Hydrocenidae

Minute amphibious snails classified with the old archeogastropoda, native to eastern and southern Asia, and southern Europe. One species is listed for southern Africa by Pilsbry and Becquaert (1927) "[They] are more or less amphibious dwellers in wet vegetation, clinging to the faces of rocks continually washed by the spray from waterfalls" (Preston, 1915). He lists eight species for the Indian subcontinent

Georissa japonica Pilsbry, 1900. x8. Japan

Valvatidae

Small wide-spired operculate snails, commonly refered to as valve snails, egg-laying and hermaphroditic. Burch (1982) lists 11 North American species. 11 are also listed for the former USSR by Zhadin (1952) while only two are listed for India, and one for Africa. Banarescu includes the following genera;

Valvata; (several subgenera listed by both Banarescu and Burch) throughout Europe, northern Asia, and North America.
Borysthenia; Eastern and central Europe.
Gagea; Endemic in Lake Ohrid.

They have a featherlike gill, visible on the left side outside the shell when the snail is active (Brown, 1991), and a ciliated pallial tentacle ex ...

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