By van Benthem Jutting (1952)
"shell short-cylindrical, somewhat more cylindrical than O. michaelis, white. First whorl smooth, following ones ornamented with extremelu fine, white transverse ribs, closely placed in the upper whorls, somewaht more distantly on the last one. Although similar in ornamentation to O. michaelis the ribs of O tenuicostatum are more delicate and more crowded with narrower interstices. Between the ribs are still more delicate spiral striae, only visible at high magnification (x50). Somewhat shining and transparent. Whorls 4, convex. Top whorl placed obliquely on the axis of the shell. spire a little more elevated than in O. michaelis. Last whorl rather small, placed obliquely under the previous one, so that the shell becomes narrower towards the base. The penultimate whorl is bulging out in the shell profile. Last whorl constricted transvesely in the middle, then widening again and curving with a sharp twist (sharper than in O. michaelis) upward and backward. Adnate. Aperture round, pointing obliquely up and back. Peristome continuous, circular or rounded-triangular, duplex. Reaching almost to the suture between the second and thrid whorls. Operculum unknown."