Any one of numerous species of marine bivalve mollusks of the genus Pecten and allied genera of the family Pectinidae. The shell is usually radially ribbed, and the edge is therefore often undulated in a characteristic manner. The large adductor muscle of some the species is much used as food. One species (Vola Jacobaeus) occurs on the coast of Palestine, and its shell was formerly worn by pilgrims as a mark that they had been to the Holy Land. Called also fan shell. See Pecten, 2.