Scallop 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. They are a cosmopolitan family of bivalves, found in all of the world's oceans, though never in freshwater. The majority of species live recumbent on sandy substrates, and 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 of their shells together. Many species of scallops are highly prized as a food source, and some are farmed as aquaculture. The word "scallop" is also applied to the meat of these bivalves when it is sold as seafood. Undated, no illustrator credited.