“O. asyndeton as well as O. telestoma have much wider spaced ribs.” (Vermeulen, 1994)
Vermuelen (1994) original descriptions on Opisthostoma dihelicton – “Spire cylindrical. Apex distinctly oblique. Whorls 3½-3 5/8, convex; last whorl rounded. Constriction with a transverse palatalis, sometimes with an inconspicuous columellaris. Tuba entirely distant from the spire, gradually narrowed towards the constriction, round below. Radial ribs very closely placed (20-26 ribs/0.5 mm on the penultimate whorl,16-22 ribs/0.5 mm half-way the tuba), not sinuous. Spiral striation present, inconspicuous. Umbilicus open, 0.1 mm across. Aperture tilted up to 15° with regard to the coiling axis, its upper margin slightly above to widely below the level of the apex. circular to slightly elliptic. Peristome distant from the spire, simple, somewhat spreading.”
Opisthostoma dihelicton – “Spire: height and width 0.8-0.9 mm; index 1.0-1.1. Total width 1.4-1.6 mm. Height aperture 0.35-0.45; width 0.35-0.40 mm.” (Vermeulen, 1994)
Type locality – “Sarawak, 1st Division, SE end of the limestone outcrop S of Bau” leg. Wilford (Vermeulen, 1994)