This beast is as vicious as the other Snapping Turtle. According to Agassiz it does not withdraw its head and limbs on the approach of danger, but resorts to more active defence. It raises itself upon the legs and tail, highest behind, opens the mouth widely, and throwing out the head quickly as far as the long neck will allow, snaps the jaws forcibly upon the assailant, at the same time throwing the body forward so powerfully as often to come down to the ground when it has missed its object. It lives mostly in the water, but makes considerable journeys overland. Both in the water and on dry land the limbs move nearly perpendicularly, and the body is raised high. On dry land a considerable part of the weight of the body is borne by the long, strong tail. "They are as ferocious as the wildest beast of prey, but the slowness of their motions, their inability to repeat the attack immediately, their awkwardness in attempting to recover their balance when they have missed their object, their haggard look, and the hideous appearance of their gaping mouth, constitute at such times a picture as ludicrous as it is fearful and revolting. Their strength is truly wonderful. I have seen a large specimen bite off a piece of a plank more than an inch thick. They take hold of a stick with such tenacity that they may be carried for a considerable distance suspended to it free above the ground. Fishes and young ducks are their ordinary prey. They lay from twenty to forty or more round eggs only about the size of a small walnut in holes which they dig in sloping banks not far from the water" (Agassiz). FAM. 2. DERMATEMYDIDAE.–The pectoral shields are widely separated from the marginals by inframarginals, the gular shields are very small or absent, and the tail is extremely short. Only two or three genera, with three or four species in Central America. The plastron is composed of nine plates. In _Dermatemys mawi_ it is large, firmly joined to the carapace, covered with {342}eleven or more shields, and there are four inframarginals; in _Staurotypus salvini_ of Mexico the plastron is cruciform, with the anterior lobe movable, covered with seven or more shields, according to the fusion of the anal shields and the presence or absence of the gulars; there are only two inframarginals. The pubic and ischiadic symphyses remain separate; the temporal fossa remains widely open, the postfrontals scarcely touching the parietals. There are 23 marginal shields in _Staurotypus_, 25 in _Dermatemys_, including the unpaired nuchal. The nuchal plate has a pair of rib-like processes like those of the Chelydridae, but some of the posterior costal plates, sometimes only one pair, meet in the middle line, overlying or suppressing the corresponding neural plates. The shell of these aquatic tortoises is rather flat, more or less keeled, especially in young specimens, and in the fully adult condition is about one foot in length.