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.