Chersaecia brachyplecta ( Benson, 1863 ) Páll-Gergely, Barna, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 17-18

Chersaecia brachyplecta ( Benson, 1863) comb. nov.

Figs 6 C–D, 7I–J

Helix (Plectopylis) brachyplecta Benson, 1863: 319 [“ad ripas fluvii Attaran prope Moulmein”].

Helix brachyplecta – Pfeiffer 1868: 396–397.

Helix (Plectopylis) brachyplecta – Hanley & Theobald 1872: 26, pl. 57, figs 7, 10. — Godwin-Austen 1875b: 613, pl. 74, fig. 8–8a. — Nevill 1878: 72. — Tryon 1887: 163, pl. 35, figs 76–77, 82–83.

Plectopylis brachyplecta – Gude 1897b: 246, fig. 37a–f.

Plectopylis (Endoplon) brachyplecta – Gude 1899d: 148; 1899e: 175; 1914b: 117–119, fig. 57a–f; 1920: 62.

Diagnosis

A large, dextral, robust, flat species (protoconch elevated) with two lamellae and a long main plica extending to the parietal callus.

Material examined

Syntype

MYANMAR: 1 shell, “Ad ripas fluvii Attaran prope Moulmein”, coll. Benson ( NHMUK 1954.6.2.282).

Additional material

MYANMAR: 1 shell, Moulmein ( NHMUK); 2 shells (figured in Godwin-Austen 1875b), Moulmein, Tenasserim, coll. Godwin-Austen ( NHMUK 1903.7.1.749).

Description

SHELL. Dextral, robust, flat, brownish, although the available specimens are largely eroded; protoconch large, consists of 3.5 whorls, matt, finely, densely, irregularly wrinkled; whorls 6–6.25 (n = 2), separated by deep suture; teleoconch finely, irregularly wrinkled; dorsal side with some reticulated sculpture, ventral surface smoother; aperture with widened sinulus; peristome strongly thickened and slightly reflected; parietal callus low, blunt, slightly S-shaped; apertural fold very long, connected to parietal callus.

One opened shell was observed. Parietal wall with two lamellae, upper end of anterior lamella curves anteriorly, whereas lower end slightly elongated in both anterior and posterior directions; posterior lamella slightly reversed S-shaped. The shell fragment having the palatal plicae was attached to the shell, but was somewhat damaged, therefore only 5 plicae were visible; all middle plicae oblique and depressed Z-shaped, or wavy; the last plica horizontal, straight.

MEASUREMENTS (in mm). D = 21.5–21.7, H = 7.6–7.8 (n = 2, type series).

Differential diagnosis

Chersaecia smithiana is larger, has a shallower umbilicus, a stronger and sharper parietal callus and, most importantly, only a single lamella.

Distribution

Chersaecia brachyplecta is known from the type locality only.

Figures

Fig. 6. Shells and protoconchs of Chersaecia Gude, 1899. A–B. C. austeni (Gude, 1899), lectotype (NHMUK 1903.06.01.1014.1). C–D. C. brachyplecta (Benson, 1863) comb. nov., syntype (NHMUK 1954.6.2.282). E–F. C. smithiana (Gude, 1897) comb. nov., syntype (NHMUK 1888.12.4.1555). Scale bars: A, C, E = 10 mm; B, D, F = 2 mm. All photos: H. Taylor.