Shell up to 90mm lomg, 90mm high, 70mm wide, juveniles round, adults roundish, becoming slightly produced posteriorly and with a slight keel, not produced anteriorly. Shell strong and heavy, with 20-22 radial ribs with concentric fine riblets or striations extending between the ribs and continuing over them in a straight or chevron pattern. The ribs appear as fluting on the inside, developed throughout the shell in some specimens but barely present in others. Some but not all specimens have a ridge along the ribs which carries the spines. (N.B. the usual diagnostic character that this species does not have such a ridge is far from infallible). Spines more like tubercles, wide-spaced, stumpy, fat, enrolled, absent in most specimen under 30mm. Teeth as for the group but the posterior lateral of the right valve may or may not have secondary toothlets below it. Growth lines indistinct. Inside of the shell white, outside cream with concentric bands of apricot and russet. Animal reddish with a long crimson foot. Edible, commercial species.
- Ribs are decorated with spines (though may be worn)
- Concentric fine riblets or striations extending between the ribs and continuing over them in a straight or chevron pattern.
Burrows in muddy sand and gravel from low water to 100m where it filters phytoplankton.
Local. Distributed from the Irish Sea to the Iberian Peninsula and into the Mediterranean and the Canaries.