Georissa leucococca Vermeulen, Liew & Schilthuizen, 2015

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 : 51-53

Georissa leucococca Vermeulen, Liew & Schilthuizen, 2015 Figure 10 A–I

Georissa leucococca Vermeulen et al., 2015: 33, fig. 19 A-B; Marzuki and Foon 2016: 317; Khalik et al. 2018: 2.

Type locality.

Malaysia, Sabah, Interior Province, Sepulut valley, Gua Pungiton (04°42.41'N, 116°36.04'E).

Type material.Holotype (Holotype by original designation). Malaysia, Sabah, Interior Province, Sepulut valley, Gua Pungiton (04°42.41'N, 116°36.04'E): RMNH/MOL 5003956 (not seen, we were unable to locate the material in RMNH collection). Paratypes. Malaysia, Sabah, Interior Province, Sepulut valley, Gua Pungiton (04°42.41'N, 116°36.04'E): NHMUK 20150572, JJV 8081.

Other material.

Gua Sanaron, Sepulut valley, Sabah (04°42.52'N, 116°36.16'E): JJV 8068. Gua Pungiton, Sepulut valley, Sabah: BOR/MOL 61. Gua Madai, Tawau province, Sabah (04°44.00'N, 118°8.00'E): JJV 1736. Batu Temurung, Sepulut valley, Sabah (04°42.45'N, 116°34.40'E): JJV 12681. Clearwater Cave, Mulu National Park, Sarawak: JJV 13098. Bukit Sarang group, Lower Tatau River valley, Sarawak: JJV 12571, JJV 12848, JJV 12849. Gunung Segu near Kampung Benuk, Penrissen valley, Sarawak (01°18.47'N, 110°17.29'E): JJV 12569. Bt. Krian, Upper Penrissen valley, Sarawak (01°12.20'N, 110°21.54'E): JJV 14217. Kampung Semedang, Lower Penrissen valley, Sarawak (01°17.49'N, 110°16.24'E): JJV 14221. Gunung Aup, Bau, Sarawak (01°21.36'N, 110°4.04'E): JJV 12570. Gunung Rapih, Bau, Sarawak (01°23.15'N, 110°8.29'E): JJV 12572 (Fig. 10). Gunung Chupak, Sungei Bukar headwaters, Sarawak (01°14.05'N, 110°20.50'E): JJV 14218, JJV 14219. Batu Staat, Sungei Sarawak Kiri valley, Sarawak (01°23.55'N, 110°14.55'E): JJV 14220.

Description.

Protoconch. Colour: white. Sculpture pattern: minutely formed, a mix of rounded, semi-elliptic to ellipsoidal. Mesh width: 1-2 µm. Teleoconch. Colour: white. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: narrow. Number of whorls: 2 ¼. SH: 0.62-0.72 mm. SW: 0.60-0.70 mm. SI: 0.97-1.06. Shell sculpture. Radial sculpture: absent, only weak growth lines at irregular intervals are visible. Spiral sculpture: present, thin, regularly spaced, appearing immediately after the protoconch, distorted by the growth lines, more prominent at the upper whorls, becoming weaker when closer to the columellar region. Aperture. Shape: semi-elliptic, straight to concave parietal side, palatal side rounded, palatal edge contiguous with the body whorl, basal side convex. Umbilicus: open, with a narrow space underneath the reflected columellar peristome. AH: 0.31- 0.37 mm. AW: 0.33-0.38 mm. AI: 0.87-0.97.

Diagnosis.

Georissa leucococca has spiral sculpture that is more prominent at the upper part of the whorls, similar to G. bangueyensis . Georissa leucococca is so far the only known Bornean Georissa with an open umbilicus and with an adult shell size of hardly more than 1 mm. It has an angular shell shape, similar to G. borneensis .

Distribution.

Georissa leucococca is widely distributed in Malaysian Borneo. The species is known to occur from west Sarawak to east Sabah.