Cardium casertanum Poli, 1791Pisidium novaezelandiae Prime, 1862Corneocyclas aucklandica Suter, 1907 Pisidium casertanum, the pea cockle or pea clam, is a minute freshwater bivalve mollusc of the family Sphaeriidae.

The shell is broad, sub-triangular or oval and is ornamented with sculpture of faint concentric striations.

The Periostracum is silky, scarcely glossy.

In colour it is whitish to grey-brown and often the shell is coated with reddish-brown deposits.

The shell is of similar shape to Sphaerium novaezelandiae but is smaller as an adult, more inflated, with a deeper hinge-plate, stronger teeth, and the ligament is not visible externally.