Inequivalve, inflated, somewhat angular, white; slightly gaping anteriorly; umbos depressed, incurved; dorsal margin straight, somewhat alate posteriorly; ventral margin straight; post-ventral margin subangu-late, anterior end rounded; a ridge, oblique, well defined, from the umbo to the posterior; ligament external; sculpture of very fine growth lines at the umbonal region, developing into irregular, somewhat undulating rugae; whole surface studded with minute granular excrescences developing with age and approaching the form of tubercles, arranged roughly parallel with the rugae; these granules are more or less cylindrical, extending from surface to surface; periostracum thin, olivaceous; interior somewhat iridescent; adductor scars strong, the anterior oblong, the posterior sub-circular ; pallial line not sinuated; hinge simple, the characteristic curved tooth in the right valve of the juvenile form having become obsolete. Length 7.5 mm., height 3.75 mm., section 3 mm. Type locality: Port Phillip, 8 fathoms.
Loc.: Gulf St. Vincent, 8-10 fathoms; Corny Point 16 fathoms; between Cape Borda and Wedge Island, 60 fathoms. S.A., Tas., Vict.