CHAPTER XX

REPTILES--MONARCHS OF THE MESOZOIC WORLD

What is a reptile? It is a cold-blooded, air-breathing vertebrate, with one occipital condyle, complete right and left aortic arches, red blood and a covering of scales. The classification of the class (Reptilia) recognizes the existence of many distinct subdivisions, as follows:

_Proreptilia_ (extinct). _Prosauria_ (extinct, except the tuatara). _Theromorpha_ (extinct). _Chelonia_--Turtles; tortoises. _Dinosauria_ (extinct; dinosaurs). _Crocodilia_--Crocodiles; alligators. _Plesiosauria_ (extinct). _Ichthyosauria_ (extinct; fish lizards). _Pterosauria_ (extinct; pterodactyls). _Pythonomorpha_ (extinct; mososaurs, etc.). _Sauria_--Lizards; snakes.

This surprising diversity of groups, each so widely isolated, as is implied by separation as subclasses--divisions of almost the highest rank--shows that the class developed in favorable circumstances that stimulated enterprise, so to speak, and resulted in rapid variation of habits, terrestrial, aquatic, arboreal, and aerial, and consequently of adaptive structure. The fact that most of the subclasses are extinct also shows us that the story of the Reptilia is mainly a tale of the departed glory recorded in the archives of the rocks; and we shall hardly be able to understand living reptiles properly without knowing something of their prehistoric development into the dominance to which they rose in the Mesozoic era, which we call Age of Reptiles, and their subsequent decadence.

The first subclass covers certain most ancient skeletons and parts of skeletons that naturalists are not yet agreed are true reptiles, some considering them stegocephalian amphibians. Anyway, they indicate plainly that it was from that group of Amphibia that the variety sprang that developed into what, in time, became the distinct reptilian type. The first distinct product of this departure from the stegocephalian stock appears in the fossils of a division of the second subclass, the Prosauria (_pro_, "before"; _saurus_, a "lizard"), named Rhynchocephalia ("beakheads"), which, although lizardlike in general form, retain many amphibian characteristics of structure. Now the amazing and extremely interesting thing about this is that a representative of this earliest of true reptiles is still living--probably the premier peer among all vertebrates, reckoned by length of ancestry. This most primitive of reptiles, illustrating how hundreds of ancient species known to us only by a few bones must have appeared and acted in life, is the tuatara of New Zealand, catalogued in science as _Sphenodon punctatum_.

It has the shape and general appearance of a big lizard, dull in color and with a granulated rather than scaly hide, and an oddly shaped head, toothless in the adult, when the jaws become somewhat like a horny beak. Yet it is not a lizard any more than it is a crocodile or a turtle, but combines features of all three in its anatomy. Hence it is what naturalists term a synthetic or generalized race (as is the case with all very primitive creatures) out of which more and more specialized groups and species may be, and are, developed, each sorting out and strengthening some particular characteristic of structure, continuously modified by adaptations to habits and environment until a separate type results. The ribs, for example, in the tuatara are remarkable for the presence of hooklike processes that project backward from each rib over the next rib behind it; such processes occur elsewhere only in the crocodiles and the birds. Behind the breastbone are rodlike bones embedded in the muscles of the belly; they occur again in the ancient fish lizards and modern crocodiles, and probably gave rise to the under shield of the turtles. And so on.

The tuatara is verging on extinction. It has nearly disappeared from the mainland of New Zealand, but is now protected on some small adjacent islands where it dwells in burrows which it digs and then shares with petrels. During the greater part of the day the tuataras sleep; and are fond of lying in the water, being able to remain submerged for hours without breathing. They feed only upon other animals.

The third subclass (Theromorpha, "beast-shaped") comprises very ancient reptiles whose remains lie in the rocks of Permian and Triassic age, principally in South Africa, and exhibit a skull, and especially teeth, so much resembling those of carnivorous mammals (for instance, those of a dog) that at first their true nature was mistaken. These creatures have excited the most profound interest, not only because they present so many differences from the Prosauria, but also, and chiefly, because it is from their ranks that we are able to trace, with no small degree of certainty, the origin of the Mammalia.

THE SOURCES OF TORTOISE SHELL AND TERRAPIN STEW

The turtles and tortoises are of a very ancient group (Chelonia) and one very distinct among reptiles, by reason of their armor. What is known as tortoise shell is the series of horny plates, in some species of beautiful texture, in others thin and dull, or even leathery in character, that covers the underlying bones that form the real protection to the animal's body. In embryo (unhatched) turtles the skeleton is much like the ordinary four-footed type, with the vertebræ separate, a full series of ribs, and the limb bones in their proper places. As growth proceeds, however, changes occur rapidly, but least in the oceanic "leathery" turtle, in whose skin nodules of bone expand and join into a mosaic of plates covered with a thick, coriaceous hide. But this skin remains quite separate from the skeleton beneath, which fact places this animal in an order Athecæ ("lacking a case"), quite by itself. All other chelonians are classified in a second order Thecophora ("case-bearing"), and in them the changes that go on in the skin to produce the turtle's shell are far more complete.

