Georissa trusmadi, 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 : 51

Georissa trusmadi sp. n. Figures 9 A–K

Type locality.

Loloposon Cave, Gunung Trus Madi, Sabah, Malaysia (05°39.00'N, 116°29.51'E).

Type material.

Holotype. Loloposon Cave, Gunung Trus Madi, Sabah, Malaysia (05°39.00'N, 116°29.51'E): MZU/MOL 16.17 (Fig. 9 A–C). Paratypes. Loloposon Cave, Gunung Trus Madi, Sabah, Malaysia (05°39.00'N, 116°29.51'E): MZU/MOL 16.18 (8) (Fig. 9 D–K). Gunung Trus Madi slopes, Gua Loloposon, Interior province, Sabah (05°39.00'N, 116°29.51'E) (20): JJV 13231.

Etymology.

The species is named after the type locality, Gunung Trus Madi, Sabah.

Description.

Protoconch. Colour: orange. Sculpture pattern: rounded to irregular sculptural shape. Mesh width: 3-30 µm. Teleoconch. Colour: orange. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: narrow. Number of whorls: 2 ¾– 3 ½. SH: 1.40-1.89 mm. SW: 1.12-1.37 mm. SI: 1.22-1.38. Shell sculpture. Radial sculpture: absent, weak growth lines present throughout the shell surface. Spiral sculpture: present, strong spiral ribs, broadly spaced above the whorls, ca. 5-7 strongly raised spiral ribs on the body whorl of the adult individual, appearing immediately after the protoconch, thin spiral ribs in between the stronger ones, more densely spaced and weaker at the basal part of the body whorl. Aperture. Shape: rounded to slightly ovoid, straight to convex parietal side, palatal edge contiguous with the parietal side, basal side convex. AH: 0.59- 0.72 mm. AW: 0.66-0.79 mm. AI: 0.85-0.91. Holotype dimensions. SH: 1.67 mm, SW: 1.28 mm, AH: 0.68 mm, AW: 0.75 mm.

Diagnosis.

Georissa trusmadi is characterised by the highly raised spiral sculpture. The number of strong spiral ribs on the first whorl is lower (3-5) than on the later whorls (5-7). The spiral sculpture is similar to G. insulae and G. hungerfordi , but always shows fewer ribs. Based on the shell habitus, it is similar to G. hungerfordi from Sarawak. The latter species, however, has the spiral ribs on the body whorl less strongly raised.

Distribution.

Georissa trusmadi is only known from Gunung Trus Madi, Sabah.