Shell small, solid, rather inflated, equilateral, triangular-cordate. Colour white. The dorsal margins straight, meeting in a right angle, the ventral margin rounded. Sculpture : the umbonal region is peculiarly smooth and flattened. Within it the radial ribs are merely indicated, but without they assume sudden prominence, and in each interstice another radial arises. At the margin these ribs amount to about eighteen; they are parted by rather broader, deep, steep-sided grooves, and on their crests are spaced imbricating scales. The inner margin of the valve is denticulated to correspond with the external sculpture. The right margin develops a pseudo-lateral tooth, fitting against a distant lateral tubercle within the left socket. The socket itself is transversely striated. Height 1,95; length 2,05; depth of single valve 0,75 mm.