Marsh Tortoises, _Elodites_, occupy a place between Terrestrial Tortoises and those which are essentially aquatic. They have the carapace more or less depressed, oval, and broader behind; their feet have distinct flexible toes supplied with hooked claws, of which the phalanges are united at the base by means of an elastic skin, which enables them to separate one from the other, at the same time preserving their strength and assisting them to grasp a much larger surface. Thus they can walk upon the ground, swim on the surface of deep waters, and climb up the banks of lakes or other tranquil waters, which are their habitual dwelling-places. These Tortoises are generally of small size; being carnivorous, they feed upon small living animals. As they exhale a nauseous odour they are not used as an article of food; and further, as their carapace is neither thick enough nor beautiful enough to be manufactured as tortoise-shell, they are consequently little sought after. There are a hundred species of Elodians, or Marsh Tortoises, known, which are spread over all parts of the globe, but principally in warm and temperate regions. Such are the _Cistudo_, _Emydes_, and _Trionyx_. The Elodians have none of the sluggishness of the Land Tortoises; they swim with facility, and on land they walk with considerable rapidity. Their eggs are white, and nearly spherical, with a calcareous shell, and these are deposited in a hollow dug in the soil or sand, like the Land Tortoises, the place chosen being generally situated on the banks of some secluded stream; the number of eggs increasing as the animal approaches maturity. The Elodians are divided into _Cryptoderes_ and _Pleuroderes_: the former distinguished from the latter by the retractile power they possess of concealing their cylindrical neck, with its sheath of loose skin, under the middle of the carapace; the head, whose width is nearly equal to its height at the occiput; the eyes always lateral, and their orbit so large that the diameter of the cavity nearly equals a fourth of the whole cranium; and the jaws, which are strong, sometimes trenchant, in others are dentated on the edge. In the larger number of species the anterior extremity of the upper beak is notched with a strong tooth on each side, producing the appearance of a beak closely resembling that of birds of prey. [Illustration: Fig. 36.--Mud Tortoise (_Cistudo Europæa_).]