Plectostoma bihamulatum (Vermeulen, 1994)
Mount Baturong, Tawau, Sabah, Malaysia.
Mount Baturong, Tawau, Sabah, Malaysia.
Description by Vermeulen (1994)
"spire conical with about flat sides. Apex slightly oblique. Whorls 5 3/8-6/3/8, convex; last whorl rounded. Constriction with a parietalis, a longitudinal and a transverse palatalis, a columellaris. Tuba gradually narrowed towards the constriction, rounded or slightly angular below. Radial ribs moderately to widely spaced (3-6 ribs/0/5 mm on the penultimate whorl, 3-5 ribs/0.5 mm half-way the tuba), (hardly) sinuous, those close to the tuba not sinuous; those on the tuba not or slightly sinuous below. Spiral striation present, often inconspicuous. Umbilicus open, 0.15-0.25 mm across. Aperture tilted up to 30º with regard to the coiling axis, subrectangular to subtriangular. Peristome almost touching the spire or distant from it, double; outer peristome (somewhat) spreading beyong the inner, but graudally narrowed towards, and absent along the right side of the aperture, with an inconspicuous to distinct edge or a small projection along the left side and a (moderately) distinct edge or small, obtuse (rounded but not widely so) projection along the upper side; inner peristome protruding from the outer, spreading. Spire: height 1.6-2.3 mm; width 1.2-1.5 mm; index 1.2-1.7. Total width 2.0-2.7 mm. Height and width aperture 0.5-0.6 mm."