Georissa everetti Smith, 1895

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 : 47

Georissa everetti Smith, 1895 Figures 1B, 7 A–K

Georissa everetti Smith, 1895: 125, plate IV fig. 15; Thompson and Dance 1983: 120, figs 55-57.

Type locality.

Rumbang, W. Sarawak.

Type material.

Holotype (Holotype by original monotypy). Rumbang, Sarawak: NHMUK 1893.6.7.69 (glued on paper) (Fig. 1B) ( Thompson and Dance 1983).

Other material.

Kampung Giam, Lower Penrissen valley, Sarawak: JJV 12546. Kampung Benuk, Lower Penrissen valley, Sarawak (01°18.47'N, 110°17.29'E): JJV 12548. Kampung Temurang, Upper Penrissen valley, Sarawak (01°12.15'N, 110°16.18'E): JJV 12547. Great Cave, Niah National Park, Sarawak: RMNH/MOL 336264, JJV 10185 (Fig. 7), JJV 13119. Batu Punggul, Sepulut valley, Interior Province, Sabah: JJV 1906. Bukit Tinahas, Sepulut valley, Interior Province, Sabah (04°38.28'N, 116°37.05'E): JJV 7622.

Description.

Protoconch. Colour: orange to red. Sculpture: rounded to ellipsoidal mesh pattern, mixed with irregular sculptural shapes (whenever two or more rounded or ellipsoidal meshes are connected or combined). Mesh width: 4-30 µm. Teleoconch. Colour: orange to red. First whorl: convex. Subsequent whorls: convex, with relatively wide penultimate and final whorls. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ¾– 3 ¼. SH: 1.82-2.23 mm. SW: 1.52-1.75 mm. SI: 1.16-1.30. Shell sculpture. Radial sculpture: present, thin, forming small nodules when intersecting with spiral sculpture; these nodules are also present on the shoulder close to the suture. Spiral sculpture: present, thin, regularly spaced, oblique, appearing immediately after the protoconch, distorted/discontinuous by radial ribs. Aperture. Shape: rounded to ovoid, straight to concave parietal side, palatal edge contiguous with the body whorl, basal side convex. AH: 1.05-0.92 mm. AW: 1.09-0.96 mm. AI: 0.89-0.99.

Diagnosis.

The strong and thin oblique spiral sculpture on its shell is diagnostic for G. everetti . Georissa similis has a somewhat similar knitted sculpture pattern resulting from the intersection of radial and spiral ribbing, but the shell shape is entirely distinct, with broad penultimate and final whorls. Based on the shell shape and habitus, G. everetti resembles G. gomantonensis and G. williamsi , which, however, have clear, regular, spiral shell ribs.

Distribution.

Georissa everetti is widely distributed in Sabah and Sarawak, but is found in low abundances. The species known to occur from Padawan/Penrissen, Sarawak in the South (where Rumbang, the type locality is located), to further north, Niah, Sarawak, and Sepulut valley, Sabah.