Scallop
a well-known bivalve, one of those with a single muscle closing the shell. The valves are fan-shaped, the left often more or less flat, the right more arched; both are marked with sinuous radiating ridges, to which the name Pecten (Latin, "a comb") refers. The hinge line is without teeth, and is extended laterally in two ears. The beautiful coloring of the shells is remarkable SCALP even among bivalves. On the margins of the mantle there are hundreds of small sparkling eyes of different degrees of visual efficiency. The small finger-shaped foot is usually marked with bright orange or red color. The scallops are widely distributed in all seas, at depth of 3 to 40 fathoms. When young they are active and able to swim a little by rapidly opening and closing their valves, but as they grow older they become more sedentary. P. Jacobæus, a native of the Mediterranean, is the scallop shell which pilgrims were accustomed to wear in front of their hat in token of having visited the shrine of St. James at Compostella. P. maximus, found on many parts of the British coasts, is about six inches broad. About 180 living species are known, and over 400 are recorded as fossils from Carboniferous strata.