the margins of water. It feeds on mice,
toads, or small birds; and, as it is an excellent climber, is frequently
seen on trees in search of birds' nests. It is a bold and daring serpent,
enters barns and out-houses without fear, and has been known to destroy
young chickens. Its specific name _constrictor_ would imply that it
suffocates or crushes its prey, but this according to Holbrook is at least
doubtful. In the {614}breeding season it is extremely irascible, and will
frequently attack persons passing at a distance of several steps; the tail
then quivers with rage, making a quick vibrating motion, which in forests
and among dead leaves sounds not unlike the Rattle-Snake; it now elevates
the head one or two feet from the ground, and darts upon its adversary;
luckily its bite is harmless, and not more painful than the scratch of a
pin.
"It will even descend from trees to attack its enemy if teazed, yet it does
not twine itself around the legs, as is commonly supposed.
"The same power of charming its prey has been attributed to the Black as to
the Rattle-Snake, and with still less appearance of reason; for this is a
nimble animal, and can pursue its prey, while the Rattle-Snake must lie in
wait for his. It is remarkable that the birds most commonly found 'charmed'
are the Cat-bird (_Turdus carolinensis_) or red-winged Black-bird (_Icterus
phoeniceus_). These birds choose thick and shady places on the margins of
streams for their residence, and generally build their nests on such shrubs
as the alder; the latter bird not unfrequently takes the precaution to
select such bushes as are on small islands, or such as have their roots
surrounded by water, and thus their home is more secure. Now the Black
Snake chooses precisely the same localities, knowing probably the haunts of
its prey. The serpent begins the war by besieging the nest; the old bird,
aware of its intention, attacks it with fluttering and uncertain motions,
accompanied by a plaintive cry of distress, and is then said to be
'charmed.' The snake is at last either driven off, or it captures the young
and not unfrequently the old bird too.
"Sometimes the old bird, by her cries, calls in the assistance of her
neighbours to drive away the aggressor. I have seen more than a dozen birds
thus engaged with a large Black Snake that had probably just committed some
depredation, but was now quietly stretched on a rock, basking in the sun;
and it was not a little singular that birds of very different genera, and
those seldom seen together, all united in this warfare against a common
enemy, and finally compelled him to seek shelter among some low, thick
shrubs, by the violence of their assault."
_Zaocys_, with about half-a-dozen species in South-Eastern Asia, is closely
allied to _Zamenis_. _Z. carinatus_, of the Malay {615}Islands, grows to 10
feet in length; it is consequently one of the largest harmless Colubrine
snakes. The scales form only sixteen to eighteen rows. The sub-caudals are
double. The general colour above is dark olive, passing into greenish brown
farther back. The under parts are yellowish; black and yellow posteriorly.
The fifth and sixth labials border the eye.
[Illustration: FIG. 162.–_Zaocys carinatus._ × ¼.]
_Coluber._–The maxillary teeth are of equal size, but the anterior
mandibular teeth are the longest. The head is distinct from the neck. The
nasals are distinct; not fused with the loreals. The eye is rather large,
with a round pupil. The scales, smooth or keeled, have apical pits; the
ventrals are rounded or angulate laterally; the sub-caudals are double.
They all lay eggs and constrict their food. Nearly fifty species in the
Periarctic region.
_C._ (_Elaphis_) _quatuorlineatus_ s. _quaterradiatus_ inhabits Italy and
South-Eastern Europe. It occurs also in the Southern Tyrol. The scales of
this large snake, which grows to nearly 6 feet in length, are arranged in
twenty-five rows, and are feebly {616}keeled. The anal is divided. Adult
specimens have a yellowish-brown ground-colour with a pair of black streaks
on each side of the back. A black line extends from the eye to the angle of
the mouth; the under parts are yellow, mostly closely spotted with brown.
This snake is good-tempered, and keeps well in captivity. They live on
sparrows, mice, lizards, etc., and are very fond of eggs. Large specimens
can swallow several fowls' eggs in succession; the crushed remains of the
shells are later disgorged. This handsome snake climbs extremely well in
search of birds and their eggs, and it is not afraid of the water. The prey
is caught either with the teeth or by a rapid twist of the tail; in any
case, the prey is always strangulated by the constriction of coils thrown
round it. A sparrow thus secured is literally passed through the moving
coils along the snake's body into a position convenient for swallowing.
Hungry snakes catch and secure several birds or mice before eating them. My
own specimens became almost affectionately tame, never attempted to bite,
and took food from the hand.
_C. leopardinus_ is smaller, but is one of the handsomest snakes of
Southern Italy, South-Eastern Europe, and Asia Minor. It is closely allied
to the previously described species. The ground-colour is pale brown with a
dorsal series of dark brown or reddish, black-edged, transverse spots, and
a lateral alternating series of smaller black spots, or with two dark
brown, black-edged stripes bordering a yellowish vertebral stripe; usually
with a forked black mark on the occiput and nape. The under parts are
white, checkered with black, sometimes with the latter colour prevailing.
_C. flavescens_ s. _aesculapii_ is the Aesculap-Snake, for which the almost
unknown name of _longissimus_ has now been unearthed in deference to the
fetish of priority. This snake is of an extremely graceful and slender
build, with a very long tail. Its home is the South of France, Italy, and
South-Eastern Europe. It occurs sporadically in the Tyrol, for instance
near Bozen, in Austria, at Baden near Vienna, in Germany only in the
Taunus, especially at Schlangenbad, which has received its name from the
frequent occurrence of this snake. This sporadic distribution favours the
idea that these snakes were introduced by the Romans as inmates of the
temples erected to Aesculapius at such watering-places. Specific characters
are the smooth and shiny scales, {617}which are arranged in twenty-one to
twenty-three rows, the distinctly angulate ventrals and the double anal and
sub-caudals; the fourth and fifth of the upper labials border the eye,
which has a round pupil. The coloration is very variable, as a rule
olive-brown above with a dark streak behind the eye; the upper lips and a
triangular patch on the temples are yellow; the under parts are uniform
pale yellow. Some specimens are pale golden brown; others are very dark,
almost black; while some have four darker stripes along the body, and
lastly whitish specks occur on the upper surface. Large Aesculap snakes
grow to a length of 5 feet. Their food consists chiefly of mice. They
become very tame, although many of them at first bite furiously. Their
climbing capacities are astonishing, the snakes being able to scale high
and vertical walls provided there is the slightest "foothold." Some of my
specimens escaped in the room and were at last found near the ceiling,
resting on the rods of the curtains, up the folds of which they had managed
to wriggle. Boulenger kept one for many years in a glass cage, where the
snake entwined himself round the branches of a stick and allowed us to take
him with the stick out of its socket and to inspect him. Being kept in an
inhabited room, the snake did not exactly hibernate, creeping into the moss
at the bottom of the cage; but it refused to feed, and remained in a rather
drowsy condition coiled up on its favourite stand. During the pairing
season they frequently resort to the water, at Schlangenbad at least; the
few eggs are deposited under dry moss or in dry, decayed wood, and are
hatched in about six weeks.
_C._ (_Rhinechis_) _scalaris_ has the smooth scales disposed in
twenty-seven rows. The snout is strongly projecting, and has a V-shaped
dark mark on the top; a black streak runs through the eye, and another
black spot lies below the eye. Young specimens are pale brown with a series
of dark H-shaped marks on the back, suggesting a ladder, hence the specific
name. In the adult these marks are replaced by a pair of brown stripes
running along the back; the under parts are always uniform yellow. Total
length about 3 feet. This snake is restricted to the Iberian Peninsula and
to the South of France. Most specimens are very ill-tempered. The young
live upon locusts and small lizards, the old eat mice and small birds. In
captivity they also take dead animals–a rare habit with snakes.
{618}_Dendrophis_ with about ten species inhabits South-Eastern Asia and
Australia. They are typical Tree-Snakes. The scales are keeled, and form
only thirteen or fifteen rows; those of the vertebral row are enlarged; the
ventrals have a pair of suture-like lateral keels and a notch on each side,
arrangements which are of great assistance in climbing, these snakes being
able to slide up the branches of trees in almost straight lines instead of
having to twist and undulate their way up.
[Illustration: FIG. 163.–_Dendrophis punctulatus._ × ½.]
_D. punctulatus_, of Northern and Eastern Australia, is olive-brown above,
uniform or with black edges and yellow outer borders to the scales. The
upper lips, the throat and anterior ventrals, are yellowish. Total length
up to 6 feet.
_Leptophis_ is a Neotropical genus of Tree-Snakes. The body and the
extremely long, whip-like tail are very slender. The head is very distinct
from the neck; the eye is large, with a round pupil. The scales form
thirteen or fifteen rows; the ventrals are sometimes angulate laterally;
the sub-caudals are double. _L._ (_Ahaetulla_) _liocerus_ is a beautiful
snake, green above {619}with a golden lustre, while the under parts are
yellow or white. The total length of this species amounts to 6 feet, the
tail then being nearly 2 feet long. These graceful Tree-Snakes live upon
small reptiles and birds and their eggs. When shaken out of a tree or
frightened off they let themselves fall down from considerable heights,
coiling body and tail like a watch-spring, and alighting on the ground upon
the spiral, which breaks the fall.
[Illustration: FIG. 164.–_Leptophis liocerus._ × ½.]
_Coronella._–The teeth are nearly all of equal size and form continuous
series. The scales are smooth and have apical pits; the sub-caudals are
double. The head is scarcely distinct from the neck. The pupil is round.
This genus, with nearly twenty species, is widely distributed except in the
Australian region, the northern half of Asia, and South America. We can
mention only the two European species, one of which occurs in England.
{620}[Illustration: FIG. 165.–_Coronella laevis_, Smooth Snake (left), and
two _Vipera berus_, Common Viper (right). × ½.]
{621}_C. austriaca_ s. _laevis_, the Smooth Snake. The scales are arranged
in nineteen rows. Mostly the third and fourth labials border the eye. The
anal shield is divided. The general colour is brown or reddish above, often
with one or two lighter stripes, with small dark brown or red spots; two
dark brown or red stripes on the nape, usually confluent with a large dark
patch on the occiput; a dark streak extends from the nostril through the
eye to the angle of the mouth. The under parts are red, orange, brown, grey
or blackish, either uniform or speckled with black and white. The
coloration is, however, subject to much variation, and some specimens
strikingly resemble some of the Common Viper, which is also very variable
in its coloration. The resemblance is enhanced when the Smooth Snake
broadens its head by widening the jaws, as it is in the habit of doing. Two
such similarly coloured specimens are represented in Fig. 165. On closer
inspection the differences are great enough, the harmless snake having
smooth scales, and the top of the head being covered with large shields;
while the Viper has keeled scales, the top of the head being covered mostly
with scales, a vertical (not round) pupil, and, moreover, when attacked,
usually coils itself into a spiral disc with the head standing out in the
middle, ready to strike. However, these two species are sometimes mistaken
for each other.–The Smooth Snake prefers lizards as food to anything else,
but it also takes mice. The prey is hunted chiefly in the late afternoon
and in the evening, and is constricted by the coils of the snake. When
caught or even when handled after months of captivity, the Smooth Snake
bites deliberately and firmly, selecting a suitable spot, for instance a
finger, opens the mouth widely and almost chews the spot. The bite is of
course quite harmless, and scarcely draws blood, few of these snakes
attaining a length of more than 2 feet. They are viviparous, bringing forth
about half-a-dozen young at a time. The range of the Smooth Snake extends
over the greater part of temperate Europe, from England and the Iberian
Peninsula to Berlin, and south-eastwards to Asia Minor. In England it
occurs in a few counties only, for instance in Hampshire and in
Dorsetshire.
_C. girondica_, of the South of France, Italy, the Iberian Peninsula and
North-Western Africa, much resembles the English Smooth Snake, from which
it differs in a few points only. The scales are arranged in twenty-one,
rarely in nineteen, rows; usually the fourth and fifth labials border the
eye; and the rostral {622}shield, covering the end of the snout, is much
broader than high. The coloration is variable, but there is always a pair
of elongated blackish spots or a U-shaped mark on the nape.
SUB-FAM. 3. RHACHIODONTINAE.–With only a few teeth on the posterior part of
the maxillaries, on the palatines and dentaries. Some of the vertebrae in
the region of the lower neck have strongly developed hypapophyses, which
are directed forwards and pierce the oesophagus. They are used for filing
through or breaking the birds' eggs which seem to be the chief food of
these snakes.
[Illustration: FIG. 166.–_Dasypeltis scabra._ × ½.]
_Dasypeltis scabra_, the only species, inhabits Tropical and South Africa;
although it reaches scarcely more than two feet and a half in length, such
a specimen is able to swallow an ordinary fowl's egg. Pigeons' eggs are
swallowed by snakes little more than one foot in length, which seems at
first sight quite impossible. The swallowed egg distends the skin to its
utmost capacity; it then slides down further, the snake makes some slight
contortions and the swelling collapses; after a while the broken and
sucked-out shell is vomited out as a crumpled up {623}mass. Miss Durham has
illustrated this curious process in a series of drawings.[190]
SERIES B. OPISTHOGLYPHA.
One, or a few, of the posterior maxillary teeth have a groove or furrow in
front, which conducts the secretion of the enlarged upper labial glands.
Apparently all these snakes are more or less poisonous, paralysing their
prey before or during the act of deglutition. So far as man is concerned
they are rather harmless, since the poison is not very strong, not
available in large quantities, and above all because the small poison-teeth
stand so far back that the snakes cannot easily inflict wounds with them.
The Opisthoglypha are of considerable morphological interest, since they
connect the Colubridae with the Viperidae, the characteristic poisonous
apparatus of which seems to have been derived from that of the
Opisthoglypha by the reduction or shortening of the anterior portion of the
maxillaries and the harmless teeth, so that the posterior or poison-fangs
come to the front.
The Opisthoglypha comprise about three hundred species and are
cosmopolitan, including Madagascar but excepting New Zealand. They contain
truly terrestrial, arboreal, and thoroughly aquatic forms.
SUB-FAM. 1. DIPSADOMORPHINAE.–The nostrils are lateral and the dentition is
well developed. Long-tailed, terrestrial, and arboreal forms. Most of the
arboreal species are green above, often with white or yellow longitudinal
bands, while the under parts are white or yellow. They feed chiefly upon
lizards, birds and their eggs.
_Dipsadomorphus_ s. _Dipsas_ (part).–Typical, very long-bodied and
long-tailed Tree-Snakes, with a vertical pupil. The median or vertebral row
of smooth scales is enlarged; the broad ventral scales are bent at an
obtuse angle on the sides, the resulting ridge assisting in climbing. The
sub-caudals are arranged in two rows. Ten to fourteen maxillary teeth are
followed by two or three enlarged, grooved fangs.
_D. trigonatus_, of India, grows to one yard in length. Yellowish olive or
pale grey above, with a white, black-edged {624}zigzag band along the back,
or with a series of white, black-edged spots.
_D. cyaneus_, of Northern India, Assam, etc., is a beautiful Tree-Snake,
green above, with the skin between the scales black, uniform greenish
yellow below. Total length up to 4 or 5 feet.
_Dipsas_ e.g. _D. bucephala_.–Maxillaries with eleven or more teeth.
Pterygoids toothless. Body strongly compressed, with thirteen rows of
smooth scales; the vertebral row enlarged; sub-caudals double; tail very
long. Tropical South America.
_Leptognathus_ with many species in Central and South America, like
_Dipsas_, but with teeth on the pterygoids.
_Coelopeltis._–Terrestrial and diurnal, with a round pupil. The row of
small maxillary teeth is followed by one or two much larger, grooved fangs
situated at a level below the posterior border of the eye. The first
half-a-dozen mandibular teeth are much larger than the rest. The scales of
the adult are more or less distinctly grooved longitudinally, hence the
generic name, and are arranged in seventeen or nineteen rows. The
sub-caudals form two rows; the ventrals are rounded off laterally. Two
species in the Mediterranean countries and in South-Western Asia.
_C. monspessulana_ s. _lacertina_ is one of the largest snakes in Europe,
reaching a length of 6 feet, of which the tail takes up 18 inches.
Olive-brown or yellowish or reddish above, frequently with small, dark,
light-edged spots. The sides are often blackish, with whitish specks. The
under parts are yellowish white, with or without brownish markings. Some
specimens are very green, with a dull blackish neck. One of the specific
names of this terrestrial snake is the latinised form of Montpellier; the
other refers to the shape of the head, which is not unlike that of a
lizard, partly owing to the concave forehead. This species inhabits rather
dry localities studded with shrubs, where it hunts for lizards, birds, and
mice. It is sure to attract notice by its loud hissing when it is
disturbed. When driven into a corner it strikes out furiously, but does
not, as a rule, bite. I have caught some which after a few days became
quite gentle. Small animals become torpid a few minutes after they have
been bitten.
_Macroprotodon cucullatus_ occurs in Andalucia, the Balearic Islands, and
in North Africa. The dentition is peculiar. The {625}fourth and fifth
maxillary teeth are enlarged, followed by an interspace, then follow
several small teeth, and lastly the two enlarged, grooved teeth. The sixth
mandibular tooth is very long, separated by a space from the much smaller
posterior teeth. The general colour of this sand-loving snake is pale brown
or grey above with small spots or streaks on the trunk, and with a large
black patch behind the head extending over the sides of the neck, hence the
specific name. The under parts are bright red or yellowish, sometimes
spotted with black. Total length under 2 feet.
SUB-FAM. 2. ELACHISTODONTINAE.–With only a few teeth on the posterior part
of the maxillary and dentary bones, and on the palatines and pterygoids.
Some of the vertebrae in the thoracic region have much-developed unpaired
hypapophyses, which are directed forwards and pierce the dorsal wall of the
gullet. In this respect _Elachistodon westermanni_, of Bengal, the only
species, bears a striking resemblance to the South African Aglyphodont
_Dasypeltis_ (see p. 622), and it is probable that this apparently very
rare Indian snake also swallows eggs. It is brown above, with a yellowish
vertebral stripe; yellowish below.
SUB-FAM. 3. HOMALOPSINAE.–The nostrils of these absolutely aquatic and
viviparous snakes are valvular, and are situated on the upper surface of
the snout. The eyes are small with vertical pupils. The two dozen species,
mostly very ugly, inhabit the rivers and estuaries of the East Indies from
Bengal to North Australia. Some species have very small and narrow ventral
scales, recalling the Hydrophinae, or the burrowing snakes, none of which
use their ventral scales for locomotory purposes.
_Homalopsis buccata_, _Cerberus rhynchops_ and _Hypsirhina_, e.g. _H.
plumbea_, have well-developed ventral scales; the other scales of the first
two genera are keeled, those of the third are smooth. In _Hipistes_ the
whole head is covered with very small scales; all the scales of the body
are smooth except the very narrow ventrals, which have double keels. _H.
hydrinus_, of Siam and the Malay Peninsula, has a compressed body, and in
its general appearance much resembles the Hydrophinae. It lives, like its
allies, upon fishes, and it swims far out into the sea.
SERIES C. PROTEROGLYPHA.
The anterior maxillary teeth are deeply grooved, or so folded {626}as to
appear hollow or perforated. Behind these enlarged poison-fangs the maxilla
carries a series of smaller, solid teeth; hence the term "proteroglyphous,"
which means that the anterior teeth are grooved, in opposition to
"opisthoglyphous." Both series have been developed independently.
The Proteroglypha are all extremely poisonous, mostly viviparous, and
widely distributed over the whole of the Australian, Palaeotropical and
Neotropical regions, with the exception of Madagascar and New Zealand; they
extend northwards into the warmer parts of North America, and they also
range over a great portion of the Palaearctic sub-region, being found in
North Africa and South-Western Asia. They form two natural sub-families:
Elapinae, with cylindrical tails, and Hydrophinae or Sea-Snakes, with
laterally compressed tails.
SUB-FAM. 1. ELAPINAE.–The tail is cylindrical. The Elapinae comprise nearly
150 species, which have been grouped into a great number of, mostly
somewhat imaginary, genera. In Australia they constitute the great majority
of Snakes, there being besides the deadly Elapinae only a few Pythons and
Typhlopidae, and very few Colubrinae.
[Illustration: FIG. 167.–Map showing the distribution of the Elapine
Snakes.]
_Naja._–The pair of large and grooved poison-fangs are separated by an
interspace from one to three small, faintly grooved teeth near the
posterior end of the maxillaries. The scales are smooth and without pits,
and are arranged in fifteen to twenty-five oblique rows on the trunk,
although more occur in the region of the neck; the vertebral row is not
enlarged. The head is but slightly distinct from the neck. Each nostril
lies between two nasals and the internasal. The sub-caudals form two rows.
The pupil is round. The neck-region can be expanded {627}into a hood by the
spreading and moving headwards of the ribs. Several species in Southern
Asia and in Africa.
[Illustration: FIG. 168.–_Naja tripudians_ (the Cobra). × ⅕.]
_N. tripudians_ (the "Cobra").–The coloration varies much. The typical form
is yellowish to dark brown with a black and white spectacle-mark on the
dorsal side of the hood, and with a large black and white spot on each side
of the corresponding under surface. Other specimens are uniform pale brown
to blackish grey, without any markings on the hood. The Cobra is widely
distributed, from Transcaspia to China and to the Malay Islands; in the
Himalayas it ascends to about 8000 feet above the level of the sea. Very
large specimens are said to attain more than 6 feet in length, but a cobra
of 5 feet, inclusive of the tail of 9 inches, is considered large. The
Cobra prefers places which afford it a convenient hole to retire into; for
instance, deserted hills of termites, ruins, heaps of stones and stacks of
wood, and it has the disagreeable habit, like the harmless Rat-snake,
_Zamenis mucosus_, of making itself at home in inhabited houses, probably
attracted by the rats. Its chief food consists of small Vertebrates;–frogs,
lizards, rats, occasionally fishes and {628}small birds. It drinks much,
and hunts chiefly in the late afternoon and in the evening, although it
possesses a round pupil. It avoids hot sunshine. Many observations show
that the cobras live in pairs, otherwise they do not take much notice of
each other or of other kinds of snakes. The female lays about a dozen
soft-shelled eggs as large as those of pigeons.
This cobra is used by Indian conjurers. The "dance" is the habit of these
snakes of erecting themselves, when agitated, upon the hinder third or
quarter of their length, whilst they spread out the hood and sway the head
and neck to the right and left, always in an attitude ready for striking.
They are docile and by nature not vicious. Most of the performing cobras
have their teeth drawn, and they then know well that they cannot bite. They
only strike at the hand, just as uninjured specimens soon avoid biting into
the iron rod with which they are lifted up in menageries. The drawing of
the teeth is an operation which has to be repeated, since reserve-teeth
soon take the place of the lost pair.
I cannot refrain from relating an abstract of a ridiculous episode which
happened in the Munich Aquarium in the year 1882. One of six specimens of
the African species _Naja haje_ was missing. The police closed the
establishment, which during the following eight days was turned inside out
without any other effect than that two other, harmless, snakes were
discovered. Twice the building was fumigated with sulphur, until the Cobra
was at last found suffocated, fifteen days after the beginning of the
search. This snake caused the owner of the Aquarium a loss of nearly £1500.
But the cruel joke was, that during the commotion the man who had collected
and sold the six snakes declared upon oath that their teeth had been so
well drawn and the germs of possible reserve-teeth had been so thoroughly
destroyed that the snakes were rendered absolutely harmless. But he was not
believed, in spite of a commission of professors and doctors appointed, who
experimented upon the remaining five Cobras with sulphur and did not find
any poison-fangs, "although the mouth was probed and poked into as far down
as the larynx."
