This invertebrate, a marine gastropod endemic of the western Mediterranean, is probably the most threatened species in the Mediterranean region, and is stricty protected by Spanish and European legislation. Until the end of the 19th century it was distributed over most of the western basin of the Mediterranean. However, throughout the 20th century it suffered an important regression, mainly due to its collection for food, and is now considered extinct in most of the continental European coasts. At present, the main populations are found on the Mediterranean coasts of North Africa and in the south of the Iberian Peninsula.
Its shell can exceed 100 mm in maximum diameter, although it usually measures between 40 and 80 mm. It has a very characteristic shell, with strong ribs very thick radial and scalloped edge. Adults are very sedentary and only move short distances to feed on cyanobacteria and algae embedded in the rock, taking advantage of the swell periods and returning later to their resting place.
This is a hermaphrodite species, and individuals can mature first as a male and later become a female, or the other way round.