Additions to the knowledge of the land snails of Sabah (Malaysia, Borneo), including 48 new species Author Vermeulen, Jaap J. Author Liew, Thor-Seng Author Schilthuizen, Menno text ZooKeys 2015 531 1 139 http://dx.doi.org/10.3897/zookeys.531.6097 journal article http://dx.doi.org/10.3897/zookeys.531.6097 1313-2970-531-1 C845838EC9124BD8AB4E07980F91959E C845838EC9124BD8AB4E07980F91959E Taxon classification Animalia Stylommatophora Ariophantidae Microcystina planiuscula Vermeulen, Liew & Schilthuizen sp. n. Figure 33 Holotype . Malaysia , Sabah , Mt. Trusmadi , Gua Dawaras ( RMNH.5003936 ). Examined material from Sabah. Interior Province. Gunung Trusmadi slopes: Gua Loloposon (leg. J.J. Vermeulen, V 13220); Gua Dawaras (leg. M. Schilthuizen, V 12742; leg. M. Schilthuizen, V 9868). Description. Shell very small, thin, translucent, yellowish brown, discoid-lenticular; spire almost flat. Surface glossy. Whorls moderately convex. Protoconch with 7-10 very fine, widely and regularly spaced spiral grooves. Teleoconch: very fine, widely and sometimes irregularly spaced spiral grooves on the upper and lower surface; these sometimes (partly) absent on the outer whorls. Radial sculpture teleoconch: scattered, inconspicuous growth lines; very slight, irregularly spaced folds just below the suture. Umbilicus open, narrow; columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 1.5 mm; width up to 2.6 mm; diameters of the first three whorls 0.7-0.8 mm, 1.2-1.3 mm, c. 2.3 mm respectively; number of whorls up to 3 1/8; height aperture up to 1.2 mm; width aperture up to 1.4 mm. Figure 33-34. 33 Microcystina planiuscula sp. n. 33A Frontal view 33B Apical view 33C Umbilical view (Malaysia, Sabah, Gunung Trusmadi, Gua Dawaras, RMNH.5003936, holotype) 34 Microcystina appendiculata (Von Moellendorff, 1893). 34A Frontal view, shell 1.5 mm high 34B Apical view 34C Umbilical view (Malaysia, Sabah, Segama valley, North end of limestone ridge on East bank Tabin River, V 7781). Habitat in Sabah and distribution. Primary forest on limestone soil, 1600-1700 m alt. Sabah: Mt. Trusmadi only. Endemic to Sabah. Cross diagnosis. Identified by the distinctly more rapidly expanding whorls than in any other species in Group 2. Etymology. The name refers to the shell shape [planiusculus (L.) = somewhat flattened].