Mediterranean scallop shell. Illustration of the shell of the Mediterranean scallop (Pecten jacobaeus), a small saltwater clam in the family Pectinidae. Shells of bivalve molluscs such as clams consist of two articulating parts, or valves. The lower valve of this species is convex and light-coloured, while the upper valve (seen here) is flat and brownish. The Mediterranean scallop is associated with Saint James, and is also known as the Pilgrim's scallop , as the shells were used as cups by pilgrims in the Middle Ages.