CROCODILE (Crocodilia), an order of Reptiles which, in the possession of a four-chambered heart, and of distinct sockets for the teeth, and in the traces of a diaphragm, differs from the other reptilian orders, and shows an approach in organization to warm-blooded animals. The presence of a four-chambered heart does not prevent that commingling of venous and arterial blood previous to its entrance into the system, which is common to all reptiles, as this is effected in the present order by means of a com-munication between the main arterial and venous tubes, immediately outside the heart. Crocodiles are further characterized by the presence of a partial dermal skeleton, developed in the leathery integument, consisting of numerous square bony plates, keeled in the centre, and forming a complete dorsal shield. The vertebrae of the neck bear upon each other by means of rib-like processes, the neck being thus deprived to a great extent of its mobility ; hence the difficulty experienced by crocodiles in turning. The limbs are short and insufficient to support its entire weight; it consequently drags its body somewhat along the ground. The toes, of which there are five on each of the posterior limbs, and four on the anterior pair, are more or less webbed, while the three inner ones only are provided with claws. The nostrils, eyes, and ears have lids or valves by which they can be closed at will, and the nostrils do not open into the cavity of the mouth, but are carried back to the pharynx, which can also be shut off from the outside by means of a valvular apparatusan arrangement of the greatest possible service to those reptiles in prevent-ing suffocation while seizing and holding their prey beneath the surface of the water. The tongue is attached all round to the bottom of the mouth, and for this reason the croco-dile was formerly supposed to be destitute of that organ. The teeth, which are numerous, sharp, and conical, are arranged in a single row in both jaws, each tooth having its own socket, and the hollow at its base containing the germ of a larger one, which by its growth gradually displaces the other. Three and even four generations of teeth, incased within each other, are often thus contained in a single socket, but the number of teeth above the surface remains the same at all ages. The fourth tooth on each side of the lower jaw is larger than the others, and fits into a notch or pit in the upper surface. As in snakes, the lower jaw is attached to a process connected with and ex-tending backwards from the skull, which greatly adds to the animal's gape, while giving it the appearance, in opening its mouth, of moving both jaws. Beneath the lower jaw are two orifices connected with glands which secrete a musky substance.
Crocodiles are amphibious, leaving the water to bask in the sun on the mud-banks of rivers and marshes, or to devour the prey they have previously drowned. They are oviparous, depositing their eggsfrom twenty to sixty in number, and inclosed in a calcareous shellin holes made in the sand or mud of the river side, where they are left to be hatched by the heat of the sun, or as is the case with certain American species, in hillocks formed by themselves, which they hollow out and fill with leaves and other decay-ing vegetable matter, where the eggs are hatched by the heat generated in the decomposing mass. On quitting the egg the young crocodiles are led to the water by the female parent, who feeds them for some time with food which she herself disgorges, and otherwise shows the greatest solicitude for their safety. The male takes no part in rearing the young, but is said on the contrary to attack and devour them when not prevented by his mate. Large numbers also fall victims to the rapacity of fishes and turtles, while the smaller Caruivora and certain birds destroy great quan-tities of the eggs. The eggs, which in the common croco-dile are nearly as large as those of a goose, are in spite of their musky flavour held in great estimation as an article of food in the regions where they occur, and this leads to a still further diminution of the crocodilian progeny. During the first year the young are said to feed on the larvae of insects and on small fishes. Crocodiles are inhabi-tants of the rivers and marshy lagoons of tropical and sub-tropical regions, a few only frequenting the brackish water of estuaries. One speciesthe Alligator of North America has a range sufficiently north of the tropics to encounter ice in winter, while one of the Indian crocodiles ascends the courses of the rivers it frequents to such a height above the sea that the water it occupies is often frozen. During the dry season these reptiles bury themselves in the mud and remain dormant until the return of moister con-ditions, and they have thus been known to exist without food for a whole year. Tennent states that in Ceylon he has met with the mud case from which the Marsh Crocodile of that island had recently withdrawn, and he also tells of an officer who, camping out one night, was disturbed by a strange motion of the earth beneath his beda phenomenon explained in the morning by the emergence of a crocodile. They also bury themselves in the mud on the approach of danger, and when taken unawares they feign death as a means of escape. The writer above alluded to states that on one occasion his party came upon a sleeping crocodile, which on being struck, after it had awakened and seen itself surrounded, lay perfectly quiet and apparently dead ; in a little while it was seen to glance furtively about, and then make a rush towards the water. On receiving a second blow it again feigned death, and this time no amount of poking could elicit the slightest sign of life, until a lad by gently tickling it under the fore leg caused the reptile BO far to forget itself as to draw up its limb. They resort to a somewhat similar stratagem in order the more readily to reach their prey. Lowering their head and tail they allow themselves to be carried down by the current of the stream, and in this position are said to bear the closest resemblance to floating logs of wooda disguise well fitted to allay suspicion in the animal they are seeking to approach. They feed on fishes, and on the numerous quadrupeds which visit their haunts in order to drink. The latter they seize and drag into the water, holding them under the surface till life is extinct, and afterwards con-veying the dead body to the nearest sand-bank or river island, where it is often hidden until putrefaction has rendered it sufficiently digestible. Although timid they do not hesitate to attack man when off his guard, and bathing in tropical rivers is rendered dangerous by their presence.
There are three families of living crocodilesGaviáis, True Crocodiles, and Alligators. The Gaviáis are readily distinguished by their greatly elongated and narrow snout, and by the uniform size of their teeth (the five or six front pairs excepted), of which the Gangetic species has fifty-two or fifty-four above, and fifty or fifty-two below. It inhabits the lower parts of Indian rivers, especially the Ganges, where it performs the useful office of devouring the carcases of animals that otherwise would pollute the sacred river. It attains a length of over 17 feet, and the male is furnished with a large and prominent swelling in front of the nostrils.
