Shape most irregular; usually the anterior auricle is longer, but at times the reverse applies; some smaller examples have no anterior ear or only an obsolete posterior auricle; some again are practically without ears; the posterior ear is set at a lower level than the anterior, owing to an excava¬tion behind the umbos for the passage and attachment of the expanding byssus; the longer ear is generally the more pointed distally, and sometimes the shorter is club-shaped; the "hammer handle" is rarely set at right angles to the hinge line, but usually directed forwards; margins of shell are often corrugated and twisted; colour, pale, dirty-horn tint, except where the animal lies, where it may be of a bluish or greenish-black ; interior smooth, polished, horn-coloured; where the animal body lies it is nacreous, blackish-violet, except beneath the resilifer for a varying extent where it is bluish; extending along the inner surface of each valve from the umbo to the ventral margin, is a ridge lying a little in front of the axis of the shell. Holotype: length across auricles 120 mm., height 150 mm., section 17 mm.—Wallaroo. (Reg. No. D.12033, S.A. Mm) Lives, affixed by its byssus, in sand. Juveniles, fragile and paper-like, are found attached to the interior of dead Pinnae, where sand has drifted in; they are quite destitute of lobes or ears.
Loc.: Not uncommon on beach; Gulf St. Vincent to Fremantie. S.W.A., S.A., and Shark Bay. Dredged alive to 22 fathoms. Not recorded from the South-East of South Australia, nor from Tasmania.