Microcystina gratilla Van Benthem Jutting, 1950

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 : 43-44

Taxon classification Animalia Stylommatophora Ariophantidae

Microcystina gratilla Van Benthem Jutting, 1950 Figure 36, 39

Microcystina gratilla Van Benthem Jutting, 1950: 448; Liew et al. 2010: Appendix S1 in online Supporting Information. Type from Indonesia, Java, near Bogor. Wilhelminaia gratilla (Van Benthem Jutting) Maassen, 2001: 96.

Microcystina sp. “BO-04”, Schilthuizen et al. 2002 a: 257; Schilthuizen et al. 2002b: 42; Schilthuizen and Vermeulen 2003: 96; Schilthuizen 2004: 94.

Examined material from Sabah.

Interior Province. Crocker Range N.P., West of the km 10 marker on the road Tambunan-Ranau, Mahua Waterfall (leg. J.J. Vermeulen, V 12741). Gunung Trusmadi (leg. M. Schilthuizen & P. Koomen, V 12740). West Coast Province. Kinabalu N.P., Poring Hot Springs, along path to waterfall (leg. J.J. Vermeulen, V 13006); Monggis-Tambuyukon trail between 896 and 1016 m (leg. T.S. Liew, BOR/MOL 4139, BOR/MOL 4141); Serinsim-Nombuyukon trail between 548 and 877 m (leg. T.S. Liew, BOR/MOL 4140, BOR/MOL 4143).

Description.

Shell very small, thin, translucent, yellowish brown to brown, lenticular; spire almost flat to moderately elevated, conical with a rounded apex. Surface glossy. Whorls moderately convex. Protoconch: spiral striation absent, with or without a few inconspicuous, scattered radial riblets towards the teleoconch. Teleoconch: with or without traces of very fine (only just visible at 40 times magnification), widely and somewhat irregularly spaced, shallow, rather sharply outlined grooves which are somewhat interrupted towards the protoconch, but which are continuous on the outer whorls. Radial sculpture teleoconch: inconspicuous growth lines, next to these inconspicuous to distinct, well-spaced to densely placed, shallow grooves, often at irregular intervals. Umbilicus open, narrow, columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 2.2 mm; width up to 3.6 mm; diameters of the first three whorls 0.4-0.5 mm, 0.8-1.0 mm, 1.2-1.6 mm respectively; number of whorls up to 4 7/8; height aperture up to 1.3 mm; width aperture up to 1.3 mm.

Habitat in Sabah and distribution.

Primary and secondary forest on sandstone bedrock, up to 900 m alt., elsewhere up to 2400 m alt. Sabah: Mount Kinabalu, Mount Tambuyukon; Mount Trusmadi, Crocker Range. Also in Kalimantan. Distribution: Java; Madura, Bali; Flores.

Cross diagnosis.

Very similar to Microcystina muscorum , but the sculpture, at least on the protoconch, is different; see below Microcystina muscorum . Juvenile Microcystina appendiculata in which the spur protruding from the columellar corner of the peristome has not yet developed can be distinguished by the absence of well-spaced radial grooves on the teleoconch. Juvenile Microcystina physotrochus has a protoconch with more distinct radial riblets.

Remarks.

Most Sabah shells have a comparatively high spire.