Plectostoma pyrgiscus (Vermeulen, 1994)  

By Vermeulen (1994)

"Spire conical with flat sides. Apex oblique. Whorld 6, convex; last whorl rounded. Constriction with a transverse palatalis (only observed through the shell wall). Tuba free from spire, gradually narrowed towards the constriction, rounded below. Radial ribs on the spire tather widely spaced (4 ribs/0.5 mm on the penultimate whorl), slightly sinuous, but those close to the tuba not sinuous; those on the tuba widely spaced (1-2 ribs/0.5 mm half-way), not sinuous. Spiral striation distinct. Umbilicus open, 0.15 mm across. Aperture hardly tilted with regard to the coiling axis, its upper margin widely below the level of the apex, circular. Peristome simple, slightly spreading. Spire:height 1.8 mm; width 1.0 mm; index 1.8. Total width 1.9 mm. Height and width aperture 0.4 mm."