Scallop (/ˈskɒləp/ or /ˈskæləp/) is a common name that is primarily applied to any one of numerous species of saltwater clams or marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. The common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea.Scallops are a cosmopolitan family of bivalves, found in all of the world's oceans, though never in freshwater. They are one of very few groups of bivalves to be primarily free-living; many species are capable of rapidly swimming short distances and even of migrating some distance across the ocean floor. A small minority of scallop species live cemented to rocky substrates as adults. Some others species are more simply attached, by means of a filament they secrete. The majority of species, however, live recumbent on sandy substrates, but when they sense the presence of a predator such as a starfish, they are able to escape by swimming swiftly but erratically through the water using a form of jet propulsion created by repeatedly clapping the valves of their shells together. Scallops have a well-developed nervous system. Unlike most other bivalves, they have numerous simple eyes situated around the edges of their mantles.Many species of scallops are highly prized as a food source, and some are farmed as aquaculture. The word "scallop" is also applied simply to the meat of these bivalves when it is sold as seafood. In addition the name "scallop" is used as part of the name of dishes based on the meat of scallops, and is even applied to some dishes not containing the meat of these bivalves, dishes that are prepared in a similar fashion. The brightly colored, symmetrical, fan-shaped shells of scallops, with their radiating, often fluted sculpture, are valued by shell collectors, and have been used since ancient times as motifs in art, architecture and design.