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A [[mollusc]]  belonging to the class ''[[Bivalvia]]'', such as [[clam|clams]], [[oyster|oysters]], and [[scallop|scallops]].<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> Bivalves are found worldwide in aquatic habitats, including many freshwater varieties.

A [[mollusc]]  belonging to the class ''[[Bivalvia]]'', such as [[clam|clams]], [[oyster|oysters]], and [[scallop|scallops]].<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> Bivalves are found worldwide in aquatic habitats, including many freshwater varieties.

The word '''bivalve''', means having two shells. The two bivalve shells are hinged together at one place and can be closed tightly by a powerful muscle, the ''adductor.''

The word '''bivalve''' means having two shells. The two bivalve shells are hinged together at one place and can be closed tightly by a powerful muscle, the ''adductor.''

Although it is not obvious, the shells of bivalves have an exponential spiral form just like those of gastropods ([[snail]]s). It is not obvious because the mathematical relationships between the change in angle and change in size are such that a bivalve shell only involves a small angle, and the shell is almost flat.  

Although it is not obvious, the shells of bivalves have an exponential spiral form just like those of gastropods ([[snail]]s). It is not obvious because the mathematical relationships between the change in angle and change in size are such that a bivalve shell only involves a small angle, and the shell is almost flat.