Opisthostoma auriforme Vermeulen, 1994  

[Jaap Vermeulen, 1994]

Spire cylindrical. Apex oblique. Whorl 3 1/4 - 3 3/8, convex; convex; the penultimate obtusely angular on the right side if the shell is observed in front view, the ultimate obtusely angular. Constriction with a parietalis which continues far into the tuba; wih a distinct, short angularis covering the suture, with a transverse palatalis. Tuba touching the spira over its entire length, slgihtly bulging and rather abruptly narrowed towards the constriction, obtusely angular below. Radial ribs on the spire moderately spaced (4-5 ribs/0.5 mm on the penultimate whorl), not sinuous; those on the tuba widely spaced (2-3 ribs/0.5 mm half-way the tuba), with a shallow, semi-circular loop below. Spiral striation present. Umbilicus open, 0.1 mm across, but often (almost) entirely covered by the tuba. Aperture tilted up to 15 degrees with regard to the coiling axis, its upper margin widely above the level apex, elliptic, with the continuation of the parietalis clearly visible along its lower side if the aperture is observed in front view. Peristome double, outer peristome widely spreading beyond the inner, but gradually narrowed towards, and absent along the tight side of the aperture; inner peristome protruding from the outer, somewhat spreading, its outer surface and the upper surface of the outer peristome with closely placed, slightly irregular lamella. Spire: height 1.1-1.3 mm; width 1.2-1.3 mm; index 0.9-1.0. Total width 1.7-1.8 mm. Height aperture 0.4-0.6 mm; width 0.5-0.6 mm.