Cobras have quite a number of enemies. Peafowl and Jungle-cocks are said to
be partial to young snakes; pigs eat them greedily, and are to a certain
extent immune against {629}their bite. The same applies, according to the
most recent observations, to the famous Mongoos. Sir E. Tennent, in his
_Natural History of Ceylon_, quoted several times in the present book,
makes the following remarks about the immunity of this little creature:–
"I have found universally that the natives of Ceylon attach no credit to
the European story of the Mongoos (_Herpestes griseus_) resorting to some
plant, which no one has yet succeeded in identifying, as an antidote
against the bite of the venomous serpents on which it preys. There is no
doubt that, in its conflicts with the cobra and other poisonous snakes,
which it attacks with as little hesitation as the harmless ones, it may be
seen occasionally to retreat, and even to retire into the jungle, and, it
is added, to eat some vegetable.... A number of plants, such as the
_Ophioxylon serpentinum_ and _Ophiorhiza mungos_, the _Aristolochia
indica_, the _Mimosa octandria_, and others, have each been asserted to be
the Ichneumon's specific.... If the Ichneumon were inspired by that courage
which would result from the consciousness of security, it would be so
indifferent to the bite of the serpent, that we might conclude that, both
in its approaches and its assault, it would be utterly careless as to the
precise mode of attack. Such, however, is far from being the case; and next
to its audacity, nothing can be more surprising than the adroitness with
which it escapes the spring of the snake under a due sense of danger, and
the cunning with which it makes its arrangements to leap upon the back and
fasten its teeth in the head of the cobra. It is this display of
instinctive ingenuity that Lucan celebrates where he paints the Ichneumon
diverting the attention of the Asp by the motion of his bushy tail, and
then seizing it in the midst of its confusion. See _Pharsalia_, lib. iv.
verses 729-734."
There is a widespread belief in the efficacy of "Snake-stones," which are
generally pieces of charred bone, well polished, occasionally pieces of
chalk or some similar porous substance, which, if pressed upon the bleeding
wound, are supposed to absorb the poison. Snake-charmers profess to prepare
such "stones," and to preserve the composition as a secret. The manufacture
is a lucrative trade. The Boers bought them, imported from India, at high
prices. Mr. Selous saw one, or heard of one, that was kept as an heirloom.
Snake-stones are {630}also made, and used, in Mexico, of charred hartshorn;
they are called "piedras ponsonas."
The use of the Snake-stone, called "Pamboo-Kaloo," has probably been
communicated to the Singhalese by the itinerant snake-charmers who resort
to the island from the coast of Coromandel.
Although Sir E. Tennent describes several instances of the successful
application of snake-stones as well authenticated, he has never himself
been an eye-witness. Although two cases have been fully described, they do
not at all exclude the possibility, nay the probability, that the Tamils
imposed upon the Europeans in order to sell the snake-stones.
"No doubt the snake-stones, owing to their porous nature, adhered to the
bleeding wound, became saturated with blood, and then fell off. Very
likely, in case of a poisonous bite, some of the venom would be sucked up
too, but we do not know if those snakes were still in the possession of
their poison-fangs. Properly conducted experiments with snake-stones have
proved as little efficacious as the application of dry cup.
"Theoretically snake-stones as quick absorbent agents of the blood with the
poison are good; they will certainly prevent some of the poison from
entering the system, but that would, at best, be a partial cure only.
"In March 1854 a friend of mine was riding, with some other civil officers
of the Government, along a jungle path in the vicinity of Bintenne, when he
saw one of two Tamils, who were approaching the party, suddenly dart into
the forest and return, holding in both hands a Cobra de capello, which he
had seized by the head and tail. He called to his companion for assistance
to place it in their covered basket, but in doing this, he handled it so
inexpertly that it seized him by the finger, and retained its hold for a
few seconds, as if unable to retract its fangs. The blood flowed, and
intense pain appeared to follow almost immediately; but with all expedition
the friend of the sufferer undid his waist-cloth, and took from it two
snake-stones, each of the size of a small almond, intensely black and
highly polished, though of an extremely light substance. These he applied,
one to each wound inflicted by the teeth of the serpent, to which they
attached themselves closely; the blood that oozed from the bites being
rapidly imbibed by the porous texture of {631}the article applied. The
stones adhered tenaciously for three or four minutes, the wounded man's
companion in the meanwhile rubbing his arm downwards from the shoulders
towards the fingers. At length the snake-stones dropped off of their own
accord; the suffering of the man appeared to subside; he twisted his
fingers till the joints cracked, and went on his way without concern.
Whilst this had been going on, another Indian of the party, who had come
up, took from his bag a small piece of white wood, which resembled a root,
and passed it gently near the head of the cobra, which the latter
immediately inclined close to the ground; he then lifted the snake without
hesitation, and coiled it into a circle at the bottom of his basket. The
root by which he professed to be enabled to perform this operation with
safety he called the "Naya-thalic kalanga" (the root of the snake-plant),
protected by which he professed his ability to approach any reptile with
impunity."
The following narrative, communicated to Sir E. Tennent by H. E. Reyne, of
the Department of Public Works, Colombo, seems to exclude the possibility
of deception:–
"A snake-charmer came to my bungalow in 1854, requesting me to allow him to
show me his snakes dancing. As I had frequently seen them, I told him I
would give him a rupee if he would accompany me to the jungle and catch a
cobra that I knew frequented the place. He was willing, and as I was
anxious to test the truth of the charm, I counted his tame snakes, and put
a watch over them until I returned with him. Before going I examined the
man, and satisfied myself he had no snake about his person. When we arrived
at the spot, he played on a small pipe, and after persevering for some
time, out came a large cobra from an ant-hill, which I knew it occupied. On
seeing the man it tried to escape, but he caught it by the tail and kept
swinging it round until we reached the bungalow. He then made it dance, but
before long it bit him above the knee. He immediately bandaged the leg
above the bite, and applied a snake-stone to the wound to extract the
poison. He was in great pain for a few minutes, but after that it gradually
went away, the stone falling off just before he was relieved. When he
recovered he held a cloth up, which the snake flew at, and caught its fangs
in it; while in that position, the man passed his hand up its back, and
having seized it by the throat, {632}he extracted the fangs in my presence
and gave them to me. He then squeezed out the poison on to a leaf. It was a
clear oily substance, and when rubbed on the hand produced a fine lather. I
carefully watched the whole operation, which was also witnessed by my clerk
and two or three other persons."
_N. haje_ is the common hooded cobra of Africa, the "Aspis," so called on
account of its shield or hood–the "Spy-Slange" of the Boers. As a rule the
spectacle-marks on the neck are absent or indistinct, the general colour
varies much, either brown above, yellowish beneath, with or without brown
spots; or dark brown above with yellowish spots, dark brown beneath; or
blackish above and beneath. The name Spy-Slange, meaning Spitting Snake,
refers to the habit which this and other African Cobras have of letting the
poison drop from the mouth like saliva when they are excited. This is not a
particularly economical habit, nor is it of the slightest use to the snake.
_N._ (_Ophiophagus_ s. _Hamadryas_) _bungarus_ s. _elaps_ is the
"Hamadryad" or "Snake-eating Cobra" or "King Cobra." It has a well
dilatable hood; the very variable coloration is yellowish to black, with or
without an olive gloss. Many specimens have more or less distinct dark
cross-bands or rings around the body, while others are olive above with
black-edged scales, and others again are very dark above and beneath. The
distinctive, specific character is the small number of scales, these
forming only fifteen rows on the middle of the body, nineteen or twenty-one
on the dilatable neck. There is a pair of large occipital shields behind
the parietals.
This snake reaches the length, enormous for a poisonous snake, of 12 feet
or more. Its size and very poisonous nature make it the curse of the
jungle. It ranges from India to South China, and to the Philippines. The
food seems to consist entirely of other snakes.
_Sepedon haemachates_ is another hooded snake in South Africa, where it is
known as the "Ringhals," _i.e._ banded neck. It differs from _Naja_ by the
absence of small teeth on the maxillaries behind the fangs, and by the
strongly keeled scales, which form nineteen rows. The general colour is
black above variegated with yellow or pale brown; the under parts are also
black, often with one or two whitish bands across the lower portion of the
neck.
{633}The Rev. G. Fisk[191] mentions the case of two young "Ringhals," of 10
and 9 inches in length, having been attacked and partly devoured by a
mouse, supposed to be _Dendromys melanotis_, which was put with the snakes
in a band-box. On the habits of the Ringhals see Symonds.[192]
[Illustration: FIG. 169.–_Sepedon haemachates_ (the "Ringhals"). × ⅕.]
_Bungarus._–The scales are smooth, and form thirteen to seventeen rows. The
spine is very prominent, and the median row of scales which covers the
ridge is much enlarged. There is no dilatable hood. In other respects
_Bungarus_ is closely allied to _Naja_; about half-a-dozen species, in
South-Eastern Asia.
_B. fasciatus_ reaches a length of 5 feet. The general colour is bright
yellow, alternating with blackish rings.
_B. coeruleus_ s. _candidus_ is the dreaded "Krait," occurring in the whole
of the Indian sub-region. It is dark brown or bluish black with narrow
cross-bars or white specks, or it is alternately barred brown and yellow;
the under parts are uniform white. Total length rarely 4 feet.
The "Krait" seems to cause more deaths in India than any other snake, since
it is very common, especially in Bengal and in {634}Southern India, and
often creeps into the houses. It lives chiefly on rats, lizards, and
snakes.
_Callophis._–With only thirteen rows of smooth scales. The head is small,
not distinct from the neck. The small eye has a round pupil. The short tail
has two ventral rows of scales. The whole body is cylindrical. Several
small species, one or two feet in length, in South-Eastern Asia. _C.
macclellandi_ in India and Indo-China is reddish brown above, yellow below,
with regular, equidistant, black, light-edged cross-bands or rings. Total
length up to 2 feet.
_Doliophis_ differs from _Callophis_ mainly by the enormously developed
poison-glands which, instead of being restricted to the head, extend along
the anterior third of the body, gradually thickening, and terminating in
front of the heart with club-shaped ends. Owing to the extension of these
glands, which can be felt through the skin as thickenings at the end of the
first third of the body, the heart has been shifted farther back than in
any other snake. Several species in Indo-China and in the Malay Islands,
_D. intestinalis_ with many colour-variations.
Australia suffers from an abundance of Elapine snakes, of which we will
mention only the three commonest.
_Pseudechis_ e.g. _Ps. porphyriaceus_, the "Black Snake" of Australia, has
seventeen rows of smooth scales on the body, a few more on the neck, which
however is not, or is only slightly, dilated. A few of the sub-caudal
scales are undivided, the rest are paired. The head is distinct from the
neck; the pupil is round. Total length up to 5 or 6 feet. The general
colour above is black, with the outer row of scales red at the base; the
ventral scales are red with black edges. The females are generally more
brown than black, and are therefore sometimes known as "Brown Adders." They
live on small mammals, birds, lizards and other snakes.
_Notechis scutatus_ s. _Hoplocephalus curtus_, the "Tiger Snake," has
rather small eyes with round pupils. The head is distinct from the
cylindrical body, which is covered with fifteen to nineteen rows of smooth
scales. The sub-caudals are single. The head of this variably coloured
snake is mostly black, the body olive brown with dark cross-bands; towards
the tail the coloration becomes more uniformly blackish. The under parts
are pale {635}yellow. The range of this very common snake extends over
Tasmania and Australia.
_Acanthophis antarcticus_, the "Death Adder," is easily recognised by the
peculiar tail, the end of which is laterally compressed, beset with a few
rows of enlarged imbricating scales, and terminates in a thin horny spine.
The head is distinct from the neck, and flat; the eye has a vertical pupil.
The short and thick body is covered with twenty-one or twenty-three rows of
keeled scales. The anterior caudals are single, the posterior double. The
colours of the upper parts are a mixture of brown, reddish and yellow, with
dark cross-bands. The belly is pale yellow, often spotted with brown or
black. The end of the tail is yellow, reddish brown or black. The total
length of this stout and ugly viviparous creature remains under 3 feet. It
is widely distributed from South Australia to the Moluccas. The use of the
peculiar tail very probably consists in attracting or fixing the attention
of small animals; the snake, lying coiled up on a dry and sandy spot,
slightly raising and vibrating the tip of the tail.
_Elaps_ is an entirely American genus, with many species, most of which are
extremely prettily coloured, red and black in alternate rings being a
favourite pattern. The maxillaries carry no teeth behind the poison-fangs.
The scales of the body are smooth and form fifteen rows. The tail is short.
The small eye has mostly a vertical pupil. The head is very small, not
distinct from the neck. The squamosal and quadrate bones are short, and the
gape of the mouth is so limited that these beautiful snakes, although
possessing strong poison, are practically harmless to man. One of the
prettiest is _E. corallinus_ of the forests of Tropical South America and
the Lesser Antilles. The whole body, above and below, is adorned with about
twenty deep black rings, which are edged with yellow and again separated by
red rings equalling in width the black ones. Sometimes the red rings are
dotted with black, and the black dots may form additional rings between the
red and the yellow. Total length under 3 feet.
SUB-FAM. 2. HYDROPHINAE (Sea-Snakes).–The tail is strongly compressed,
sometimes the body also. All the scales are small, and there are often no
enlarged ventrals. The eyes are small, with round pupils. All these snakes
are very poisonous and live in the sea, often at considerable distances
from the land, {636}with the exception of one species of _Distira_, _D.
semperi_, which is confined to the land-locked freshwater Lake Taal at
Luzon in the Philippines. They live on fish, and range from the Persian
Gulf to Central America. In conformity with their absolutely aquatic life
they are viviparous, and they die when kept out of the water for any length
of time. About fifty species are known.
_Enhydrina valakadien s. bengalensis_ has scales with a small tubercle or
keel, which is stronger in the males; the ventrals are very small, forming
a scarcely enlarged series. The maxillaries carry two or more small grooved
teeth in addition to the poison-fangs. The back is olive or dark grey, with
black transverse bands, which are most distinct in the young. The under
parts are white. This species ranges from Persia to the Malay Islands.
[Illustration: FIG. 170.–_Enhydrina valakadien_ (left upper figure) and
_Hydrophis obscura_ (right lower figure). × ¼.]
_Hydrophis_ e.g. _H. obscura_.–The body is long; the head and neck are very
slender, the body becoming much thicker farther back. The small teeth
behind the poison-fangs are not grooved. The ventral scales are very small,
the others are keeled, strongly so {637}in the males. The general
coloration of this Sea-Snake, which reaches about one yard in length, is
dark olive-green above with yellowish cross-bars, which form complete rings
round the slender part of the body. Other specimens are pale olive, with
dark cross-bands. This species occurs in the Bay of Bengal and the Malay
Archipelago.
As a rule Sea-Snakes are not found in mid-ocean. After leaving Ceylon, the
steamer meets them again in the Straits of Malacca. Those which occur near
the south coast of Japan, e.g. _Distira cyanocincta_, are found there only
in the summer, and are probably carried there by the south-west monsoon.
According to Semper the gravid female visits the shores of low islands,
there to give birth to its young between the rocks, and she remains with
her offspring for some time. Semper once found a large female, probably
_Platurus fasciatus_ s. _colubrinus_, coiled up amongst rocks, and between
the folds were at least twenty young, each already about 2 feet long.
Boulenger[193] has written an interesting popular account of Sea-Snakes.
FAM. 8. AMBLYCEPHALIDAE.–Some thirty species of Neotropical and Oriental
Snakes have been separated from the Colubridae on account of the
pterygoids, which are widely separated from the quadrates, the posterior
ends of the pterygoids not reaching beyond the level of the occipital
condyle. This condition can be ascertained when the mouth is opened widely.
The prefrontals are not in contact with the nasals. The squamosals are
reduced to pad-like vestiges. Externally the Amblycephalidae are easily
distinguished from the Colubridae by the absence of a longitudinal median
mental groove. The head is thick, very distinct from the neck, and gives
these harmless snakes a "poisonous" appearance. The pupil is vertical.
_Amblycephalus_, e.g. _A. monticola_.–Maxillaries short, with only five or
six teeth. Sub-caudals in two rows. Body compressed, covered with fifteen
rows of scales. South-Eastern Asia.
FAM. 9. VIPERIDAE.–The maxillaries are very short, movably attached to the
prefrontals and ectopterygoids, so that they can be erected together with
the large poison-fangs, which (besides reserve-teeth) are the only
maxillary teeth. The prefrontals are not in contact with the nasals. The
squamosals are very loosely {638}attached. For further details see Fig.
180. The poison-fangs are perforated, having a wide hole on the anterior
side at the base, in connexion with the large poison-gland; the hole leads
into a canal, which opens gradually as a semi-canal on the anterior surface
of the distal third or quarter of the tooth. As usual in poisonous snakes,
several reserve-teeth are stowed away behind the acting fang. When the
latter is broken off or has served its time it is cast off at the base, and
the next reserve tooth takes its place. The supply of reserve-teeth is
indefinite, half-finished teeth down to mere germs constantly growing.
All the Viperidae are very poisonous, and all, except the African
_Atractaspis_, are viviparous. They include terrestrial, arboreal,
semi-aquatic, and burrowing types. The family is cosmopolitan, excepting
Madagascar and the whole of the Australian region; it is divided into
Vipers and Pit-Vipers.
SUB-FAM. 1. VIPERINAE (Vipers).–There is no sensory external pit between
the eye and the nose, and the maxillary is not hollowed out above. The
Vipers are absolutely restricted to the Old World, ranging over the whole
of Europe, Africa, and Asia, with the exception of Madagascar; their
northern extension is limited only by the permanently frozen condition of
the underground. Nine genera with about forty species are known.
[Illustration: FIG. 171.–Map showing the distribution of the Sub-Family
Viperinae. Corsica and Sardinia should be black in the map.]
_Causus_ with a few species in Africa and _Azemiops feae_ in Upper Burmah
are the only vipers which have the head covered {639}with large symmetrical
shields, while in the other genera the head-shields are broken up into
scales or small shields. _Causus rhombeatus_ is very common in Africa, from
the Gambia to the Cape. It reaches a length of a little more than 2 feet.
Pale olive-brown above, usually with a dorsal series of large rhombic or
V-shaped dark brown, sometimes white-edged spots, and with a dark
arrow-shaped mark on the occiput; under parts yellowish white or grey.
_Bitis_ s. _Echidna_.–Very much like _Vipera_, but the nasal shields are
separated from the rostral by small scales, and the postfrontal bone is
very large. Several species in Africa.
[Illustration: FIG. 172.–_Bitis arietans_ (Puff Adder). × ¼.]
The head is very distinct from the neck, chiefly owing to the large
poison-glands and to its being, like the body, much depressed. The small
eye has a vertical pupil, and is separated from the labials by a series of
small scales. The scales are keeled, and form many, from twenty-nine to
forty-one, rows; the tail is very short, with two rows of scales below.
In _B. arietans_, the "Puff Adder," the nostrils are directed upwards. This
ugly brute is yellowish to orange brown above with regular, chevron-shaped
dark bars or other markings, helping {640}to conceal the creature when it
is lying on sandy and stony ground; the under parts are yellowish white.
The Puff Adder reaches a length of 4, or very rarely 5 feet, ranging all
over Africa, except the north coast, and extending into Southern Arabia. It
is very slow, and trusts to not being discovered when lying in the dry
grass; when approached it inflates the body and hisses loudly with a
puffing sound, watches the enemy with raised and characteristically bent
head and neck; but it bites only when actually touched or attacked. The
effect of the bite is very dangerous. Its prey consists chiefly of small
mammals, which are hunted during the night.
_B. (Echidna) nasicornis_, of Tropical West Africa, has two or three
enlarged scales above the supranasals; they stand upon erectile tissue so
as to form horn-like elevations. This "Nose-horned Viper" grows to a length
of 4 feet, and is rather prettily marked; the ground-colour is purplish or
reddish brown, with a vertebral series of large, pale, dark-edged spots and
oblique crosses. The young are at birth as much as one foot in length, and
are very tastefully coloured.
_Cerastes_ and _Echis_ prefer to burrow in sand. The lateral scales are
smaller than the dorsals, and arranged obliquely with serrated keels, so
that the snakes can cover themselves with sand by lateral shovelling
motions of the sides of the body.
_Cerastes cornutus_, the "Horned Viper" of North-Eastern Africa, from
Algeria to Arabia, extending also into Palestine, has the sides of the
ventral scales bent angularly, with an obtuse keel on either side. Above
each eye stands a large horny, spiky scale. The upper parts are pale
yellowish brown, mostly with dark spots arranged in several longitudinal
rows. The under parts are white. This, or perhaps _C. vipera_, which has no
horns, is supposed to be the species which has become famous through the
suicide of Cleopatra.
About twenty years ago a number of "Horned Vipers" were brought to the
Zoological Gardens of London, and attracted attention by their unusually
long horns. It was found that some wily Egyptian snake-catcher had tried to
manufacture a new species by taking specimens of the hornless _C. vipera_
and inserting a pair of hedgehog's spines, pushing them upwards through the
mouth.
The "Horned Viper" attains a length of two feet and a half. {641}In the
daytime it is invisible, being buried in the sand with only the eyes,
nostrils, and the "horns" appearing above the surface.
_Vipera._–The head is distinct from the neck, and is covered with small
scales and a few larger shields. The eye is separated from the labials by
scales; the nasals are in contact with the rostral shield or separated by
one naso-rostral shield. The scales on the body are strongly keeled; they
are in two rows on the short tail. This genus with about ten species ranges
over Europe, Asia, and the greater part of Africa.
[Illustration: FIG. 173.–_Cerastes cornutus_, the "Horned Viper" (right),
and _Vipera ammodytes_, the "European Nose-horned Viper" (left). × 1.]
_V. berus_, the Common European Viper (see Fig. 165, p. 620). The snout is
not turned up at the end; between the small head-scales there is generally
a pair of well-developed parietal and frontal shields. The scales of the
trunk form twenty-one rows. The coloration is very variable, there being
grey, brown, red, or black specimens in the same country, and the
much-spoken-of black zigzag line along the back is so often indistinct that
it is a character not to be relied upon. Usually the grey, yellowish,
olive, brown or red ground-colour is set off by a dark zigzag band along
the spine, and by a series of lateral spots; an oblique or St. Andrew's
cross or two diverging bold streaks of dark brown or black are usually
present on the back of the head, and there is a dark streak behind the eye.
The under parts are grey, brown, or black, uniform or speckled; the end of
the tail is usually yellow or red.
{642}[Illustration: FIG. 174.–Skin of Viper. × 1. (From White's _History of
Selborne_.)]
According to Boulenger, who is making a special study of the individual
variations of Vipers (concerning colour, scaling, number of vertebrae,
etc.), some specimens are entirely black in the males through extension of
the black markings, in the females through darkening of the ground-colour.
Males are usually distinguishable from females by darker, deep black
markings and lighter ground-colour. The females are mostly larger than the
males. The largest specimen in the British Museum measures 700 mm. = 28
inches, but a viper 2 feet long may be considered a very large specimen.
