Shell solid, inequivalve, inequilateral. Outline subrectangular, longer than high. Sculpture of about 29 to 35 radial ribs, with a mean value of 33.1 ± 1.5 ribs, as broad or slighly broader than the interspaces, becoming distinctly nodulose towards the margin. Umbones at the posterior 1/3 of the length, broadly rounded with a slight depression. Upper valve (rv) larger than the lower valve (lv). Taxodont hinge in a straight line, narrower in the middle, wider at the edges. Internal ventral margin strongly crenulate. Periostracum persistent, of appressed lamellae with erect bristles.
shell whitish with a dark brown periostracum.
common size :
20-25 mm in length, 12-16 mm high.
The species resembles most Anadara inaequivalvis. Recent biometric analyses of the two species revealed that A. demiri has a narrower and less globose shell, but no significant difference in the number of ribs of the two species (Morello and Solustri, 2001). Juveniles of the two species are extremely similar and positive identifications should be based on adults or complete growth series. The native Anadara polii (Mayer, 1868) differs in having a more solid shell and much more convex ventral margin.
BIOLOGY / ECOLOGY
Seems well adapted to harbour conditions and can even prosper in heavily contaminated areas.
rocky and hard substrata as well as muddy and sandy-muddy bottoms.