Glycymeris nummaria

Glycymeris nummaria is a species of saltwater clam, a marine bivalve mollusc in the family Glycymerididae, the bittersweet clams. The shell of an adult Glycymeris nummaria can be as large as 60 millimetres (2.4 in). It is quite thick, almost circular in shape, with a sculpture of radiating striae and fine concentric lines. The surface is dull and may be dark or pale brown, but also whitish-yellowish. Inside of the shell is glossy, white or pale yellow, often with irregular brown markings.