The Common Viper has a wide range, from Wales to Saghalien Island, and from
Caithness to the north of Spain. It ascends the Alps to a considerable
altitude, up to 6000 feet. J. Blum[194] has published an elaborate
statistical account of the Viper in Germany, unfortunately confining
himself strictly to the political frontiers. According to the map attached
to his work, the Viper is common all over Germany with the exception of
South-Western and parts of Middle Germany. It is absent in Alsace, the
Bavarian Palatinate, Rhenish Prussia, Hesse, the northern half of Baden,
Würtemberg, and Franconia, countries which, speaking broadly, have a warm
subsoil, composed of Red Sandstone and Basaltic formation. As a rule the
Viper prefers heaths, moors, and mixed woods with sunny slopes. Brambles,
clumps of nettles, hedges, the edges of little copses, heaps of stones, are
favourite places of retreat, affording shelter, holes, and the vicinity of
mice, which form its chief sustenance. At harvest-time it is often found in
cornfields, and it frequently hides in the sheaves. Vipers are fond of
basking on certain spots, on the top of a stone, the stump of a tree, or a
patch of sand: a shower of rain or even passing clouds drive them back into
their holes. They are eminently nocturnal, when they regularly "beat" their
district, biting and paralysing their prey before swallowing it. A fire
kindled at night is sure to draw vipers near; the same applies to other
vipers, for instance _Cerastes_, which appears in perplexing {643}numbers
at the camp-fire. They cannot climb, and they avoid going into water. The
pairing takes place as a rule from March to May, a number of individuals,
mostly males, collecting around the females, and forming entangled lumps of
snakes; parturition takes place in the following July and August. In
exceptionally warm winters they have been known to pair in December, having
left their winter-quarters. They hibernate for about six months, more or
less according to the climate, congregating in great numbers, sometimes in
dozens. With very rare exceptions Vipers do not take food in captivity, but
prefer starving themselves to death. The bite is as a rule not fatal. The
seriousness of the case depends of course upon many circumstances, as for
instance the state of concentration of the venom, the position and depth of
the bite, and last but not least upon the general condition of health of
the victim. General depression aggravated by nervousness, weakness of the
bitten limb, occasional breaking out of the wound, are of frequent and
protracted occurrence. (See also p. 590.)
_V. aspis_ is a more southern and western European Viper, occurring from
France to the Tyrol, and in Italy. The snout is slightly turned up at the
end, and still more so in _V. latastei_ of Spain and Portugal. In _V.
ammodytes_, of South-Eastern Europe, the raised portion is produced into a
soft, scaly appendage (see the lower figure on p. 641). Vipers are
sometimes unpleasantly common in certain localities. This was for instance
the case at the drill-ground near Metz, and the military authorities paid a
price for each viper delivered to them. The supply of the latter increased
to an alarming extent until the German authorities discovered that a
regular trade had been established across the frontier, and that the French
Lorrainers were importing vipers briskly.
_V. russelli_, the "Daboia" or Russell's Viper, is one of the scourges of
India, Ceylon, Burma, and Siam. The scales form about thirty rows on the
body. The upper surface of the head is covered with small, imbricating,
usually keeled scales. The general colour is pale brown above with three
longitudinal series of black, light-edged rings, which sometimes encircle
reddish spots. The under parts are yellowish white, uniform, or with small
crescentic black spots. Total length up to about 5 feet. The poisoning
symptoms are described on p. 590.
{644}SUB-FAM. 2. CROTALINAE ("Pit-Vipers").–With a deep cavity or pit
between the eye and the nose, lodged in the hollowed-out maxillary bone.
This pit is lined with a modified continuation of the epidermis, and is
amply supplied with branches from the trigeminal nerve. It is undoubtedly
sensory, but we do not know its function. A good anatomical account of this
organ has been given by West.[195] Some of the Pit-Vipers have a rattle at
the end of the tail; these are the Rattle-Snakes. The rattle is composed of
a number of horny bells which fit into each other. The oldest or terminal
bell is in reality the horny covering of the tip of the tail, and with each
moult or shedding of the skin the youngest bell becomes loose, but is held
by the new covering which has been developed in the meantime. There is thus
produced an ever-increasing number of loosely-jointed bells, but now and
then most or all the bells break off, probably when they are worn out, and
a new set is gradually developed. Rattles with a dozen bells are, for
instance, very rare. They naturally increase in bulk with the age of the
snake, but the number of joints is no indication of the snake's age.
[Illustration: FIG. 175.–Rattle of Rattle-Snake. (From White's _History of
Selborne_.)]
[Illustration: FIG. 176.–Map showing the distribution of the Sub-Family
Crotalinae.]
Pit-Vipers have a very wide distribution. They are divided into four genera
with about sixty species. Rattle-Snakes are {645}restricted to America, but
other Pit-Vipers occur in North and South America and in the southern half
of Asia.
_Ancistrodon._–Without a rattle. The upper surface of the head is covered
with nine large shields, but the internasals and prefrontals are sometimes
broken up into scales. The scales of the body have apical, sensory pits.
About ten species, some in Central and North America, others in the Caspian
district (_A. halys_), in the Himalayas (_A. himalayanus_), in Ceylon,
Java, etc.
[Illustration: FIG. 177.–_Ancistrodon piscivorus_ (Water-Viper). × ¼.]
_A. piscivorus_ s. _Trigonocephalus cenchris_ (part), the "Water-Viper,"
inhabits North America from Carolina and Indiana to Florida and Texas. The
general colour is reddish to dark brown, with darker cross-bands or with
C-shaped markings; a dark, light-edged band extends from the eye to the
angle of the mouth. The under parts are yellowish, spotted with black, or
the latter is the prevailing colour. Total length up to 5 feet. The
Water-Viper is semi-aquatic and lives chiefly on fishes, but it also eats
other snakes and various Amphibia, Birds, and Mammals. This snake is very
good-humoured in captivity, and becomes {646}easily tame. A gentleman in
Berlin, rather too much addicted to making pets of poisonous snakes, had a
pair which propagated regularly. When I was a boy he invited me to feed the
young Water-Vipers with fishes cut into strips, and I enjoyed this
immensely until he warned me not to touch the mother, which might bite
strangers.
[Illustration: FIG. 178.–_Ancistrodon contortrix_ (Moccasin-Snake or
Copper-head). × ¼.]
_A. contortrix_ s. _Trigonocephalus cenchris_ (part), the "Moccasin-Snake"
or "Copper-head," is one of the few poisonous snakes which possess a loreal
shield, _i.e._ a shield intercalated between the pre-oculars and the
nasals; below it lies the pit. The general colour is yellowish to pink or
pale brown, with dark brown or red cross-bars or triangular marks. The
under surface is yellowish or reddish, speckled with grey or brown, and
with a lateral series of large blackish spots. Total length of full-grown
specimens about one yard. The Moccasin-Snake ranges from Massachusetts and
Kansas to Northern Florida and Texas. It prefers swampy localities or
meadows with high grass, where it hunts for small Mammals and Birds.
_Lachesis._–Without a rattle. The upper surface of the head is covered
with very small shields or with scales. About forty {647}species in
South-Eastern Asia and in Central and South America.
_L._ (_Bothrops_ s. _Craspedocephalus_) _lanceolatus_ inhabits nearly the
whole of South America, extending into Mexico and the Lower Antilles,
_e.g._ Martinique, Guadaloupe, and Santa Lucia, where it is known as the
"Fer-de-Lance," and is the curse of the sugar-plantations on account of its
being so very common and so deadly poisonous. The Mongoose was introduced
as a possible antagonist, but the little Indian Mammal wisely left the
dangerous reptile alone, and has in some places established himself as
another pest–as a destroyer of poultry. The Fer-de-Lance grows to a length
of 6 feet, establishes itself everywhere–in swamps, plantations, forests,
in the plains and in the hills–and is very prolific, producing, according
to its size, dozens of young which are 10 inches long, very active and
snappy.
[Illustration: FIG. 179.–Head of _Lachesis lanceolatus_ after removal of
the skin. × 1. _D_, Duct, bent upon itself, from the poison-gland into the
tooth; _Dig_, digastric muscle or opener of the jaw; _N_, nostril; _P.G_,
poison-gland; _S.Gr_, sensory groove or pit; _S.Q_, point of junction of
the squamosal and quadrate; _T.a_, _Temp.a_, anterior, and _T.p_,
posterior, temporal muscle.]
_L._ (_Trimeresurus_) _gramineus_ s. _viridis_, to mention one Asiatic
species, grows to less than 3 feet in length, is bright green above,
sometimes with faint blackish bars; green, yellow, or whitish below, and
with a light streak along the outer row of scales. The end of the tail is
usually bright red. This beautiful snake has a prehensile tail and is
arboreal. Its range extends over the whole of India, to Hong-Kong and to
Timor, and even into the Andaman and Nicobar Islands.
_Sistrurus._–With a rattle. The upper surface of the head is covered with
nine large shields. A few species in North America east of the Rocky
Mountains, e.g. _S. miliarius_.
{648}_Crotalus._–With a rattle. The upper surface of the head is covered
with small scales. Range from Southern Canada and British Columbia to
Northern Argentina, but not in the West Indian Islands. About ten, mostly
closely-allied species.
[Illustration: FIG. 180.–Skull of a Rattle-Snake, _Crotalus durissus_. × 1.
A, Lateral view, jaws slightly opened; B, ventral view; C, lateral view,
the jaws opened fully in the position of striking; D, dorsal view. Compare
this with the diagrammatic figures on p. 588, where the mechanism has been
explained. _Col_, Columella auris; _Cond_, condyle; _Cr_ (in B), sphenoidal
crest for the attachment of the powerfully developed ventral
cranio-cervical muscles; _E.P_, ectopterygoid or transverse bone; _F_,
frontal; _Max_, maxillary; _P_, parietal; _P^1_, post-orbital process;
_Pal_, palatine; _Pmx_, pre-maxillary; _Pr.f_, prefrontal; _Ptg_,
endopterygoid; _Q_, quadrate; _Sq_, squamosal.]
{649}The effect of the poison of Rattle-Snakes has been discussed on
p. 589.
_C. horridus_ is the common Rattle-Snake of the United States; _C.
confluentus_ is the species in Western and _C. durissus_ the common species
in South-Eastern North America. Very large Rattle-Snakes, _C. durissus_,
attain a length of 8 feet, others not often more than five. They prey
chiefly upon small Mammals, hunting for them at night. In the daytime they
are also about, mainly in order to bask. Although they occasionally take to
the water in pursuit of their prey, they dislike being wetted by rain,
withdrawing then into their holes, appropriating as a rule those of
ground-squirrels, rats, and Prairie-dogs. The often-repeated story about
Rattle-Snakes living in neighbourly friendship in the holes of
Prairie-dogs, together with the little Prairie-owls, is an exaggeration. We
do not know how many of the original inmates are eaten. Pairing takes place
in the spring. During the cold months they hibernate under ground, often in
considerable numbers.
Rattle-Snakes have few enemies besides man and pigs. The latter kill and
eat them wherever they can. The rattle is decidedly useful to the snake as
an instrument of warning off any approaching possible enemy, since no snake
likes to bite unless in self-defence or in order to kill its prey. The
noise of the rattle is very loud in dry weather, much duller on clammy
days; it is a shrill sound like that of a rattling alarm-clock, and a
well-conditioned snake in a room can make conversation well-nigh
impossible, and can keep on rattling for half an hour or longer. The rattle
is kept in such rapid lateral vibrations that it shows only a blurred
image, the rattle standing with its broader sides vertically, not
horizontally. They endure captivity for many years, and become tame enough
not to hiss and to rattle whenever they are approached.
_C. horridus_ is grey-brown above, usually with a rusty vertebral stripe
and with V- or M-shaped blackish cross-bands; the under surface is
yellowish; the end of the tail is blackish. The supra-ocular shields are
smooth and much narrower than the scaly space between them, and there is
only one pair of internasals.
_C. durissus_ s. _adamanteus_ differs from the previous species chiefly by
possessing two pairs of internasals; and the dark {650}markings on the body
form a handsome pattern of rhombs with lighter centres and yellowish edges.
This is the largest species of Rattle-Snake, reaching a length of 8 feet.
_C. confluentus_ has broader, transversely striated, supra-ocular shields.
The specific name refers to the continuous series of large brown or red
rhomboidal spots on the back.
[Illustration: FIG. 181.–_Crotalus durissus_ s. _adamanteus_
(Rattle-Snake). × ¼.]
_C. terrificus_ ranges from Arizona to Argentina, and is the only species
of Rattle-Snake in South America. It differs from the others by having a
pair of prefrontal shields behind the pair of internasals.
{651}INDEX
Every reference is to the page: words in italics are names of genera or
species; figures in italics indicate that the reference relates to
systematic position; figures in thick type refer to an illustration; f. =
and in following page or pages; n. = note.
Abdominal armour, of _Cricotus_, 287;
of Microsauri, 289;
of Prosauri, 290
Abdominal ribs, of Rhynchocephali, 292, 298;
of Dinosauria, 414;
of _Megalosaurus_, 421
Aberrant scaling of Lacertilia, 495
_Ablepharus_, 560;
eyelids, 494
_Acanthodactylus vulgaris_, _559_
_Acanthophis antarcticus_, _635_
Acentrous vertebrae, _i.e._ those without a centrum or body, 4
_Acris_, 186, _189_;
_A. gryllus_, _207_ f.
Acrochordinae, _606_
_Acrochordus javanicus_, _607_
_Acteosaurus_, _489_
_Actinodon_, _83_, 287, 288
Adams, visit to the Mugger-peer, 455 f.
Adaptive characters of Anura, 142
Adhesive apparatus, of tadpoles, 57, 57;
of Tree-frogs, 187;
of _Thoropa_, 209;
of finger-discs of Raninae, 239;
of Geckos, 505, 505
_Aelurosaurus_, _307_
Aestivation, of Crocodiles, 457;
of Tortoises, 357, 365, 404
_Aetosaurus_, 432;
_Ae. ferratus_, _433_, 448
_Agalychnis_, _189_, _206_
_Agama_, _520_;
_A. sanguinolenta_, _520_;
_A. stellio_, _521_, 521
Agamidae, _513_, _515_ f.
_Agamura_, tail, 506
Agassiz, on habits of Alligator Turtle, 341;
of _Trionyx_, 407
Age of Chelonia, how to estimate, 326;
great age attained by Tortoises, 369, 376, 377;
_see also_ Growth, rate of
Aglossa, 139, _140_, _143_ f.;
distribution, 143
Aglypha, _592_, _606_ f.
_Ahaetulla_ s. _Leptophis_, _618_, 619
Aistopodes, _81_
Aldabra, gigantic tortoises of, 373 f., 375
Algae, destructive to shell of tortoises, 357
Allantois, an embryonic outgrowth from the posterior part of the gut,
acting as a respiratory organ, 278
_Alligator_, _450_, _466_ f.;
_A. mississippiensis_, _467_ f.;
skull, 468;
nesting, 469;
_A. sinensis_, 471
Alligator Turtle, 340
_Allopleuron hofmanni_, 380
_Allosaurus_, _422_
Alpine, Newt, _126_;
Salamander, _119_
Altitude, high, in which Anura have been found, 181
_Alytes_, _157_ f.;
_A. cisternasi_, _160_;
_A. obstetricans_, _158_;
urino-genital organs, 49
Amblycephalidae, _592_, 593, _637_
_Amblycephalus monticola_, _637_
_Amblyrhynchus_, 528;
_A. cristatus_, _533_
_Amblystoma_, skull, 17, 94, 96, _109_, _110_ f., 112;
_A. jeffersonianum_, _111_;
_A. mavortium_, _115_;
_A. opacum_, _110_;
_A. persimile_, _111_;
_A. punctatum_, _110_;
_A. talpoideum_, _110_;
_A. tigrinum_, _111_ f.;
metamorphosis of, 112 f.
Amblystomatinae, _102_, _109_
_Ameiva_, 549
Amnion, a membrane round the embryo, 278
Amphibia, 3 f.;
definition, 5;
systematic position, 5;
numbers of species, 4
Amphicondylous, _i.e._ the occipital part of the skull articulates with
the neck by a right and a left knob, 4
_Amphignathodon_, 185;
_A. guentheri_, _188_
Amphignathodontinae, _139_, _188_
_Amphisbaena_, _566_;
_A. fuliginosa_, _566_
Amphisbaenidae, _514_, _565_ f.
_Amphiuma_, 88, 96;
_A. means_ s. _tridactyla_, _100_, 101
Amphiumidae, _94_, _97_ {652}
_Amphodus_, _210_;
_A. wucheri_, 211
Anaconda, 603, 603
_Anaides_ = _Autodax_ (q.v.), _107_
Anal sacs of Chelonia, used as additional respiratory organs, 330
_Anarosaurus pumilio_, _477_
_Anchisaurus_, 415, 417, _421_;
skull of _A. coelurus_, 421
_Ancistrodon_, _645_;
_A. contortrix_, _646_, 646;
_A. halys_, _645_;
_A. himalayanus_, _645_;
_A. piscivorus_, _645_, 645
Anderson, on nest of _Gavialis_, 452
Andrews, on _Amblystoma_, 110
_Andrias scheuchzeri_, 84
Anelytropidae, _514_, _564_
_Anelytropsis papillosus_, _564_
Anguidae, _513_, _537_ f.;
distribution, 501, 529
_Anguis fragilis_, _539_, 539
_Aniella pulchra_, _564_
Aniellidae, _514_, _564_
Annandale, on habits of _Calotes_, 518;
of _Liolepis_, 527;
of _Rhacophorus_, 247;
of _Varanus salvator_, 544
_Anodonta_, as food of _Trionyx_, 407
_Anodontohyla_, _236_
_Anolis_, _528_;
_A. carolinensis_, _529_
Anomodontia, _309_
Anura, 7;
characters, 138;
classification, 139 f., 141;
phylogenetic tree of, 142
Anus, asymmetrical position of, 60
Apoda, _84_ f.;
affinities, 88;
distribution, 89;
eyes, 86;
skin, 87;
skull, 84, 85;
spermatozoa, 87;
tentacular apparatus, 88;
vertebrae, 86;
visceral arches, 86
_Archaeopteryx_, 417
_Archegosaurus_, vertebrae, 13, _82_, 287
Arcifera, of Cope, 140;
of Boulenger, 140
Arciferous, type of shoulder-girdle, 24, 25
_Arion_, slug, eaten by tortoises, 363
Arrau-turtle (_Podocnemis_), 391 f.
Arteria cutanea magna, 144;
A. sacralis of Anura, 144
_Arthroleptis_, _241_, _242_;
_A. seychellensis_, _243_, 243
_Ascaphus_, _153_
_Asterophrys_, _161_
Athecae, _333_;
definition of name, 337
_Atlantosaurus_, 415, _419_;
_A. immanis_, _419_, 420
Atlas and Axis, _i.e._ first and second cervical vertebrae; of
_Cryptobranchus_, 13;
of Crocodilia, 283;
of Chelonia, 283, 316;
of _Sphenodon_, 283, 294;
atlas fused with axis, 307
Atoposauridae, _453_
_Atractaspis_, _638_;
dentition, 593 n.
Atria, the thin-walled receptive parts (auricles) of the heart
Auditory columellar apparatus, of Amphibia, 24;
of Anura, 29
Australian, Anura, spawning time and habits of, 201;
Lacertilia, 502
_Autodax_, 96, _104_, _107_;
_A. lugubris_, _107_;
_A. iecanus_, _107_
Autosauri, _491_ f.
Axis;
_see_ Atlas
Axolotl, 65, _112_ f., 112;
Neoteny of, 65, 112
_Azemiops feae_, _638_
Balancers of Amphibia, 45
_Baptanodon_, 483, _484_
Barfurth, on absorption of Tadpole's tail, 61
Bartlett, on _Boa constrictor_, 602;
on _Pipa_, 152
_Basiliscus_, 528, _530_;
_B. americanus_, _530_, 530
Bates, on habits of _Podocnemis_, 392 f.
_Batrachomyia_, fly infesting Bufonidae, 177
_Batrachophrynus_, _224_;
_B. macrostomus_, 225;
_B. brachydactylus_, 224
_Batrachopsis_, _161_
_Batrachoseps_, 96, _104_
_Batrachylodes_, _241_
_Batrachyperus_, 96;
_B. sinensis_, _109_
Baur, on _Sphargis_, 336
_Bdellophis_, _90_
Bedriaga, on Axolotl, 114;
synopsis of Urodelous Larvae, 59 n.
Bell, J., on classification, 8
Bell, Napier, on habits of _Iguana_, 531
_Belodon_, 305, _434_, 448
Bemmelen, on _Sphargis_, 336
Berg, on _Spelerpes fuscus_, 106
Bert, quoted, 571 n.
Bidder's organ, 49, 52
Biedermann, on change of colour in _Hyla_, 35
Birds not related to Dinosaurs, 416 f.
_Bitis arietans_, _639_, 639;
_B. nasicornis_, _640_
Black Snake, of Australia, _634_;
of North America, _613_
Blainville, de, on classification, 7
_Blanus cinereus_, _566_
Blood, shape of red corpuscles, 4;
temperature, 67 f.
Blood-sucker = _Calotes ophiomachus_, 519
Blum, quoted, 642 n.
_Boa_, _602_;
_B. constrictor_, _602_;
_B. dumerili_, _602_;
_B. madagascariensis_, _602_
Boettger, on influence of climate and country upon reptiles, 492 f.
Boidae, _592_, _596_ f.;
skull, 596, 597
Boinae, _601_ f.
_Bombinator_, _154_ f., 155;
habits, 156 f.;
tadpoles, 157;
abnormal vertebrae, 22;
shoulder-girdle, 25;
urino-genital organs, 49;
_B. igneus_, _154_, 155;
_B. pachypus_, _155_
_Bothrops_, _647_
Boulenger, classification of Amphibia Caudata, 9; {653}
on vertebrae of _Pelobates_, 20;
on vertebrae of _Bombinator_, 22;
number of phalanges in Anura, 27;
on poison of Amphibia, 36;
on vocal sacs, 48;
on modes of fecundation and nursing habits, 54, 56;
synopsis of Tadpoles, 59 n.;
on tadpoles of _Rana opisthodon_, 260;
on classification of Anura, 140, 141;
on _Pipa_, 152;
on _Scaphiopus solitarius_, 165;
on _Alligator sinensis_, 471;
on _Lanthanotus_, _542_;
on aberrant scaling, 495;
on _Heloderma_, 540 n.;
on classification of Snakes, 592;
on Sea-Snakes, 637;
on _Sphargis_, 336
_Boulengerula_, _90_
Box-Tortoises, _362_, 364, 365
Brachial plexus, of Anura, 39
_Brachycephalus_, 226, _227_;
_B. ephippium_, _231_
_Brachylophus_, distribution, 501, _528_
Brain, of _Scaphognathus_, 485;
small size of, in Dinosaurs, 425
Branchial arches, of Urodela, 16;
of Anura, 42
Branchiosauri, _80_
_Branchiosaurus_, skull, 80;
_B. salamandroides_, _80_
Brauer, on development of Apoda, 92;
on nursing habits of _Arthroleptis_, 243
Breeding of Axolotl, 113
_Breviceps_, shoulder-girdle, 26, 225, 226, _227_, _232_;
_B. mossambicus_, _232_
_Brithopus_, _308_
Brongniart, on classification, 7
_Brontosaurus_, 415, _418_;
_B. excelsus_, 418
_Brontozoum_, 415, 417;
_B. giganteum_, _420_
Brood-pouches, of Anura, 151, 248;
of _Hyla goeldii_, 198;
of _Nototrema_, 202;
of _Rhinoderma_, 228
_Brookesia_, _580_
Brown Adder, _634_
Brown Frog, Common, 251 f., 255
Brücke, quoted, 571
Buchholz, on _Chiromantis_, _244_ f.
