The shell is opaque whitish, the anterior end often translucent whitish strongly compressed, very inequilateral, inequivalve, the right valve projecting beyond the other ventrally in the middle and posteriorly. The beaks are near the anterior fourth. Posterior dorsal margin straight in the anterior half, then somewhat concave. Anterior dorsal margin shortly sloping in front of the inconspicuous beaks, then vertical, finally turning squarely forward, straight or hooked up. The posterior end is somewhat rostrate, truncate. Ventral margin convex, lightly sinuate posteriorly. The flat valves have a weak, irregular sculpture of coarse, very low, concentric growth wrinkles, finer and generally distinctly cut on the rostral segment, which is bounded by a low radial ridge in the left valve, and usually an impression in the right.
Length 12.4 mm., height 5.5 mm., diam. 1.3 mm.