Naggsia oligogyra sp. nov.

urn:lsid:zoobank.org:act: 13CE6536-3C26-421E-ACA1-270750697E3A

Figs 31F, 32 G–H

Diagnosis

A large, flat, dextral species with few (5) whorls; parietal wall with a single lamella, and a main plica free from the deeply situated apertural fold.

Differential diagnosis

The shell of the new species resembles N. laomontana, which has about a whorl more and only a single lamella on the parietal wall.

Etymology

The species is named after its few whorls, from the Greek ‘ oligos ’, meaning few and ‘ gyros ’, meaning whorl.

Material examined

Holotype THAILAND: 1 shell (D = 21.0 mm), Chiang Mae Province, Doi Pha San Sao Mountain, 1 km W of Ban Prang Ma-o, 19°25′58.26″ N, 99°4′14.02″ E, 500 m a.s.l., 19 Jun. 1987, F.G. Thompson leg. (UF 346781).

Paratypes THAILAND: 2 broken shells, same data as for holotype (UF 448574); 1 broken shell, same data as for holotype (HNHM 97457).

Description

SHELL. Dextral, flat, with five rapidly increasing whorls, separated by a rather shallow suture; only strongly weathered shells were available for study, and therefore the sculpture could not be observed in detail; protoconch with fine ribs; teleoconch with inconspicuous, irregular riblets and paler reddish transverse stripes; peristome relatively thin, only slightly reflected and thickened; parietal callus low and blunt; apertural fold weak, situated far from parietal callus.

One shell was opened. Parietal wall with a single, straight lamella having slight horizontal extensions above and below in both anterior and posterior directions; main plica free from lamella, starts near upper end of lamella, and does not reach apertural fold. Palatal wall with six plicae; first situated close to upper suture, short; second to fifth oblique, second being the longest; sixth curved, concave.

MEASUREMENTS (in mm). D = 21.0, H = 6.3 (holotype).

Distribution

The new species is known from the type locality only, where it occurs together with C. leiophis (Fig. 17).