Budgett, on breeding habits of _Phyllomedusa_, 204;
on _Paludicola_, 220;
on _Lepidobatrachus_, 218;
quick development of _Phryniscus_, 231;
on _Bufo marinus_, 179
_Bufo_, sacral vertebra, 22;
shoulder-girdle, 26;
urine-genital organs, 49;
development of adhesive apparatus, 57;
_B. agua_, _178_;
_B. americanus_, _178_;
_B. calamita_, _181_ f.;
_B. ceratophrys_, _179_;
_B. empusus_ and _B. peltocephalus_, dermal ossifications, 179;
_B. jerboa_, 166;
_B. lentiginosus_, _178_, _179_;
map of distribution, 167, _168_, _169_ f.;
_B. marinus_, _178_;
_B. mauritanica_ s. _pantherina_, _184_;
_B. melanostictus_, _177_, _179_;
_B. quercinus_, _178_;
_B. variabilis_ = _viridis_, _180_;
_B. viridis_, _180_ f., 493;
_B. vulgaris_, 170 f., 172;
large-sized specimens, 171;
immured in buildings, 174;
diseases, 176;
distribution, 177
Bufonidae, _139_, _166_ f.;
distribution, 167;
affinities, 166
Bufoniformes, 139
Bullfrog, of America, _Rana catesbiana_, 261;
of India, _Callula pulchra_, 234;
_Rana tigrina_, 261
_Bungarus coeruleus_ s. _candidus_, _633_;
_B. fasciatus_, _633_
Butler, on fat-bodies, 500
_Cabrita_, 551
_Cacopus_, shoulder-girdle, 25, 225, 226, _228_
_Cacosternum_, 225, _227_
_Caiman_, _450_, _471_;
vomer, 435;
_C. niger_, _471_, _472_;
_O. palpebrosus_, _471_;
_C. sclerops_, _471_;
_C. trigonatus_, _471_, _472_
Calcareous deposits in the skin of Amphibia, 31, 34
_Calliphora silvatica_, fly infesting _Bufo_, 176
_Callophis macclellandi_, _634_
_Calluella_, 235, _236_
_Callula_, 226, _228_, _234_;
_C. pulchra_, habits of, _234_ f.
_Callulops_, 225, _228_
_Calophrynus_, 225, _227_
_Calotes_, _517_;
_C. emma_, _518_;
_C. mystaceus_, _519_;
_C. ophiomachus_, _519_;
_C. versicolor_, _518_
_Calyptocephalus_, 179, _212_, _215_
_Camptosaurus_, _426_
_Capitosaurus_, _83_
Carapace, 321 f., 319, 320, 322, 323;
posterior portion movable in _Cinyxis_, _364_, 365;
carapace of tortoises, evolution of, 337;
composition of, 324 f.;
reduction of component elements, 325;
reduction in thickness, 373;
correlative changes, 328;
of _Sphargis_, 335 f.;
of _Chelone_, 379;
of _Testudo_, 322;
of Pleurodira, 389;
reduction in Trionychidae, 325;
fenestration, 325;
with hinge in _Cinyxis_, 364, 365
_Cardioglossa_, _274_
Carettochelydidae, _313_, _314_
_Carettochelys_, 337, 389, 390;
_C. insculpta_, _404_;
absence of horny shields, 325
Carpet Snake, _598_, 599
Carpus (_see also_ Limbs), of _Eryops_, 286;
of _Sphenodon_, 294;
of Chelonia, 320, 320;
of Eusuchia, 440
_Casarea_, _603_
Case, on _Sphargis_, 336
_Cassina_, _240_
_Causus_, _638_;
_C. rhombeatus_, _639_
_Centrolene geckoideum_, _211_
_Cerastes cornutus_, _640_, 641
Ceratobatrachidae, 141 {654}
Ceratobatrachinae, _139_, _237_ f.
_Ceratobatrachus guentheri_, _237_
_Ceratohyla_, 211
_Ceratophora_, _517_;
_C. stoddarti_, _517_;
_C. tennenti_, _517_
_Ceratophrys_, _212_, _215_ f.;
_C. cornuta_, 216;
_C. dorsata_, 215;
_C. ornata_, 216, 217
Ceratopsia, _430_
_Ceratosaurus_, 413, 416, 417;
_C. nasicornis_, _422_, 422
_Cerberus rhynchops_, _625_
_Cetiosaurus_, _419_
_Chalarodon_, _528_;
geographical distribution of; 501
_Chalcides_, _562_;
_Ch. bedriagae_, 563;
_Ch. guentheri_, 563;
_Ch. lineatus_, 563;
_Ch. ocellatus_, 563;
_Ch. tridactylus_, 563
_Chamaeleon_, _573_;
_Ch. bifidus_, 580;
_Ch. calcaratus_, 579;
_Ch. parsoni_, 580;
_Ch. pumilus_, 579, 575;
_Ch. vulgaris_, 573, 574, 575
Chamaeleontes, _567_ f.;
distribution, 568;
skull, 568, 569;
tongue, 569 f.;
colour-changing mechanism, 570, 571, 573 f.;
eggs, 572
Chamaeleontidae, _573_ f.
_Chamaerops humilis_, dates of, eaten by _Testudo_, 367
Chameleon, misnamed _Calotes_, _518_;
misnamed _Polychrus_, _529_
Chauvin, Marie von, on Axolotl, 113;
on _Salamandra atra_, 120
_Chelodina_, suppression of neural plates, 324;
intergular shields, 389, 315;
skull, 399;
_Ch. longicollis_, _402_ f., 403
_Chelone_, skull, 317;
skeleton, 320;
plastron, 321;
shields, 327;
intergular shields, 325;
_Ch. mydas_, _381_ f.;
various modes of fishing, etc., 382, 383;
_Ch. imbricata_, _384_, 385
Chelonemydidae, 380
Chelonia, 312;
number of species, 312;
affinities of, 312;
classification, 313;
key to living families, 314;
plastron, names of the horny shields, 315; 321, 325;
vertebrae, 314 f., 316;
skull, 280, 317, 356, 364, 379, 400, 405;
skeleton of _Testudo_, 319;
of _Chelone_, 320;
pectoral arch, 318;
pelvis, 319;
plastron, bones of, 321;
limbs, 320;
bony shell, 321 f., 322, 323;
evolution of, 337;
evolution of the horny shields, 326 f., 327;
regeneration, 329;
sense-organs, 329;
digestive apparatus, 330;
respiration, 331;
growth of _Chrysemys_, 349
Chelonidae, _313_, _314_, _378_ f.;
affinities of, 380
Chelydidae, _313_, _314_, _399_;
distribution, 332, 333
_Chelydosaurus_, _82_, 287
_Chelydra_, 328;
_Ch. serpentina_, _338_
Chelydridae, _313_, _314_, _338_;
distribution of, 332
_Chelydropsis_, nuchal plates, 324
_Chelys fimbriata_, _400_;
skull, 400, 401;
intergular shields, 325
_Chersydrus granulatus_, _607_
_Chioglossa_, 96, _115_;
_Ch. lusitanica_, _121_
_Chirixalus_, _241_
_Chiroleptes_, 209, _213_, _221_;
_Ch. platycephalus_, _221_
_Chiromantis_, 238, _241_, _244_;
_Ch. petersi_, _244_;
_Ch. xerampelina_, _244_
_Chirotes_, 564;
_Ch. canaliculatus_, _566_
_Chirotherium_, _83_
_Chlamydosaurus kingi_, 522, 523
Choanae, or inner nasal openings, 47
Chorda dorsalis, the axial rod between the gut and the spinal cord,
around which the vertebrae are formed, 12
_Chorophilus_, 186, _189_;
_Ch. ornatus_, _208_
Chromatophores, 35
_Chrysemys_, costal plates of, 325;
green colour of, 328, _346_ f.;
colour of iris, 329;
_Ch. concinna_, _346_, 349, 350;
_Ch. elegans_, _346_;
_Ch. picta_, 346, _347_, 348;
_Ch. rubriventris_, _346_
_Chthonerpeton_, 87, _90_
_Cimoliasaurus_, _478_;
_C. australis_, _478_;
_C. cantabrigiensis_, _478_;
_C. chilensis_, _478_;
_C. haasti_, _478_
Cinosternidae, _313_, _314_, _342_;
distribution, 332
_Cinosternum_, 342 f.;
arrangement of neural plates, 324;
_C. leucostomum_, _342_, 344;
_C. odoratum_, _342_, 343;
_C. pennsylvanicum_, _342_, 344
_Cinyxis belliana_, _365_;
_C. erosa_, _364_, 365;
_C. homeana_, _364_
_Cistecephalus_, _310_
_Cistudo_, arrangement of neural plates, 324;
_C. Carolina_, 361 f., 364;
colour of iris, 329
_Claosaurus_, _429_
Clarke, on habits and development of _Alligator_, 467
Classification of Amphibia, historical account, 7 f.
Clawed Toad (_Xenopus_), _146_ f.
Claws or nails of Amphibia, 32
Cleithra = the pair of additional clavicles;
of Stegocephali, 79;
of _Pareiasaurus_, 304, 305
_Clemmys_, _356_ f.;
_C. caspica_, _358_;
_C. insculpta_, _359_;
_C. leprosa_, _356_ f., 353;
skull, 356
_Clepsydrops_, _308_
_Clidastes tortor_, _490_
Cloaca, of Chelonia, 330;
of Crocodiles, 445;
of Lacertilia, 498
_Cnemidophorus_, _549_;
_C. sexlineatus_, _549_
Cobra, _627_, 627
Coccyx, _s._ Os coccygeum, of Anura, 20, 21, 22 {655}
_Coecilia_, _89_
Coeciliidae, _89_ f.;
distribution of, 89
_Coelopeltis_, _624_;
_C. monspessulana_ s. _lacertina_, _624_
_Coelurus_, _415_;
_C. gracilis_, _423_
Colombo, gigantic tortoise of, 377
Coloration, warning colours of Amphibia, 38, 156;
protective, of Amphibia, 191, 238, 252;
of deserticolous reptiles, 494
_Colosthetus_, 238, _242_
Colour, changes of, in Anura, 35;
in _Calotes_, 518, 519, 520;
in Geckos, 509;
in Lacertilia, 498;
mechanism of changing, in Chameleons, 570, 571
_Coluber_, _615_ f.;
_C. aesculapii_ = _flavescens_ = _longissimus_, _616_ f.;
_C. leopardinus_, _616_;
_C. (Rhinechis) scalaris_, _617_
Colubridae, _593_, _606_ f.
Colubrinae, _607_ f.
Columella cranii, 496, 550, 551
Columellar auditory chain, of Amphibia, 4;
of Anura, 29;
of Crocodiles, 446;
of Lizards, 496
Comoro Islands, Tortoises of, 373
_Compsognathus_, _415_, 416, 417;
_C. longipes_, _423_, 425
Condyle, occipital, of Theromorpha, 302;
exaggerated importance of its character, 285
_Conolophus subcristatus_, _532_
Conus arteriosus, continuation of the heart beyond the ventricles so far
as it contains valves, 6
Cope, on classification of Amphibia, 9;
of Anura, 140, 141;
on _Siren_, 136;
on hand-skeleton of _Eryops_, 286;
on _Sphargis_, 336;
classification of Lacertae, 513;
classification of Snakes, 592
_Cophophryne_, 167, _168_
_Cophyla_, _236_
Copper-head, _646_, 646
Copulatory organs, of Lacertilia, 499;
absent in _Sphenodon_, 294;
of Chelonia, 330;
of Snakes, 585
Coqui, 214
_Coronella_, _619_;
_C. austriaca_ s. _laevis_, _619_, 620;
_C. girondica_, _621_
_Cornufer_, _241_, _243_;
_C. corrugatus_, _244_;
_C. johnstoni_, _243_;
_C. solomonis_, _244_;
_C. unicolor_, _244_
_Corythomantis_, _189_, _207_;
_C. greeningi_, 207
Costal plates of Chelonia, 324 f., 322, 323
_Craspedocephalus_, 647
Crested Newt, 125, 125
_Cricotus_, 285, _285_;
_C. heteroclitus_, 287
_Crinia_, _213_;
spawning, 223
Crocodilia, _431_ f.;
skeleton, 434 f.;
skull, 280, 434 f.;
atlas and axis, 283, 431, 439;
affinities, 432;
teeth, 437;
skin, 442;
dermal armour, 442;
skin glands, 443;
tongue, 443;
respiratory organs, 444;
"diaphragm," 444;
digestive organs, 444;
cloaca, 445;
heart, 445;
ear, 445;
eye, 446;
geographical distribution, 446, 446;
voice, 447;
habits, 447;
propagation, 447;
classification, 448
Crocodilidae, _454_
_Crocodilus_, _450_, _454_ f.;
teeth, 437;
skin glands, 443;
_C. acutus_, _446_, 449;
_C. americanus_, _466_;
skull, 466;
_C. biporcatus_ = _porosus_, _458_;
rate of growth, 459;
_C. cataphractus_, _465_;
_C. intermedius_, _466_;
_C. johnstoni_, _466_;
_C. niloticus_ = _vulgaris_, _460_ f., 449, 461;
habits, 462 f.;
_C. palustris_, 449, _454_;
skull, 455;
_C. porosus_, _458_;
skull, 458;
_C. vulgaris_, 449, _460_ f.
Crotalinae, _644_
_Crotalus_, _648_;
rattle of, 644;
_C. adamanteus_, _649_, 650;
_C. confluentus_, 649, _650_;
_C. durissus_, 648, _649_, 650;
_C. horridus_, _649_;
_C. terrificus_, _650_
_Cryptobranchus_, 84, _96_, _99_;
fossil, 84;
_C. alleghaniensis_, _97_;
_C. japonicus_, 98, 99
_Cryptoclidus_, shoulder-girdle, 474, 475, _478_
Cryptodira, _313_, _338_
_Cryptopsophis_, _89_;
_C. multiplicatus_, _92_
_Cryptotis_, _213_
Cutis, of Amphibia, 33 f.
_Cyamodus_, _311_
_Cyclanorbis_, _411_;
nuchal plate, 324
_Cycloderma_, _411_
_Cyclodus_ s. _Tiliqua_, _561_;
_C. gigas_, _561_, 562
_Cyclorhamphus_, _212_
_Cynognathus_, 301, 302, 303;
_C. berryi_, _307_;
_C. crateronotus_, _306_;
_C. platyceps_, _307_
Cystignathidae, _139_, _209_ f.;
distribution, 161
Cystignathinae, _139_, _211_ f.
_Cystignathus_ = _Leptodactylus_, 210, _218_
Dab = _Uromastix_, _526_, 526
_Daboia_, _643_
_Dactylethra_;
see _Xenopus_, _146_ f.
Darwin, on _Conolophus_, 532 n.;
on tortoises of Galapagos Islands, 377
_Dasypeltis scabra_, _622_, 622;
dentition, 593 n.
Davison, on breeding of _Amphiuma_, 101
_Dawsonia_, _289_
Death Adder, _635_
Denburgh, van, on _Autodax_, 107
_Dendrobates_, _272_;
_D. braccatus_, _273_;
_D. tinctorius_, _272_, 273;
_D. trivittatus_, _273_;
_D. typographus_, _273_;
various uses of its poison, 38
Dendrobatinae, _139_, _237_, _272_ f.; {656}
distribution, 239
_Dendrophis_, _618_;
_D. punctulatus_, _618_, 618
Dendrophryniscinae, _139_, _224_
_Dendrophryniscus brevipollicatus_, _224_
Dentition, of snakes, 582, 592, 593;
_see_ also Teeth
Dermal armour, of _Cricotus_, 287;
of Microsauri, 289;
of Prosauri, 290;
of Theromorpha, 302;
of Chelonia, 321 f., 337;
of Dinosauria, 415;
of Pseudosuchia, 433;
of Parasuchia, 434;
of Crocodiles, 442
Dermal ossification in Anura, 179, 190, 210
Dermatemydidae, _313_, _314_, _341_;
distribution of, 332
_Dermatemys mawi_, _341_, 342
_Dermatochelys coriacea_, _333_ f., 334
_Dermophis_, _89_, _93_;
_D. thomensis_, _93_
Deserticolous reptiles, 493 f.
Desmognathinae, _102_
_Desmognathus_, 96, _102_;
_D. fuscus_, _102_, 103
_Deuterosaurus_, _308_
Development, of Anura, 56 f., 57;
of horny teeth, 58;
of Apoda, 92;
of _Crocodilus_, 465;
of _Alligator_, 467
_Diadectes_, _308_
_Diademodon_, _309_
_Diaglena_, 185, _189_;
_D. jordani_, _207_;
_D. petasata_, _207_
Diaphragm, of Anura, 144;
of crocodiles, 444
Diapophyses (the lateral or "transverse" processes of the neural arches)
of Anura, 138, 141
Dibamidae, _514_, _564_
_Dibamus novae-guineae_, _564_
_Dicamptodon_, 96;
_D. ensatus_, _109_
_Diclonius_ = _Hadrosaurus_, _429_
_Dicynodon_, 301, 302, 303, _310_;
skull, 280;
_D. leoniceps_, _310_;
_D. orientalis_, _310_;
_D. tigriceps_, _310_
Digestive apparatus, of Chelonia, 330;
of crocodiles, 444;
of Lacertilia, 498
Digits = Fingers and Toes.
Number of digits in Urodela, 15, 16;
in Anura, 26;
terminal phalanges, 26;
number of joints, 27;
adhesive discs, 27;
variability in numbers, 563;
digits of _Eryops_, 286;
of Crocodiles, 441;
of Plesiosauri, 475;
of Geckos, 505
_Dimetrodon_, _308_
_Dimorphodon macronyx_, _486_
Dinosauria, _412_;
affinities of, 415;
analogies with Birds, 416
_Diplocynodon_, 448;
_D. hastingsiae_, _454_
_Diplodocus longus_, _419_ f.;
skull, 419
_Diplovertebron_, _287_, 288
Dipsadomorphinae, _623_ f.
_Dipsadomorphus_, _623_;
_D. cyaneus_, _624_;
_D. trigonatus_, _623_
_Dipsas bucephala_, _624_
Discoglossidae, _139_, _152_ f.
_Discoglossus_, urino-genital organs, 49, _153_;
_D. pictus_, 153 f.
_Dissorophus multicinctus_, _82_
_Distira cyanocincta_, _637_;
_D. semperi_, _636_
Distribution, geographical;
_see_ Maps
Dolichosauri, _489_
_Dolichosaurus longicollis_, _489_
_Dolichosoma longissimum_, _81_
_Doliophis intestinalis_, _634_
Dollo, on _Sphargis_, 336
_Dracaena_, _547_;
_D. guianensis_, _549_
_Draco_, _516_;
_D. dussumieri_, _516_;
_D. volans_, _516_, 516
Duméril, 7, 139;
and Bibron, on classification of Snakes, 592
Dwarf Chameleon, _579_
Dyscophinae, _139_, _235_ f.
_Dyscophus_, _236_;
_D. antongili_, _236_
Ear, of Chelonia, 330;
of Crocodiles, 445 f.;
of Snakes, 583
Ear-opening of deserticolous reptiles, 494
_Echeneis remora_, used for turtle fishing, 382
_Echidna_ s. _Bitis_, _639_, 639
_Echis_, _640_;
_E. arenicola_, deserticolous, 493
_Edalorhina_, _212_
Eggs of Amphibia, 53;
mode of deposition in Amphibia, 54-56;
of _Ichthyophis_, 91;
and spermatophore of _Triton viridescens_, 128;
nursing and taking care of, 55;
by _Pipa_, 151;
by _Alytes_, 159;
by _Rhacophorus reticulatus_, 248;
by _Nototrema_, 188, _202_;
by _Amphignathodon_, _188_;
by _Hyla goeldii_, 198, 198;
by _Leptodactylus mystacinus_, 219;
by _Rhinoderma_, _228_;
by _Rhacophorus_, _248_;
by _Desmognathus fuscus_, 103, 103;
number of: in _Bufo vulgaris_, 175;
in _Bufo viridis_, 181;
in _Hyla arborea_, 193;
in _Rana esculenta_, 270
Eggs of Reptilia: _Sphenodon_, 299;
Chelonia, 331;
_Testudo graeca_, 369;
_T. ibera_, 369;
_T. elegans_, 371;
_T. polyphemus_, 372;
_Emys orbicularis_, 355;
_Clemmys leprosa_, 358;
_Chelone mydas_, 382;
_Thalassochelys caretta_, 387;
_Podocnemis expansa_, 393 f., 398;
_Trionyx_, 408;
mode of laying by _Emys_, 355;
by _Podocnemis_, 393;
used commercially, 394 f.;
enormous destruction of, 395, 399;
_Crocodilus_, 463, 464 f.;
_Alligator_, 470;
eggs and nest of _Gavialis_, 452;
Lacertilia, 499;
increasing in size after deposition, 499;
Geckos, 506, 508, 509, 511;
_Tarentola_, 509;
_Lacerta viridis_, 555;
_Chameleons_, 572
Egg-sac, of _Salamandrella_, 110 {657}
Egg-tooth, of Lacertilia, 499
Eimer, on habits of _Lacerta_, 552;
on _L. coerulea_, 558
_Elachistodon westermanni_, _625_
Elachistodontinae, _625_
_Elaphis_ s. _Coluber_, _615_ f.
Elapinae, _626_
_Elaps corallinus_, _635_
Elasmosauridae, _478_
_Elasmosaurus_, _478_
_Elginia_, 301, 304;
_E. mirabilis_, skull, 280, _305_
_Elosia_, _212_
_Elseya_, 389, 399
Emerald Lizard, _555_
Emery, on hand-skeleton of _Eryops_, 286
_Empedias molaris_, _308_
_Emyda_, _411_
_Emydura_, 389, 399
_Emys_, _350_ f.;
_E. blandingi_, _355_;
_E. europaea_ = _orbicularis_, _351_ f., 353
Enaliosauri, _476_
_Endothiodon_, _307_
_Engystoma_, _227_, _231_;
_E. carolinense_, _232_
Engystomatidae, _139_, _225_ f.
Engystomatinae, _139_, _225_ f.
_Engystomops_, 166, _168_
_Enhydrina valakadien_ s. _bengalensis_, _636_, 636
_Enygrus_, _601_
_Eosphargis_, 336, 337
Epichordal type of vertebrae, 20, 145
Epidermis, of Amphibia, 31 f.;
sense-organs in, 33
_Equisetum_, eaten by _Uromastix_, 525
_Eremias_, 551;
deserticolous, 493
_Erpetosuchus_, _433_
_Eryops_, 285, _286_;
trunk-vertebrae, 286, 288, 304;
_E. megacephalus_, 286
_Eryx_, _604_;
_E. jaculus_, _604_;
deserticolous, 493
Escuerzo = _Ceratophrys_, 216
Espada, on _Rhinoderma_, 228
Eublepharinae, _512_
_Euchirosaurus_, _83_, 287
_Eunectes murinus_, 603, 603
_Euprepes vittata_, _562_
_Euproctus_ = _Triton_, _130_
_Eurysternum_, 380
Eustachian tubes, of Anura, 29;
of Pelobatidae, 161;
of Aglossa, 143
_Eusuchia_, _434_
Eye, of Apoda, 86;
of Chelonia, 329;
of deserticolous reptiles, 494;
of Chameleons, 569;
of Snakes, 583
Eyed Lizard, _556_, 556
Eyelid, of Geckos, 504, 512;
transparent in _Chelodina_, 329;
lower, transparent in Lacertidae, 551;
in Scincidae, 560
Fasting, of _Chrysemys_, 347
Fat-bodies, of Amphibia, 49, 52;
of Lacertilia, 500
Fecundation, various modes of, in Amphibia, 54;
in Apoda, 87
Fer-de-Lance, _647_
Ferreiro = _Hyla faber_, _196_ f.
