Geotrochus conicoides (Metcalfe, 1851)

Vermeulen, Jaap J., Liew, Thor-Seng & Schilthuizen, Menno, 2015, Additions to the knowledge of the land snails of Sabah (Malaysia, Borneo), including 48 new species, ZooKeys 531, pp. 1-139 : 104-106

Taxon classification Animalia Stylommatophora Trochomorphidae

Geotrochus conicoides (Metcalfe, 1851) Figure 86

Helix conicoides Metcalfe, 1851: 71. Trochomorpha conicoides (Metcalfe) Wallace, 1865: 407. Nigritella conicoides (Metcalfe) Godwin Austen, 1891: 42. Dendrotrochus conicoides (Metcalfe) Kobelt, 1897: 50. Trochonanina conicoides (Metcalfe) Von Martens, 1908: 284. Eurybasis conicoides (Metcalfe) Van Benthem Jutting, 1941: 23. Geotrochus conicoides (Metcalfe) Van Benthem Jutting, 1959: 143. Type from Borneo (unspecified).

Examined material from Sabah.

West Coast Province. Pulau Gaya, 8 km Northwest of Kota Kinabalu (leg. M. Schilthuizen, BOR/MOL 2937). Pulau Tiga (leg. UMS students, BOR/MOL 899). Tawau Province. Tawau Hills N.P., path up to Bukit Bombalai (leg. J.J. Vermeulen, V 13167).

Description.

Shell medium-sized, rather thin, opaque, uniformly pale to dark brown (some material from Sarawak a paler brown just below the suture), (low-)conical with almost flat to distinctly concave sides, apex slightly to distinctly protruding. Surface more or less dull or with a silky luster above the periphery, shiny below. Whorls: Apical whorls moderately convex, next whorls approx. flat to slightly convex, outer whorls often flat; suture impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, (distinctly) compressed at the periphery, slightly to rather distinctly concave just below the periphery, slightly to moderately convex towards the umbilical region. Protoconch 1 7/8-2 1/2 whorls, smooth. Teleoconch. Radial sculpture: above and below the periphery inconspicuous growth lines, somewhat raised locally. Spiral sculpture: last whorl with a sharp, distinctly pinched peripheral ridge; start of fifth whorl with 5-17 rather densely placed to somewhat spaced, low and thin spiral threads, the 2-5 threads close to the periphery usually slightly more distinct, the others very inconspicuous or (almost) absent; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed. Dimensions: Height 7.7-10.0 mm; width 16-19.8 mm; h/w 0.42-0.53; peripheral keel of the last whorl at 0.57-0.66 of the shell height, measured from the apex; diameters of the first 4 whorls 1.3-1.5 mm, 2.0-2.5 mm, 2.5-4.0 mm, 4.2-5.6 mm respectively; number of whorls 7-8, height aperture 2.8-3.8 mm; width aperture 8-9.5 mm.

Habitat in Sabah and distribution.

Primary and old secondary forest on sandstone and volcanic bedrock, lowland conditions. Living on decaying wood. Sabah, scattered localities: Labuan, Pulau Tiga; Pulau Gaya, Tawau Hills. Also in Sarawak. Distribution: Sumatra. A record from Morotai, Moluccas ( Van Benthem Jutting 1941: 23) is probably erroneous.

Cross diagnosis.

Generally characterized by the conical spire, but low-conical specimens occur. These approach the Geotrochus labuanensis group in general shape but have a more distinctly protruding apex and more distinctly concave sides. Also, relative to the shell height, the peripheral keel is positioned closer to the base of the shell, and the lower surface of the shell is often rather distinctly concave towards the periphery.

See also the remarks under Geotrochus scolops .