If you peel off the horny shields on the upper shell, or "carapace," you will find beneath them a central, lengthwise row of squarish plates of bone, on each side of these a row of similar plates, and outside of these a marginal row of small plates--all knit together at the edges, the zigzag lines of juncture, or "sutures," being plainly visible.

When we dissect a turtle we find no layer of skin or flesh beneath these plates, but discover that they lie directly on the bones of the skeleton and are a part of it. This is what has happened: The vertebræ have grown together, and the backbone is a tube upon which the original nodules in the skin have become fixed, and have broadened into the central line of plates. Those nodules that lay above the ribs have become fused with them so that no trace of ribs is left, except where their heads have become fused with the backbone, and they have broadened into the side rows of plates; and the marginal skin has become transformed into the marginal plates. Similar alterations have produced the under shell, or "plastron," replacing the skin; and adaptive changes have altered the usual relations of the limb bones to the rest of the external skeleton. The carapace and plastron are usually connected by a "bridge" of bone.

Into the space within this shell most tortoises may withdraw the head and tail which, like the feet, are covered with horny scales. The head has good eyes, and a nose with a lively sense of smell, which the creature utilizes in selecting its food; but its hearing appears to be dull. The mouth has no teeth, but the lips are coated with horn, making a parrotlike beak that can inflict a severe bite. Horny spines often grow on the legs, or tail, or both, assisting in both defense and offense.

The chelonians are a very ancient race, and one that has changed remarkably little since its beginning. The great age accounts for the very wide distribution of turtles closely related, and also for the fact that they inhabit land, fresh and salt water; those of the land being, no doubt, the oldest. All turtles lay eggs, the shell of which varies, according to kind, from a parchmentlike envelope to a hard, shining shell; but the process of generation is slow and curiously complicated.

The respiration of the Chelonia is interesting. The lungs are spongy masses, attached to the upper shell. As the rigid case does not permit of their expansion by breathing, the necessary vacuum is made partly by the neck and limbs, which act like pistons as they are drawn in and out, the air being swallowed or pumped into the lungs. Most chelonians may exist for a very long time without breathing, and can stay for hours or even days under water. No animal, perhaps, is harder to kill; and all turtles have long lives, the giant turtles of the Galapagos and their kin living more than 100 years.

The list of Thecophora begins with the suborder Cryptodira, whose members have the carapace covered with horny shields, and consists of the family Chelydridæ, composed of our two snapping turtles, the familiar northern one, and the southern alligator snapper. They inhabit stagnant pools, especially deep channels in swamps and slow rivers such as the bayous of the lower Mississippi Valley, and often show only the tip of the nose as they prowl about close beneath the surface in search of prey--anything they can seize. They take the hook readily if baited with fish or flesh, but stout tackle and a strong arm are needed to land one when full grown; and the act is dangerous to the catcher, for they are the ugliest brutes in the country, and to be bitten by one is a very serious experience. Nevertheless, the young are caught for market in large numbers, for they are excellent food. One curious fact about them is not generally known, namely, that when lying still, like a piece of old log covered with mud and moss, they protrude a pair of wormlike filaments from the tip of the tongue, whose wavering attracts fishes to their doom. Louis Agassiz says of the great alligator snapper of the Southern States, which when walking on land carries its body high on the long legs, much like an alligator:

"They are as ferocious as the wildest beast of prey, but the slowness of their motions, their inability to repeat the attack immediately, their awkwardness in attempting to recover their balance when they have missed their object, their haggard look, and the hideous appearance of their gaping mouth, constitute at such times a picture as ludicrous as it is fearful and revolting. Their strength is truly wonderful. I have seen a large specimen bite off a piece of plank more than an inch thick.... Fishes, salamanders and young ducks are their ordinary prey. They lay from twenty to forty or more round eggs, only about the size of a small walnut, in holes which they dig in sloping banks not far from the water."

These snapping turtles probably represent well the disposition and habits of the extinct predatory reptiles; and give us a hint of why the race succumbed to the more active and intelligent mammals that were growing up around them toward the close of the Mesozoic.