_Feylinia_, _564_
Fingers, number of, in Urodela, 15;
number of joints in Anura, 26, 27;
terminal modifications of, in Anura, 26;
mechanism of adhesive discs in Hylidae, 187
Fire Salamander, _115_
Firmisternal shoulder-girdle, 24, 25
Firmisternia, 140
Fischer-Sigwart, on growth of _Alytes_, 159 f.;
on growth of _Bufo_, 175;
on gestation of _Chalcides_, 563
Fletcher, on spawning of Australian frogs, 201, 223
Flower, S. S., on habits of _Rhacophorus_, 249;
_Phrynella pollicaris_, 233;
_Callula pulchra_, 234
Flying Dragon, _516_
Flying Frog, _Rhacophorus_, 245 f., 246
Foot, tridactyle, in _Hallopus_, 423;
bird-like in _Compsognathus_, 423
Fore-limb, of Urodela, 15;
of Anura, 26;
of Proreptilia, 286;
of Microsauri, 289;
of Prosauri, 290, 298;
of Theromorpha, 302;
of Chelonia, 320;
of Dinosauria, 414, 423, 425, 427;
of Crocodilia, 440;
of Plesiosauria, 475;
of Ichthyosauria, 481;
of Pterosauria, 485;
of Pythonomorpha, 489;
of Lacertilia, 497
Frog, _see_ Rana.
Grassfrog, 251;
Water-frog, 263, 268, 269
Gage, on _Triton viridescens_, 129
Galapagos Islands, tortoises of, 372, 377 f.
_Galesaurus_, _307_
_Gampsosteonyx_, _271_;
_G. batesi_, _238_, _240_
Gasco, on spawning of newts, 124
Gastrechmia, 140, 141, _232_
Gastrocentrous vertebrae, defined, 282
Gaupp, on frogs' respiration, 47 n.
Gavialidae, _451_ f.
_Gavialis_, 435, 436, _451_;
_G. gangeticus_, _452_;
skull, 449, 452
_Gavialosuchus_, _453_
_Gecko_, _511_;
_G. stentor_, _511_;
_G. verus_ = _guttatus_ = _verticillatus_, _511_
_Geckolepis_, deserticolous, 493
Geckones, _502_ f.;
distribution, 500, 503;
adhesive apparatus, 505, 505;
voice, 506;
reproduction of tail, 506;
eyelids, 504, 512
Geckonidae, _507_ f.
Geckoninae, _507_ f.
Gegenbaur, on classification, 9
_Gegenophis_, 87, _90
Geikia_, _310_ {658}
Genital organs, of Amphibia, 48 f., 49
_Genyophryne_, _236_;
_G. thomsoni_, _236_
Genyophrynidae, 141
Genyophryninae, _139_, _236_
Geographical distribution, principles of, 69 f.;
regions and sub-regions, 74 f. (for details _see also_ Maps);
of Apoda, 89;
of Urodela, 95, 96;
of Anura, 143, 161, 167, 185, 239;
of Chelonia, 331 f., 332, 333;
of Crocodilia, 446;
of Lacertilia, 500 f., 515, 529, 543, 552, 565, 568;
of Snakes, 585
_Geomolge_, 96
_Geosaurus_, _451_
_Geotriton_, 97
_Geotrypetes_, _89_
_Gerrhonotus_, _538_;
_G. coeruleus_, _538_
Gerrhosauridae, _514_, _559_
_Gerrhosaurus flavigularis_, _559_
Gharial, _452_;
_see_ also _Gavialis_
Gigantic Tortoises, _372_ f.
Gila Monster, _541_
Gills, definition, 40;
development of, 41, 43;
retention of, 40;
external and internal, 43 f.;
operculum of, 44;
of _Nototrema_, 203
Gill-clefts, 42;
of Urodela, 42;
of Anura, 42
Girtanner, on musical appreciation of tortoises, 368
Glass-Snake, _538_
_Glauconia_, _594_
Glauconiidae, _592_, _594_
_Glyphoglossus_, 225, 226, _228_, _233_;
_G. molossus_, _233_
Goeldi, on _Hyla faber_, 197;
on habits of _Podocnemis expansa_, 397 f.
_Gomphognathus_, _308_, 309
_Gondwanosaurus_, _83_
_Gongylus_, _562_
Goniopholidae, _453_
_Goniopholis_, 448, _453_;
_G. crassidens_, _453_;
_G. simus_, 453
_Gordonia_, 301, 303, _310_;
skull, 280
Grass-Frog, 251 f., 255
Grass-Snake, _608_ f.
Greek Tortoise, _365_ f.
Green Lizard, _555_
Green Toad, _180_
Green, or Edible, Turtle, _381_ f.
Groenberg, on _Pipa_, 149
Growth, rate of, in _Testudo ibera_, 370;
_Chrysemys picta_, 349;
_Emys orbicularis_, 351, 355
Gular shields of Chelonia, 315
Gundlach, on _Leptodactylus_, 219
Günther, 140;
on gigantic Tortoises, 374;
on classification of Snakes, 592
Gutzeit, on horny teeth of Tadpoles, 58
_Gymnodactylus_, tail, 506, _512_, 512;
deserticolous, 493
Gymnophiona, _84_ f.
_Gymnophis_, _90_
_Gymnophthalmus_, aberrant scaling, 495
Haast, on habits of _Sphenodon_, 299
_Hadrosaurus mirabilis_, _429_
Haeckel, on classification, 9
_Hallopus victor_, _423_
Hamadryad, _632_
Hand-skeleton, excalation of second finger in _Eryops_, 286
_Haptoglossa_, 96
Hardun = _Agama stellio_, _521_
_Hatteria_–see _Sphenodon_, 293 f.
Hawksbill-Turtle, _384_ f.
Hay, on _Sphargis_, 337
Hearing of Chelonia, 330
Heart, modification of, in lungless Amphibia, 47
Hedonic glands (ἡδονή, lust), 443
_Heleioporus_, _213_, _222_;
_H. albopunctatus_, _222_;
_H. pictus_, _222_
_Helix virgata_, eaten by _Hyla coerulea_, 200
_Heloderma horridum_, _540_;
_H. suspectum_, _540_, 541
Helodermatidae, _513_, _540_ f.
_Hemidactylus turcicus_, _508_, 508
Hemiphractinae, _139_, _210_ f.
_Hemiphractus_, _210_
_Hemisus_, 225, 226, _228_, _232_;
shoulder-girdle, 25;
_H. guttatum_, _232_;
_H. sudanense_, _232_
Hensel, on _Bufo marinus_, 179;
on tadpoles of _Thoropa_, 209;
on nest-building of _Leptodactylus_, 219
Herodotus, on Crocodiles, 462
_Herpele_, _90_
_Herpestes griseus_ (Mongoos), 629
Hibernation, temperature of blood during, 68;
of Tortoises, 347, 349, 354, 358, 360, 363, 365, 369, 376;
of Crocodiles, 447
Hinckley, on tadpoles of _Hyla versicolor_, 195
Hind-limbs, of Urodela, 15;
of Anura, 27;
of Prosauria, 289;
of Theromorpha, 302, 305;
of Chelonia, 321;
of Dinosauria, 414, 423, 425, 427, 429;
of Crocodilia, 440;
of Plesiosauria, 476;
of Ichthyosauria, 480;
of Pterosauria, 486;
of Lacertilia, 497;
of Ophidia, 593, 594, 596
_Hipistes hydrinus_, _625_
Holbrook, on the Black Snake, _613_;
on habits of _Alligator_, 470 f.
Holoblastic eggs;
the whole mass of the egg undergoes the process of cleavage, 53
Homalopsinae, _625_
_Homalopsis buccata_, _625_
Homing of turtles, instances of, 386
_Homoeosaurus pulchellus_, _292_ {659}
_Homopholis_, deserticolous, 493
Homothermous, defined, 68
_Hoplocephalus curtus_, _634_
_Hoplurus_, _528_;
geographical distribution, 501
Horned Toad = _Ceratophrys_, 215 f., 216, 217
Horned Viper, _640_, 641
Horny nail, on tail of Chelonia, 328
Horny scales, of Chelonia, 328
Horny shields, of Chelonia, 314, 315, 322, 323, 326 f., 327;
their growth, 326
Horny teeth, of Anura, 58
Hose, on reproduction of tortoise-shell, 386
Howes, on development of _Sphenodon_, 298
Humerus of _Sphenodon_, 294
Hutton, on Starred Tortoise, 370 f.
Huxley, on classification, 9
_Hydraspis_, 389;
skull, 399
_Hydromedusa_, 389, _404_;
_H. tectifera_, _404_
Hydrophinae, _635_
_Hydrophis obscura_, _636_, 636
_Hydrosaurus_, _543_
_Hyla_, _189_ f.;
_H. arborea_, _190_ f., 190;
var. _meridionalis_, _191_;
var. _savignyi_ = _japonica_, 191;
_H. aurea_, _201_ f.;
spawning, 201;
_H. carolinensis_ s. _lateralis_, _194_;
_H. coerulea_, _198_ f., 199;
spawning, 223;
_H. dasynotus_ and _H. nigromaculata_, dermal ossifications of, 190;
_H. ewingi_, _201_;
spawning, 223;
_H. faber_, peculiar nursing habits, 196 f.;
_H. femoralis_, _194_;
_H. goeldii_, _198_, 198;
female with eggs, 198;
_H. maxima_, _196_;
_H. nebulosa_ s. _luteola_, _197_;
nest-building, 198;
_H. polytaenia_, _198_;
_H. squirella_, _194_;
_H. vasta_, _195_;
_H. versicolor_, _194_ f.
Hylaeformes, 139
_Hylaeobatrachus croyi_, _83_
_Hylaeosaurus_, _425_
_Hylambates_, 238, _240_
_Hylella_, 186, _189_, _203_
Hylidae, _139_, _185_ f.;
distribution, 185, 186;
mechanism of climbing, 187;
map of distribution, 185;
distribution, 186
Hylinae, _139_, _189_ f.
_Hylixalus_, 238, _242_
_Hylodes_, _212_;
_H. martinicensis_, _214_ f., 214;
_H. abbreviatus_ = _Thoropa miliaris_, 209
_Hylonomus_, 288, _289_
_Hyloplesion longicostatum_, _289_
_Hylopsis_, _212_;
_H. platycephalus_, _224_
_Hylorhina_, _212_
_Hymenochirus_, 143, 144, _149_
_Hynobius_, 96, _109_
Hyoid apparatus, of Urodela, 16;
of Anura, 31;
of Chelonia, 318;
of _Chelys_, 400;
of Lacertilia, 496
_Hyperodapedon gordoni_, _292_
_Hyperolia_, _213_;
spawning, 223
Hyperphalangeal limbs, of Eusuchia, 441;
of Ichthyosauri, 480
_Hypogeophis_, 87, _89_, _92_;
_H. alternans_, _92_;
_H. rostratus_, _92_
_Hypopachus_, 226, _227_, 235
_Hypsilophodon foxi_, _427_
_Hypsirhina plumbea_, _625_
Iberian Water-tortoise, 357 f.
Ichthyodea, distribution of, 95
_Ichthyophis_, skull, 85, 88, _89_ f., 91;
_I. glutinosa_, _90_, 91;
_I. monochrous_, _90_
Ichthyopsida, 5, 277
Ichthyopterygia, 476
Ichthyosauri, _483_ f.
Ichthyosauria, _478_ f.;
skull, 281, 479;
vertebrae, 480;
limbs, 481;
shoulder-girdle, 481
_Ichthyosaurus_, _483_;
_I. communis_, _483_;
_I. campylodon_, _483_;
_I. quadriscissus_, 483;
_I. tenuirostris_, _483_;
_I. trigonodon_, _483_
_Idiochelys_, 380
_Iguana_, 306, 528, _531_;
_I. tuberculata_, _531_
Iguanidae, _513_, _528_ f.;
distribution, 501, 529
_Iguanodon_, 416, 417, _427_;
_I. bernissartensis_, _428_, 428;
_I. mantelli_, _427_
Ihering, on breeding habits of _Phyllomedusa_, 205 f., 206
Ikeda, on nursing habits of _Rhacophorus_, 248
_Ilysia_, _595_
Ilysiidae, _592_, _594_
Inframarginal shields, 326, 315
Intergular shields of Chelonia, 325, 315
Iris, colour of, in Chelonia, 329
_Ixalus_, 238, _241_
Jaw, lower, of _Salamandra_, 17;
of Urodela, 18;
of Anura, 30
Keller, quoted, 571 n.
_Keraterpeton_, _81_, 288;
_K. crassum_, _81_
Kidneys of Amphibia, 48 f., 49
Klinckowstroem, on _Pipa_, 149
Kollmann, on Neoteny, 64
Krait, _633_
Labial glands of _Heloderma_, 498
_Labyrinthodon_, _83_
Labyrinthodonta, _82_
_Lacerta_, _553_;
_L. agilis_, _554_;
_L. muralis_, _557_;
_L. ocellata_, _556_ f., 556;
_L. pater_, _556_;
_L. schreiberi_, _555_;
_L. tangitana_, _556_;
_L. viridis_, _555_;
skull, 550;
_L. vivipara_, _553_
Lacertae, _513_ f.
Lacertidae, _514_, _549_ f.;
skull, 550;
distribution, 552
Lacertilia, 491 f.; {660}
skeleton, 494 f.;
skin, 497;
change of colour, 498
_Lachesis gramineus_, _647_;
_L. lanceolatus_, _646_, 647
Land-tortoises, _364_ f.
Lanthanotidae, _514_, _541_ f.
_Lanthanotus borneensis_, _541_
_Laosaurus_, _427_
_Lariosaurus_, 473, 474;
_L. balsami_, _477_
Larvae, of _Ichthyophis_, 91;
of _Hypogeophis_, 92;
of _Amblystoma_, 112;
of _Triton waltli_, 131
Latreille, on classification, 7, 8
Laurenti, on classification, 7
Leathery Turtle = _Sphargis_, 333 f., 334
Lechriodonta, distribution of, 95;
defined, 102
_Lepidobatrachus_, _212_, _218_
_Lepidophyma_, _547_
Lepospondylous, defined, 79
_Leptobrachium_, _161_;
_L. carinense_, _166_
_Leptodactylus_, _212_, 218 f.;
_L. albilabris_, 219;
_L. mystacinus_, 219;
_L. ocellatus_, 219;
_L. typhonius_, 219 f.
_Leptognathus_, _624_
_Leptophis_, _618_;
_L. liocerus_, _618_, 619
Leslie, on _Xenopus_, 146
Leuckart, on classification, 8
Leydig's duct, defined, 48, 49
_Lialis burtoni_, _567_
Limbs, of Amphibia, 26, 27;
Stegocephali, 79, 83;
_Eryops_, 286;
Microsauri, 289;
Prosauri, 291;
_Sphenodon_, 298;
Theromorpha, 302;
Pareiasauri, 305;
Chelonia, 320, 319, 320;
_Sphargis_, 335;
Chelonidae, 379;
Dinosauria, 414 f., 418, 420;
_Compsognathus_, 423;
Stegosauri, 426 f.;
_Iguanodon_, 428, 428;
Eusuchia, 440;
Plesiosauria, 475, 475;
_Lariosaurus_, 477;
Ichthyosauria, 480;
Pterosauria, 485, 485;
Lacertilia, 495;
Geckones, 505;
Chameleons, 568;
reduction of, in Lacertilia, 497;
in Ophidia, 593, 594, 596
_Limnodynastes_, _213_, 222;
spawning, 223
_Limnomedusa_, _212_
Linnaeus, on classification, 7
_Liodon haumuriensis_, _490_
_Liolepis belli_, _527_
_Liopelma_, 153;
_L. hochstetteri_, _160_
_Liophryne_, 225, _227_
_Liosaurus_, _529_
Lissamphibia, _84_ f.
Lizard, Common English, _553_;
Emerald, _555_;
Eyed, _556_, 556;
Green, _555_;
Sand, _554_;
Wall, _557_
Lizards, _491_ f.
Locality, sense of, in Tortoises, 368, 387
Loggerhead Turtle, _387_;
individual varieties of shields, 327, 388
Longevity, of _Testudo daudini_, 376;
_T. graeca_, 369;
_T. ibera_, 369;
_T. sumeirei_, 377
_Loxocemus bicolor_, _598_
_Loxomma_, _83_
_Lucilia bufonivora_, fly infesting _Bufo_, 176
Lungs, definition, 40;
suppression of, 46;
of Aglossa, 144;
of Lacertilia, 499
Luth, or Leathery Turtle, 333 f., 334
_Lycosaurus_, _307_
_Lygosoma_, distribution, 501
Lymph-spaces, in the cutis of Anura, 34
_Lyriocephalus scutatus_, 517, 518
_Lytoloma_, 336, 380
_Mabuia_, _562_;
distribution, 501;
eyelids, 494;
_M. vittata_, _562_
_Macroclemmys_, 326;
_M. temmincki_, _340_ f., 340
_Macroprotodon cucullatus_, _624_
Macrorhynchidae, _451_
Madagascar, Lacertilia of, 502
_Malacoclemmys terrapin_, _359_ f.;
commercial breeding-farms, 360
Malpighian, body, 49;
stratum, 32
Mammalian affinities of Theromorpha, 303, 309
_Manculus_, 96, _103_, _106_;
_M. quadridigitatus_, _106_
Mandible, composition of, in Crocodiles, 437;
very Mammalian in _Gomphognathus_, 309
_Mantella_, 274
_Mantophryne_, 225, _227_
Maps showing geographical distribution, of Coeciliidae, 89;
Urodela, 95;
Aglossa, 143;
Cystignathidae, Discoglossidae, Pelobatidae, 161;
Bufonidae, 167;
Hylidae, 185;
Ranidae, 239;
Chelydidae, 332, 333;
Chelydridae, 332;
Cinosternidae, 332;
Dermatemydidae, 332;
Pelomedusidae, 332;
Platysternidae, 332;
Trionychidae, 333;
Crocodilia, 446;
Geckonidae, 503;
Agamidae, 515;
Anguidae, 529;
Iguanidae, 529;
Zonuridae, 529;
Varanidae, 543;
Lacertidae, 552;
Amphisbaenidae, 565;
Chamaeleontes, 568;
Snakes, dangerously poisonous, 585;
Elapinae, 626;
Crotalinae, 644;
Viperinae, 638
Marbled Newt, _126_
Marginal plates of Chelonia, 325, 322, 323
Marginal shields, 326
Marsh, on Axolotl, 115
Marsh Crocodile, _455_
Marshall, on distribution of Uropeltidae, 595
Mascarene Islands, tortoises of, 373 f.
Mason, on habits of _Calotes_, 519;
on Python legends, 599;
on _Varanus_, 544
_Mastodonsaurus_, _83_
Matamata = _Chelys fimbriata_, _400_, 401
Mauritius, gigantic tortoises, 373 f., 376
Mecodonta, distribution of, 95; {661}
defined, 102
_Megalixalus_, 238, _240_
_Megalophrys_, _161_;
tadpole, 60
_Megalosaurus_, 416;
_M. bucklandi_, _421_
_Megalotriton_, _83_
_Melanerpeton_, _81_, _289_
_Melanobatrachus_, 226, _228_
_Melosaurus_, 287
_Menobranchus lateralis_, _132_
_Menopoma_, _97_
Mento-Meckelian cartilages, 30
Meroblastic eggs; part of the egg only undergoes the process of cleavage,
53
Merrem, on classification, 8
Mesosauridae, _476_
_Mesosaurus_, _476_;
_M. tenuidens_, _476_
Metamorphosis of Tadpoles, 56 f.
Metasternum of Anura, 26, 25;
taxonomic value, 141;
definition, 26
Metatarsalia of Theropoda, 420
_Metopias_, _83_
_Metopoceros cornutus_, _532_
_Metriorhynchidae_, _451_
_Metriorhynchus_, atlas and axis, 283, 431, _451_
Metzdorff, on Axolotl, 113
_Micrixalus_, _241_
_Microgomphodon_, _308_, 309
_Microhyla_, _228_
Microsauri, _288_
Midwife-toad, 158
_Mimosa_ (plant), 629
_Miolania_, 390
_Mixophyes_, _213_;
spawning, 213
_Mixosaurus_, limbs, 480, 481, _483_
_Molge_–see _Triton_, _122_
_Moloch horridus_, _527_, 527
Mongoos and Cobra, 629
Monitor, _543_
_Morosaurus grandis_, _419_;
pelvis, 419
Mosasauri, _489_ f.
_Mosasaurus_, _489_;
_M. camperi_, _490_
Moult of Geckos, 510;
of Chameleons, 571;
of Snakes, 583
Mud-diver, _165_
Mud-turtle, 342
Mugger, _454_
Müller, J., on classification, 8
Müllerian duct, 49, 51
Musical appreciation of Tortoises, 368
_Myobatrachus_, 166, 167, _168_;
_M. gouldi_, _184_, 227, _236_
_Mystriosaurus_, 432, _451_
Nails or claws of Amphibia, 32
_Naja_, _626_;
_N. bungarus_ s. _elaps_, _632_;
_N. haje_, 628, _632_;
_N. tripudians_, _627_, 627
_Nannobatrachus_, 238, _240_
_Naosaurus claviger_, _308_
Natterjack, _181_
_Naultinus elegans_, 506
Neck, mode of withdrawing in Chelonia, 328 f.
_Nectes_, 166, _168_;
_N. subasper_, _169_
_Nectophryne_, 166, _168_;
_N. afra_, _169_;
_N. tuberculosa_, _169_;
_N. guentheri_, _169_;
_N. hosei_, _169_;
_N. misera_, _169_
_Necturus_, pelvis, 15, 96, _132_;
_N. maculatus_, _132_
Neoteny, 63 f.;
defined, 64
Nephrostomes, 48, 49
_Nephrurus asper_, tail, 506
Nerves, spinal, of Amphibia, 38;
cranial, 39
Nest, of _Crocodilus_, 463;
of _Gavialis_, 452
Neural plates, of Chelonia, 323 f., 322, 323;
suppression of plates, 324;
in Pleurodira, 389;
of _Dermatemys_, 342
_Neusticosaurus_, _477_
Newt, Common, _127_;
Crested, 125, 125;
Marbled, _126_;
Spotted, _127_
Newton, E. T., on fossil Reptiles, 303 n.
Nile Crocodile, 461
_Nodosaurus_, _430_
Nose-horned Viper, _640_
_Notaden_, 166, 169;
_N. bennetti_, _167_
_Notechis scutatus_, _634_
Nothosauri, _476_ f.
