Description
Author: Jan Delsing
Text ID: 128945
Text Type: 1
Page: 0
Created: 2023-12-30 19:57:21 - User Delsing Jan
Language: EN
Text function: [[t:1955853,textblock=128945,elang=EN;Description]]
Spire conical with flat sides. Apex slightly oblique or not. Whorls 3 7/8-4 1/4; top whorls convex; last whorl obtusely angular at the periphery, only slightly convex above and below. Constriction with an inconspicuous parietalis or not, a transverse palatalis, an inconspicuous knob-shaped transverse basalis or not. Tuba abruptly narrowed towards the constriction, angular below. Radial ribs on the spire rather closely placed (5-6 ribs/0.5 mm on the penultimate whorl), distinctly sinuous on the lower half of the whorls, but those close to the tuba widely spaced (1-3 ribs/0.5 mm), hardly visible but on the periphery with a deeply trough-shaped to almost tubular, curved projection, abrading to a scar with a single deep loop when the shell is observed in front view; those on the tuba similar but with a longer projection below which is slightly swollen at the tip. Spiral striation absent. Umbilicus open, 0.40-0.45 mm across. Aperture tilted 40-50° with regard to the coiling axis, its upper margin widely above the level of the apex, circular to elliptic. Peristome touching the spire, double; outer peristome widely spreading beyond the inner but on the side which touches the spire with a deep sinus flanked at both sides by a distinct, widely rounded wing; inner peristome not or hardly protruding from the outer, spreading. Spire: height 1.4-1.7 mm; width 1.2-1.4 mm; index 1.1-1.3. Total width 2.5-2.6 mm. Height aperture 0.7 mm; width 0.5-0.6 mm.
Distribution. — Borneo: Sarawak, 4th Div., G. Subis only.
Notes. — 1. Well characterized by its low and wide spire, its very large tuba, and its deeply notched outer peristome.
2. The name 'stellasubis’, 'the star of G. Subis was thought to be an apt epitheton for this spectacular species.
Vermeulen, J. J., 1994. Notes on the non-marine molluscs of the island of Borneo 6. The genus Opisthostoma (Gastropoda Prosobranchia: Diplommatinidae), part 2.