Anatomical diagram of a giant scallop, a species in the family Pectinidae. Colors are close to those in an actual animal, though shown with greater than natural contrast for emphasis. Not shown are the left gill, the veins on the left side of the body, and the left shell or "valve". The hinge line corresponds to the animal's dorsal side, though when living it usually rests "sideways", on its right. The giant scallop is equilateral and very nearly equivalved (having left and right valves close to the same size and shape), though this is not true of all, or even most, members of its family.
The scallop's nervous system is centered around the visceral ganglia, which constitute a kind of molluscan "brain". The head-to-tail longitudinal axis reaches from the anterior ear to the middle of the adductor muscle, making only a very small portion of the animal morphologically the "front" and the rest corresponding to its "back". The final loop of the intestine goes directly through the ventricle of the heart before it reaches its u-shaped terminus.