This brings us to the great family Testudinidæ, which is scattered over the whole world except Australia, and contains almost all the ordinary tortoises, mud turtles and terrapins, some of which are entirely aquatic, others amphibious, others wholly terrestrial. Among the most typical and widely distributed are those of the genus Chrysemys, to which "mud turtles" belong. The commonest species in the Eastern States is the painted turtle _Chrysemys picta_; in the West, _C. marginata_. These and other species of North and South America are very pretty when young, the ground color of the upper shields being green, variegated with yellowish or blackish markings, often in delicate patterns. They are carnivorous, depend mainly on fish, but eat many insects and their larvæ. In winter they hibernate in holes in a bank of their pond.

To the genus Clemmys is credited the "sculptured" wood tortoise, the keeled plates of whose back are marked with fine concentric grooves and radiating black lines; and the equally common speckled one, black with round, orange spots. Both spend long periods wandering in woods and fields in search of worms and insects. Closely related to them are the salt-marsh tortoises known as terrapins, which are so much of a luxury in the eyes of those fond of good dinners that probably the favorite one, the "diamond back," would be extinct had not protective measures, and cultivation in captivity, saved the life of the species. Several other terrapins are to be found in the marshes of the Southern States, but not in other countries. Another relative is the interesting little "box tortoise," which is often kept as a pet, and will become very tame; its highly convex shell is colored black and yellow, or orange-brown, but no two are alike. The eyes of the male are red, those of the female yellow. It is naturally enough a "box" tortoise, for, by means of a flexible joint line across the plastron, the fore and hinder halves can be brought up to the ends of the carapace, shutting the whole body inside a tight box that will defy all enemies not strong enough--as are wolves, bears, and big cats--to tear it to pieces. This tortoise is exclusively American. It has become, as a species, wholly terrestrial, so much so that, although it is fond of drinking often, if it falls into the water it will drown. It thus leads us to the true land tortoises that fill the remaining genera of this family.

The typical and most numerous of these belong to the genus Testudo, with about forty species scattered over all warm or temperate parts of the world except Australasia. Typically grazers and fruit eaters, they occasionally vary their diet with worms, snails, and insects. The eggs are hard-shelled, and the males are usually smaller than their mates. Most land tortoises hibernate in the ground during the cold half of the year, or they æstivate during the hot and dry seasons when in the tropics, but this is not an invariable rule. Several species of these land tortoises are common and well known in Europe and also in India, and are often kept as pets. They show considerable intelligence, and are decidedly fond of listening to music. Our best known American representative is the "gopher" (_Xerobates polyphemus_) of Florida, Georgia, and Texas. This turtle is nearly a foot long, with a high, rounded shell, dull brown in color, and the forefeet covered with hornlike scales and some spines--an armature for digging. The deserts along the Mexican border have several local species.

In this family belong the "gigantic" tortoises of the islands east of Africa and west of South America, now all but extinct, save a few in captivity in zoölogical gardens. In fact they differ from ordinary land tortoises mainly in size and in such minor points as distinguish the various species; some of them, indeed, are not excessive in bulk. The largest on record is a male of _T. daudini_, of South Aldabra, whose shell was sixty-seven inches long, and whose living weight was 500 pounds. A fossil species of the late Miocene in India had a shell six feet long, and then and later tortoises almost as big inhabited both Europe and North America, and more recently Madagascar. Their survivors are now restricted to two widely separated regions--the Galapagos Islands, 600 miles off the coast of Ecuador, and the Mascarenes and other western islands in the Indian Ocean. The most interesting thing about this matter is the presence of these tortoises on these widely scattered islands, and the effects of their isolation. It must be noted that when discovered by European voyagers no one of these islands, except the Comoros, was inhabited by men, and none had any large or harmful beasts of prey.

On these peaceful islands plenty of food, an equable climate, and absence of enemies, enabled the tortoises in vast numbers to grow to a size impossible to their relatives on the mainlands. "Scattered over the many islands they were prevented from interbreeding, and thus it has come to pass that not only every group of islands, but, in the case of the Galapagos, almost every island has, or had, its own particular kind." How did these huge chelonians get to these islands? None like them is found on any continent at present, although they had a wide distribution in geological ages. We must conclude that those of the Madagascar region, at least, are the descendants of tortoises once populating "Lemuria," that land area which until mid-Tertiary time occupied the region of the western Indian Ocean, and of which the existing islands are the remains. A similar theory, for which there is geological evidence, may account for the survival of the Galapagos giant tortoises after those of the mainland had died off.

