Alycaeus perakensis Crosse, 1879a

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 : 36-37

Alycaeus perakensis Crosse, 1879a Figures 7S, 24, 31V

Alycaeus perakensis Crosse, 1879a: 206-208, plate 7, figure 7; Crosse 1879b: 339-340; Möllendorff 1886: 310; Sykes 1903: 195; Tension-Woods 1888: 1068; Tielecke 1940: 345; Davison 1995: 236; Schilthuizen et al. 1999: 353; Clements et al. 2008: 2760; Foon et al. 2017: 13, figure 4F.

Alycaeus (Orthalycaeus) perakensis : Möllendorff 1891: 342; Kobelt and Möllendorff 1897: 150.

Alycaeus (Alycaeus) perakensis : Kobelt 1902: 348; Laidlaw 1928: 35; Chan 1998a: 4; Chan 1998b: 1.

Alycaeus perakensis perakensis : Maassen 2001: 23; Tarruella and Domènech 2011: 72.

Type locality.

Buket Pondong (= PRK 55 Gunung Pondok), Perak (4°46'57"N, 100°50'01"E).

Type material.

Syntypes. Buket Pondong (= PRK 55 Gunung Pondok), Perak: MNHN IM-2000-31793/1 (Seen), MNHN IM-2000-31794/1 (Seen), MNHN IM-2000-31795/1 (Seen).

Other materials.

KDH 01 Bukit Baling, Kedah: BOR/MOL 6525/1, BOR/MOL 6854/5, BOR/MOL 8527/1, BOR/MOL 8528/2. KDH 02 Gunung Pulai, Kedah: BOR/MOL 6858/2. PRK 55 Gunung Pondok, Perak: BOR/MOL 272/1, BOR/MOL 6849/1, BOR/MOL 8349/29, BOR/MOL 8350/23, BOR/MOL 11479/46, BOR/MOL 11506/31, BOR/MOL 11539/50, BOR/MOL 11563/20, ZRC 1997.25/5, ZRC 1975.2.22.175-182/12, ZRC 1975.2.22.36-66/31, ANSP 423056/2. PRK 61 Gua Badak, Perak: ZRC 1975.2.22.160-174/15. PRK 62 Gunung Dayak, Perak: BOR/MOL 277/5, BOR/MOL 6201/3, ZRC 1975.2.22.127-159/33. PRK 64 Bukit Kepala Gajah, Perak: BOR/MOL 6852/1, BOR/MOL 8354/33, BOR/MOL 8355/5, BOR/MOL 10088/31, BOR/MOL 10124/15, BOR/MOL 10136/18, BOR/MOL 10166/21, BOR/MOL 13001/2. Mykarst-171 Tasik Temenggor Hill S2, Perak: BOR/MOL 6243/1. Hill 40 m east of Sungai Siput Hospital, Perak: BOR/MOL 271/1, BOR/MOL 6877/1, BOR/MOL 8385/24, BOR/MOL 8386/1. Limestone outcrop 50m from roadside, Kampung Pahit, Klian Intan, Perak: BOR/MOL 6874/1, BOR/MOL 8379/22, BOR/MOL 8380/9. 'Bat Cave’ Hill, roadside towards Perlop 1 and 2 oil palm plantations, Perak: BOR/MOL 6878/1, BOR/MOL 8387/17, BOR/MOL 8388/5, BOR/MOL 9770/11, BOR/MOL 9799/3, BOR/MOL 9833/1, BOR/MOL 9877/4. Batu Kebelah, Kampung Kenang Baru, Jalong Tinggi, Perak: BOR/MOL 6879/1, BOR/MOL 8389/5, BOR/MOL 8390/5, BOR/MOL 9546/23, BOR/MOL 9565/2, BOR/MOL 9573/5, BOR/MOL 9585/17. Lenggong, Perak: ZRC 1997.24/4 specimens. Perak: RMNH 153573/3, RMNH 153574/2. Banang Pupo, Yala, Thailand: ANSP 446394/3.

Description.

Protoconch. Smooth.

Shell shape. Conical. Shell height: 5.98-7.27 mm. Shell width: 6.48-8.62 mm.

Spire. Spire height: 1.83-2.64 mm. Spire width: 2.80-3.39 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: 0.61-0.88 mm.

Aperture and peristome. Aperture circular, expanded. Aperture height: 3.06-4.32 mm. Aperture width: 2.86-4.10 mm. Peristome double, not thickened, notched at suture. Peristome orientation 43-49° oblique with respect to the coiling axis.

Spiral lines. Distinct. Regularly spaced. Approximately 17-35 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs pronounced, evenly spaced. Approximately 8-14 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 9-15 ribs per 1 mm.

Radial ribs running posterior of breathing tube. Radial ribs pronounced, widely and regularly spaced, approximately 9-16 ribs per 1 mm. Prior to aperture, radial ribs become absent.

Operculum. Concave, rounded. Exterior covered with thin calcareous layer, surface finely granulated with a scattered arrangement of calcareous spikes. Interior covered with proteinaceous coating, smooth.

Shell colour. Whorls yellow. Peristome white.

Living animal. Body cream-white. Head pink. Tentacles brown.

Habitat and ecology.

Lives on both dry and wet limestone walls. Some individuals have been spotted on tree trunks and fallen logs beside limestone cliffs. In shady forests on limestone hills.

Distribution range and habitat.

Restricted to central and northern Perak as well as northeastern Kedah (Bukit Baling and Gunung Pulai). Elsewhere, in Yala, Thailand ( Sykes 1903, Laidlaw 1928, ANSP 446394).

Differential diagnosis.

Alycaeus perakensis is most similar to Alycaeus roebeleni in conical shell shape but differs in being smaller (smaller by about 0.97 mm in shell height, 1.96 mm in shell width), aperture margins more circular and has a less expanded ultimate whorl. Alycaeus perakensis is distinguished from Alycaeus kapayanensis and Alycaeus kurauensis sp. n. by its much larger shell (larger by about 1.43 mm in shell height, 2.32 mm in shell width), more expanded penultimate whorl, operculum exterior with spikes and more oblique peristome. Shells of A. perakensis vary in the degree of expansion of the ultimate whorl.

Discussion.

Historically, the lack of access to type specimens and poor original diagnosis have led to the misidentification of A. selangoriensis sp. n., A. clementsi sp. n. and A. kapayanensis as A. perakensis ( Laidlaw 1932, van Bethem Jutting 1960a, Clements et al. 2008). Alycaeus perakensis shells are consistent in shell size and spire height but varies in the degree of expansion of the ultimate whorl with no particular geographic pattern. Tielecke (1940) used A. perakensis as a representative species for Alycaeus in his comparison of cyclophorid reproductive anatomy. Möllendorff (1894) considered A. perakensis to be closely related to A. roebeleni . Alycaeus perakensis shells were also collected from Biserat and Banang Pupo, Yala, southern Thailand ( Sykes 1903, Laidlaw 1928, ANSP 446394).