Myidae Lamarck 1809

Shell of Mya arenaria....

Platyodon cancellata.

Mya arenaria. Form 2.3 mm. long..., removed from burrow in sand and showing attachment of byssus (b) to numerous sand grains (s.g.).

Mya arenaria, soft-shelled, or Rhode Island clam.

Mya arenaria.

Mya arenaria, showing extended animal.

Soft-Shell Clam. From Life. Annisquam, Mass..

Mya arenaria. Ten camera outlines of shells varying in length from 0.4 mm to 7.5 mm. They are intended to illustrate the change from a rounded outline in smaller individuals to the elongated condition of older forms. There is at first a more rapid posterior, and subsequently a more rapid anterior, growth of shell, which causes the relative position of the umbo to shift forward, and then back to a position midway between the two extremities of the shell.