Material seen. — SABAH. Sandakan Zone: limestone hill 7 miles E. of Lamag, 3 miles NNW. of Laab, near road Lahad Datu-Sandakan, near Kinabatangan R. (leg. Wilford, UF 194804/8; do. 194805/>10); Bt. Goman¬tong, 30 km S. of Sandakan (BMNH/5, see above; UF 160198; leg. Wilford, UF 194798/M0; do. 194799/>10; V 1589/4). "North Borneo" (UF 133021/2).

Spire conical with slightly concave to slightly convex sides. Apex not oblique. Whorls 5 1/8-6 3/8, convex; last whorl rounded to slightly angular. Constriction with a parietalis, a longitudinal and a transverse palatalis, a columellaris which continues as a knob- to ridge-shaped transverse basalis. Tuba gradually narrowed towards the constriction, rounded below. Radial ribs on the spire rather closely placed to moderately spaced (4-5 ribs/0.5 mm on the penultimate whorl), sinuous or not, but those close to the tuba not sinuous; those on the tuba moderately spaced (3 ribs/0.5 mm half-way), slightly sinuous below. Spiral striation present, often inconspicuous. Umbilicus open, 0.25-0.40 mm across. Aperture tilted up to 30° with regard to the coiling axis, circular, elliptic or slightly angular. Peristome touching the spire or distant from it, double; outer peristome spreading beyond the inner, gradually to rather abruptly narrowed towards, and absent along the right side of the aperture, usually with a distinct, obtuse (rounded but not widely so) wing along the upper side, and sometimes a similar but less conspicuous wing along the lower side; inner peristome moderately protruding from the outer, often with a few protruding lamellae on its outer surface, spreading. Spire: height 1.5-2.2 mm; width 1.2-1.6 mm; index 1.2-1.5. Total width 2.0-2.5 mm. Height and width aperture 0.5-0.6 mm.
Distribution. — Borneo: Sabah, Sandakan Zone, isolated limestone hills in the Kinabatangan Valley.

1. Known from two populations only. The population found on a limestone scarp N. of Batu Laab shows less variability than the population at Bt. Gomantong: all specimens have the peristome adnate to the spire.
2. Part of a species complex, see note under 0. lissopleuron.