Plectostoma perspectivum (Vermeulen, 1994)  

By Vermeulen (1994)

"spire conical with about flat sides. Apex slightly oblique or not. Whorls 5 1/8 - 5 5/8, moderately convex; last whorl rounded to slightly angular. Constriction with a short, sometimes inconspicuous parietalis, a transverse palatalis, a small columellaris. Tuba gradually narrowed towards the constriction, rounded or slightly angular below, Radial ribs widely spaced (1-2 ribs/0.5 mm on the penultimate whorl and half-way on the tuba), those on the spire with a shallowly concave to deeply trough-shaped projection on the lower half of the shorls, abrading to a sinuous or deeply looped scar; but those close to the tuba with a deeply through-shaped projection on the periphery, abrading to a scar with a single deep loop when the shell is observed in front view; those on the tuba similar but with an almost tubular, curved projection below which is swollen at the tip. Spiral striation absent, rarely inconspicuous. umbilicus open, 0.40-0.55 mm across. Aperture tilted up to 45 degrees with regard to the coiling axis, its upper margin about level with the apex or widely above it, circular to elliptic. Peristome distant from the spire, double; outer peristome narrowed towards, and absent along the right and lower side of the aperture, along the upper side with a widely projecting, large, widely rounded wing which has (strongly) recurved margins, and is often truncated to its right side; inner peristome distinctly protruding from outer, spreading. Spire: height 1.7-2.0 mm; width 1.3-1.5 mm; index 1.3-1.4. Total width 2.5-3.0 mm. Height and width aperture 0.6-0.7 mm."