Taxon classification Animalia Stylommatophora Trochomorphidae

Geotrochus subscalaris Vermeulen, Liew & Schilthuizen sp. n. Figure 91

Geotrochus heraclea (not of E.A. Smith, 1895) Solem, 1964: 27.

Holotype. Malaysia, Sabah, Sandakan Province, Kinabatangan valley, Batu Pangi (RMNH.5003931).

Examined material from Sabah.

Sandakan Province. Kinabatangan valley, Batu Mawas (leg. T.S. Liew & M. Schilthuizen, BOR/MOL 1956, BOR/MOL 2251, BOR/MOL 1991); Batu Materis (leg. M. Schilthuizen, BOR/MOL 2430, BOR/MOL 2426); Batu Keruak (leg. T.S. Liew & B. Elahan, BOR/MOL 1847); Batu Pangi (leg. J.J. Vermeulen & M. Schilthuizen, V 9634, BOR/MOL 2421); Batu Tai (not Bod Tai) near Gomantong (leg. J.J. Vermeulen & M. Schilthuizen, V 9597); Batu Tomanggong Besar (leg. M. Schilthuizen, BOR/MOL 2428, BOR/MOL 2429; leg. M. Schilthuizen, A. van Til & B. Elahan, BOR/MOL 2973; leg. T.S. Liew & B. Elahan, BOR/MOL 2284); Batu Tomanggong Kecil (leg. M. Salverda & H. van Oosten, BOR/MOL 2427); Batu Tulug (Batu Putih) along road Lahad Datu-Sandakan, North of bridge over Kinabatangan River (leg. J.J. Vermeulen & H. Duistermaat, V 1490); Gomantong Hill 30 km South of Sandakan (leg. J.J. Vermeulen & H. Duistermaat, V 1627; leg. M. Schilthuizen, BOR/MOL 894; leg. T.S. Liew & J.P. King, BOR/MOL 3668); Tandu Batu (leg. J.J. Vermeulen & M. Schilthuizen, V 9626); Unnamed hill near Sukau Police Station (leg. T.S. Liew & B. Elahan, BOR/MOL 2220). Segama valley, North end of limestone ridge on East bank Tabin River (leg. J.J. Vermeulen & M. Schilthuizen, V 7763). Tawai Mountains near Telupid (leg. J.J. Vermeulen, V 1259). Tawau Province. Batu Baturong c. 50 km W.S.W. of Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1852). Danum Valley (leg. H.A. Rutjes, BOR/MOL 888, BOR/MOL 2936; leg. M. Schilthuizen, BOR/MOL 2934); Gua Madai c. 40 km S.S.W. of Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1741). Segama valley, hill N.W. of crossing road Sandakan-Lahad Datu with the Segama River (leg. J.J. Vermeulen & H. Duistermaat, V 1657); ‘Kirk’s Cave’ 8 km North of Lahad Datu (leg. J.J. Vermeulen, V 1253); Sabahmas Cave (leg. J.J. Vermeulen, V 7469, BOR/MOL 897). Tabin Wildlife Reserve (leg. T. Kimsin & H.N. Chai, BOR/MOL 898). Semporna area, Segarong Hills, Batu Tengar, 25 km E.S.E. Of Kunak (leg. J.J. Vermeulen & H. Duistermaat, V 1816); Bukit Pababola, 25 km E.S.E. of Kunak (leg. J.J. Vermeulen & H. Duistermaat, V 1780).

Description.

Shell rather small, rather thin, about opaque, yellowish to pale brown, moderately low-conical with slightly concave to slightly convex sides; apex slightly to moderately protruding. Surface with a silky luster. Whorls: Apical whorls moderately convex, outer approx. flat to slightly convex; suture impressed, between the outer 4-5 whorls slightly below the periphery; last whorl acutely angular, compressed at the periphery, rounded below the periphery. Protoconch 2 1/8-2 1/4 whorls, smooth. Teleoconch. Radial sculpture: above the periphery some growth lines, locally grading into inconspicuous riblets; below the periphery indistinct growth lines only. Spiral sculpture: last whorl with a sharp, pinched peripheral keel; start of fifth whorl with 6-10 thin, widely spaced spiral threads: Usually 1-2 (slightly) more distinct close to the periphery, as well as 5-10 inconspicuous above these; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed. Dimensions: Height 6.2-7.3 mm; width 11-13.0 mm, h/w 0.52-0.59; diameters of the first 4 whorls 1.1-1.4 mm, 1.9-2.4 mm, 2.7-3.6 mm, 4.0-4.8 mm respectively; number of whorls 6 1/4-8, height aperture 3.2-4.0 mm; width aperture 6.0-7.2 mm.

Habitat in Sabah and distribution.

Primary and secondary forest and more degraded vegetation types on limestone soil, up to 200 m alt. Sabah: East coast. Endemic to Sabah.

Cross diagnosis.

Most similar to Geotrochus whiteheadi, differs by the suture which is situated slightly below the periphery in the outer whorls.

Etymology.

The name refers to the slightly protruding peripheral keel, creating a small notch in between the whorls in lateral view [sub-scalaris (L) = a little resembling a ladder].