The Alligator Tortoise (see engraving) is one of the most extraordinary animals of the present tribe of Tortoises. In many respects, not only externally, but internally, it exhibits an approach to the crocodiles or alligators, and may be regarded as forming an intermediate link. Its strong hooked mandibles, its powerful limbs, its claws which resemble those of an eagle, its depressed body and long tail, ridged above with elevated scales, harmonize with a certain expression of ferocity, and render it repulsive. Nor is its character out of keeping with its aspect; it is one of the most savage and destructive of its race, and preys not only upon fish and frogs, but also upon small aquatic quadrupeds and birds. This Tortoise is a native of Carolina and the warmer districts of North America, diversified by morasses, lakes, and rivers; but it does not appear to be common. We have ourselves only seen one living specimen in this country, which was a young male, about two feet six inches in total length; but when adult it exceeds three feet, and is of great weight and power. Rivers and lakes are indifferently tenanted by it, and it swims with great celerity. It pursues frogs and other aquatic reptiles, and even fish, seizing them with its jaws, and tearing them in pieces by means of its talons; it lurks among the luxuriant and floating leaves of water-plants, and suddenly darting out its head, catches with a snap the unwary duck, or other animal swimming within its reach. The strength of its jaws is surprising; so violent and forcible is their bite, that as Mr. Bell has himself witnessed, a stick of half an inch in diameter, is at once snapped asunder; indeed, as we can testify, it is not safe to approach one of these Tortoises unguardedly; they are extremely vicious, and will snap at the hands of a person, if brought too near them, and even follow up the attack. Mr. Bell records the instance of a sailor, whose finger was actually snapped off by a specimen of a trionyx, (one of the savage fluviatile Tortoises,) on ship-board; the animal was placed in the Surrey Zoological Gardens.

The young Alligator Tortoise, which came under our own observation, would snap violently and repeatedly at a stick, or any other thing held towards it, or at the hands or arms. We notice this the more particularly, because we have seen persons, deceived by the apparently tranquil and dormant state of large fresh-water Tortoises, advance their hands to touch them, ignorant of the suddenness with which they make their snap, and of the severity of their bite.

The carapace of the Alligator Tortoise is of an oblong oval figure, depressed with three longitudinal ridges or keels above; and having for the posterior margin a notch and three points on each side, formed by the scales. The two last genera of the present tribe are both peculiar to America.

GENUS STAUROTYPUS.

Of these, one, Staurotypus, is characterized by the head being large, elongated, and pyramidal, the mandibles hooked, and the under jaw (see annexed figure) furnished with fleshy excrescences. The plastron is solid, but with the anterior part moveable. In the females the tail is short; in the males thick and long. Two species are known, both Mexican; the first, S.triporcatus, has the carapace three keeled above; the second, S. odoratus, has the carapace with a single

keel only. This species is said to smell strongly of musk.

GENUS CINOSTERNON.

The genus Cinosternon has the head also pyramidal, and the throat furnished with pendulous excrescences; but the plastron has the anterior and posterior parts moveable upon an intermediate fixed portion. In other respects it is very closely allied to the preceding genus