Alycaeus charasensis, Foon, Junn Kitt & Liew, Thor-Seng, 2017

Foon, Junn Kitt & Liew, Thor-Seng, 2017, A review of the land snail genus Alycaeus (Gastropoda, Alycaeidae) in Peninsular Malaysia, ZooKeys 692, pp. 1-81 : 15-16

Alycaeus charasensis sp. n. Figures 7K, 12, 31H

Type locality.

PHG 73 Bukit Charas, Pahang (3°54'35"N, 103°08'48"E).

Type material.

Holotype. PHG 73 Bukit Charas, Pahang: BOR/MOL 12981. Paratypes. PHG 75 Bukit Tenggek, Pahang: BOR/MOL 264/2. PHG 73 Bukit Charas, Pahang: BOR/MOL 267/3, BOR/MOL 6891/1.

Other examined materials.

PHG 73 Bukit Charas, Pahang: BOR/MOL 8399/14, BOR/MOL 8401/26, BOR/MOL 8402/166, BOR/MOL 12982/120, ZRC 1975.2.21.431-434/4, ZRC 1975.2.22.444-677/234, ZRC 1975.2.24.132- 153 /22, ZRC 1975.2.24.1-43/43, ZRC 1975.2.24.93-131/38, ZRC 1975.2.24.83-89/6. PHG 75 Bukit Tenggek, Pahang: ZRC 1975.2.24.44-/>1.

Etymology.

Subspecific epithet named after the type locality, Bukit Charas.

Description.

Protoconch. Smooth.

Shell shape. Conical. Shell height: 5.09-5.82 mm. Shell width: 5.23-6.62 mm.

Spire. Spire height: 1.57-2.11 mm. Spire width: 2.38-2.77 mm. Number of whorls: up to 5. Spire shape: oblong conical. Whorl periphery rounded. Umbilicus open.

Whorl constriction. At about 4 ⅞ whorls posterior of protoconch.

Breathing tube. Length: 0.46-0.57 mm.

Aperture and peristome. Aperture circular, moderately expanded. Aperture height: 2.58-2.90 mm. Aperture width: 2.47-2.84 mm. Peristome double, not thickened, slightly notched at suture. Peristome orientation 34-43° oblique with respect to the coiling axis.

Spiral lines. Indistinct, regularly spaced. Approximately 16-60 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs indistinct, unevenly spaced. They are sometimes absent and are replaced by evenly spaced radial growth lines.

Radial ribs running perpendicular to breathing tube. Radial ribs pronounced, white and thick, evenly spaced. Approximately 8-15 ribs per 1 mm.

Radial ribs running posterior of breathing tube. Radial ribs absent immediately posterior of constriction, becoming pronounced and evenly spaced at the middle until prior to aperture. Approximately 7-19 ribs per 1 mm.

Operculum. Concave, rounded. Exterior covered with thin calcareous layer, with indistinct appressed multilamellae. Interior covered with proteinaceous coating, smooth, with indistinct appressed multilamellae.

Shell colour. Whorls yellow, fading to white posterior of constriction. Peristome white.

Living animal. Body cream-white with fine brown blotches. Head brown. Tentacles brown.

Habitat and ecology.

Lives on rock surfaces covered with powdery lichen at higher and drier areas of the limestone hills, often at open places exposed to ambient sunlight. They never appear on wet and mossy sections of limestone rocks and are not found in lower parts of limestone hills that are shaded by forest cover.

Distribution range.

Restricted to Bukit Charas and Bukit Tenggek, eastern Pahang.

Differential diagnosis.

Alycaeus charasensis sp. n. shares similar variability in shell shape with Alycaeus alticola sp. n. but consistently differs in having a larger shell, wider ultimate whorl, widely spaced spiral lines and uneven, widely spaced radial growth lines in place of radial ribs. Alycaeus charasensis sp. n. is distinguished from other tall spired, conical yellow shelled Alycaeus in Peninsular Malaysia by its lack of distinct radial ribs.

Discussion.

A. charasensis sp. n. is among the larger yellow, conical shelled Alycaeus in Peninsular Malaysia.