The next family is that of the big sea turtles (Chelonidæ), such as the green turtle, whose flesh is so highly prized a substance for delicate soups (but almost all turtle flesh is good eating), the hawksbill and the loggerhead. They abound in all warm seas, and reach a large size, the green turtle often having a shell three to four feet long, but smooth, while that of the hawksbill is covered with horny plates with high keels and an overlapping arrangement, which are the tortoise shell of commerce. The green turtle is wholly vegetarian in diet, feeding on the large seaweeds, while the others are carnivorous, devouring fishes, mollusks, etc. All three resort in summer to sandy beaches, dig holes, and bury a great quantity of eggs.

There remains a large group of fresh-water turtles, distinguished, in addition to other important structural peculiarities, by the fact that they withdraw the head under the shell by a sidewise bending of the long neck. They are entirely carnivorous, and occur in all tropical and some temperate countries, the ferocious "soft shells" of the Mississippi Valley and northeastward belonging here. A very curious one is the matamata of Guiana and northern Brazil, the biggest of its tribe, becoming more than three feet long. It gets its living by stratagem rather than by activity. The back of its shell is so roughened by coarse bosses that it looks like the bark on an old log, and ragged flaps of skin project from head and neck. These are kept in constant motion, and attract the attention of passing fishes and other creatures, whose curiosity often takes them too near the treacherous jaws of the concealed monster.

Our list of turtles ends with the one probably of most importance to mankind of all the kinds in the world. This is the "arrau" of the Amazon and Orinoco basins, where it is very abundant, and not only an essential element in the subsistence of the native Indians, but of great commercial importance on account of the eggs, which are periodically collected in enormous quantities, chiefly for their oil. This oil is eaten, like the eggs themselves, or is used for burning in lamps, or as an addition to tar. The turtles are likewise eaten by man and beast. This turtle is large, sometimes three feet long; and it deposits a great number of soft-shelled eggs in the sand.

DINOSAURS--ANCESTORS OF BIRDS

No class of the extinct reptiles is so familiar, by name at least, as is that of the dinosaurs, mainly because of the enormous size of some of them, and the fact that their prodigious skeletons are exhibited complete in many museums. No other land animals ever approached some of them in bulk. A great number of species have been exhumed, yet as a group these reptiles are only imperfectly known, for the fossils are not scattered throughout the whole extent of Mesozoic deposits, but only in two limited periods of that era separated by two or three millions of years. All of them had short, compact bodies, long tails, and long legs for a reptile, and instead of crawling they walked or ran, sometimes upon all fours, more generally on the hind limbs, like ostriches. They ranged in size from that of a cat to the prodigious bulk of the diplodocus or the brontosaurus, seventy feet long and perhaps twenty feet high at the hips, while an East African species appears to have been even far bigger. Some were herbivorous, and dwellers mainly in marshes and swamps; others ranged the uplands, armored for defense against huge predatory kinds, and still others had horny beaks like birds. It is believed, in fact, that our birds are descended from the same stock as these creatures, through an early offshoot.

CROCODILES AND ALLIGATORS

These repulsive and ferocious reptiles (Crocodilia) are the bulkiest of the whole class, and most resemble the ancient aquatic dinosaurs, with which they are undoubtedly allied, although their precise derivation is undetermined. Their general shape is in conformity with the reptilian model, rather than indicative of any close relationship to lizards; indeed their closest living relatives are the tuatara and the chelonians. They have four legs of nearly equal size in modern examples, but in some of the older extinct forms of the Lias and Jurassic strata the hind legs were much longer than the fore pair, and broadly webbed, while other features indicate a purely marine life; but it appears plain that the crocodilians originated as land dwellers whose descendants, early in the history of the group, took to an amphibious method of life.

The eyes, nostrils, and external ears are situated on the upper surface of the head, so that breathing, seeing, and hearing are unimpaired in the water, the upper part of the head being usually raised above the surface when swimming. The nostrils and ears have valves which are shut when the animal is under water.

Crocodiles and alligators are mainly carnivorous, feeding on mammals and waterfowl, for which they lie in wait close to the edge of the water, sweeping them in by a blow of their tail, but the gavials feed almost exclusively on fish. All are oviparous, laying oval, hard-shelled eggs.

The order is represented by a single family, Crocodilidæ, including six genera scattered through the tropical and subtropical parts of the globe in the strange fashion that characterizes many of the ancient groups of which present species are mere relics. Thus the American genus of alligators has also a species in China; and the Old World crocodiles are represented by a single, narrowly restricted species in the region of the Gulf of Mexico. Our common alligator (_A. mississippiensis_) inhabits the low coastal rivers and swamps from North Carolina to the Rio Grande, and remains abundant in the steaming bayous along the lower Mississippi, and in the swamps of Louisiana, but in Florida has been killed off, not only by the demand for its hide (as leather), but in a wanton way by tourists and sportsmen, until now its numbers are greatly reduced. It would have become nearly extinct were not its prolificness great, each female depositing thirty-five to forty eggs in the layers of the cone-shaped heap of a nest she makes on the bank.

