Shell subcylindrical, swollen below, sharply truncated above, produced and rounded anteriorly. Colour porcelain white, glossy. Sculpture of longitudinal, irregularly spaced ribs traverse the whole shell, anteriorly they are weak threads, posteriorly they wax stouter and form tubercles as they obliquely mount the vertex. Between these the shell is closely girt by about forty spiral grooves and their complementary ridges. Whorls four, the earlier ascending, the last descending. Suture deeply channel led. Apex mamillate, rising above the crown. Aperture very oblique, racquet shaped. Outer lip springing from the wall considerably below the vertex, rounded posteriorly, parallel with the body whorl as far as the waist of the shell, then curving outwards. Columella broad, sinuate, folded over a slight umbilical chink. Callus on body whorl distinct, forming a decided angle posteriorly. Length 1,75 mm, breadth 1 mm.

This species perhaps stands nearest to R. amphizosta Watson, from which it is easily distinguished by the even more pulled anterior half, the descent of the last whorl, and by the coarser, more prominent sculpture. The young shells differ altogether in contour from the adult, but may be recognised by their peculiar sculpture.

From Japan to Central Pacific