Faintly nacreous, thin, fragile, semi-translucent, subtrigonal, inflated, very inequilateral, the posterior end being four times the length of the anterior, posteriorly rounded, anteriorly truncate, dorsal and ventral margins nearly straight; colour buff; sculptured by many, 18 to 30, narrow ridges radiating from the umbo, with broad, shallow furrows, closer and weaker posteriorly; anterior side with a broad radial fold; entire surface roughened with fine dense grains, usually packed in lines of growth; umbo unbroken, elevated, incurved, directed anteriorly; a lateral anterior hinge-tooth in left valve with a corresponding groove in right valve; chondrophore narrow, posterior to the umbo; interior glossy; adductor scars distinct, low down; pallial sinus well developed, the apex of its angle reaching to the ninth radial from the anterior end. Length 24 mm., height 19 mm., section 40 mm. Type locality: three miles off Port Arthur, Tasmania, 50 fathoms.
Loc.: 35 miles south-west of Neptune Islands, 104 fathoms. S.A., Tas., Vict.
Remarks: It is a deeper water species.