Young alligators feed mainly on fish, but the old ones take more and more to getting birds and beasts for their dinner, stealing on them quietly as they swim, or when they approach the water to drink. The prey is dragged down and drowned. In the crocodilian throat the passage for air from the nostrils reaches much farther back above the mouth than in other animals, and the entrance of the windpipe may be closed by pressing together the base of the tongue and the soft palate, enabling the alligator to drown its prey without drowning itself. In two particulars our alligator is singular--its fear of man and its voice. When surprised basking on shore, as it likes to do, it will rush with awkward haste for the water; and there will get away or out of sight whenever a man appears. Hence it is safe to bathe in waters infested by alligators, which will retreat from the feared bather as far as possible. Nevertheless when an alligator is cornered it can and will make a very dangerous fight with jaws and tail that are truly formidable. But it rarely attacks unprovoked, except where a mother finds you tampering with her nest. As to its noise-making, the alligator is unique among reptiles in giving voice to a really loud noise, or bellow, which may sometimes be heard for a mile or more. It varies according to the size of the reptile from the gentle "mooing" of a small one to a "thundering and tremendous blast" by a big male.

In the half-submerged morasses of Florida, from Lake Worth southward, dwells a true crocodile, closely allied to that of the Nile, and first discovered there by William T. Hornaday in 1875. It differs from the alligator in the pattern of scales, in the relative length and vertical flatness of the tail, and especially in having a long, pointed snout instead of the broad, spade-shaped head of the alligator. Its general habits present no novelty, but it is more agile and, in captivity, more vicious than its cousin, while showing a similar dread of man in its wild home. This crocodile is found from northeastern Mexico south to the coast of Ecuador, especially in salt marshes.

Central and South America are the habitat of several species of caymans, which differ from alligators mainly in their teeth and the fact that protective scales cover the belly; they are blackish in color, and vary in size and markings, the largest, known on the Amazon as the black cayman, or "jacare usassu," growing to be twenty feet long; but the Indians pay little attention to it.

Crocodiles proper (genus Crocodilus) are distinguished by the fact that some of their foremost teeth fit into a notch of the upper lip, and are therefore exposed, as is not the case with alligators or gavials. One species lives in West Africa, another in India, another is wholly marine in habits (as were some of its extinct progenitors) and ranges from eastern India and southern China to northern Australia, a fourth is Australian, and a fifth Central American; but the best known of all is the so-called Nilotic crocodile of the upper Nile and the rivers of east central Africa. Formerly it occupied the whole course of the Nile, and was one of the sacred animals of the priestcraft of ancient Egypt. In Madagascar it is extraordinarily abundant, and has there the peculiar habit of digging long, ventilated burrows in the river bank, in which it lies, and where it stores its prey. Large old specimens may become fifteen feet in length, and their life is probably very long, for new teeth grow as fast as the old ones are lost, and when adult they have no known enemies except one another, but their eggs are sought for by several kinds of birds, lizards, and so forth, and the old ones devour many infants.

Crocodiles abound in all the sluggish rivers and estuaries of central Africa, and are more destructive of human life than even lions or leopards, and kill much game and many domestic animals. Lying in wait close to the bank, they make a rush, seize by the nose or leg any animal as it stoops to drink; or, stealing close to an antelope or goat standing at the edge of the river, they will, with a sweep of the tail, knock it into the water, and grasping it with their jaws bear it down to a horrible death. The crocodile does not at once tear its victim to pieces, as do the alligators, but pushes it into some hole in the bank to decompose before being consumed. Major J. Stevenson-Huntington says:

"At Sheshike, on the Zambezi, a paramount chief, who lived some forty years ago, used to derive great amusement from watching slaves and criminals being thrown to the crocodiles, his chair being brought to the river's bank in the cool of the afternoon that he might enjoy the spectacle in comfort. The crocodiles at this place never forgot those halcyon days, and, until very recently, it was almost certain death for anyone to drink at the river, or attempt to draw water, except within one of the protecting screens of logs which were erected for the purpose.... On the other hand there are some large pans in Amatongaland, which, although full of the reptiles, are said to be quite safe to bathe in, attacks on human beings being unknown.... Always cunning and suspicious, the crocodile at times evinces considerable audacity in the pursuit of his prey. Natives are occasionally knocked off the gunwales of their canoes by a flick from the tail. I recollect Major Gibbons, standing upright in the stern of our little aluminum steam launch on the Zambezi, with the tiller between his feet, nearly losing his balance through an attack of this kind. I have heard of a native, sleeping on a hot night in the doorway of a hut close to the river, being attacked and dragged in."

