(Müller, 1776)
Description (shell):
Shell brittle, inequilateral; anterior ears about three times as long as the posterior. Inequivalve, prominent byssal notch in the right anterior ear. Almost circular in outline except for the protruding ears. Sculpture of up to 40 radiating ribs interspersed with as many narrower riblets. Numerous small broad spiny tubercles occur in single rows on the riblets but often in double rows on the ribs; these tubercles are so abundant that they almost cover the ribs completely. Fine concentric lines also ornament the shell. Growth stages are not clear. Ears with strong concentric folds and radial ribs without spiny tubercles (C. sulcata-detail).
Size:
Up to 25.5 mm.
Colour:
Off-white, yellowish brown, red-brown, pink or orange.
Distribution:
It has been reported from Iceland and the northern Northern North Sea to the Mediterranean and north-west Africa (Distr. C. sulcata).