Nothosauridae, _477_
_Nothosaurus_, 474;
_N. mirabilis_, _477_
Notocentrous vertebrae, defined, 19
Notochord = Chorda dorsalis, _q.v._
_Nototrema_, _189_;
_N. cornutum_, _203_;
_N. marsupiatum_, _202_;
_N. oviferum_, _202_;
peculiar gills of embryos, 203;
_N. pygmaeum_, _202_;
_N. testudineum_, _202_
Nuchal plate of Chelonia, 323 f.;
of Pleurodira, 389
Nuchal shield of Chelonia, 326, 327;
of Pleurodira, 389, 399
Nuptial excrescences of Anura, 33
Nursing, habits, of _Arthroleptis seychellensis_, 243;
of _Chiromantis rufescens_, 244;
of _Rhacophorus_, 248;
of _Rhinoderma_, 228 f.;
of _Pipa_, 151;
of _Hyla faber_, 196 f.;
of _H. nebulosa_, 198;
of _H. goeldii_, 198;
of _Nototrema_, 203;
of _Phyllomedusa_, 204 f.;
of _Leptodactylus_, 219 f.;
of eggs by _Desmognathus_, 103, 103;
by _Autodax_, 108
_Nyctibatrachus_, _240_
_Nyctimantis rugiceps_, _189_, _206_
_Nyctixalus_, 238
Occipital condyle, of Reptilia, 278;
exaggerated importance of, 285;
of Theromorpha, 302;
of Pareiasauri, 305;
of _Cynognathus_, 307;
of _Crateronotus_, 307;
of _Dicynodon_, 310;
of Eusuchia, 437;
of Amphisbaenidae, 496
Odontaglossa, 140
_Oligodon_, dentition, 593 n.
_Omosaurus_ = _Stegosaurus_, _425_ {662}
Omosternum of Anura, 25;
taxonomic value, 141
_Onychodactylus_, 96;
_O. japonicus_, _109_
Operculum of gills, 44
_Ophiderpeton_, _81_
Ophidia, 491, _581_ f.
_Ophiophagus_, _632_
_Ophiops_, 551
_Ophioxylon_ (plant), 629
_Ophisaurus_, _538_;
_O. apus_, _538_;
_O. gracilis_, _538_
_Ophthalmosaurus_, limbs, 481, 481, 484
Opisthocoelous, definition, 12
Opisthoglossa, 140
Opisthoglypha, _592_, _606_ f., _623_ f.
Oppel, on classification, 7
_Oreobatrachus_, _241_
_Oreophrynella_, _227_
_Ornithocheirus_, _486_
_Ornithomimus_, 417;
_O. grandis_, _429_
Ornithopoda, 425, _426_
_Ornithopsis_, _419_
Ornithoscelida, 416
_Ornithosuchus_, _433_
_Orthocosta_, 288, _289_
Orthopoda, _424_
Ossifications, dermal, in Anura, 31, 34, 179, 190, 210, 211
Osteoderms = ossifications in the skin, of _Sphargis_, 337;
of _Caiman_, 337;
of Lizards, 504, 513, 514
_Osteolaemus_, _450_;
_O. tetraspis_, _466_
Ouaran, _543_
_Oudenodon_, 301;
_O. rugosus_, _310_
Ovary, 49
Oviduct, 49, 51
Owen, on fossil Reptiles, 303 n.
Oxydactyla, 140
_Oxyglossus_, 239, _241_
_Pachytriton_, 96, _115_;
_P. brevipes_, _132_
Painted Terrapin, _347_, 348;
rate of growth, 349
_Palaeobatrachus_, vertebral column, 22, 145
_Palaeohatteria longicaudata_, _291_;
skull, 280, 304
_Paludicola_, resembles _Engystomops_, 166, _212_, _220_;
_P. fuscomaculata_, 220;
_P. biligonigera_, 221
_Paludina_, as food of _Trionyx_, 407
Parasternum = the sum total of the Abdominal ribs, _q.v._;
of _Sphenodon_, 298;
of Crocodilia, 440;
of Ichthyosauria, 480
Parasuchia, _433_
Pareiasauri, 301, 302, _304_
_Pareiasaurus baini_, _304_
Parrots, feathers dyed with poison of _Dendrobates_, 272
_Pelobates_, variation of vertebrae, 19;
sacral vertebra, 22, _161_ f.;
_P. fuscus_, _162_;
_P. cultripes_, _163_, 164;
_P. syriacus_, _164_
Pelobatidae, _139_, _160_ f.;
distribution, 161
_Pelodytes_, _161_, _165_;
_P. punctatus_, _165_;
_P. caucasicus_, _166_
_Pelomedusa galeata_, _391_
Pelomedusidae, _313_, _314_;
distribution, 332, _390_ f.
_Pelosaurus_, _81_
Pelvic, plexus of Anura, 39
Pelvis, of Urodela, 15;
of Anura, 22, 27;
of _Eryops_, 286;
of Microsauri, 289;
of _Sphenodon_, 298;
of Theromorpha, 302;
of Pareiasauri, 305;
of _Cynognathus_, 307;
of _Dicynodon_, 310;
of Chelonia, 319, 319, 320;
of Pleurodira, 388, 389;
of Dinosauria, 414;
of Eusuchia, 441;
of Plesiosauria, 476;
of Ichthyosauria, 480;
of Pterosauria, 485;
of Pythonomorpha, 489;
of Lacertilia, 496
Perennibranchiata, 8, 9;
not a natural group, 65
Petrels living with _Sphenodon_, 299
_Petrobates_, 288, _289_
Phalanges, number of, in Urodela, 15;
in Anura, 26, 27, 238;
in Stegocephali, 79;
in _Palaeohatteria_, 291;
in Chelonia, 320, 321;
in _Chelone_, 379;
in _Scelidosaurus_, 425;
in _Camptosaurus_, 427;
in _Laosaurus_, 427;
in _Iguanodon_, 428;
in Eusuchia, 441;
in Plesiosauria, 475;
in _Lariosaurus_, 477;
in Ichthyosauria, 481, 481;
in Pterosauria, 485, 485;
shape in Anura, 138;
peculiar in _Pipa_, 151
Phaneroglossa, _152_
Phanéroglosses, 139
_Phanerotis_, _213_
Phisalix, on poison of Amphibia, 37
_Pholidosaurus_, _451_
Phractamphibia, _78_ f.
Phrynaglosses, 139
_Phrynella_, _227_;
_Ph. pollicaris_, 233
_Phryniscus_, 226, _227_, _230_;
_Ph. nigricans_, _230_
_Phrynobatrachus_, _241_
_Phrynocara_, 235, _236_
_Phrynocephalus_, _521_;
deserticolous, 493;
coloration, 494;
_Ph. helioscopus_, _522_;
_Ph. interscapularis_, _522_;
_Ph. mystaceus_, _522_
_Phrynoderma_, _241_
_Phrynomantis_, 226, _228_
_Phrynopsis_, _241_
_Phrynosoma_, 305, _533_;
_Ph. coronatum_, _534_, 535;
_Ph. cornutum_, _533_, 534
_Phyllobates_, _242_;
_Ph. bicolor_, _242_;
_Ph. trinitatis_, _242_
_Phyllodactylus_, _507_;
_Ph. europaeus_, _507_
_Phyllodramus_, 238, _242_
_Phyllomedusa_, _189_, _203_ f.;
_Ph. bicolor_, _203_;
_Ph. dacnicolor_, _203_;
_Ph. hypochondrialis_, breeding habits and development, _204_; {663}
_Ph. iheringi_, _205_;
breeding habits, 206
Phylogeny, of Amphibia, 66;
of Anura, 142 f.;
of Reptilia, 282;
of Lacertilia, 515;
of Ophidia, 592
_Physignathus lesueuri_, _523_, 524
Pigment in the skin, 34
_Pipa_, 143, 144, _149_ f., 150
Pit-Vipers, _644_
Placodontia, _311_
_Placodus_, 301;
_P. gigas_, _311_
Plastron, of Chelonia, 315, 321, 321;
provided with hinges, 323;
sexual characters of, 331;
movable in _Emys_, 350;
of Chelonidae, 321, 321, 322, 380;
of Pelomedusidae, 390;
of Chelydidae, 399;
of Trionychoidea, 406
_Platecarpus_, _490_
_Platemys_, suppression of neural plates, 324;
skull, 399
Plathander = _Xenopus_, _146_ f.
_Platurus fasciatus_ s. _colubrinus_, _637_
Platydactyla, 140
_Platydactylus facetanus_, _509_, 508
_Platyhyla_, _236_
_Platypelis_, 235, _236_
Platysternidae, _314_, 326, _345_
_Platysternum megacephalum_, _345_
_Plectromantis_, _212_
_Plesiochelys_, 380, 389
Plesiosauri, _477_ f.
Plesiosauria, _473_ f.;
vertebrae, 474
Plesiosauridae, _478_
_Plesiosaurus_, 475, _478_;
_P. conybeari_, _478_;
_P. dolichodirus_, _478_
_Plethodon_, 94, 96, _104_, _106_;
_P. erythronotus_, _107_;
_P. glutinosus_, _106_
Plethodontinae, 102, _103_
_Plethodontohyla_, 235, _236_
Pleurodira, _313_, _388_ f.
_Pleurosaurus_, _294_
_Pleurosternum_, 390
_Plioplatecarpus_, _489_
Pliosauridae, _477_
_Pliosaurus grandis_, _477_
Plover, Egyptian, and Crocodile, 462
_Podocnemis_, 390, _391_;
_P. expansa_, _391_ f.;
Bates, on habits of, 392 f.
Poikilothermous, defined, 67
Poison, of Amphibia, 37, 38;
peculiar use of, 272
Poison-apparatus, of _Heloderma_, 540;
of Snakes, 586 f.
_Polacanthus_, _425_
_Polychrus marmoratus_, _529_
_Polyodontophis_, _605_ n.
Portschinsky, on parasitic flies, 177 n.
Postpubis, of Dinosaurs, 414, 424, 426
Pouchet, quoted, 571
Predentary bone, of Dinosaur, 424
Prehallux, of Anura, 28
Prepubis, of Dinosaurs, 414, 424, 426
_Proganochelys_, 389
Proganosauria, 476
Proreptilia, _285_
Prosauri, _290_
Prosauria, _288_
_Prostherapis_, _242_
Protection of Amphibia by poison, 38
Proteidae, 94, 96, _132_ f.
Proteroglossa, 140
Proteroglypha, _625_
_Proteus_, 96;
_P. anguinus_, _133_, 134
Protorosauri, _290_, 304
_Protorosaurus lincki_, _291_
_Protosphargis_, 336
_Protostega_, 336
_Protriton_, _80_, 81
_Psammodromus hispanicus_, _558_;
_P. algirus_, _558_
_Psammosaurus_, _543_
_Psephoderma_, 337
_Psephophorus_, 336, 337
_Pseudechis porphyriaceus_, _634_
_Pseudis_, _212_, _213_;
_P. paradoxa_, _213_ f.
_Pseudobranchus_, 96;
_P. striatus_, 137
Pseudocentrous, defined, 79
_Pseudophryne_, 166, _167_, _168_;
spawning, 223;
_P. australis_, _168_;
_P. bibroni_, _168_
_Pseudopus_, aberrant scaling, 495;
_P. pallasi_, _538_
_Pseudosphargis_, 336
_Pseudosuchia_, _432_
_Ptenopus_, _507_;
deserticolous, 494
_Pteranodon longiceps_, _487_
Pteranodontes, _487_
_Pternohyla_, 179, _189_;
_P. fodiens_, _207_
Pterodactyli, _486_
_Pterodactylus longirostris_, _487_;
_P. spectabilis_, _487_
Pterosauri, _486_
Pterosauria, _484_ f.
_Ptyas_ = _Zamenis_, _611_
_Ptychozoon_, tail, 506;
_P. homalocephalum_, _512_, 512;
adhesive apparatus, 505
Pubis, of Dinosaurs, 414, 424, 426
Puff Adder, _639_, 639
Pygopodidae, _514_, _567_
_Pygopus lepidopus_, _567_
_Python_, _598_;
_P. molurus_, _600_, 600;
_P. regius_ = _P. sebae_, _601_;
_P. reticulatus_, _598_;
_P. spilotes_, _598_, 599
Pythoninae, _598_ f.
Pythonomorpha, _487_ f.
_Pyxis arachnoides_, _365_
Radde's "law of the steppe," 493
_Rana_, _241_, _249_ f.;
sacral vertebrae, 22;
shoulder-girdle, 25;
urino-genital organs, 49;
Tadpoles' horny teeth, 58;
vocal sacs, 250;
nuptial excrescences, 250;
large glandular complexes, 250;
distribution, 251;
species with finger-discs, 250;
_R. afghana_, 250; {664}
_R. agilis_, _257_;
_R. albolabris_, 250;
_R. alticola_, 250;
_R. arvalis_, _257_;
_R. catesbiana_, _261_;
_R. chalconota_, 250;
_R. chloronota_, 250;
_R. clamata_, _262_, 263;
_R. corrugata_, 250;
_R. curtipes_, 250;
_R. cyanophlyctis_, 250;
_R. elegans_, 250;
_R. erythraea_, _250_;
_R. esculenta_, _263_;
mechanism of tongue, 268;
vocal sacs, 269;
var. _chinensis_, _267_;
var. _lessonae_, _265_;
var. _ridibunda_, _264_;
var. _typica_, _265_;
_R. fontinalis_, _262_;
_R. glandulosa_, 250;
_R. gracilis_, _261_;
_R. graeca_, _259_;
_R. guppyi_, _261_;
_R. halecina_, _263_;
_R. hexadactyla_, 250;
_R. iberica_, _258_;
_R. latastei_, _259_;
_R. liebigi_, 250;
_R. mascareniensis_, 250;
_R. montezumae_, 250;
_R. mugiens_, _261_;
_R. opisthodon_, _260_;
_R. oxyrhynchus_, 250;
_R. rugosa_, 250;
_R. silvatica_, _259_;
_R. temporalis_, 250;
_R. temporaria_, _251_ f., 255;
_R. tigrina_, _261_
Ranidae, _139_, _237_ f.
_Ranidens_, 96;
_R. sibiricus_, _109_
Raniformes, 139, 140
Raninae, _139_, _237_, _238_ f.;
distribution, 239
_Rappia_, _241_
Rat Snake, _611_, 612
Rattle of Rattle-Snake, 644
Rattle-Snake, _648_ f., 648, 650
Reduction of limbs, in Urodela, 16;
in Lacertilia, 497
Regeneration, in Amphibia, 66 f.;
of tail in _Sphenodon_, 298;
of shell in Chelonia, 329;
of horny shields in Chelonia, 329, 386;
of tail in Lacertilia, 495;
of tail in Geckos, 506
Regions, geographical, 74 f.
Reproduction of Tortoise-shell, 386
Reptilia, defined, 277;
principal characters of, 278;
classification of, 279;
diagram of affinities of principal groups, 282;
affinities to Mammalia, 303, 309
Respiration, mode of, in Chelonia, 331;
assisted by anal sacs, 330
Respiratory organs, of Amphibia, 40
Rhachiodontinae, _622_
_Rhacophorus_, 151, 186, 238, _241_, 244, 246;
_Rh. leucomystax_, _247_;
tadpoles, 249;
_Rh. maculatus_, nesting, 248;
_Rh. madagascariensis_, _245_;
_Rh. maximus_, _245_;
_Rh. pardalis_, _246_, 246;
_Rh. reinwardti_, _247_;
_Rh. reticulatus_, _248_;
_Rh. schlegeli_, nesting, 248
_Rhampholeon spectrum_, _580_
_Rhamphorhynchus longicaudatus_, 486;
_Rh. phyllurus_, _486_;
_Rh. muensteri_, 487
_Rhamphosuchus crassidens_, _453_
_Rhinatrema_, _89_
_Rhinemys_, 389, 399
_Rhinochelys_, 390
_Rhinoderma_, 226, _227_, _228_;
_Rh. darwini_, _228_ f.
_Rhinophis_, 91;
_Rh. sanguineus_, _596_
_Rhinophrynus_, 166, _168_;
_Rh. dorsalis_, _185_, 227
_Rhinophrys_, 167
_Rhombophryne_, 225, _227_
Rhynchocephali, _292_
_Rhynchosaurus_, _292_
_Rhytidosteus_, _83_
Ribs, of Urodela, 14;
of Anura, 21;
of Microsauri, 288;
of _Sphenodon_, 297;
of Theromorpha, 302;
of _Cynognathus_, 307;
of _Microgomphodon_, 309;
of Chelonia, 315, 320, 324;
of Dinosauria, 413;
of Crocodilia, 438;
of Parasuchia, 434;
of Eusuchia, 439;
of Lacertilia, 495;
of Geckones, 504;
much elongated in certain Iguanidae, 529;
meeting ventrally in Chameleons, 568
Ridewood, on hyoid apparatus of Anura, 31
Ringhals, _632_, 633
Ritter and Miller, on _Autodax_, 107
Robinson, on peculiar use of _Varanus_, 546
Rodriguez, gigantic tortoises, 374
Rostral bone of Ceratopsia, 430
Round Island snake, 603
Sacral vertebrae of Anura, 21, 22
_Salamandra_, _115_ f.;
trunk-vertebra, 14;
skull, 17;
lower jaw, 17;
distribution, 96, _115_ f.;
_S. atra_, _119_ f.;
_S. caucasica_, _121_;
_S. maculosa_, _115_ f.
_Salamandrella_, 96, _109_;
_S. keyserlingi_, _109_;
_S. schrenki_, egg-sac, 110
Salamandridae, _94_, _102_
_Salamandrina_, 96, _115_;
_S. perspicillata_, _122_;
skull, 17
Salamandrinae, _102_, _115_
Sarasin, P. and F., 10;
on Coeciliae, 88;
on _Ichthyophis_, 90
Sauria, _491_ f.
_Saurichnites salamandroides_, _83_
Sauropoda, _418_
Sauropsida, 5, _277_
Sauropterygia, 476
_Saurosternum_, _291_
Scales of Apoda, 87
Scaling, aberrant, 495
_Scaphiophryne_, 225, 226, _227_
_Scaphiopus_, _161_, _164_;
_S. solitarius_, _165_
_Scapteira_, deserticolous, 494
Scapula, attached to thoracic vertebrae, 487
_Scelidosaurus_, 416;
_S. harrisoni_, _425_
Scheuchzer, on _Homo diluvii testis_, 84
Schlegel, on _Cryptobranchus_, 100
Schuberg, on mechanism of finger-discs of Hylidae, 187
Schwalbe, on _Salamandra atra_, 120
Scincidae, _514_, _559_ f.
_Scincus officinalis_, _561_ {665}
_Sciurus bicolor_, squirrel, 248
_Scolecomorphus_, _90_
Sea Snakes, _635_
Seeley, on fossil Reptiles, 303 n.
_Seeleya_, _81_, _289_
Segmental duct, 49
Sense-organs, of Chelonia, 329 f.;
of Crocodiles, 445 f.
_Sepedon haemachates_, _632_, 633
_Seps_, _562_
Seychelles, gigantic tortoises of, 373
Shell of Chelonia, 321 f., 319, 320, 321, 322, 323, 327;
partial regeneration of, 329;
correlated changes, 328
Shields, horny, of Chelonia, 322, 323, 325 f., 327;
evolution of, 326 f.;
individual variation in, 326, 327;
periodical peeling of, 328
Shoulder-girdle, of Urodela, 14;
of Anura, 24, 25, 138 f.;
arciferous, 24, 25, 138;
firmisternal, 24, 25, 138;
of Aglossa, 144;
of Microsauri, 289;
of Protorosauri, 290;
of Theromorpha, 302;
of Pareiasauri, 305;
of _Dicynodon_, 310;
of Chelonia, 318, 319, 320;
of Dinosauria, 414;
of Eusuchia, 440;
of Plesiosauria, 474;
of _Cryptoclidus_, 475;
of Ichthyosauria, 480, 481;
of Pterosauria, 485;
of _Pteranodon_, 487;
of Pythonomorpha, 488;
of Lacertilia, 496
Shufeldt, on Axolotl, 114;
on _Heloderma_, 540 n.
_Simosaurus_, _477_
_Siphonops_, 86, 87, _90_
_Siredon_ (Axolotl), 112
_Siren_, 96;
_S. lacertina_, 136, 136
Sirenidae, _94_, 96, _136_
_Sistrurus miliarius_, _647_
Skeleton, figured, of _Testudo_, 319;
of _Chelone_, 320;
of _Brontosaurus_, 418;
of _Ceratosaurus_, 422;
of _Stegosaurus_, 426;
of _Iguanodon_, 428;
of _Triceratops_, 430;
of _Pterodactylus_, 485
Skin, of larval Amphibia, 31;
shedding of, 32;
glands, 32;
pigment, 34;
change of colour, 35;
poison, 36;
of Apoda, 87;
of _Pipa_, 149;
forms receptacles for eggs, 151, 248;
of Eusuchia, 441 f.
Skin-glands, of Crocodiles, 443;
of Lacertilia, 497;
of Geckones, 504;
of Snakes, 583
Skull, of Urodela, 16 f., 17;
of _Amblystoma_, 17;
of _Salamandrina_, 17;
of _Salamandra_, 17;
of Anura, 28 f.;
of Apoda, 84, 85
Skull, of Reptilia, 280, 281:
–of Proreptilia: _Cricotus_, 287;
_Eryops_, 286:
–of Microsauri, 289:
–of Protorosauri, 280;
_Palaeohatteria_, 280, 291:
–of Rhynchocephali (_Sphenodon_), 280, 295, 295:
–of Theromorpha, 280, 301, 303;
_Elginia_, 280, 305 f.;
_Cynognathus_, 280, 306;
_Gordonia_, 280, 310;
_Dicynodon_, 280, 310;
Theriodontia, 306;
Mammalian resemblances, 308 f.;
_Lycosaurus_ 307;
_Endothiodon_, 307;
_Gomphognathus_, 308;
Anomodontia, 309, 280;
_Oudenodon_, 310;
_Placodus_, 311:
–of Mammalia, generalised, 281:
–of Chelonia, 316 f., 280;
_Sphargis_, 335;
Chelydridae, 280, 338;
_Chelydra_, 280, 338;
Chelonidae, 317, 378, 379;
_Chelone_, 317, 378;
_Thalassochelys_, 379;
_Clemmys_, 356;
_Testudo_, 364;
_Chelys_, 400, 344;
_Trionyx_, 405, 404;
_Chrysemys_, 280, 346;
_Cistudo_, 280, 361;
Pleurodira, 388, 400;
Pelomedusidae, 390;
Chelydidae, 399, 400;
Trionychoidea, 404, 405:
–of Dinosauria, 412 f., 422;
_Anchisaurus_, 421;
_Ceratosaurus_, 422;
_Diplodocus_, 419:
–of Crocodilia, 280;
Pseudosuchia, 432;
Parasuchia, 433;
Eusuchia, 434 f.;
_Gavialis_, 452;
_Crocodilus americanus_, 466;
_C. niloticus_, 460;
_C. palustris_, 455;
_C. porosus_, 458;
_Alligator_, 468:
–of Plesiosauria, 473;
_Nothosaurus_, 477:
–of Ichthyosauria, 479;
_Ichthyosaurus_, 281:
–of Pterosauria, 484;
_Dimorphodon_, 281:
–of Pythonomorpha, 488;
_Clidastes_, 281:
–of Lacertilia, 281;
Geckones, 504;
Agamidae, 281, 515;
_Uromastix_, 281;
Iguanidae, 528;
Anguidae, 537;
Helodermatidae, 540;
Varanidae, 281, 542, 543;
_Varanus_, 281;
Tejidae, 547;
Lacertidae, 281, 550, 550;
_Lacerta_, 281;
Scincidae, 559;
Amphisbaenidae, 565;
Chamaeleontes, 568, 569:
–of Ophidia, 281, 596, 597, 588;
_Eunectes_, 596, 597;
_Crotalus_, 588
Slow-worm, _539_, 539
Slugs eaten by tortoises, 363
Smell, sense of, of Chelonia, 330
Smith, the, = _Hyla faber_, peculiar nursing habits, 196 f.
