First record of subterranean rissoidean gastropod assemblages in Southeast Asia (Mollusca, Gastropoda, Pomatiopsidae) Author Grego, Jozef text Subterranean Biology 2018 25 9 34 http://dx.doi.org/10.3897/subtbiol.25.23463 journal article http://dx.doi.org/10.3897/subtbiol.25.23463 1314-2615--9 9F789679CD744D54A7F2B0087E154571 Thamkhondonia vacquiei sp. n. Figs 15-18 Type locality. Laos; Khammouane Province, Ban Na village 20 km NNE of Thakhek; Tham Khon Don Cave 17°33.82'N ; 104°52.30'E , 161 m a.s.l., Earthquake Dome 3 km from the south entrance, sand sediments on cave river banks (Fig. 2B). Type material. Holotype: type locality: J. Grego and M. Olsavsky leg. 11-12 February 2017 (NHMUK 20180006). Paratypes: type locality (NHMUK 20180019 - 5 specimens; HNHM102772 - 5 specimens; OSUM 42385 - 5 specimens; coll. Grego F0875 - 274 specimens); Laos, Khammouane Province, 3 km NW of Ban Na Village, sand on the bottom of Nam Don river source at 149 m a.s.l.; J. Grego leg. 07 February 2017, 17°33.20'N ; 104°52.38'E (coll. Grego F0856 - 1 specimen) (Fig. 2A). Measurements. Holotype: H 3.35 mm; W 1.51 mm; BW 1.25 mm; BH 1.65 mm; AH 0.95 mm; AW 0.90 mm; H/W 2.22; AH/AW 1.06; W/BW 1.21; H/BH 2.03; H/AH 3.53; W/AW 1.68; Paratype 1: H 3.00 mm; W 1.40 mm; BH 1.20 mm; BW 1.55 mm; AH 0.90 mm; AW 0.85 mm; H/W 2.14; AH/AW 1.06; W/BW 1.17; H/BH 1.94; H/AH 3.33; W/AW 1,65. Diagnosis. Thamkhondonia vacquiei sp. n. differs from the two syntopic species T. moureti sp. n. and T. smidai sp. n. by its shorter and more robust shell shape with a proportionally larger aperture and by its much finer and more numerous spiral sculpture. Description. The whitish translucent, conical shell has six convex whorls with a weak slightly wavy suture. The surface sculpture consists of 11-12 weak spiral cords crossed by fine axial ribs. The aperture is oval ear-shaped with an indication of a posterior canal that extends slightly beyond the shell periphery outline. The peristome is sharp and expands only on the columellar side. The lateral edge of the labral lip is sinuous and a weak axial varix is present parallel to the labral edge. The umbilicus is slit-like. Etymology. Named after my friend Jean-Francois Vacquie (Castelnau d'Estretefonds , France), a French speleologist who participated in the explorations of Tham Khon Don Cave and supported our activities during the 2017 field trip. Distribution. Only known from the type locality and nearby sites in Tham Khon Don Cave as well as in the related source of Nam Don River. Ecology. The same as Pseudoiglica pseudoiglica sp. n.