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Littleneck clams; the pictured mollusks are of the species Mercenaria mercenaria.

Maxima clam (Tridacna maxima).

Look up clam in Wiktionary, the free dictionary.

Clams are shelled marine or freshwater mollusks belonging to the class Bivalvia (Kingdom Animalia, Phylum Mollusca^[1]). While the term "clam" has no taxonomic significance in biology, in general use, the term clam refers to a bivalve (a mollusk whose body is protected by two symmetrical shells) that is not an oyster, mussel, or a scallop, and that has a more-or-less oval shape, or alternately, to a freshwater mussel (Merriam-Webster Dictionary.). An exception to the oval shape is the razor clam, which has an elongate shell suggesting a straight razor. Clams are invertebrates, with shells divided into two pieces called valves. These pieces are joined with a hinge joint, and with two adductor muscles that open and close the shells. Clams have no brains or eyes but they do have a heart, kidneys, mouth, and anus. Clams, like most mollusks, also have an open circulatory system, which means that their organs are surrounded by watery blood that contains nutrients and oxygen. Clams eat plankton, but are eaten by small sharks and squid. Some quahogs on the eastern American coast may be 200 years old. In culinary use, clam most often refers to the hard clam (Taxonomically, Mercenaria mercenaria) but may refer to other species such as the soft-shell clam Mya arenaria. They are eaten raw, steamed, boiled, baked or fried: the method of preparation depends partly on size and species. Clam chowder is a popular soup in the U.S. and Canada. In Italy they are often an ingredient of mixed sea dishes, or are eaten together with pasta.

• The ark clams, family Arcidae
• The nut clams, family Nuculidae
• The pointed nut clams, family Nuculanidae
• The duck clams or trough shells, family Mactridae
• The marsh clams, family Corbiculidae
• The file clams, family Limidae
• The hard clam or Northern Quahog: Mercenaria mercenaria
• The Soft clam: Mya arenaria
• The surf clam: Spisula solidissima
• The ocean quahog: Arctica islandica
• The Pacific razor clam: Siliqua patula
• The giant clam: Tridacna gigas
• Asian or Asiatic clam: genus Corbicula
• Peppery furrow shell: Scrobicularia plana
• Pismo clam: Tivela stultorum (8 inch shell on display in the Pismo Beach Chamber of Commerce)
• Geoduck clam: Panopea abrupta or Panope generosa (largest burrowing clam in the world)
• The Atlantic jackknife clam: Ensis directus

• Clam bake
• Clam boil

1. ^ Animal Diversity Web, http://animaldiversity.ummz.umich.edu/site/accounts/information/Bivalvia.html