Despite this frequent attack on large prey, fishes are the main reliance of the African crocodiles for subsistence.

As opposed to this terrifying record from eastern Africa, the "long-snouted" crocodile of the west coast rivers offers a mild reputation, since it is content with fish, frogs and water birds as food, and fears men more than it is feared by them. The natives hunt it for the sake of its flesh. Crocodile meat is considered good in all uncivilized parts of the world, but most white men dislike its musky flavor; the same may be said of the eggs of these reptiles.

The Orient possesses a variety of crocodiles, the best known of which are the marsh crocodile, a near relative of the African species, and the gavial, placed in the genus Gavialis, and distinguished by its long, slender snout and weak teeth. This gavial abounds in the Ganges and other rivers of northern India and Burma, where it is numerous, and frequently exceeds twenty feet in length. A second species is found in the Malayan archipelago. It feeds almost exclusively on fish, and so rarely harms man or beast that it is regarded as harmless. The marsh crocodile, or "mugger," is also of great size, and inhabits the rivers and marshes of India, Ceylon, and the Malayan islands. It is a fish eater and an arrant coward, feared by no one under ordinary conditions. It was, perhaps, originally, as a matter of gratitude for this harmlessness, that the custom arose among the Hindus of venerating this reptile. In some places, as notably near Karachi, large numbers of muggers are kept captive in ponds, and attended by priests and devotees who guard and feed them.

A third species is the formidable "estuarine" crocodile, which frequents the tidal portions of rivers from the Bay of Bengal to China and Australia. It exceeds all of its race in stature, usually exceeding twenty feet long, and one old specimen on record was thirty-three feet from tip to tip. It is held in great fear by fishermen, for in many cases it develops man-eater proclivities, and has all the ferocity and resourcefulness of its Nilotic cousin. The salt-water habitat of this species recalls the fact that among the many kinds of fossil crocodilians known, from the Lias onward, one was a purely marine form.

The crocodiles are followed in the classification of the reptiles by several extinct groups, known only as fossils of the Mesozoic Age. The first of these is the subclass Plesiosauria, containing a series of predatory creatures characterized by very long necks, short tails, and feet that in the older forms indicate a terrestrial existence, but later exhibit a progressive change to paddles, showing that finally the plesiosaurs were wholly aquatic. This was accompanied by a steady increase in size, until finally a length of at least forty-five feet was reached--chiefly by extension of the neck--in the elasmosaurus of the Cretaceous rocks of Kansas.

Another subclass, Ichthyosauria, restricted to the Mesozoic Age, were large, swimming, marine "fish lizards" with a somewhat whalelike form, the front limbs transformed into paddles, and the snout in the form of a long bill filled with sharp teeth. They lived on fishes, cuttlefish, mollusks, etc., and had the general habits of sharks. They died out early in the Cretaceous epoch, and left no descendants.

A third extinct subclass is that of the pterodactyls, or "flying dragons" (Pterosauria), which possessed the air throughout the Mesozoic Age, and filled the place of birds in the fauna of that period, although they had no relationship to the real birds that came later. Some were no larger than sparrows, but later ones spread their leathery wings twenty feet or more. The origin and real affinities of these winged reptiles are unknown and they left no descendants.

We find in the Cretaceous formations skeletons of very long, slender marine reptiles (Pythonomorpha) with a lizardlike head and all four limbs in the form of paddles, of which the mososaurs are the best known. These were the latest of the Mesozoic reptiles; and about the time of their disappearance we begin to find the earliest fossil suggestions of the subclass Sauria which contains our modern orders Lacertilia, the lizards, and Ophidia, the serpents. Neither of these owe their ancestry to any of the fossil groups just mentioned, in spite of superficial resemblances, but "their origin has probably to be looked for among the Prosauria, of which Sphenodon (the tuatara, see page 183) is the only surviving member." They are also very distinct from crocodiles in structure.

LIZARDS AND CHAMELEONS--TURNCOATS OF THE WOODS

Lizards (Lacertilia) are creatures of hot climates, and especially of deserts, and they exhibit an almost endless variety of shape, size, structure, and adaptations to their surroundings and a mode of life that is primarily dictated by their food. The majority are terrestrial, but some species are semiaquatic. There are climbing, swiftly running, and even flying forms, while others lead a subterranean life like earthworms. Most of them subsist on animal food, varying from tiny insects and worms to birds and mammals, while others live upon a vegetable diet.

