Anomia simplex is a marine bivalve with a thin, translucent shell, often called a 'potato chip shell'. The lower (right) valve is flat and permanently attached to a hard substrate by a stalk-like byssus, which passes through a hole in the shell near the hinge (Morris 1975; Gosner 1978, Yamaguchi 1998). The upper (left) valve is dome-like. The shell is roughly circular, but the margins can be undulating or jagged. The usual size range is 25-50 mm, but can occasionally reach 75 mm. The color varies from sulfur yellow to copper red, and sometimes silvery, grey, or black. The shell attaches to rocks, shells, wood, or man-made structures (Morris 1975; Gosner 1978).

Anomia simplex assumes the shape of the surface upon which it attaches, often becoming ridged or misshapen as a result. (See ribbed exemplars)