988 ZOOLOGY. 
animal. The principal food of the land tortoise consists of vegetable matter, 
as fungi, of slugs, &c. Other species are found in the Old World, as C. 
enropea (pl. 81, fig. 41, and pl. 90, fig. 12). Sternotherus, with some resem- 
blance to the last genus, has the anterior half only of the lower shell movable. 
The single North American species, S. odoratus, or the stinkpot of the 
Middle States, is a small species, exclusively aquatic, and often caught on a 
hook. It exhales a very disagreeable musky smell. Commonly confounded — 
with this species is Kinosternon pennsylvanicum, a turtle of about the 
same size, but with the lower shell in three pieces, of which the middle 
is fixed, and the anterior and posterior move on this by cartilaginous 
hinges. The next noteworthy genus is Chelonura, or the snapping-turtle 
of the United States. Of this, there are two species, one confined to the 
South-West, and of immense size. The genus H’mys includes species 
with depressed bodies and immovable plastron; five toes to the feet, the 
posterior with four claws only. Of this single genus there are 17 species 
known in the United States. The most remarkable is HE. terrapin, the 
common diamond-back terrapin, so highly prized by epicures. It is caught 
in the brackish waters of the Chesapeake, and other bays and rivers, and 
commands a high price. Another species, #. picta (pl. 81, fig. 42), 18 ex- 
ceedingly abundant. 
In the second sub-family of the Hmydide, or the Pleurodeles, the neck 
and head are not capable of complete retraction within the anterior part of 
the shell, but only partially to one side. The cranium is more or less 
depressed, and the eyes are more or less superior, and approximated. The 
skin which covers the neck is closely adherent to the subjacent muscles, and 
follows the neck in all its movements. None of the species belong to North 
America; many, however, to South America. The most remarkable is 
the Chelys matamata, or matamata tortoise of Cayenne, remarkable for the 
numerous fringes and other appendages which give it so grotesque an ap- 
pearance. 
Fam. 3. Trionycide. This family is known by the complete absence 
of scales upon the body, the shell being covered by a soft skin, and with 
free and flexible borders detached from the sternum. The feet and head 
are equally clothed with a naked skin, the latter without visible tympanum, 
-and with nostrils prolonged into a kind of tube. The feet are provided 
with five toes each, with, however, but three claws. The species are all 
highly aquatic, with a much depressed shell, which, with their oar-shaped 
feet, well fits them for rapid progression in the water. But two genera are 
known, Tryoniz and Cryptopus ; species of which are found in North 
America, Asia, ant Africa. Two species of Trionyx are found in the 
United States, where they are known as the soft-shelled turtle. One 
species is exceedingly abundant in the Mississippi and its tributaries. It 
bites readily at a night line, and is esteemed, in many places, a great 
delicacy. 
Fam. 4, or the Chelonide proper, includes the marine species, which are 
all of immense size. Their carapace is much depressed, and the upper jaw 
usually presents a curved beak somewhat like that of a hawk. The feet 
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