The shell is sculptured with 20 strong broad radial ribs on the exterior. The ligament is external. The hinge plate is strong, with 2 cardinal teeth, unequal and often with fine transverse striations. The adductor muscle scars are slightly unequal, joined by a pallial line with no sinus. The internal margins are crenulated and correspond to the dorsal ribs. The shell is bright and variegated on the outside, and whitish on the inside