BIVALVIA OF THE POLISH MIDDLE JURASSIC AND REMARKS ON THEIR PALEOECOLOGY PUGACZEWSKA. H.: Bivalvia of the Polish Middle Jurassic and remarks on their

Sixty Middle Jurassic species of Bivalvia from Poland including a new one (Gontomya rudnikensts sp. n.) are described and their occurrence in profile and dependence on environment are considered. It has been stated that epifaunal suspension-feeders to intaunal suspension-feeders ratio in one of the investigated profiles (mzyca) from the Polish Lowlands is comparable to that of the Lower Oxford Clay in England; the deposit-feeders are less numerous in the Polish profile. Ornamentation variability and anisometric growth changes as well as changes of hinge structure during ontogeny in some investigated bivalves have been noticed