Chersaecia austeni (Gude, 1899)

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 14-15

Chersaecia austeni (Gude, 1899)

Figs 6 A–B, 7A–B

Plectopylis austeni Gude, 1899b: 15 , fig. 97a–f [“Diyung Valley, Singpho, Assam ”].

Plectopylis (Chersaecia) austeni – Gude 1899 d: 148; 1899 e: 175; 1914 b: 90–91, fig. 38.

Chersaecia austeni – Páll-Gergely et al. 2015 c: 10.

Diagnosis

A medium-sized, flat, dextral, yellowish species with very coarse reticulated sculpture, an elevated parietal callus, strong apertural fold, a single lamella on the parietal wall with a short main plica free from the apertural fold, and an even shorter intermediate plica, situated under the main plica.

Material examined

Lectotype (here designated)

INDIA: 1 shell, Diyung Valley , Singpho Hills, Assam, Ogle leg. ( NHMUK 1903.06.01.1014.1).

Paralectotypes (here designated)

INDIA: 1 juv. shell, 1 adult shell, same data as for lectotype ( NHMUK 1903.06.01.1014.2)

Lectotype designation

The type lot ( NHMUK 1903.06.01.1014) contains one juvenile and two adult shells of Plectopylis austeni . Additionally, it contains a sinistral shell, identical to the holotype of Plectopylis leucochila , which probably got there accidently. Because of the mixed sample and in order to avoid future confusion, one of the adult shells of Plectopylis austeni (D = 19.5 mm) is selected as lectotype ( NHMUK 1903.06.01.1014.1).

Description of the type series

SHELL. Dextral, flat, dorsal surface concave (spire sunken), colour yellowish; whorls 6.25–6.75 (n = 2), separated by a very deep suture (first whorl suture shallower); protoconch consists of 2.75 whorls, matt, almost smooth, irregularly wrinkled; teleoconch roughly reticulated, on dorsal side, inside umbilicus spiral lines dominant, whereas on the periphery of last whorl radial lines stronger; fine periostracal filaments attached to ribs (one filament per rib), which remain mainly inside suture; dorsal and ventral sides of all whorls flat, boundary between the rounded periphery of body whorl and the flat dorsal side indicated with a shallow groove; aperture oval, peristome thickened and slightly reflected; parietal callus well-developed, elevated, highest at its middle; apertural fold low, free from parietal callus; approximately as long as parietal callus.

The type lot contained three shells: two adult shells (one paralectotype had been opened), and an opened juvenile. Parietal wall with a curved lamella having a main plica in the middle line of the lamella; main plica slightly longer than lamella; there is an additional lower, short plica (denticle) under posterior end of main plica; the juvenile shell had only the main plica anterior to the lamella. Palatal plicae six; first and last straight and free, others oblique, short, and connected by a ridge.

MEASUREMENTS (in mm). D = 17–19.5, H = 5–6 (n = 2).

Differential diagnosis

Chersaecia austeni is most similar to C. dextrorsa , which is darker, has longer main and middle parietal plicae, and its palatal plicae are usually divided in the middle and not connected by a ridge.

Distribution

Chersaecia austeni 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.