Rhomboid-oval; anterior-dorsal margin almost straight; posterior-dorsal margin concave; ventral margin slightly convex; posterior side nearly vertically truncate; anterior side sharply rounded; a rounded umbonal ridge curves to the posterior inferior angle; sculpture of numerous valid, round, rude, incomplete, ill-curved concentric ribs; fine crowded, crooked, radial incisions cross the ribs and spaces, and interrupt more crowded concentric incisions, so as to produce a microscopic shagreen pattern; a depressed lanceolate dorsal area behind the umbo is antero-posteriorly striate; right valve with a narrow furrow within the dorsal margins for the edge of the left valve, the inner margin projecting behind the umbo as a laminar tooth; interior glistening, with faint radial substriations; pallial sinus moderately deep and round. Holotype: length 14.1 mm., height 10.8 mm., section 4.9 mm. Backstairs Passage, 23 fathoms. (Reg. No. D.12915, S.A. Mus.)