Material seen. — SARAWAK. 4th Div.: G. Mulu Nat. Park, lower Tutoh Valley (leg. Wilford, UF 194831/>10> incl. HOLOTYPE; do. 194847/>10).
Spire conical with flat to slightly convex sides. Apex slightly oblique or not. Whorls 5 1/8-5 7/8, convex; last whorl rounded. Constriction with a parietalis, a longitudinal and a transverse palatalis, with or without a very inconspicuous columellaris. Tuba gradually narrowed towards the constriction, rounded below. Radial ribs moderately spaced (3-4 ribs/0.5 mm on the penultimate whorl, 3 ribs/0.5 mm half-way on the tuba), those on the spire sinuous; those on the tuba (slightly) sinuous below. Spiral striation fine. Umbilicus open, 0.15-0.20 mm across. Aperture hardly tilted with regard to the coiling axis, circular. Peristome double; outer peristome spreading beyond the inner, but rather abruptly narrowed towards, and absent along the right side of the aperture, with a distinct, obtuse (rounded but not widely so) wing along the upper side, and usually a similar but less conspicuous wing along the lower side; inner peristome slightly protruding from the outer, spreading. Spire: height 1.7-2.1 mm; width 1.2-1.4 mm; index 1.4-1.6. Total width 2.1-2.3 mm. Height aperture 0.5-0.6 mm; width 0.5 mm.
Distribution. — Borneo: Sarawak, 4th Div., G. Mulu Nat. Park.

1. Very similar to, and sympatric with 0. pulchellum. It is regarded as a different species because of its consistently smaller size, the presence of spiral striation, and the absence or near absence of a columellaris in the constriction.
2. The name refers to the two small wings at opposite sides of the aperture.