Georissa corrugata, Zacaery Khalik, Mohd, P. Hendriks, Kasper, J. Vermeulen, Jaap & Menno Schilthuizen,, 2019

Zacaery Khalik, Mohd, P. Hendriks, Kasper, J. Vermeulen, Jaap & Menno Schilthuizen,, 2019, Conchological and molecular analysis of the " non-scaly " Bornean Georissa with descriptions of three new species (Gastropoda, Neritimorpha, Hydrocenidae), ZooKeys 840, pp. 35-86 : 44-47

Georissa corrugata sp. n. Figure 6 A–I

Type locality.

Batu Tomanggong, Kinabatangan valley, Sandakan, Sabah, Malaysia (05°31.86'N, 118°18.24'E).

Type material.

Holotype. Batu Tomanggong, Kinabatangan valley, Sandakan, Sabah, Malaysia (05°31.86'N, 118°18.24'E): MZU/MOL 16.15 (Fig. 6 A–C) Paratypes. Batu Tomanggong, Kinabatangan valley, Sandakan, Sabah, Malaysia (05°31.86'N, 118°18.24'E): MZU/MOL 16.16 (Fig. 6 D–I). Batu Punggul, Sepulut valley, Sabah: JJV 1903 (1). N Borneo: RMNH/MOL 152848. Batu Keruak, Kinabatangan valley, Sabah (05°31.38'N, 118°17.10'E): BOR/MOL 1467, BOR/MOL 1844, BOR/MOL 11661 (1). Unnamed hill, Kinabatangan valley, Sabah (05°31.11'N, 118°17.23'E): BOR/MOL 2218 (1, juvenile).

Etymology.

The name is derived from a Latin word corrugatus, meaning “wrinkled”, referring to the coarse and irregular radial sculpture.

Description.

Protoconch. Colour: white. Sculpture pattern: parallel lines of varying width, widening before splitting in two. Mesh width: 3.1-6.2 µm, with the distance between each of the sculptural units as wide as the mesh width. Teleoconch. Colour: white. First whorl: rounded. Subsequent whorls: rounded. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ½– 3. SH: 1.14-1.43 mm. SW: 1.01-1.11 mm. SI: 1.10-1.29. Shell sculpture. Radial sculpture: present, more prominent after the first whorl, wavy, irregular and widely spaced, often distinctly higher and strongly projected on and above the periphery. Spiral sculpture: present, regularly spaced, thin, discontinuous due the interruption by radial sculpture. Aperture. Shape: rounded to slightly ovoid, parietal side straight, palatal edge contiguous with the parietal side, palatal and basal sides convex. AH: 0.82-1.07 mm. AW: 1.00-1.09 mm. AI: 0.75-1.02. Holotype dimensions. SH: 1.71 mm, SW: 0.99 mm, AH: 0.52 mm, AW: 0.58 mm.

Diagnosis.

The wavy and irregular, widely spaced and strong radial sculpture, with thin regularly arranged spiral sculpture in between is diagnostic for G. corrugata . Georissa similis and G. borneensis have a somewhat similar arrangement of radial and spiral sculpture, but do not carry the protoconch sculpture consisting of parallel lines. The shell shape and size of G. corrugata are similar to G. similis . Besides the difference in the protoconch sculpture, the latter species also has more densely arranged radial sculpture on the teleoconch.

Distribution.

Georissa corrugata is distributed on the limestone hills of the lower Kinabatangan valley, known to occur from Gomantong to Batu Tomanggong, but always in low densities compared to other Georissa species. The species has also been found in the Sepulut valley, ca. a hundred km further to the southwest.