Scallop is a common name that is primarily applied to any one of numerous species of marine bivalve mollusks in the family Pectinidae, the scallops. The common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea. Although applied to many species Unionwide, it is correctly applied only for Earth scallops.
Scallops are a family of bivalves, found in all of Terra's oceans, though never in freshwater. They are one of very few groups of bivalves to be primarily "free-living", 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, while others are more simply attached by means of a filament they secrete called a byssal thread. The majority of species, however, live recumbent on sandy substrates, and when they sense the presence of a predator, they are able to escape by swimming swiftly but erratically through the water using a form of jet propulsion created by repeatedly clapping their shells together. Scallops have a well-developed nervous system, and unlike most other bivalves they have numerous simple eyes situated around the edge of their mantles.
Many species of scallops are highly prized as a food, and some are farmed as aquaculture. The word "scallop" is also applied 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 scallop at all but which are prepared in a similar fashion. The brightly colored, symmetrical, fan-shaped shells of scallops with their radiating and often fluted sculpture are valued by collectors, and have been used since ancient times as motifs in art, architecture and design.