Thick, ventricose, obliquely subquadrangular, umbos terminal; prodissoconch relatively small, prominent, semicircular, its outer margin denned by an elevated rim; anterior margin inclined at an angle of from 60 degrees to 70 degrees to the dorsal margin; sculpture of about 14 feeble angular radial ribs, crossed by regularly disposed concentric threads, which form imbricating serratures at the intercrossing; shell covered with a tawny subpellucid periostracum, which is raised into setae on the radial costae (corresponding with the serratures thereon), and extends as a fringe around the ventral margins of the valves; ligamental pit lanceolate, directed obliquely backwards for one-third or one-half length of the posterior hinge line; the transverse crenulations on the posterior of the hinge line are reduced to short crowded striae. Holotype: length 3.75 mm., height 4.5 mm., section 3 mm. (large example)—Derwent Bay, Tasmania.

South Australia. Beachport to 40 miles west of Eucla, 40-150 fathoms. S.W.A., S.A., Tas., Vict.