The true Crocodiles have the so-called canine tooth of the lower jaw fitting into a notch or furrow in the upper surface ; the hind legs are bordered by a serrated fringe, and the toes are almost completely webbed. Of these there are twelve species, four of which are Asiatic, occurring eastward from the rivers and estuaries of India to Australia; three are African, one ranging from Egypt to the Cape, the others confined to the rivers of West Africa; while four belong to the Neotropical Begion of Central and South America. The Common Crocodile (Orocodihis vulgaris) may be taken as typical of the family. It inhabits the chief rivers of Africa, but is best known as a denizen of the Nile, where in ancient times the Egyptians regarded it as a divinity. At Memphis and other cities temples were raised in its honour, in which live crocodiles were kept, these sacred reptiles being reared with the greatest care, fed luxuriously, and adorned with costly trinkets. They were thus rendered perfectly tame, and took part in the religious processions and other ceremonies performed in their honour. When dead their bodies were embalmed, and extensive grottoes have been discovered at Maabcleh containing large numbers of those reptilian mummies. The inhabitants of several Egyptian cities, however, regarded the crocodile with entirely opposite sentiments, considering it to be the incarnation of Typho, the genius of evil; and among these the ichneumon, as the deadliest foe of the crocodile, was thought worthy of divine honours. Once a year the people of Apollinopolis had a solemn hunt, in which they killed as many crocodiles as possible, casting the dead bodies before the temple of their god ; and so expert had they grown in this sport that they did not hesitate to enter the Nile, and bring the crocodile ashore by force. Crocodiles appear to have been formerly abundant in all the known parts of the Nile, but have now disappeared from the delta, and according to a recent authority are rarely seen to the north of Beni Hassan, and are evidently receding from below the second cataract. This is largely owing to the constant persecution they are subjected to by the passengers on board the Nile steamers, to which also must be attributed their exceeding wildness, for it is now almost impossible to come within rifle shot of them. A small black-headed plover (Charadrius melanoce-phalus) may often be seen perched on the reptile's back, attracted by the numerous insects which find a con-genial residence there; and this active little bird, by rising in the air and uttering a shrill cry, gives its bulky patron timely warning of the approach of man. Towards the sources of the Nile the crocodile is still abundant. Sir Samuel Baker states that when navigating the Albert Nyanza he observed every basking place covered with them, the creatures lying parallel to each other like trunks of trees prepared for shipment, and that on one bank he counted twenty-seven of large size. The flesh of this species is eaten by the natives, but it does not seem suited to the European palate. " To my taste, " says the authority just referred to, " nothing can be more disgusting than crocodile flesh. I have eaten almost everything, but although I have tasted crocodile I could never succeed in swallowing it. The combined flavour of bad fish, rotten flesh, and musk is the carte de diner offered to the epicure." In Siam the flesh of another species is regularly sold in the market as human food. The Common Crocodile usually measures about 15 feet in length.
Alligators differ from the preceding group in having the canine tooth fitting into a pit in the upper jaw; the hind legs are also destitute of fringe, and the toes are less com-pletely webbed. They are found in America only, and with _ one exception are confined to its tropical parts. The Alligator (Alligator mississiyjjjiensis) occurs in the rivers and swamps of Mexico and the United States, where it is a source of danger to all animals venturing to enter the water. In winter this species retires into holes on the river banks, and there hybernates. While thus dormant it is often got at by the negroes, who unearth it for the sake of the tail, which they reckon a delicacy. It is said to attain a length of 15 to 18 feet. The remaining eight species of alligators are found chiefly in South America, where they are known as Caymans and Jacarés. They abound in the Amazon and the Orinoco, the silence of whose lonely banks is seldom broken except by their nocturnal bellowings. According to Humboldt they re-semble their Old World allies in lying basking in the sun-shine, wherever a shallow in the river discloses a sand-bank, " with open jaws, motionless, their uncouth bodies often covered with birds."
Fossil remains referable to the order Crocodilia occur for the
first time in the Trias, and continue to appear in allied forms during
succeeding periods. These have been very fully investigated,
and Professor Huxley has given a remarkably complete sketch
of the life-history of the entire order, recent and fossil. This he
divides into three sub-orders. I. In the ParasucMa, among other
characters, both pterygoid and palatine bones are destitute of bony
plates to prolong the nasal passages, and the centra of the vertebrae
ore amphiccelian, as in fishes. To this group belongs the earliest
of the crocodilesthe Triassic StagonoUpis of the Elgin sandstone,
which somewhat resembled a cayman, with the snout of a gavial.
II. In the ifesosuchia, the bony plates of the palatine bones
prolong the nasal passages and give rise to posterior nares, and
the vertebral centra are amphiccelian. This group includes such
forms as Telcosaurus and Steneosaurus, ranging from the Liassic
to the Cretaceous formations. III. In the JEusucJiia, both pterygoid
and palatine bones give off plates which prolong the nasal pas-
sages, and the centra of the vertebra; are mostly proccelous. The
species contained in this group make their appearance in the
Greensand of North America and in the Eocene of Europe, and to
it belongs all the existing crocodiles. This group was at one time
much more generally distributed than it is at present, representatives
of gaviáis, crocodiles, and alligators, now so widely apart, and
altogether absent from Europe, being found together in the Eocene
beds of the south-west of England. The greatly restricted range
which characterizes their present distribution seems to mark the
crocodiles as a declining group. . (J. GI.)