Shell size to 40 mm; shell thick, quadrangular in outline, showing a distinct groove from umbo to mid-posterior margin. Posterior slope concave. Sculpture of about 35 ribs covered with scale-like lamellae. Color whitish with reddish-brown smudges. Differs from the similar Americardia media, among other features, by ribs that are triangular, instead of rectangular, in cross-section, and by the more finely imbricate nature of the scales on the ribs.