О формах сохранности ископаемых двустворчатых моллюсков

The article reviews the degree of the main taxonomic features expression in the shell of fossil bivalves for various forms of preservation. It is shown that a combination of such forms of preservation as an internal mold and an imprint can often be more preferable than the shell form of preservation for a more complete taxon characterization. For the first time, an image of a bivalve shell with a preserved color pattern is given for the Permian deposits in Northeast Russia.