Shell oval to subcircular, conoidal, thin, light brown, finely ribbed. The fine, equidistant, equal, rounded riblets number from 25 to 50, interstitial riblets are mostly absent; a few concentric distinct growth-lines are commonly present. Colour light brown, the riblets white. Apex at about the anterior third, near the centre in subcircular examples ; nucleus very small, oval, dark brown. Inside shining, with the central area dark brown, the border much lighter in colour. Length, 7-5 mm. ; breadth, 6 mm.; height, 2,25 mm. (type). Other specimens measure 11 mm. by 9 mm. by 4,5 mm., and 8 mm. by 6,5 mm. by 3 mm.

This species has more equal, equidistant, and finer riblets than R. inconspicua ; there is an almost constant absence of shorter interstitial riblets ; no rays on the inside and no marginal border are present, and the sharply defined uniformly dark-brown central area is characteristic. It is probable that the shells were washed down from shallower water, as all the specimens I saw were empty, and more or less worn.

New Zealand. Near the Bounty Islands, in 50 fathoms