Shell large, solid, irregularly shaped, the outer or dorsal margin a little exceeding the inner or ventral margin, the posterior extremity rounded. Sculpture of longitudinal flat ribs rarely becoming obsolete, rarely developing scales. The muscle scars exceeding more than half the length of the shell, which is generally entirely embedded in life; edges of both scars subangulate, sloping inwards to the narrow groove, which separates them, the muscular impression being below the extremity of the scar.
Distribution: Australia.