The Precious Cardiomya, Cardiomya gemma AE Verrill and Bush, 1898, is a locally found bivalve that rarely exceeds 1/4 inch in size. Its delicate shell is characterized by 4-5 radial, well-separated ridges on the central part of the shell, and the rostrum that protrudes from its posterior end (arrow in figure). The rostrum houses the bivalve's raptorial incurrent siphon, the main structure involved in the capture of prey by this carnivorous mollusk. Cardiomyas and related species feed on small crustaceans that they ingest by quickly contracting an internal septum, in a "pump-like" fashion.
Precious Cardiomya, Cardiomya gemma. Arrow points to shell rostrum. Photos by José H. Leal.