Shell small, rather sturdily built, almost spherical, subovate in outline, weakly depressed, quite smooth, slightly glassy, white. The upper surface is convex. The protoconch is hyperstrophic, small, with ¾ of whorl, apparently smooth; its diameter is of about 190 mu. Protoconch I partially visible, separated from the Protoconch II by a strong axial rib. The teleoconch has between 2.15-2.25 whorls in adult specimens. The spire increases uniformly. The suture is clear but not deep and a slight depression appears below it. The aperture is almost circular, slightly pyriform; the columella strongly curved, a little angled and opisthocline. There is a short callus which totally covers the umbilicus. The apertural border is sharp and the peristome continuous, a little wider at the base. The surface of the shell is covered with numerous very fine spiral striae, and axial growth lines which form some folds near the base. Under high magnification there can be seen that the spiral striation is formed by very small, impressed, irregular and poorly limited cords which are more evident on the upper part of the whorls.
Holotype: height 0.84 mm, width 0.94 mm. Dimensions of the largest specimens 1.0 x 1.1 mm. Soft parts unknown.

Tomura sphaerica differs from T. depressa, by its smaller size, the more globose shape of its shell and by having its entire surface covered by spiral threads.
It can be separated from T. abscondita because the callus formed by the thickening of its internal lip completely covers the umbilicus. It differs from T. bicaudata by its sculpture and the lack of a periumbilical cord.