Length 15 mm, height 20 mm, breadth 10 mm. Shell solid, oval, attached to substratum with right valve. Surface with strong 7─8 radial ribs of which distal portion wavy because of growth lines. Ventral margin serrated. Internally left valve with a pair of ridges that fit to a pair of groove on the right valve. Adductor muscle scar single.
Distribution:
North Carolina, Florida, Texas, West Indies, Bermuda and off Suriname. Sublittoral.