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DescriptionThe shell is thick and can grow up to 3 or 4 cm in length. The shell is overall oblong in shape but highly irregular with no two specimens being alike. Dull white in colour with a yellow-brown periostracum that has a coarse texture. Two distinct ridges extend posteriorly from the beak on each valve. In juveniles, the ridges posses short spines that are often worn away in older specimens. The shell is sculptured with thick concentric ridges. The inside of the shell is white.This species is a suspension feeder, catching particles of food as it passes. The type of substratum selected by juveniles determines whether they become burrowers or nestlers. Those settling on hard rock will attach by thread-like hairs and become nestlers while juveniles settling on soft rock become burrowers. The adults are able to bore into rock by mechanical abrasion using the valves of the shell. The initial penetration of the rock by juveniles may involve chemical as well as mechanical means.