The Semelidae are a family of saltwater clams, marine bivalve molluscs in the order Cardiida.

Members of this family have rounded or oval, elongated shells, much flattened.

The two separate siphons are very long, sometimes several times the length of the shell.

These siphons have a characteristic cruciform muscle at their base.

[1] Genera of Semelidae (with some notable species also listed) include:[2]