Profil taxonu
Obrázky
Autor: Vermeulen, J.J.
Popis
Material seen. — SARAWAK. 1st Div.: SE. end of limestone outcrop S. of Bau (leg. Wilford, UF 194692/10, inch HOLOTYPE; do. 194693/10).
Spire cylindrical. Apex distinctly oblique. Whorls 3 1/2-3 5/8, convex; last whorl rounded. Constriction with a transverse palatalis, sometimes with an inconspicuous columellaris. Tuba entirely distant from the spire, gradually narrowed towards the constriction, rounded below. Radial ribs very closely placed (20-26 ribs/0.5 mm on the penultimate whorl, 16-22 ribs/0.5 mm half-way the tuba), not sinuous. Spiral striation present, inconspicuous. Umbilicus open, 0.1 mm across. Aperture tilted up to 15° with regard to the coiling axis, its upper margin slightly above to widely below the level of the apex, circular to slightly elliptic. Peristome distant from the spire, simple, somewhat spreading. Spire: height and width 0.8-0.9 mm; index 1.0-1.1. Total width 1.4-1.6 mm. Height aperture 0.35-0.45 mm; width 0.35-0.40 mm.
Distribution. — Borneo: Sarawak, 1st Div., limestone range SE. of Bau.
Notes. — 1.0. asyndeton as well as 0. telestoma have much wider spaced ribs.
2. The name refers to the fact that the densely ribbed shell somewhat resembles a twice-coiled spring.
Spire cylindrical. Apex distinctly oblique. Whorls 3 1/2-3 5/8, convex; last whorl rounded. Constriction with a transverse palatalis, sometimes with an inconspicuous columellaris. Tuba entirely distant from the spire, gradually narrowed towards the constriction, rounded below. Radial ribs very closely placed (20-26 ribs/0.5 mm on the penultimate whorl, 16-22 ribs/0.5 mm half-way the tuba), not sinuous. Spiral striation present, inconspicuous. Umbilicus open, 0.1 mm across. Aperture tilted up to 15° with regard to the coiling axis, its upper margin slightly above to widely below the level of the apex, circular to slightly elliptic. Peristome distant from the spire, simple, somewhat spreading. Spire: height and width 0.8-0.9 mm; index 1.0-1.1. Total width 1.4-1.6 mm. Height aperture 0.35-0.45 mm; width 0.35-0.40 mm.
Distribution. — Borneo: Sarawak, 1st Div., limestone range SE. of Bau.
Notes. — 1.0. asyndeton as well as 0. telestoma have much wider spaced ribs.
2. The name refers to the fact that the densely ribbed shell somewhat resembles a twice-coiled spring.
Vermeulen, J.J., 1994. Notes on the non-marine molluscs of the island of Borneo 6. The genus Opisthostoma (Gastropoda Prosobranchia: Diplommatinidae), part 2
Autor: Jan Delsing