Shell large, heavy almost equivalve, stongly inequilateral; beaks near the anterior margin. Shell more or less compressed with a triangular projection at the anterior end. Outline almost circular, as hight as broad, with dorsal area straight, yet shorter than length; posterior margin slightly curved, anterior margin flexous. Rough sculpture of concentric ridges which are usually more projecting at the margins and radial rows of wide appressed scales. Hinge without teeth. Ligament in a single triangular depression.
Externally greyish green with white or yellowish radial rows of scales. Internally very pearly with a pale blue or violet cast. Margins brown to black.