The two valves are quite different; the left one is deeply concave, has a raised margin and is fixed to the substrate while the right one is flattish and fits inside the other.

The valves are thick with variable surface sculpturing, the whitish colour being obscured by mud, algal growth and encrusting organisms.

[1] Right and left valve of the same specimen: The species is found in shallow water on the Atlantic coast of North, Central and South America.

Its range extends from Virginia in the United States southwards to San Matías Gulf in Patagonia.

[3] Other mollusc remains found in these middens include the bivalves Mytilus edulis and Plicatula gibbosa, which grow on hard surfaces, and Erodona mactroides, Tagelus plebeius, Mactra sp., Anomalocardia flexuosa, and the gastropods Buccinanops deformis and Heleobia sp., all of which are found on soft sediment in the intertidal and shallow subtidal zones; this suggests that they were gathered locally from the estuarine environment.