Lizards, like snakes, have a scaly skin covered with a thin, horny pellicle which is shed from time to time, flaking off in pieces except in the wormlike species, where it is sloughed whole as by snakes. In most lizards the scales are well developed, and "shingle" the back and sides of the body, but in some they are like little tubercles, giving a granular appearance--a good example of which is the "Gila monster" of Arizona. Lizards are, as a rule, adaptively colored according to their habitat, so that browns and grays prevail in the sand-running species or those, like the monitors and iguanas, that are mostly aquatic; but brilliant hues in varied, even fantastic, patterns adorn many of the small, agile, tropical kinds, whose safety lies in their swiftness of movement and cleverness in hiding. This is supplemented in most species by the capability of changing color, a faculty that is most serviceable in the chameleons, by rendering them more or less invisible to the hawks and other animals that try to catch and eat them. Some of the more sluggish, earth-dwelling kinds are further protected by many spines sprouting from the skin, as is familiar in our western "horned toad," and in the fearsome-looking "moloch" of Australia; and the iguanas are provided with an erectile spiny crest along the ridge of their backs, most notable in the basilisks.

A strange characteristic of most lizards with slender tails is the power to part with them at a moment's notice. If an enemy seizes this appendage, which often is held temptingly aloft, it breaks off and its owner escapes before the would-be captor has had time to recover from his surprise. Within a short time a new tail is developed, but it is never so perfect as the original organ.

Most lizards lay eggs, few in number, and with shells hard in some families, parchmentlike in others, that are hidden in a hole in a dead stump or some similar place of concealment, and are left to be hatched by the warmth of the sun. Many lizards retain their eggs until nearly ready to hatch, and so are practically viviparous. The embryos have an "egg tooth," as do turtles and snakes.

The Lacertilia are naturally divisible into three sections, namely, geckos, typical lizards, and chameleons.

The geckos are a large and ancient family represented in all tropical countries, and some species are common along both shores of the Mediterranean, but none reach the United States. They are small, plump, flat-headed, and mostly somber in color, but this is changeable; the skin has a granular surface, but regular scales cover the desert-dwelling species. One peculiarity of the group is the adaptation of the foot to the habit of climbing about rocks and trees. The undersurface of the toes has a series of plates, which serve as adhesive pads wherewith the animal is enabled to climb not only trees and the smooth rocks, but a windowpane or to run along the ceiling with the ease of a fly. Another peculiarity is the fact that the eyeball is covered by a "watch glass" of transparent skin, under which the little animal rolls its eyes and stares at you with vigilant interest. Geckos are nocturnal in habit, and as evening approaches come out from their retreats and become active in hunting for insects, and in avoiding the other lizards, snakes, and so forth, that would like to seize and eat them; and it is then that are heard their low, two-syllabled, clucking calls that give them the name "gec-ko." These funny little lizards are utterly harmless, come into houses, and are easily tamed, yet are regarded in many countries with superstitious dread and that foolish fear of poison that is attached to most small lizards and newts. In the Orient several strangely modified forms exist.

The lizards proper (Lacertæ) number several hundred species classified in eighteen families, and differ vastly in size, shape, food, and place and manner of life. Some, like the degraded slowworms, are limbless, scaleless and in their serpentine form and underground life resemble worms more than anything else. Others, such as the "flying dragons" of Malayan forests, have developed great winglike expansions of the skin on the sides, folded close to the body as they climb about the trees, but capable of being spread as supports when they wish to take a long gliding leap to some distant perch; and an Australian species has similar skin expansions that can be raised into a broad ruff around the neck that gives the little animal a terrifying aspect. The many kinds that live in deserts have the dull hue of the ground, or may bristle with spines, of which the squat "horned toad" of California is an excellent example; while those that scamper about the trees and rocks of the equatorial region are often brilliantly striped or spotted in reds, greens and blues. Many are pugnacious and able to bite severely, but the only one whose bite is poisonous is the heloderma of the Mexican border. This is a fat, sluggish, black and yellow creature, about a foot in length, that inhabits the hot desert sands. Fortunately it is slow to anger, but when it does bite there flows into the wound a poison which has the same effect as the venom of the rattlesnake, although less copious and virulent. Severe illness, and in a few cases death, have resulted from the bite of this ugly creature, which is more commonly known as the "Gila monster," because it is prevalent in the valley of the Gila River in southern Arizona.

