a group of turtles that reproduce on dry land but spend the greater part of their lives in rivers, lakes, and swamps. Freshwater turtles feed mainly on animal substances. Four-fifths of all extant turtles are freshwater species. The 170 species make up 54 genera from nine families. In all, there are three orders: Trionychoidea, Pleurodira, and Cryptodira. The last order includes five families: Chelydridae, Platy-sternidae, Kinosternidae, Dermatemydidae, and Emydidae.
The Emydidae include 25 genera, embracing 77 extant species. They are distributed in Europe, northwestern Africa, North America (Sonora subregion), South America (Guiana-Brazilian subregion), and southern and southeastern Asia. They are especially numerous in Asia. Some species are small, and others are medium-sized. The carapace is streamlined and sometimes brightly colored. The digits are usually webbed, since they are very mobile. Freshwater turtles feed on invertebrates and small vertebrates, especially fish; a small part of their diet consists of plant substances. The eggs, which have a calcareous shell, are buried in pits on the shore. Freshwater turtles usually hibernate in the water, digging into the slime. When they are not in hibernation, they spend their nights in the slime. Some species of Emydidae have secondarily adapted to almost constant life on dry land (for example, the North American box turtle and the turtle Geoemyda trijuga).
A number of Emydidae are commercially valuable for their flesh and eggs. Two species are found in the USSR. The turtle Clemmys caspica inhabits lakes, ditches, and mountain streams in Daghestan, Transcaucasia, and southern Turkmenia. Its carapace, which is immovably joined to the plastron, is 15–20 cm long. The species Emys orbicularis is distributed in middle and southern European USSR, in the Caucasus, and in Kazakhstan (as far as Kzyl-Orda). It inhabits slow-moving and stagnant waters. The oval carapace reaches 25 cm in length and is mova-bly joined to the plastron.
L. I. KHOZATSKII