Smooth Snake, _619_, 620
Snakes, _581_ f.;
skull, 581 f., 281, 588, 596, 597 f.;
vertebrae, 582;
general anatomical structure, 583 f.;
geographical distribution, 585 f., 585;
classification, 592 f.
Snake-charming, 631
Snake-poison, 586 f.
Snake-stones, 629 f.
Snapping Turtle, _338_ f.
Soft-shelled Turtle, 408
Sound produced by rubbing of scales of _Teratoscincus_, 507
Spade-foot, _162_
_Spelerpes_, 94, 96, 97, _103_, _104_, 106;
_S. altamazonicus_, _104_;
_S. bilineatus_, _104_;
_S. fuscus_, _104_, _105_;
tongue, 106;
_S. infuscatus_, _104_;
_S. lineolus_, _104_;
_S. parvipes_, _104_; {666}
_S. porphyriticus_, _105_;
_S. salmoneus_, _105_;
_S. subpalmatus_, _104_;
_S. uniformis_, _104_
Spencer, on habits of _Chiroleptes_, 221 f.
Spermatophores, 53, 128
Spermatozoa of Amphibia, 52 f.
Sphargidae, _313_, _314_, _333_ f.;
affinities, 336;
morphology of shell, 337
_Sphargis coriacea_, _333_ f., 334;
absence of horny shields, 325
_Sphenodon_, 288, 290, 305, 306, 432;
_S. punctatum_, 293, _294_;
skull, 295;
cervical vertebrae, 297;
habits, 298 f.
_Sphenophryne_, 225, _227_
_Sphenosaurus_, _82_, 287
Spiny-tailed Lizard, _524_ f.
Spiracle, development, 45
Spotted Newt, _127_
Spy-Slange, _632_
St. Helena, gigantic tortoises introduced, 375
_Stagonolepis_, _434_
Stannius, 8, 139;
on vertebrae of _Pelobates_, 20
_Staurotypus salvini_, _342_
Stegocephali, 78 f.;
St. Lepospondyli, _80_ f.;
St. Temnospondyli, _81_ f.;
St. Stereospondyli, _83_ f.;
vertebrae, 78 f.;
shoulder-girdle, 79;
dermal armour, 79
Stegosauri, _425_
_Stegosaurus armatus_, _425_;
_S. ungulatus_, _426_, 426
_Stenodactylus_, deserticolous, 494;
sleeping attitude, 509
_Stereocyclops_, _227_, _231_;
_S. incrassatus_, _231_
_Stereorhachis_, _308_
Stereospondylous vertebrae, defined, 284
_Sternothaerus_, 324, 389, _390_;
_S. derbianus_, _391_;
shields of, 327
Sternum, of Urodela, 15;
of Anura, 25;
taxonomic value, 141, 142;
of _Sphenodon_, 297 f.;
Protorosauri, 290;
Dinosauria, 414;
Eusuchia, 440
Stewart, quoted, on _Heloderma_, 540 n.
Stinkpot Terrapin, 342
Suboccipital (first spinal nerve) of Anura, 144
Subregions, geographical, 74 f.
Surinam Toad, 149, 150
_Syrrhopus_, 212
Systomata, 139
Tadpoles, horny teeth of, 58 f.;
of _Megalophrys_, 59, 60;
absorption of tail, 61 f.;
of _Xenopus_, 147, 148;
of _Bombinator_, 157;
of _Alytes_, 159;
of _Hyla arborea_, 193;
of _H. versicolor_, 195;
of _Bufo viridis_, 181;
of _B. calamita_, 183;
of _B. vulgaris_, 176;
of _Thoropa miliaris_, 209;
of _Pseudis paradoxa_, 213;
of _Hylodes martinicensis_, 214;
of _Rhinoderma darwini_, 229;
of _Arthroleptis seychellensis_, 243;
of _Rana temporaria_, 255;
of _R. opisthodon_, 260;
of _R. esculenta_, 270
Tail, of Anura, 21, 24;
its absorption, 61;
of Chelonia, 328;
of Geckos, various shapes, 506;
reproduction of, 506
_Tarentola mauritanica_, 508, _509_ f.
Tarsus (_see_ also Limbs), of Chelonia, 319, 320, 321;
of Dinosauria, 416, 418, 420, 421, 423, 426;
of Theropoda, 420;
of _Compsognathus_, 423;
of _Iguanodon_, 428
Teeth, of Anura, 30, 138, 139;
substitutes for, 30, 58, 218, 237;
of Apoda, 86;
of _Rhynchosaurus_, 292;
of _Homoeosaurus_, 292;
of Rhynchocephali, 292;
of _Sphenodon_, 296;
of Theromorpha, 301;
of _Elginia_, 306, 280;
of _Cynognathus_, 306, 280;
of _Lycosaurus_, 307;
of _Galesaurus_, 307;
of _Endothiodon_, 307;
of _Empedias_, 308;
of _Stereorhachis_, 308;
of _Gomphognathus_, 308;
of _Tritylodon_, 309;
Mammalian resemblances, 309;
of Anomodontia, 309;
of _Dicynodon_, 280, 310;
of _Gordonia_, 280;
of _Placodus_, 311;
of Sauropoda, 418 f., 419;
of Theropoda, 420 f., 422;
of Orthopoda, 424 f.;
of Eusuchia, 437;
of Ichthyosauri, 479;
of Snakes, 582
Tejidae, _514_, _547_ f.
Teju, _548_, 548
Teleosauridae, _450_
_Teleosaurus_, _451_
_Telerpeton elginense_, _291_
Temnospondylous vertebrae, defined, 284
Temperature of blood, 67 f.;
of water for Crocodiles, 460
Tennent, on immunity of Cobras, 629 f.;
on turtles at Ceylon, 384, 386;
on habits of _Crocodilus palustris_, _456_ f.;
on habits of _C. porosus_, 459;
on peculiar use of _Varanus_, 545;
on habits of Gecko, 511
Tentacular apparatus of Apoda, 45, 86, 88
_Tephrometopon_, 493
_Teratoscincus_, deserticolous, 493;
eye, 494;
_T. scincus_, _507_
Terrapin, _359_ f.
Testis, 49
Testudinidae, _313_, _314_, _345_;
distribution, 332
_Testudo_, 365;
skeleton, 322, 323;
shields of, 327;
_T. abingdoni_, 376, _378_;
_T. atlas_, 372, 377;
_T. daudini_, _375_, 376;
_T. elegans_, _370_ f.;
_T. elephantina_, _374_;
_T. elephantopus_, _378_;
_T. ephippium_, _378_;
_T. gigantea_, _374_;
_T. graeca_, _365_ f.;
habits, 367;
eggs, 369;
great age, 369;
_T. grandidieri_, 373;
_T. horsfieldi_, _370_;
_T. ibera_, _366_;
age attained, 369;
rate of growth, 370;
_T. marginata_, _367_;
_T. perpigniana_, 372;
_T. polyphemus_, _371_ f.; {667}
_T. sumeirei_, _376_;
_T. vosmaeri_, 373, 377
_Tetradactylus_, _559_;
_T. africanus_, _559_;
_T. seps_, 559
Tetrapoda, Credner's name for "four-footed" creatures in opposition to
the fishes, which have fins, 4, 11
Thalassemydidae, 380
_Thalassochelys caretta_, individual variation of shields, 326, 327,
_387_;
skull, 379
Thecophora, definition of term, 337, _338_
Theobald, on _Varanus_, 544
Theriodontia, _306_
Theromorpha, _300_, 301;
skull, 280, 301;
their affinity to Mammals, 303 f., 309
Theropoda, _420_
Thilenius, quoted, 571 n.
_Thoracosaurus_, _451_
_Thorius_, 96, _103_;
_Th. pennatulus_, _103_
_Thoropa_, 186, _189_;
_Th. miliaris_, _209_
Tiger Snake, _634_
_Tiliqua_ s. _Cyclodus_, _561_
Toad, _see_ Bufo, 169;
common Toad, 170, 172
Toes, number of, in Urodela, 16;
in Anura, 28;
of Geckos, structure, 505, 505
_Tomistoma_, 435, _450_;
_T. schlegeli_, _453_
Tongue, of Amphibia, nerve-supply, 39;
shape of, in Anura, 47;
of _Spelerpes_, 106;
absent in Aglossa, 145;
of _Rana esculenta_, 268;
of Crocodiles, 443;
of Lacertilia, 498;
of Chameleons, 569 f.
Tortoise, Greek, _365_ f.;
habits, 367 f.;
Moroccan, _366_;
habits, 367 f.;
Starred, _370_ f.;
Gopher, 371 f.;
Gigantic Land-Tortoises, 372 f.
Tortoises = Chelonia, _312_ f.
Tortoise-shell of commerce, 386
Trachea, of Crocodiles, 443
_Trachysaurus_, 560, _560_;
_T. rugosus_, _560_, 561
Tree-frogs, 185 f.;
change of colour, 35
_Trematosaurus_, 80, _83_
_Triceratops_, 413;
_T. prorsus_, _430_, 430;
_T. flabellatus_, _430_
_Trichobatrachus_, _240_;
_T. robustus_, _271_
_Trigonocephalus cenchris_, _645_, 645, _646_, 646
_Trimerorhachis_, _82_
Trionychidae, _313_;
distribution, 333
Trionychoidea, _313_, _314_, _404_ f.;
habits, 407
_Trionyx_, nuchal plate, 324;
skull, 405;
plastron, 406;
number of costal plates, 325;
_T. ferox_, _408_, 409;
_T. formosa_, _411_, 411;
_T. gangeticus_, _410_, 410;
_T. hurum_, 410;
_T. triunguis_, _410_
_Triprion_, 179, 185, _189_;
_T. petasatus_, _207_
_Trirhachiodon_, _309_
_Triton_, _122_ f., 96, _115_, 125, 128, 131;
fossil, 83;
spermatophores, 53;
_T. alpestris_, 123, _126_;
_T. asper_, 123, _130_;
_T. blasii_, _126_;
_T. boscai_, 123, _127_;
_T. cristatus_, 122, _125_, 125;
_T. hagenmuelleri_, 123;
_T. helveticus_, _127_;
_T. italicus_, _127_;
_T. marmoratus_, 122, _126_;
_T. montadoni_, _127_;
_T. montanus_, 123, _130_;
_T. palmatus_, _127_;
_T. poireti_, 123;
_T. punctatus_ = _vulgaris_, _127_;
_T. pyrenaeus_, _130_;
_T. pyrrhogaster_, 123, _128_;
_T. rusconii_, 123, _130_;
_T. sinensis_, 123, _128_;
_T. taeniatus_ = _vulgaris_, _127_;
_T. torosus_, 123, _128_;
_T. viridescens_, 123, _128_;
egg, 128;
_T. vittatus_, 122, _128_;
_T. vulgaris_, 123, _127_;
_T. waltli_, 123, _130_, 131
_Tritylodon_, 301, _309_
_Tropidonotus_, _607_;
_T. natrix_, _608_ f.;
_T. ordinatus_, _611_;
_T. sirtalis_, 610, _611_;
_T. tesselatus_, _611_
_Tropidosaura_, _558_
Tuatera, 293
_Tupinambis_, _548_;
_T. teguixin_, _548_;
_T. nigropunctatus_, _548_, 548
Turtles, _378_ f.;
skull, 317, 379;
skeleton, 320;
plastron, 321;
on Laysan Islands, 383;
Green or Edible, _381_ f.;
Hawksbill, _384_, 385
_Tylototriton_, 96, _115_;
_T. andersoni_, 130;
_T. verrucosus_, _132_
Tympanic cavity, reduction of, in Anura, 30;
in Ophidia, 583
Tympanum of Aglossa, 143
_Typhlomolge_, 96;
_T. rathbuni_, _135_
_Typhlonectes_, 87, _90_;
_T. compressicauda_, _93_
Typhlopidae, _592_, _593_ f.
_Typhlops_, 91;
_T. braminus_, _594_;
_T. vermicularis_, _594_
_Typhlosaurus_, _564_
_Typhlotriton_, 94, 96, 102;
_T. spelaeus_, _103_
_Uraeotyphlus_, 86, _89_
Ureter, 48 f., 49
Urino-genital organs, 48 f., 49
_Urocordylus_, _81_, 288
Urodaeum of Chelonia, 330
Urodela, _94_ f.;
geographical distribution, 96
_Uromastix_, _524_;
_U. acanthinurus_, _526_, 526;
_U. hardwicki_, _525_
Uropeltidae, _592_, _595_
_Uropeltis_, _595_;
_U. grandis_, _595_
_Uroplates_, 512
Uroplatinae, _512_
Urostyle, of Anura, 23;
of Chelonia, 328
Varanidae, _514_, _542_ f.;
skull, 542;
distribution, 543
_Varanus_, _543_;
_V. gouldi_, _546_;
_V. griseus_, skull, 542;
_V. niloticus_, _543_;
_V. salvator_, _543_ f., 546
Vas deferens, 48 f., 49
Vertebrae, procoelous, definition, 19, 138;
acentrous, _i.e._ without a centre or body, 4; {668}
amphicoelous, defined, 12;
of Urodela, 11;
gastrocentrous, defined, 282;
lepospondylous, 5;
defined, 78;
notocentrous, 4;
defined, 19;
opisthocoelous, defined, 12, 138;
pseudocentrous, 4, 78;
stereospondylous, defined, 79, 284;
temnospondylous, 13;
defined, 79, 284;
development of–in Urodela, 12, 13;
in Anura, 19;
of trunk of _Salamandra_, 14;
epichordal, 20;
sacral, of Anura, 22;
shifting forwards of sacral attachment of ilium, 23;
of Reptilia, composition of, 283, 288;
trunk-vertebrae of _Eryops_, 283, 286, 286;
of _Cricotus_, 287;
of Microsauri, 289;
of _Sphenodon_, 294, 296, 297;
atlas and axis of _Sphenodon_, 283;
of Theromorpha, 302;
of Pareiasauri, 305;
atlas fused with axis in _Cynognathus_, 307;
of _Dimetrodon_, with peculiar processes, 308;
of Chelonia, 314 f.;
atlas of _Trionyx_, 283;
of _Chelys_, 283;
of Dinosauria, 413;
hollow in Dinosaurs, 415, 420;
of Eusuchia, 438 f.;
atlas and axis of _Crocodilus_, 283;
of _Metriorhynchus_, 283;
of Pterosauria, 485;
of Ichthyosauria, 480;
of Pythonomorpha, 488;
of Lacertilia, 494;
of Geckones, 503;
of Snakes, 582
Vertebral column, instance of greatest shortening, 144;
of Urodela, 11, 13;
of Stegocephali, 78;
of Anura, 18 f., 21, 22;
_Palaeobatrachus_, 22;
_Pipa_, 22, 143;
_Hymenochirus_, 22, 143;
_Bombinator_, 22;
_Xenopus_, 21, 143;
of Apoda, 86;
number of vertebrae of _Protorosaurus_, 291;
of _Palaeohatteria_, 291;
of _Homoeosaurus_, 292;
of _Sphenodon_, 297;
of _Cynognathus_, 306;
of _Iguanodon_, 428;
of Eusuchia, 440;
of Plesiosauria, 474;
of Elasmosauridae, 478
Vesiculae seminales, 49, 51
Viper, Common, _641_ f., 620, 642
_Vipera_, _641_;
_V. ammodytes_, 641, _643_;
_V. aspis_, _643_;
_V. berus_, _641_, 642, 620;
_V. latastei_, _643_;
_V. russelli_, _643_
Viperidae, 592, 593, _637_
Viperinae, _638_
Viperine Snake, _610_
Vis, de, on _Chlamydosaurus_, 523
Viviparous, Chameleon, 572;
Lacertilia, 499;
Geckos, 506
Vocal sacs, 47 f.;
of _Paludicola_, 220;
of _Rhinoderma_, used as brood-pouches, 228
Voeltzkow, on nesting of Crocodiles, 462 f.;
on _Testudo daudini_, 375
Voice, 47
Wagler, 8
Wallace, on _Rhacophorus_, 246 f.
Wall-Lizard, _557_
Warning, attitudes, of _Bombinator_, 157;
colours, 38, 116, 156;
of _Heloderma_, 541
Water-Viper, _645_, 645
Weismann, on Axolotl, 64, 114
Werner, on _Eryx_, _604_
White's aged Tortoise, 369
Wilder, on _Desmognathus_, 103
_Xantusia_, _547_
Xantusiidae, _514_, _547_
_Xenobatrachus_, 225;
_X. ophiodon_, _228_
Xenopeltidae, _593_, _605_
_Xenopeltis unicolor_, _605_
_Xenopus_, 143;
distribution, 143, 144, _146_ f.;
_X. calcaratus_, 146;
_X. laevis_, _146_ f., 147;
_X. muelleri_, 146
_Xenorhina_, _228_
Xenosauridae, _513_, _536_
_Xenosaurus grandis_, _536_
_Zachaenus_, _212_
_Zamenis constrictor_, _613_;
_Z. gemonensis_ s. _viridiflavus_, _612_;
_Z. hippocrepis_, _613_;
_Z. mucosus_, _611_, 612
_Zanclodon_, 417, 421
Zander, on habits of _Agama_, 520;
of _Phrynocephalus_, 522;
of _Eryx_, _604_
_Zaocys carinatus_, _614_, 615
_Zatachys_, _82_
Zeller, on spermatophores, 53;
on _Proteus_, _134_
Zonuridae, _513_, _536_
_Zonurus derbianus_ s. _giganteus_, _536_, 537
END OF VOL. VIII
_Printed by_ R. & R. CLARK, LIMITED, _Edinburgh_.
THE CAMBRIDGE NATURAL HISTORY
EDITED BY
S. F. HARMER, Sc.D., F.R.S. and A. E. SHIPLEY, M.A., F.R.S.
_In Ten Volumes. Fully Illustrated. Medium 8vo. 17s. net each._
PROTOZOA, COELENTERATES, ECHINODERMS, etc.
VOLUME I.
PROTOZOA, by MARCUS HARTOG, M.A., D.Sc.; PORIFERA (SPONGES), by IGERNA B.
J. SOLLAS, B.Sc.; COELENTERATA AND CTENOPHORA, by S. J. HICKSON, M.A.,
F.R.S.; ECHINODERMATA, by E. W. MACBRIDE, M.A, F.R.S.
_NATURE._–"Taken in conjunction with the earlier published volumes, the
work seems to fulfil the purpose of providing an intelligible and
adequate survey of the entire animal kingdom without giving undue
prominence to particular groups.... The illustrations are excellent."
_FIELD._–"The book can be in the strongest manner recommended to those
for whose benefit it has been written. We know of no work from which a
more truly scientific account of the Protozoa, Echinodermata, and other
lower forms of animal life could be gained."
_OUTLOOK._–"There is much valuable matter in these well-planned sections
which will render the volume, like the others which have preceded it, a
necessary book of reference in every well-equipped library."
WORMS, ROTIFERS, AND POLYZOA
VOLUME II.
FLATWORMS AND MESOZOA, by F. W. GAMBLE, D.Sc.; NEMERTINES, by Miss L.
SHELDON; THREADWORMS AND SAGITTA, by A. E. SHIPLEY, M.A., F.R.S.;
ROTIFERS, by MARCUS HARTOG, M.A., D.Sc.; POLYCHAET WORMS, by W. BLAXLAND
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F.R.S.; GEPHYREA AND PHORONIS, by A. E. SHIPLEY, M.A., F.R.S.; POLYZOA,
by S. F. HARMER, Sc.D., F.R.S.
_CAMBRIDGE REVIEW._–"Several of the groups treated of in this volume are
unknown, by sight even, to the general reader, and possess no popular
name whatsoever; and as only a few insignificant details are known of the
habits of the animals composing them, their treatment in the volume
before us has necessarily been to a large extent anatomical. This
circumstance renders the book of especial value to students, more
particularly as in some cases the articles on the groups in question are
the first comprehensive ones dealing with their respective subjects....
Most of the articles are of a very high order of merit–taken as a whole,
it may be said that they are by far the best which have as yet been
published.... We may say with confidence that the same amount of
information, within the same compass, is to be had in no other zoological
work."
_NATURAL SCIENCE._–"This second volume of the Cambridge Natural History
is certain to prove a most welcome addition to English Zoological
literature. It deals with a series of animal groups, all deeply
interesting to the specialist in morphology; some important from their
economic relations to other living things, others in their life-histories
rivalling the marvels of fairy-tales. And the style in which they are
here treated is also interesting; history and the early observations of
the older writers lend their charm; accounts of habits and mode of
occurrence, of life, in a word, from the cradle to the grave, are given
in ample detail, accompanied by full references to modern and current
literature. The whole is admirably illustrated."
MOLLUSCS AND BRACHIOPODS
VOLUME III.
MOLLUSCS, by the Rev. A. H. COOKE, M.A.; BRACHIOPODS (RECENT), by A. E.
SHIPLEY, M.A., F.R.S.; BRACHIOPODS (FOSSIL), by F. R. C. REED, M.A.
_TIMES._–"There are very many, not only among educated people who take an
interest in science, but even among specialists, who will welcome a work
of reasonable compass and handy form containing a trustworthy treatment
of the various departments of Natural History by men who are familiar
with, and competent to deal with, the latest results of scientific
research. Altogether, to judge from this first volume, the Cambridge
Natural History promises to fulfil all the expectations that its
prospectus holds out."
_FIELD._–"We know of no book available to the general reader which
affords such a vast fund of information on the structure and habits of
molluscs."
_KNOWLEDGE._–"If succeeding volumes are like this one, the Cambridge
Natural History will rank as one of the finest works on natural history
ever published."
_ATHENÆUM._–"The series certainly ought not to be restricted in its
circulation to lecturers and students only; and, if the forthcoming
volumes reach the standard of the one here under notice, the success of
the enterprise should be assured."
VOLUME IV.
CRUSTACEA, by GEOFFREY SMITH, M.A.; TRILOBITES, ETC., by H. WOODS, M.A.;
LIMULUS, LINGUATULIDA, AND TARDIGRADA, by A. E. SHIPLEY, M.A., F.R.S.;
SPIDERS, MITES, SCORPIONS, ETC., by C. WARBURTON, M.A.; PYCNOGONIDS, by
D'ARCY W. THOMPSON, C.B., M.A.
[_In the Press._
PERIPATUS, MYRIAPODS, AND INSECTS–PART I.
VOLUME V.
PERIPATUS, by ADAM SEDGWICK, M.A., F.R.S.; Myriapods, by F. G. SINCLAIR,
M.A.; INSECTS, Part I., INTRODUCTION, APTERA, ORTHOPTERA, NEUROPTERA, AND
A PORTION OF HYMENOPTERA (SESSILIVENTRES AND PARASITICA), by DAVID SHARP,
M.A., M.B., F.R.S.
_FIELD._–"Although written for the student and the specialist, the book
is not the less adapted to all intelligent readers who wish to make
themselves thoroughly acquainted with the habits, structure, and the
modern classification of the animals of which it treats. To such it
cannot be recommended too strongly."
_SCIENCE GOSSIP._–"Every library, school, and college in the country
should possess this work, which is of the highest educational value."
