Table 1

Comparison of generic and specific diversities among hydrobiid faunas of ancient lakes (from data compiled by Boss 1978) and the Cuatro Ciénegas Basin (Hershler 1983)

Location	Number of Genera	Number of species
Lake Baikal, Soviet Union	5	40
Lake Tanganyika	3	3
Lake Ohrid, Yugoslavia	5	39
Lake Titicaca, Peru-Bolivia	7	21
Lake Inle, Burma	2	5
Cuatro Ciénegas	9	12