Scallop Shell

As a juvenile, this scallop is free swimming. When it reaches a diameter of about 1 inch, it permanently cements its right valve to rock or another hard surface. As the animal grows, the exterior of the thick valves become encrusted and overgrown with marine organisms and is often host to boring sponge. Although it is very slow growing, this scallop can live 50 years and reach a diameter of 10 inches. The mantle is orange with rows of blue eyes along the margins. The purple rock scallop inhabits water from the low intertidal zone to a depth of 260 feet. Look for it in crevices and under boulders in rocky areas. It is preyed on by the purple sea star ( Pisaster ochraceus ) and can be easily depleted by human harvesters. http://www.beachwatchers.wsu.edu/ezidweb/animals/Crassadomagigantea.htm

Scallop maybe?