Arca imbricata Brugière, 1822
The Mossy Ark is approximately two inches long, and shaped something like a rectangular box. A fresh Mossy Ark is likely to be covered with a dark brown, moss-like covering known as the periostracum. Older, worn specimens will lack this shag. Beneath this periostracum the bivalve is purplish white. The valves have irregular growth lines, and several distinct ribs on the posterior end. One end (the anterior) of the “box” is rounded, the other end (posterior) more pointed. The two valves gape at the center. The beaks (the somewhat pointy “nose” of the shell) are far apart. The area between the beaks may be marked with geometric patterns. The edge, or margin, of the shell is smooth.
The clam attaches itself to rocks in shallow water from North Carolina to the West Indies and Brazil. It is also found on Bermuda beaches.