Three species are described, one as a native of Cayenne, one of Mexico, and one of Pennsylvania. The latter, (C. Pennsylvanicum,) is very common in the United States, where it lives in muddy waters, and feeds on frogs and small fishes. It smells strongly of musk. It is about seven or eight inches in length.

TRIBE II. PLEURODERA.

In this tribe, as already stated, the neck is not properly retractile; so that the head is concealed, not by being drawn back in a straight line, but by the neck folded to one side of the opening of the shell. Besides this, the arms are incapable of being completely drawn within the carapace and plastron. It may be remarked, that in all the genera which compose this tribe, (one alone excepted,) the head is more or less depressed; and that the eyes, instead of having a lateral situation, are placed almost on its upper surface, and are seated very close together, the vision being directed obliquely upwards. In two genera only, the top and sides of the head are furnished with scales or plates. The jaws have sharp-cutting edges. The tail is usually short and pointed. The pelvis is always solidly united both to the carapace and plastron. M. Bibron enumerates seven genera belonging to this tribe, of which one, (Peltocephalus,) forms the link between this and the preceding tribe.

GENUS PELTOCEPHALUS.

In this genus the head is thick, nearly four-sided, and conical, covered with large plates, slightly overlaying each other. The jaws are extremely powerful and sharpedged; the upper has an acute hook at its extremity. The eyes are lateral; the plates of the carapace in some degree overlay each other like tiles; the limbs are robust; the claws straight and strong; the tail is short.

One species only is known, a native of Cayenne and Brazil; it is the TRACAXA Of Spix, (P.tracaxa, Bibr.) Ser engraving.

GENUS CHELODINA.

Among the most remarkable of the genera belonging to the present tribe, is that termed Chelodina, of which three species are described. These animals, as far as the head and neck are concerned, remind us rather of a snake than a Tortoise. The head is very long and flat, and covered with a thin skin; the jaws are feeble; the mouth is wide; the neck is strangely elongated, and simply tuberculous; the carapace is depressed and oval; the plastron broad. The species longest known is the NEW HOLLAND CHELODINA, (C. Novæ Hollandiæ; T. longicollis, Shaw). See engraving.

This extraordinary Tortoise is a native of New Holland, and was first described by Shaw. It is said to be active in the water, and to prey upon various aquatic reptiles and fishes, which its long neck enables it to seize, as they approach near the place of its concealment in the mud, or among the vegetation of the pools or stagnant waters in which it dwells. It is a rare species, and seldom seen in collections.

The other two species are both natives of South America.

GENUS CHELYS.

The genus Chelys is, in some respects, even more remarkable than the preceding. It includes but one species, the Matamata, to which we have already alluded, and which we shall now describe more fully.

The MATAMATA, (Chelys matamata, Dumeril; C. fimbriata, Spix; see engraving,) was first introduced to science by Bruguière, in the "Journal d'Histoire Naturelle, Paris," 1792. It is a native of South America; and the name we have adopted, is that given to it by the aborigines of Cayenne, where it was once very common, as it is still in various parts of Guiana. Its flesh is said to be highly esteemed, and its present scarcity at Cayenne is owing, according to Latreille, to this cause, an incessant warfare being maintained against it. During the day, according