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.