File:Argopecten purpuratus (purple scallop) 2.jpg

English: Argopecten purpuratus (Lamarck, 1819) - interior of the left valve of a purple scallop. (~7.9 centimeters across at its widest)

Orientation: anterior to the right; posterior to the left; dorsal at top; ventral at bottom

Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates.

Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood.

The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record.

Scallops are distinctive bivalves with nearly symmetrical valves. The convexity and color of the two valves of an individual can vary dramatically in many species.

Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Pectinoida, Pectinidae

Locality: unrecorded/undisclosed/unspecified

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More info. at: en.wikipedia.org/wiki/Scallop and

en.wikipedia.org/wiki/Argopecten_purpuratus