Habitat: it lives in the infra and circalittoral zones, on rocky bottoms, fixed by its byssus. Distribution: common all over the Mediterranean.
Notes: shell solid, equivalve, inequilateral, subquadrangular in outline, oblong and enlarged posteriorly. Typical ventral margin, concave in the adult specimens. From umbo there branch out about twenty radial ribs prominent and, in part, either coarsely squamous or granulated, that can be noted from inside too with the margin denticulated. The whole surface is crossed by thin growth striae squamous. White-yellowish uniform in colour pattern but there can be often found specimens with stains and flammulae either pink or brown in colour. Very changeable in outline. Juvenile specimens are less stretched, sharper in outline and they have an apex more protuberant. There were described many varieties in form, among which we point out those set up by B.D.D. (1892): oblonga, ohtusata. unicolor, and de Gregorio's ones (1885): tirisa. interans, pita. The adult specimens average measures are around 20 mm in width.