Plectopylis cyclaspis (Benson, 1859)

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 91-94

Plectopylis cyclaspis (Benson, 1859)

Figs 35I , 41E

Helix catinus Benson, 1859a: 185 [“prope Moulmein, provinciae Tenasserim”].

Helix cyclaspis Benson, 1859b: 273 (nom. nov. pro Helix catinus Benson, 1859 , non Helix catinus Pfeiffer, 1857: 64 ).

Helix revoluta Pfeiffer, 1867: 64 [“in insulis Andamanicis”].

Helix (Plectopylis) cyclaspis – Benson 1860: 245–246 [“Farm Caves near Moulmein”]. — Hanley & Theobald 1870: 7, pl. 13, fig. 10. — Godwin-Austen 1875b: 613, pl. 74, fig. 10. — Nevill 1878: 72. — Tryon 1887: 164–165, pl. 35, fig. 9.

Plectopylis cyclaspis – Stoliczka 1871: 222–223, pl. 15, figs 4–6. — Gude 1897b: 244, fig. 34a–d.

Plectopylis (Plectopylis) cyclaspis – Gude 1899d: 148; 1899e: 175; 1914b: 130–132, fig. 65a–d; 1920: 63.

Diagnosis

A medium-sized, sinistral species with brownish purple shell and very conspicuous, sharp keel.

Type material

Benson (1859a) wrote the following in the original description of Helix catinus : “The single specimen transmitted for examination is in such a corroded state, that the true nature of the sculpture can merely be guessed at.” In the type collection of the NHM there are three shells having an intact sculpture with the following data: Damalthat, NHMUK 1898.12.04.1520–22, 3 syntypes. These three shells surely do not represent type specimens of P. cyclaspis .

Material examined

MYANMAR: 3 shells, Burma, Moulmein, coll. Oldham, Pres. 1951 ( NHMUK); 2 shells, Moulmein ( NHMUK); 2 juv. shells, Moulmain, coll. Godwin-Austen ( NHMUK); 4 shells, Molmein ( NHMUK); 2 shells, Burma ( NHMUK 1871.9.23.48); 2 juv. shells, Moulmain, coll. Godwin-Austen ( NHMUK); 2 shells, Tenasserim, Moulmein, coll. Godwin-Austen, (“P.Z.S., 1874”) ( NHMUK); 4 shells, Moulmein ( NHMUK 1906.2.2.148); 2 shells, Burma, Moulmein, coll. J.S. Hawkins ( NHMUK 1954.6.2.270–271); 3 shells, Burmah, Moulmein, coll. Salisbury ex Beddome ( NHMUK).

Description

SHELL. Sinistral, strongly built, brownish purple, basal side lighter; protoconch consists of 2.75–3 whorls, matt, almost smooth or sometimes extremely finely granulated and roughly wrinkled; teleoconch irregularly wrinkled, without spiral lines; fresh shells with flat periostracal folds on keel; whorls 6.25– 6.5, strongly, sharply keeled, suture not conspicuous, an additional groove runs above suture; umbilicus narrow; aperture strongly facing downwards (in direction of ventral side); peristome conspicuously protruding in elongation of keel, which results in a concave bay between the parieto-palatal edge of peristome and the position of keel; peristome strongly thickened and reflected; parietal callus almost straight or very slightly S-shaped; apertural fold strong, free from parietal callus; umbilicus relatively narrow and deep.

Two opened shells were examined. Lambda-complex complete; left leg weak, right leg much stronger, has a very long anterior elongation; upper branch very long, parallel with upper suture; lower plica short, does not extend beyond lambda-complex; main plica absent. Palatal plicae typical of Plectopylis .

MEASUREMENTS (in mm). D = 18.9–19, H = 8.4–8.5 (NHMUK 148.06.2.2, n = 3).

CHARACTERS OF THE GENIAL STRUCTURE. Stoliczka (1871) published a description and drawings of the genitalia of this species.

RADULA. The characters of the radula of P. cyclaspis and P. bensoni (under the name achatina ) were described by Stoliczka (1871). According to him, the central tooth is very small, and the laterals have a large main cusp, and an ectocone with two or three cusps. This shape is unusual in the family Plectopylidae . Lateral teeth in all species of Plectopylis examined so far have a single large endocone, and a smaller ectocone with a single cusp. Therefore, the description of the radular teeth by Stoliczka (1871) is considered as inaccurate, probably due to insufficient instruments.

Differential diagnosis

Plectopylis cyclaspis cannot be confused with any other plectopylid species due to its conspicuous keeled whorls.

Distribution

All known samples were collected in the vicinity of Moulmein ( Myanmar). See also Remarks.

Remarks

Stoliczka (1871) claimed that the type locality of P. revoluta (Andaman Islands) is probably incorrect, because he received thousands of other shells from those islands, but none of them were plectopylids. Gude (1914b) concluded that Plectopylis revoluta ( Pfeiffer, 1867) is probably a synonym of P. cyclaspis . The species called P. revoluta in the recent literature is described here as P. malayana sp. nov.

Figures

Fig. 35. Parietal (A–E, G, I–L, N) and palatal (F, H, M, O) plication of species of Plectopylis Benson, 1860. A. P. anguina Gould, 1847, paralectotype (NHMUK 20140812). B. P. repercussa Gould, 1856, lectotype (MCZ 169336). C. P. bensoni var. repercussoides Gude, 1899, holotype (NHMUK 1922.8.29.46). D. P. cairnsi Gude, 1898, holotype (NHMUK 1922.8.29.47). E–F. P. cairnsi (UF 76761). G–H. P. crassilabris sp. nov., paratype (UF 448577). I. P. cyclaspis Benson, 1859 (NHMUK 1906.02.02.148). J. P. karenorum (W. Blanford, 1865) from “Pegu”, Myanmar (NHMUK). K. P. linterae var. fusca Gude, 1898 (NHMUK 1888.12.04.1541–3). L–M. P. malayana sp. nov., paratypes from the type locality (coll PGB). N–O. P. thompsoni sp. nov., paratype (UF 448578). Arrows below the letters indicate the direction of the aperture. Not to scale.

Fig. 41. Shells and living specimens of species of Plectopylis Benson, 1860. A. P. crassilabris sp. nov., holotype (UF 279203). B. P. crassilabris sp. nov. (UF 346364). C–D. Living specimens photographed in the Khao Wong National Park, Aug.–Sep. 2010. E. P. cyclaspis (Benson, 1859) (NHMUK 1888.12.4.1520–1522). F. P. karenorum (W. Blanford, 1865), probable syntype (NHMUK 1906.2.2.263). Scale bar: A–B, E–F = 10 mm; C–D not to scale. Photos: T. Deli (A), B. Páll-Gergely (B), S. Damrongsiri (C–D) and H. Taylor (E–F).