Alycaeus ikanensis, 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 : 27

Alycaeus ikanensis sp. n. Figures 18, 31L

Alycaeus perakensis var. minor nomen nudum, Clements et al. 2008: 2760.

Type locality.

KTN 06 Gua Ikan, Kelantan (5°21'14"N, 102°01'33"E).

Type material.

Holotype. KTN 06 Gua Ikan, Kelantan: BOR/MOL 12972. Paratypes. KTN 06 Gua Ikan, Kelantan: BOR/MOL 6834/23.

Other examined materials.

KTN 06 Gua Ikan, Kelantan: BOR/MOL 6193/2, BOR/MOL 6632/17.

Etymology.

Named after the type locality, Gua Ikan.

Description.

Protoconch. Smooth.

Shell shape. Conical. Shell height: 4.02-4.58 mm. Shell width: 3.58-4.16 mm.

Spire. Spire height: 1.42-1.78 mm. Spire width: 1.83-2.03 mm. Number of whorls: up to 4 ½. Spire shape: oblong conical. Whorl periphery rounded. Umbilicus open.

Whorl constriction. At about 4 ¼ whorls posterior of protoconch.

Breathing tube. Length: 0.35-0.42 mm.

Aperture and peristome. Aperture circular, moderately expanded. Aperture height: 1.59-1.87 mm. Aperture width: 1.60-1.96 mm. Peristome double, not thickened, notched at suture. Peristome orientation 16-27° oblique with respect to the coiling axis.

Spiral lines. Distinct. Regularly spaced. Approximately 22-30 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs pronounced, evenly spaced. Approximately 9-19 ribs per 1 mm.

Radial ribs running perpendicular to breathing tube. Radial ribs pronounced, white and thicker than those anterior of breathing tube, evenly spaced. Approximately 13-18 ribs per 1 mm.

Radial ribs running posterior of breathing tube. Radial ribs absent immediately posterior of constriction, becoming pronounced and unevenly spaced towards the aperture.

Operculum. Concave, rounded. Exterior covered with very thin and indistinct calcareous layer, surface finely granulated, with very indistinct appressed multilamellae. Interior proteinaceous layered, smooth, very indistinct appressed multilamellae.

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

Living animal. Unknown.

Habitat and ecology.

Lives on limestone walls and boulders covered with mosses. In shady forests on limestone hills.

Distribution range.

Restricted to Gua Ikan, central Kelantan.

Differential diagnosis.

Alycaeus ikanensis sp. n. is distinctive in being the smallest species among conical, yellow shelled Alycaeus species in Peninsular Malaysia. Alycaeus ikanensis sp. n. is distinguished from A. costacrassa sp. n. by its consistently much smaller shell (smaller by about 0.62 mm in shell height, 0.90 mm in shell width) and narrower ultimate whorl.

Discussion.

Limestone hills adjacent to the type locality Gua Ikan may also harbour populations of the species.