Georissa pachysoma Vermeulen & Junau, 2007 Figure 15 A–K

Georissa pachysoma Vermeulen & Junau, 2007: 216, fig. 7.

Type locality.

Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Lebik.

Type material.

Holotype (Holotype by original designation). Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Lebik: RMNH/MOL 109084. Paratypes. Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Lebik: JJV 12628 (10), JJV 12837 (2).

Other material.

Bukit Sarang group, Lower Tatau River valley: JJV 12626, JJV 12844, JJV 12845, JJV 12846. Upper Tatau River valley, upper Kakus River limestone scarps: JJV 12847. Bt. Besungai 0.5 m SW of Batu Gading, Long Lama, Baram valley (03°52.00'N, 114°25.00'E): JJV 4940. Slopes and cliffs along path to Great Cave, Niah National Park: JJV 10216. N side of limestone area, Painted Cave, Niah National Park: JJV 10391. Bukit Lebik and Bukit Anyi, Bukit Sarang, Bintulu, Sarawak (02°39.31'N, 113°02.47'E): MZU/MOL 17.62- MZU/MOL 17.84.

Description.

Protoconch. Colour: red to brown. Sculpture: a mix of triangular, rounded, and irregular sculptural shapes. Mesh width: 2-12 µm . Teleoconch. Colour: red to brown. First whorl: convex. Subsequent whorls: convex, broad at the final whorl. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ¾– 3 ¼ . SH: 1.20-1.65 mm. SW: 0.95-1.23 mm. SI: 1.19-1.34. Shell sculpture. Radial sculpture: absent, weak growth lines at irregular intervals only. Spiral sculpture: present, rather thin, widely spaced in the centre of the whorls, densely spaced close to the suture and the periphery, ribs appear immediately after the protoconch, ca. 12-15 medium raised spiral ribs, distorted/discontinuous where they are crossed by the growth lines. Aperture. Shape: rounded to semi-elliptic, straight to concave parietal side, palatal side convex and tilted below, palatal edge contiguous with the body whorl, basal side convex. AH: 0.54- 0.70 mm. AW: 0.57-0.72 mm. AI: 0.90-1.00.

Diagnosis.

Georissa pachysoma is characterised by a dark red to brown colour of the shell, similar to G. nephrostoma, but the latter species has wavy spiral ribs while G. pachysoma does not. In shell habitus, G. pachysoma closely resembles G. hungerfordi, but the colour and spiral sculpture of G. hungerfordi (orange in colour in living or freshly dead specimens, with highly raised spiral sculpture) is entirely different from G. pachysoma .

Distribution.

Georissa pachysoma is widely distributed from Bukit Sarang, Bintulu to further north in Baram and Niah, Sarawak.

Molecular analysis.

ML and Bayesian analyses of G. pachysoma (16S: n = 4; CO1: n = 4) show that G. pachysoma forms one clade with 100% BS and 100% PP, sister to the rest of the “non-scaly” group species, except for G. hungerfordi + G. gomantonensis + G. filiasaulae + G. insulae .