Tresus

Bivalvia, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. The class includes the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. The shipworms bore into wood, clay, or stone and live inside these substances.

Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two shells of equal size connected by two adductor muscles and have a powerful burrowing foot. They live in both freshwater and marine environments; in salt water they prefer to burrow down into the mud and the turbidity of the water required varies with species and location; the greatest diversity of these is in North America.

The Atlantic jackknife clam, Ensis leei, also known as the bamboo clam, American jackknife clam or razor clam, is a large edible marine bivalve mollusc found on the North American Atlantic coast, from Canada to South Carolina. The species has also been introduced to Europe. The name "razor clam" is also used to refer to different species such as the Pacific razor clam or Razor shell.

The Atlantic surf clam, also called the bar clam, hen clam, skimmer or simply sea clam, is a very large, edible, saltwater clam or marine bivalve mollusk in the family Mactridae. It is commonly found in the western Atlantic Ocean. Reaching up to 20 centimetres (7.9 in) or more in length, it is much larger than Spisula solida, which resides in the eastern Atlantic coastal waters.

The Pacific geoduck is a species of very large saltwater clam in the family Hiatellidae. The common name is derived from the Lushootseed (Nisqually) word gʷídəq.

The grooved carpet shell, or Palourde clam, Ruditapes decussatus, or Venerupis decussatus, is a clam in the family Veneridae. It is distributed worldwide and due to its ecological and economic interest has been proposed as a bioindicator.

The hard clam, also known as the round clam, hard-shell clam, or the quahog, is an edible marine bivalve mollusk that is native to the eastern shores of North America and Central America from Prince Edward Island to the Yucatán Peninsula. It is one of many unrelated edible bivalves that in the United States are frequently referred to simply as clams. Older literature sources may use the systematic name Venus mercenaria; this species is in the family Veneridae, the venus clams.

Mactra stultorum, previously sometimes known as Mactra corallina, is a species of edible saltwater clam, a marine bivalve mollusc in the family Mactridae, the trough shells.

Mya truncata, common name the blunt gaper or truncate softshell, is a species of edible saltwater clam, a marine bivalve mollusk in the family Myidae.

The ocean quahog is a species of edible clam, a marine bivalve mollusk in the family Arcticidae. This species is native to the North Atlantic Ocean, and it is harvested commercially as a food source. This species is also known by a number of different common names, including Icelandic cyprine, mahogany clam, mahogany quahog, black quahog, and black clam.

The Pacific razor clam, Siliqua patula, is a species of large marine bivalve mollusc in the family Pharidae.

Crassula aequilatera, known as the triangle shell, is a surf clam, a moderately large marine bivalve mollusc in the family Mactridae.