_Prof. RAPHAEL MELDOLA, F.R.S., F.C.S., in his Presidential Address to
the Entomological Society of London, said_:–"The authors of this volume
are certainly to be congratulated upon having furnished such a valuable
contribution to our literature. When its successor appears, and I will
venture to express the hope that this will be at no very distant period,
we shall be in possession of a treatise on the natural history of insects
which, from the point of view of the general reader, will compare most
favourably with any similar work that has been published in the English
language."
_ENTOMOLOGISTS MONTHLY MAGAZINE._–"We venture to think the work will be
found indispensable to all who seek to extend their general knowledge
beyond the narrowing influence of exclusive attention to certain orders
or groups, and that it will take a high position in 'The Cambridge
Natural History' series."
INSECTS–PART II.
VOLUME VI.
HYMENOPTERA _continued_ (TUBULIFERA AND ACULEATA), COLEOPTERA,
STREPSIPTERA, LEPIDOPTERA, DIPTERA, APHANIPTERA, THYSANOPTERA, HEMIPTERA,
ANOPLURA, by DAVID SHARP, M.A., M.B., F.R.S.
_SATURDAY REVIEW._–"Dr. Sharp's treatment is altogether worthy of the
series and of his own high scientific reputation. But in a work of this
sort it is not only necessary that information should be accurate, but
also that it shall be presented to the eye, so far as illustrations and
printing are concerned, in such a way as to render its matter as easily
intelligible as possible, and readily usable for purposes of reference.
Under both these heads we have nothing but commendation for Mr. Sharp's
treatise. The illustrations are indeed beautiful, and the use of the
heavy type for the headings of the various sections and leading
paragraphs materially helps the reader in the progress of his study.
Certainly this is a book that should be in every entomologist's library."
_DAILY NEWS._–"It would be hard to say too much in praise of this most
admirable volume. It is too often the case that scientific books are
written in a dull and uninteresting style. The reader will find nothing
of that kind to complain of here. The descriptions are clear, the
illustrations are excellent; while, as in the previous volumes of the
series, printing and paper are all that could be desired."
FISHES, ASCIDIANS, etc.
VOLUME VII.
HEMICHORDATA, by S. F. HARMER, Sc.D., F.R.S.; ASCIDIANS AND AMPHIOXUS, by
W. A. HERDMAN, D.Sc., F.R.S.; FISHES (EXCLUSIVE OF THE SYSTEMATIC ACCOUNT
OF TELEOSTEI), by T. W. BBIDGE[**BRIDGE??], Sc.D., F.R.S.; FISHES
(SYSTEMATIC ACCOUNT OF TELEOSTEI), by G. A. BOULENGER, F.R.S.
_ATHENÆUM._–"All who take a serious interest in the advance of
ichthyology will find this a fascinating book."
_NATURE NOTES._–"It is a thoroughly scholarly work for students, amply
sustaining the reputation of an ancient university as being in the van of
scientific progress."
AMPHIBIA AND REPTILES
VOLUME VIII.
By HANS GADOW, M.A., F.R.S.
_FIELD._–"The work is worthy of the series in which it appears, and we
cannot give it higher praise."
_SCIENCE GOSSIP._–"More than maintains the high scientific reputation of
this series. The herpetologists, or students of the Amphibia and
Reptiles, have now a standard work of the highest class."
_LANCET._–"An account of both Amphibia and Reptiles which should satisfy
the expert, and at the same time entertain the reader who is merely
interested in the tit-bits of natural history.... A book full of accurate
information and pleasant reading."
_MORNING POST._–"A delightful as well as a serviceable book.... Herein
perhaps lies the great charm and merit of Dr. Gadow's book, that, while
satisfying all the inquiries of the student, it is also in great part
written for the ordinary intelligence, and the naturalist in the crowd
may, while necessarily gliding over distressing technicalities, find in
its pages many hours of profitable and entertaining study of the habits
of the classes under notice."
_NATURE._–"In concluding the review we would express the opinion that by
this handsome volume a very important addition to science has been made;
that the beautiful illustrations, together with the clear and charming
accounts of the life-histories which it contains, will do much to
popularise the study of a rather neglected section of zoology; and that
lovers of Reptiles, of which there are more than one generally thinks,
will feel that the new knowledge imparted to them emanates from one who
is thoroughly in sympathy with their enthusiasm."
BIRDS
VOLUME IX.
By A. H. EVANS, M.A.
_IBIS._–"Mr. Evans has produced a book full of concentrated essence of
information on birds, especially as regards their outer structure and
habits, and one that we can cordially recommend as a work of reference to
all students of ornithology."
_NATURE NOTES._–"We venture to predict that, of the ten volumes of which
this excellent series is planned to consist, none will secure a wider
popularity than Mr. Evans's treatise on birds. Strange as it may appear,
among the many books on birds that have appeared of late years, we do not
recall any that covers the same ground.... We are grateful to the author
for the mine of valuable information which he has crowded between his two
covers."
_SCIENCE GOSSIP._–"General readers will find this work most useful in
obtaining a proper understanding of birds, and will be assisted by the
effective diagram of a hawk in the introduction, showing the recognised
names of every part of the exterior appearance. The expressions used in
naming the various portions are fully explained on the adjoining page. As
we have already said, the illustrations are admirable. The book is a
useful addition to any library, as it treats of nearly every known kind
of bird throughout the world."
_SATURDAY REVIEW._–"The expert and the novice alike must be at once
delighted by the accuracy and the beauty of the illustrations.... It is
astonishing to note the mass of information the author has been able to
bring together.... With a little practice any observant person would soon
learn by the help of this volume to track down any bird very nearly to
its ultimate place in classification."
MAMMALIA
VOLUME X.
By FRANK EVERS BEDDARD, M.A., F.R.S.
_NATURE._–"Cannot fail to be of very high value to all students of the
Mammalia, especially from the standpoints of morphology and
palæontology."
_ATHENÆUM._–"Mr. Beddard has produced a volume equal in interest and
value to the others in the Cambridge series."
_LAND AND WATER._–"A notable book, the result of long study, patient
labour, sound reasoning, and careful selection, for which we are deeply
indebted to the author."
_DAILY NEWS._–"A volume which, for the interest of its contents and for
its style and method of treatment, is not only worthy of its
predecessors, but may be regarded as one of the most successful of a
brilliant series."
_KNOWLEDGE._–"In this volume Mr. Beddard has undoubtedly made an
important contribution to the history of mammals, his text-book being the
only one which can be said to be up to date and to contain notices of the
many important types–both recent and fossil–discovered during the last
few years."
_FIELD._–"Its utility to the working zoological student can hardly be
overrated. It is exceedingly well illustrated."
LONDON: MACMILLAN AND CO., LTD.
----
NOTES
[1] References to explanations of the terms used below will be found in
the index.
[2] _Bull. Soc. Philom._ ii. p. 81.
[3] _Tableaux méthodiques_, p. 61.
[4] _Bull. Soc. Philom._ p. 113.
[5] _Isis_, 1821.
[6] Treviranus' _Zeitschr. f. Physiol._ 1831, p. 190.
[7] δέρη, neck; μύω, close.
[8] _Proc. Ac. Philad._ p. 209.
[9] _Americ. Natural._ xxiii. p. 849.
[10] Sarasins' _Ergebnisse ... Ceylon_, 1887-1890.
[11] Credner's term for all Vertebrates higher than fishes.
[12] Boulenger, _P.Z.S._ 1888, p 204.
[13] _P.Z.S._ 1897, p. 577.
[14] _Q.J.M.S._ xxxviii. 1896, p. 465.
[15] _Arch. ges. Physiol._ li. 1892, p. 455.
[16] _Nat. Sci._ i. 1892, p. 185.
[17] _C. R. Ac. Sci._ cix. 1889, pp. 405, 482.
[18] Orr, _Quart. J. Micr. Sci._ xxix. 1889, p. 316.
[19] "Lungenlose Salamandriden," _Anat. Anz._ 1894, p. 676; 1896, p. 182.
[20] "Nuove ricerche anatomo-fisiologiche intorno ai Salamandridi
normalmente apneumoni." Torino, 1894.
[21] _Zool. Anz._ 1896, p. 33; 1899, p. 545.
[22] _Amer. Natural_, xxx. 1886, p. 829.
[23] For the mechanism of the frog's respiration, see Gaupp, _Arch. Anat._
1896, p. 239.
[24] Boulenger, _The Tailless Batrachians of Europe, Ray Soc._ 1896.
[25] _Zeitschr. wiss. Zool._ xlix. 1889, p. 583.
[26] _Amer. Natural_, xxv. 1891, p. 753.
[27] _Zool. Jahrb. Syst._ vi. 1892, p. 447.
[28] _Ann. Nat. Hist._ (5), xvii. 1886, p. 463.
[29] J. Thiele, _Zeitschr. wiss. Zool._ xlvi. 1888, p. 67.
[30] _Zeitschr. wiss. Zool._ xlix. 1889, p. 43.
[31] M. Weber, _Ann. Jard. Botan. Buitenzorg_, Suppl. ii. 1898, p. 5.
[32] For "A Synopsis of the Tadpoles of European Batrachians," see
Boulenger, _P. Z. S._ 1891, pp. 593-627, pls. xlv.-xlvii.; also
Bedriaga, "Tableaux synoptiques pour servir à la détermination des
larves des Batraciens Urodèles," _C. R. Ass. Franç. Sci._ ii. 1891,
pp. 540-546.
[33] _Arch. mikr. Anat._ xxix. 1887, p. 1.
[34] _Arch. per zool. e per l'anat. comp._, Genova, 1861, p. 206.
[35] _Ann. sci. nat._ (5), vii. 1876.
[36] _Mem. Acc. Torino_, xxxv. 1883, and _Atti Acc. Torino_, xvii. 1883,
p. 84. See also Woltersdorff, _Zool. Garten_, 1896, p. 327.
[37] _Verh. Ges. Basel_, vii. 1882, p. 387.
[38] Barfurth, _Arch. Entwickmech._ I. 1895, p. 117.
[39] _The Horn Scientific Expedition_, 1897, p. 155.
[40] _Amer. Natural._ xxix. 1895, p. 998.
[41] _J. Morphol._ xi. 1895, p. 375.
[42] _P. Z. S._ 1895, p. 401.
[43] P. and F. Sarasin, "Zur Entwicklungsgeschichte der ceylonesischen
Blindwühle, _Ichthyophis glutinosa_." _Ergebnisse naturwiss._
_Forschungen auf Ceylon_, 1887-1890, vol. ii.
[44] "Beiträge zur Kenntniss der Entwicklungsgeschichte und der Anatomie
der Gymnophionen," _Zool. Jahrb. Anat._ x. 1897, p. 389, and xii.
1899, p. 477.
[45] The existence of such a form as _Typhlotriton_, in the adult of which
the eyes become closed up, makes such short diagnoses of the families
defective, although there is no doubt about the Desmognathine
affinities of this genus. See p. 103.
[46] _J. Coll. Japan._ i. 1887, p. 269.
[47] _J. Morphol._ xi. 1895, p. 375.
[48] _Amer. Natural._ xxxiii. March 1899, p. 231.
[49] _Amer. Natural._ March, 1899, p. 235.
[50] _Zool. Garten_, 1896, p. 88.
[51] _P. Calif. Ac._ (2) v. 1895, p. 776.
[52] _Amer. Natural._ xxxiii. 1899, p. 691.
[53] _Amer. Natural._ xxxi. 1897, p. 635.
[54] _Zeitschr. wiss. Zool._ xxvii. 1877, p. 522; xli. 1891, p. 365;
_Zool. Anz._ 1882, p. 513.
[55] _Zoolog. Garten._ 1896, p. 114.
[56] _Zeitschr. wiss. Zool._ xxv. 1875, p. 297. See also Hahn, _Rev.
Quest. Sci._ (2), i. 1892, p. 178.
[57] _Amer. Journ. Sci._ (2), xlvi. Nov. 1868, p. 364.
[58] _Zeitschr. Biol._ xxxiv. 1896, pp. 340-396.
[59] _Zeitschr. wiss. Zool._ xxix. 1877, pp. 324 f., pl. xxii.
[60] _Ann. Mus. Genova_, xvi. 1880, p. 83.
[61] _Journ. Morphol._ viii. 1893, p. 269.
[62] _Amer. Natural._ 1891, p. 1084.
[63] _P.Z.S._ 1895, p. 150.
[64] See also M. von Chauvin, _Zeitschr. wiss. Zool._ xxxviii. 1883, p.
671.
[65] E. T. Emerson, _Proc. Boston Soc._ xxxii. 1905, p. 43.
[66] _Nature_, lx. 1899, p. 389.
[67] _Amer. Natural._ xix. 1885, p. 1226.
[68] _Proc. Ac. Philad._ 1864, p. 181.
[69] _The Natural History Review_, No. xvii. 1865, p. 97.
[70] _Journ. Ac. Nat. Hist. Philad._ vi. p. 189.
[71] Beddard, _P.Z.S._ 1895, p. 841.
[72] _Phil. Trans._ B. 136, 1896, p. 1.
[73] _P.Z.S._ 1890, p. 69.
[74] _P.Z.S._ 1894, p. 101.
[75] Groenberg und Klinckowstroem, "Zur Anatomie der _Pipa americana_,"
_Zool. Jahrb. Anat._ vii. 1894, p. 609.
[76] _P.Z.S._ 1896, p. 595.
[77] _Zool. Garten_, 1885, p. 299.
[78] _P.Z.S._ 1899, p. 790.
[79] _Faune Vertebr. Suisse_, iii. 1872, p. 587.
[80] _Zool. Garten_, 1885, p. 299.
[81] For further information, cf. Portschinsky, "Biologie des mouches
coprophages et nécrophages, 2me partie. Étude sur la _Lucilia
bufonivora_, parasite des batraciens anoures."–_Horae Soc. ent.
Ross._ xxxii. pp. 225-279 (in Russian). German summary in _Zool.
Centralbl._ v. 1898, pp. 855-859.
[82] _Arch. Naturg._ xliv. 1868, p. 141.
[83] _Quart. J. Micr. Sci._ xlii. 1899, p. 3.
[84] _Arbeiten Instit. Würzburg_, x. 1895, p. 57.
[85] _Proc. Bost. Soc. Nat. Hist._ xxi. 1883, p. 104.
[86] _P.Z.S._ 1895, p. 89 (with a sketch of a pond, with nests, in Dr.
Goeldi's garden).
[87] _P.Z.S._ 1895, p. 209.
[88] _Arch. Anat. und Phys._ 1854, p. 449. Also Boulenger, _P.Z.S._ 1898,
p. 107.
[89] _Quart. J. Micr. Sci._ xlii. 1899, p. 313.
[90] _Ann. Mag. Nat. Hist._ (5) xvii. 1886, p. 461.
[91] =_Phyllobates_ (part) Bibron; cf. Boulenger, _P.Z.S._ 1888, p. 207.
[92] See Günther, _Nature_, lii. 1895, p. 643.
[93] _Quart. Micr. Sci._ xlii. 1899, p. 329.
[94] _Arch. Naturg._ xxxiii. 1867, p. 124.
[95] _Quart. J. Micr. Sci._ xlii. 1899, p. 309.
[96] _Report on the Work of the Horn Scientific Expedition to Central
Australia_, pt. ii. "Zoology," 1896, p. 164.
[97] _Proc. Linn. Soc. N.S.W._ (2), iv. 1898, p. 357.
[98] _Zool. Anz._ xvii. 1894, p. 156.
[99] _An. Soc. Espan._ i. 1822. See also Howes, _P.Z.S._ 1888, p. 231.
[100] _Quart. J. Micr. Sci._ xlii. 1899, p. 307.
[101] S. S. Flower, _P.Z.S._ 1896, p. 910.
[102] _Ibid._ p. 909.
[103] Boulenger, _Ann. Nat. Hist._ (6), iv. 1889, p. 247.
[104] See Boulenger, _P.Z.S._ 1888, p. 204.
[105] Boulenger has shown (_P.Z.S._ 1888) that Bibron's species of
_Phyllobates_, hitherto grouped amongst the Cystignathidae, are
Ranoids, closely allied to _Hylixalus_ and _Prostherapis_. The other
species now form the Cystignathoid genus _Syrrhopus_, Cope (cf.
p. 212).
[106] _P.Z.S._ 1895, p. 209.
[107] Cf. p. 273.
[108] _Zool. Jahrb. Syst._ xii. 1898, p. 89.
[109] _Monatsber. Berl. Ac._ 1875, p. 204; 1876, p. 714.
[110] _Malay Archipelago_, 2nd ed. i. 1869, p. 38.
[111] _Annotat. Zool. Jap._ i. 1897, p. 113.
[112] _P.Z.S._ 1896, p. 906.
[113] Boulenger, _Cat. Batrach. Salientia_, p. 22.
[114] _Zool. Gart._ 1885, p. 299.
[115] _Trans. Zool. Soc._ xii. 1884, p. 51.
[116] _P.Z.S._ 1884, p. 573.
[117] _British Reptiles_, 2nd ed. 1849, p. 110.
[118] Boulenger, "Tailless Batrach. of Europe," pt. ii. p. 287, _Ray
Society_, 1897.
[119] Boulenger, _op. cit._ p. 278.
[120] _Phil. Trans._ clxxxvii. 1896, B. p. 23.
[121] _Anat. Anz._ xix. 1897, p. 201.
[122] _Phil. Trans._ clxxxvii. 1896, B. p. 23.
[123] _Trans. Zool. Soc._ xv.
[124] _Trans. N. Zealand Inst._ x. 1878, p. 222.
[125] _Trans. N. Zealand Inst._ xiv. 1881, p. 276; cf. also Reischek, _op.
cit._ xiv. p. 274.
[126] Cope, the inventor of this most appropriate name, soon changed it,
unnecessarily, into Theromora (μωρός = sluggish), perhaps in order
not to emphasise too much their possible Mammalian affinities; while
others rashly called them Sauro-Mammalia. For detailed illustrations
of Theromorpha reference should be made to Owen, _British Fossil
Reptiles_, 4to, London, 1849-55, and to numerous papers by Seeley,
_Phil. Trans._ 178 (1887), 186 (1895), and by E. T. Newton in _Phil.
Trans._ 184 (1893), 185 (1894).
[127] _Cat. Chelonians_, _Brit. Mus._ 1889.
[128] It should be noted that the horny pieces of the carapace are termed
"shields" and the bony pieces "plates."
[129] πλευρόν, side; δειρή, neck.
[130] _Journ. Morph._ xv. 1897, p. 21.
[131] _Amer. Natural._ xxxii. 1898, p. 929.
[132] _Contributions to the Nat. Hist. of the U.S.A._, Boston, 1857.
[133] _Zool. Garten._ 189, p. 260.
[134] _Natural History of Selborne._
[135] _J. Asiat. Soc. Bengal_, vi. 1837, p. 689.
[136] Presidential Address. _Proc. Linn. Soc._ 1898. See also Günther,
_Gigantic Land-Tortoises_, Brit. Mus. London, 1877; Gadow, _Trans.
Zool. Soc._ xiii. 1894, p. 313; Rothschild, _Novit. Zool._, several
notes.
[137] _Notes Leyden Mus._ xvi. 1895, p. 211.
[138] _Contributions to the Natural History of the U.S.A._, vol. i. 1857,
p. 333.
[139] _P.Z.S._ 1875, p. 2.
[140] _Wanderings of a Naturalist in India_, Edinburgh, 1867.
[141] _Sketches of the Natural History of Ceylon_, London, 1861.
[142] _Sitzber. Ak. Berlin._ 1891, p. 115; 1893, p. 347.
[143] _J. Morphol._ v. 1891, p. 181.
[144] _J. China Asiat. Soc._ xiii. 1879, pp. 1-36, with Figs.
[145] Boulenger, _Trans. Zool. Soc._ xiv. 1898 (read Nov. 1893).
[146] νόθος = spurious.
[147] _Zool. Gart._ 1889, p. 1.
[148] _P.Z.S._ 1888, p. 351, and 1891, p. 466.
[149] _P.Z.S._ 1889, p. 602.
[150] _P.Z.S._ 1889, p. 452.
[151] F. Mason's _Burma_, London, 1882.
[152] _Sketches of the Nat. Hist. of Ceylon_, London, 1861.
[153] _P. Ac. Philad._ 1864, p. 224, and _P. Amer. Ass._ xix. 1871, p. 236.
[154] _Ann. Nat. Hist._ (5) xiv. 1884, p. 117.
[155] _Burma, its People and Productions_, London, 1882.
[156] _Zool. Garten._ 1895, p. 232.
[157] _Zool. Garten._ 1895, p. 257.
[158] _P. Linn. Soc. N.S.W._ viii. 1883, p. 300.
[159] _Tangweera_, London, 1899.
[160] _Voyage of the Beagle_, London, 1845, chap. xvii.
[161] For further anatomical details see Shufeldt, _P.Z.S._ 1890, p. 148;
Boulenger, _P.Z.S._ 1891, p. 109; and Stewart, _P.Z.S._ 1891, p. 119.
[162] _P.Z.S._ 1899, p. 596.
[163] _Burma, its People and Productions_, London, 1882.
[164] _Sketches of the Nat. Hist. of Ceylon_, London, 1861.
[165] _Organic Evolution._ Translation, London, 1890.
[166] Fischer, _Zool. Garten._ 1884, p. 38.
[167] _Zool. Gart._ 1882, p. 206.
[168] _Denk. Ak. Wien._ iv. 1852.
[169] _C. R. Ass. Franc._ lxxx. 1876, No. 21.
[170] _J. de l'anat. physiol._ viii. 1872, p. 401.
[171] _Morphol. Arbeit._ vii. 1897, p. 515.
[172] _Arch. Physiol._ lxi. 1895, p. 123.
[173] Fischer, _Zool. Gart._ 1882, p. 4.
[174] For a detailed anatomical account, see West, _J. Linn. Soc._ xxv.
1895, p. 419; xxvi. 1898, p. 517; and xxviii. 1900.
[175] Clifford Allbutt's _System of Medicine_, vol. ii. London, 1896, p.
809.
[176] _Erpétologic générale, Suites à Buffon_, vol. vii. Paris, 1852.
[177] _Catalogue of Snakes, British Museum_, London, 1849.
[178] _Reptiles of British India_, Ray Society, 1864.
[179] _P. Ac. Philad._ 1864, p. 230.
[180] _Catalogue of Snakes, British Museum_, London, 1893-1896.
[181] Except _Oligodon_, _Dasypeltis_ and _Atractaspis_ (see. p. 582), in
which palatal teeth are restricted to the palatines.
[182] _Atlas der Thierverbreitung_, pt. v. Gotha, 1887.
[183] W. A. Forbes, _P.Z.S._ 1881, p. 960.
[184] _Burma, its People and Productions_, London, 1882.
[185] _Rep. Brit. Ass._ 1870. _Trans._ p. 115.
[186] _P.Z.S._ 1894, p. 669.
[187] _Zool. Gart._ 1895, p. 330.
[188] _Ibid._ 1896, p. 85.
[189] The same arrangement occurs in the Colubrine genus _Polyodontophis_,
with about ten species in South-Eastern Asia, Madagascar, the Comoro
Islands, and in Central America.
[190] _P.Z.S._ 1896, p. 715.
[191] _P.Z.S._ 1887, p. 340.
[192] _P.Z.S._ 1887, p. 489.
[193] _Natural Science_, i. 1892, p. 44.
[194] _Verbreitung der Kreuzotter in Deutschland._ Frankfurt a. M. 1888.
[195] _J. Linn. Soc._ xxviii.
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