As the great family Agamidæ is confined to the Old World, so the Iguanidæ belongs to America, where several species are numerous in the tropics, and reach a size of three to five feet, much of which is tail. They live in trees, feed on vegetation, and haunt the banks of rivers into which they jump on the slightest alarm. One traveler relates that along the Mosquito Coast of Nicaragua, when a person is going in a canoe up some of the narrow, unfrequented creeks, he encounters quite a shower of iguanas, and runs some risk of getting his neck broken, for a big iguana will weigh twenty-five pounds or more. Their flesh, resembling that of chicken, is a favorite article of food and iguanas are constantly brought to rural markets. The family contains about 300 species. Among them is the common little "chameleon" (Anolis) of our Gulf States, so often sold to tourists as a curiosity, and brought north to die of cold and neglect. It is golden green on the upper surface, and white on the under, and the throat, when inflated, glows with vermilion; it is a harmless, active little tree dweller, and will change its colors to suit its surroundings with astonishing rapidity. In another genus (Sceloporus) is placed the blue-tailed, variable, "fence lizard," or "swift," which is known throughout the eastern United States; but the common small lizards of the Pacific slope belong to Gherronotus and other genera.

The largest lizards of all belong to the two families Varanidæ, the "monitors" of Africa and eastward to Australia, and Teidæ, the "tejus" of Central and South America. They are singularly alike in appearance and habits--long-tailed, slender, smooth-skinned, carnivorous creatures, living in all sorts of places, varying with the numerous species, and both hated and utilized by the natives of the various countries they inhabit. Some monitors are more than seven feet long. The American tejus, such as the big "teguexin" of Brazil, frequent forests and plantations, where their strength and speed enable them to catch all kinds of animals, from insects to worms, frogs, snakes, mice, and birds. "They take chickens and eggs from the farms, and they are frequently hunted down by dogs for the sake of their flesh, which is considered good to eat. They defend themselves with lashing strokes of their long tail and with their powerful jaws."

The chameleons differ so much from other lizards that they have been placed by some systemists in a different suborder. The chief differences are three. First, the feet, terminating rather long legs, have the fingers and toes so arranged that two digits oppose three as do our thumbs the palm of the hand, and the animal can grasp a branch just as we would, giving so firm a grip that chameleons are exceedingly agile climbers, and may take as many odd attitudes among the branches as would a monkey. Second, the eyes are very large, but the eyelids have grown together over them, leaving only a small hole out of which to look. The right and left eye roll about incessantly, and independently, giving a most comical squinting effect--but no lizard sees with both eyes at once! Third, the tongue has reached an extraordinary development. When the mouth is shut it is withdrawn into a tubular sheath at the back of the mouth; but when a fly is seen and wanted it is shot out like a released spring, seizes the fly in the flaps at its club-shaped extremity, and is quickly withdrawn. This tongue may be thrust out to a distance equal to the length of the body, less the long, tapering, prehensile tail, which is another important part of the equipment of these active tree dwellers. The skin is not scaly, but granular in appearance; and the skull is prolonged behind into a pointed helmetlike form that is distinctive of the group.

Chameleons are most celebrated, however, for their remarkable power of changing their color, but this is by no means always, or perhaps often in direct response to the hue of their immediate surroundings. Dr. Hans Gadow has made an extensive study of his captive specimens of the common chameleon of the Mediterranean region, and confesses himself baffled in the attempt to learn an explanation of the influences, external or mental, that causes the alterations of hue. One judges from his observations that they are mainly the expression of fleeting emotions--but who can read the emotions of a lizard?

But if we do not know the _why_, the _how_ of these fluctuations of color is well understood, and is briefly stated by Prof. Pycraft:

"The horny outermost layer of the skin is colorless; in the layer beneath this are embedded iridescent cells with striated surfaces. Below this, in the deepest layer of the skin, _cutis_, are a large number of cells filled with refractive granules, chiefly guanin crystals. These cause white color by diffuse reflection of direct light. Nearer the surface are cells filled with oil drops, and these give a yellow color. In the granular mass are embedded numerous color-bearing granular sacs or chromatophores, containing for the most part blackish brown or reddish pigment. The branches of these sacs being contractile, the contained granules of color are drawn away from or toward the surface of the skin, and thus, combining with the stationary color, effect a corresponding change in the coloration of the animal."

The chameleons are an African family, but a few of the fifty or so species belong also to the western coast of India and Ceylon, and one is a resident of southern Spain. They vary in size from that of a mouse to a species in Madagascar two feet long.

The lizards and snakes are the most recent developments of the reptilian line of vertebrate evolution. No undoubted lizard remains have been discovered antedating the end of the Cretaceous epoch; and no fossil evidences of snakes are much older than the mid-Tertiary, yet these are surprisingly similar to existing forms. The affinities of both groups seem to be with Pythonomorpha.