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Alligator Snapping Turtle — Part 2
Classification and Distribution.--But two genera constitute this family. Aromochelys appears to be represented by three species, all of which occur in eastern North America. The larger genus, Cinosternum, comprises about eleven species, six of which inhabit the United States and northern Mexico; one occurs in Mexico generally except the northern portion, three in Central America, and one in northern Brazil and the Guianas. The structural differences of these species are but slight, and in technical nomenclature described principally from the shape of the shields forming the plastron. The greater number of the species of both genera display much the same colouration of the upper and lower shells. Some slight characters are exhibited in the markings of the head. Generally speaking, it must be explained that many of the species are very difficult to determine. As a large series of specimens demonstrate that the characters of the plastron are subject to considerable variations, it is possible that the present number of species will be condensed, after further investigations.
The student is advised to carefully examine the plastrons (lower shells) of the species figured and to become familiar with the distribution of these turtles. By working in this fashion the determination of specimens is rendered systematic and the detailed descriptions will impart their references in a thoroughly comprehensive manner.
All of the Cinosternidae are thoroughly aquatic, frequenting slow-running streams or muddy rivers, from which they seldom venture. In such places they are admirably protected by their dull, mud-coloured shells, which are often coated with moss. These turtles exude a strong and musky odor when annoyed. They are much disliked by persons who fish in fresh-water, as they will greedily take a hook and perform such antics in the water that the sportsman is often lead to anticipate that he has captured a fish of prodigious size. When handled, they snap and bite fiercely, and, in fact, represent in miniature the actions of the formidable snapping turtle.
TABULATED LIST OF THE NORTH AMERICAN MUD TURTLES
I. Plastron very narrow; not protecting the fleshy parts.
Genus Aromochelys.
a. Yellow stripes on head; carapace of adult not keeled.
Two yellow stripes on side of head, from snout, above and beneath the eye to the neck.
COMMON MUSK TURTLE, A. odoratus.
SOUTHERN MUSK TURTLE, A. tristycha.
b. Head spotted; carapace of the adult strongly keeled. Head olive or gray, with round, black spots.
KEELED MUSK TURTLE, A. carinatus.
II. Plastron protecting the limbs and fleshy parts when lobes are closed.
Genus Cinosternum.