Malleidae

Malleidae, or the hammer oysters, is a family of saltwater clams. They are related to the pearl oysters, in the order Pterioida and the superfamily Pterioidea.

The shells of most of these animals are T-shaped, with the hinge along the top of the T, and with the byssus emerging from the hinge. An oblique ligament holds the hinge. The shell is partially nacreous. There is a single, large adductor muscle. The exhalant current exits at the hinge.