Material seen. — SABAH. Interior Zone: 4 km N. of Simatuoh, 9 km NE. of Sepulot {leg. Dorman, UF I96726/>10, incl. HOLOTYPE); 5.5 km NNE. of Simatuoh, 9 km E. of Sepulot (leg. Dorman, UF I96500/>10; do. 196508/>10; do. 196553/>10).
Spire conical with flat or slightly convex sides. Apex not or slightly oblique. Whorls 5 1/2-6 1/8, convex; last whorl rounded. Constriction with or without a parietalis, if present inconspicuous, starting about half-way the longitudinal palatalis and obliquely crossing the suture while continuing into the tuba beyond the longitudinal palatalis, with a longitudinal and a transverse palatalis, with or without a columellaris and a ridge-shaped transverse basalis. Tuba gradually narrowed towards the constriction, rounded below. Radial ribs on the spire moderately spaced (4-6 ribs/0.5 mm on the penultimate whorl), sinuous or not, those close to the tuba not or hardly sinuous; those on the tuba moderately to widely spaced (2-4 ribs/0.5 mm half-way), not or hardly sinuous below. Spiral striation absent or present. Umbilicus open, 0.30-0.40 mm across. Aperture tilted up to 30° with regard to the coiling axis, circular to elliptic, Peristome simple or double; when simple spreading, often with a somewhat thickened lip; when double outer peristome slightly spreading beyond the inner or not, if so gradually narrowed towards, and absent along the right side of the aperture, sometimes slightly widened along the upper side; inner peristome usually slightly protruding from the outer, spreading. Spire: height 1.7-2.1 mm; width 1.4-1.6 mm; index 1.3-1.5. Total width 2.4-2.7 mm. Height and width aperture 0.6-0.7 mm.
Distribution. — Borneo: Sabah, Interior Zone, a small area NE, of Sepulot.

1. Specimens from the sample UF 196926 (which includes the type specimen) differ from the others in having a spire with slightly convex sides, in the absence of spiral striation, as well as in having a simple peristome. A similar variabily occurs in 0. dormani from the same area.
2. Many specimens have a characteristic parietalis which crosses the suture with the previous whorl (hence the name) and continues into the tuba. Specimens without such a parietalis differ from 0. inornatum in having a wider umbilicus, and from 0. otostoma in lacking a small wing along the upper side of the aperture.