Genus Dreissena Van Beneden, 1835

Type species.

Mytulus [sic] polymorphus Pallas, 1771; by monotypy.

Remarks.

The dreissenid material at hand is very much broken and displays huge variability in shape and ornamentation. We have found it nearly impossible to distinguish species within the material. Our distinction of two morphotypes below will require confirmation by further designated collecting of entire specimens and populations in the region.