Shell equivalve, weakly to strongly inequilateral, elongate, with prominent hooks very distant from one another; sculpture always at least radial; often, the valves are covered with a velvety or hairy periostracum; ligament wide; hinge large, taxodont; two muscle scars.
 

Shell small, convex, whitish, with umbones rounded; sculpture strongly cancellate, mainly commarginal; periostracum thin or absent; posterior side subcarinate; margins crenated.
 

Shell medium-sized to large, thick, very convex, subovate to subquadrate; primary sculpture made up of strong, flat, radial costae separated by deep grooves; secondary sculpture of thin commarginal ribs inside the radial grooves; valves not gaping; periostracum thick, scaly near the ventral margin, often eroded on the costae.
 

« Shell oblong, subquadrate, gaping beneath; hinge-margin rather produced at each end; umbo subanterior, curved; front cardinal tooth moderate, divided into small equal crests like the hinder one; the scar of the hinder pedal muscle very large, oblong, triangular, on the hinder half of the dorsal surface of the cavity of the shell. Periostraca paleaceous. » – J. E. Gray: “A Revision of some of the Families of Conchifera or Bivalve Shells, part.III, Arcadae’, The Annals and magazine of natural history ser.2 vol.19, London 1857, p.368.
 

Shell small, subquadrate to slightly trapezoidal; ventral margin slightly convex, sometimes undulating; posteroventral margin angulose, anterior margin rounded; presence of a posterior keel; sculpture of coomarginal lamellae crossed by radial riblets; umbones prosogyrate; ligamentary area minute, opisthodetic; « edentulous gap interrupting the tooth series into a shorter anterior set and a longer posterior one. » – R. La Perna: “On Asperarca Sacco, 1898 (Bivalvia, Arcidae) andd two mediterranean species”, Boll. malacologico vol.33, Roma 1988, p.9.
 

Shell medium-sized, compressed, equivalve, inequilateral. Sides and umbones rounded; sculpture made of numerous thin radial ribs crossed by concentric striae, giving the surface a cancellate appearance; periostracum hairy, especially in the lateral areas; hinge: teeth of the middle smaller than the lateral ones.
 

Shell minute, thin, pale, convex, ventrally rounded; sculpture of concentric striae crossed by thin radials; hinge plate weak; teeth separated in two series by an area more or less distinguishable.
 

Shell small to medium-sized, characterized by the strong ridge that runs from the beak to the posteroventral extremity, and by the internally crenulated venntral margin.