Many of the mollusks in this group are caught in great abundance, but tend to be ignored. The oyster alone does not suffer neglect its subtle flavor is renowned the world over. The shell of bivalves consists of two shells, or valves, joined by a dorsal hinge. When closed, the shells completely cover the shellfish. On one side is a hinge, formed by interlocking teeth on either valve.
Mollusks tend to be shore-dwelling creatures.
Bivalves, such as mussels and oysters, are often found clinging to rocks at the mouth of rivers. As a rule, bivalves are immobile. When they do move, it is by means of the foot, which is stretched as far forward as possible, and then anchored to the ground, so that the creature can drag itself slowly forward. Some species, however, are incapable of movement. These include edible mussels and oysters.