Georissa nephrostoma Vermeulen, Liew & Schilthuizen

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 : 23-24

Taxon classification Animalia Archaeogastropoda Hydrocenidae

Georissa nephrostoma Vermeulen, Liew & Schilthuizen sp. n. Figure 20

Holotype. Malaysia, Sabah, Sandakan Province, Kinabatangan valley, Batu Keruak 2 near Sukau ( RMNH.5003955 ).

Examined material from Sabah.

Sandakan Province. Kinabatangan valley, Batu Keruak 2 near Sukau (leg. J.J. Vermeulen & M. Schilthuizen, V 9795; leg. M. Salverda & H. van Oosten, BOR/MOL 1449, BOR/MOL 1450; leg. T.S. Liew & B. Elahan, BOR/MOL 1845); Batu Pangi (leg. J.J. Vermeulen & M. Schilthuizen, V 9833, BOR/MOL 1452); Batu Tai (not Bod Tai) near Gomantong (leg. J.J. Vermeulen & M. Schilthuizen, V 9832); Tandu Batu (leg. J.J. Vermeulen & M. Schilthuizen, V 9834); Unnamed limestone hills near Sukau Police Station (leg. T.S. Liew & B. Elahan, BOR/MOL 2186; leg. T.S. Liew, BOR/MOL 2153; leg. M. Schilthuizen, BOR/MOL 1451).

Description.

Shell minute, solid, opaque or nearly so, orange to white; spire conical with convex sides; apex rounded. Surface with a silky luster. Whorls distinctly convex, rounded; last whorl rounded at the periphery. Protoconch minutely rugulose. Teleoconch: radial sculpture in some specimens consisting of growth lines, only locally somewhat raised, in others consisting of densely placed, inconspicuous to rather distinct, low and rather flat ridglets with narrow, shallow grooves in between. Spiral sculpture: virtually absent in some specimens, in others consisting of densely placed to somewhat spaced, very fine, shallow grooves cutting into the raised elements of the radial sculpture, but sometimes most conspicuous in between the radial riblets on the apical whorls. Aperture reniform, with the parietal side distinctly concave; peristome extended on the parietal side, not reflected elsewhere, embedded in the shell surface on the columellar side. Umbilicus closed. Dimensions: Height 1.35-1.60 mm; width 0.90-1.15 mm; number of whorls 2 3/4-3 1/2; height aperture 0.60-0.65 mm; width aperture 0.50-0.55 mm.

Habitat in Sabah and distribution.

Primary and secondary forest on limestone bedrock. Alt. up to c. 100 m. Sabah: Lower Kinabatangan valley only. Endemic to Sabah.

Cross diagnosis.

Most similar to Georissa similis E.A. Smith 1893; distinguished by the deeply concave parietal peristome, giving the aperture a kidney-shaped outline. In Georissa similis the parietal side of the aperture is usually straight or slightly convex, seldomly a little concave. The sculpture of Georissa nephrostoma is on average less distinct than in Georissa similis , but both species include series of almost smooth specimens.

Etymology.

The name refers to the shape of the aperture [nephros (Gr.) = kidney; stoma (Gr.) = mouth].