Protothaca pectorina (Lamarck, 1818)

The Protothaca pectorina species is similar to the Chione subrostata but is usually thicker and larger, growing up to 5 cm. The radial ribs are much stronger and more distinct, but the concentric ridges, although present, are faint, the emphasis in sculpture thus being on the radial ribs. Thus when stroked radially, the Chione feels rough but the Protothaca feels smooth. Its color varies from buff-brown to slate grey, and often bears alternating light and dark bands concentrically arranged. The lunule, is still bordered by a chocolate-brown as in C. subrostrata. The inner margin is again crenulated, but the posterior slope is more curved and less steep than in C. subrostrata when viewed from the inside. There are 2 cardinal teeth and one anterior lateral in each valve, the anterior cardinal being bifid on the left valve (but single in the right valve) and the posterior being bifid in the right valve and single in the left one ( as in C. subrostrata). The pallial sinus is fairly well developed