The carapace of the River Tortoise, _Trionyx_, is soft, covered with a flexible cartilaginous skin resting on a greatly-depressed osseous disk; its upper surface is covered with shrivelled sinuosities. As they are destitute of scales these Tortoises are said to be soft; their flesh is much esteemed, and they are angled for with hook and line, baited with small fishes or living worms and mollusks, or with dead bait, to which the sportsman gives motion and apparent life, for they are said never to approach dead prey. When they seize their victim, or defend themselves, they dart out their head and long neck with great rapidity, biting sharply with their trenchant beak, and holding on till they have bitten out the piece. From this peculiarity they are commonly known in the United States as the Snapping Turtle. Persons wading have been known to lose toes from their bite. [Illustration: Fig. 39.--Trionyx Ægyptiacus.] M. Lesueur states that towards the beginning of May the females of _Gymnopus spinifera_, belonging to this division, seek out sunny sandy spots on the river's bank for the deposit of their eggs; they are not deterred from choosing steeps of ten or fifteen feet for this purpose. Their eggs are spherical, and more fragile than those of the Marsh Tortoise. They deposit from fifty to sixty at a time. None of this group are found in Europe. The fresh-water lakes and rivers of the warmer regions, such as the Nile and the Niger, in Africa, the Mississippi, the Ohio, and the Amazon rivers, in America, the Euphrates and the Ganges, in Asia, are its habitats. Among other remarkable species in the group we here represent _Trionyx Ægyptiacus_, Fig. 39, supposed to be the +Emys+ of Aristotle.