Original Description: "Concha ovato-rotundata, inaequivalvis, aequilatera, ventricosa, glabra. Valvae radiis quinis teretibus, elatis, laevibus clavae formam ad apicem anteriorem referentibus, obsitae sunt, qui ad conchae ambitum aegre pertingunt. Valva altera gibbosior est, in ambitu leviter crenata. Auriculae pene aequales, minimae; cardo rectus. Valvae discolores: altera miniacea punctis albicantibus conspersa; atera nivea. Ostrea haec praecedenti quam maxime adfinis est: differt tamen insigniter ob valvarum ambitum non inflexum, earumdemque laevorem." {fide Poli, 1795)
Additional Description: Shell thin, inequivalve; right valve slightly more convex than left. Both valves with 5 to 6 fold like ribs, and the entire surface covered with very fine radial lines or cords. Auricles unequal. Coloration usually red to reddish brown, sometimes with cream mottling. Size: Normal adult size range is 25 to 35 mm.

Shell thin, not translucent, edges of disk crenulate. Valves inequilateral, right valve slightly more convex than left one. Left valve folded into 5 ribs, that carry often 3 stronger riblets; right valve 6 ribs. Anterior auricles 1.50-1.63 times as large as posterior ones. Anterior auricle right valve 4 ribs, left valve 3-4 ribs. Posterior auricle right valve 1-2 obscure ribs, left valve 2-3 obscure ribs. Microsculpture consisting of very fine hollow radiating riblets. Top angle varying from 86°-90°. Colour generally red, but white and cream specimens have been examined also. Colour pattern of left valve consisting of a basal colour (generally red) with white or cream markings and fine dots; right valve white with (generally red) markings near the top. Dimensions. - Largest specimen measured 26.4 mm height x 26.4 mm width x 7.0 mm depth. Distribution. - Rarely found around the Hebrides to Scotland and northern part of the North Sea
(Vikingbank) and Atlantic France. The species is mostly found in the Mediterranean and adjacent area of the Atlantic. Its southern limits seems at the Cape Verde according to literature.
Habitat. - Like the previous discussed species it is also living on silty bottoms, but at depths varying from 5 -1400 m. In the northern part of its distribution it is only known from larger depths.
Remarks. - Two extreme forms of this species occur; rather flat specimens (nominal form) and "box-shaped" specimens (dumasii). These forms can be found together, as well as intermediates, so I see no reason to separate these at (sub)specific level as former authors did.

Type Locality: Sicily.
Distribution: From the Mediterranean Sea and the adjacent areas of the Atlantic Ocean, and as far north as the North Sea. Also possibly from Cape Verde.
Habitat: Littoral to sublittoral zones, on muddy, sandy or gravelly bottoms.