A heavy rectangular shell with many fine ribs. The ribs are crossed by finer concentric ribs, so the shell appears to be crosshatched. The outer cover (or periostracum) forms a short hairy fringe around the edge of the shell.

They have no siphons and anchor themselves by byssus threads like mussels to the underside of boulders. They are found singly or in small groups.

Filter feeder.

NZ Coastal Marine Invertebrates; Vol 1.