About Isognomon californicus (Conrad, 1837)
The common name of Isognomon californicus (Conrad, 1837) is the Black Purse Shell. This species often has a flat, thin, irregular shape, with a flaky outer surface and a pearly inner surface. It is a very small species of mollusk, growing only between 1 and 1.5 inches long. Black Purse Shells can wedge themselves against rocks and lock into position, staying firmly anchored to prevent waves or other organisms from prying them loose. Isognomon californicus is endemic to the Hawaiian Islands. It inhabits brackish environments, found in crevices at or near the high tide line. It is very rarely found in calm, still water.
