Four new species of Georissa W. Blanford, 1864 (Gastropoda, Hydrocenidae) from Thailand Author Klongklaew, Kanyaporn Department of Biology, School of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand Author Poeaim, Supattra 0000-0003-1293-3820 Department of Biology, School of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand Author Dumrongrojwattana, Pongrat Department of Biology, Faculty of Science, Burapha University, Bangsaen, Chonburi 20131, Thailand text Zoosystematics and Evolution 2024 2024-10-04 100 4 1347 1360 journal article 304167 10.3897/zse.100.128717 a7f81ef5-5178-48c8-8d40-80b29116daad FD4C02D2-01F9-4A4C-817B-F81B27F22A41 Georissa sagitta Klongkaew, Poeaim & Dumrongrojwattana sp. nov. Figs 2 C , 4 I – L , 5 I – L Type examined. Holotype • ZRCBUU 0904 (Fig. 2 C ); SH = 2.61 mm , SW = 1.63 mm , AH = 0.79 mm , AW = 0.98 mm , W = 4.25–4.5 . Paratypes • ZRCBUU 0905 (Fig. 4 I – L ) (10 shells); Shell measurements: SH = 2.44–2.88 mm (2.65 ± 0.14 mm ), SW = 1.63–1.84 mm (1.70 ± 0.07 mm ), AH = 0.79–0.97 mm (0.87 ± 0.05 mm ), AW = 0.95–1.09 mm (1.00 ± 0.04 mm ), W = 4–4.5 (all type material from type locality; 20 July 2019 , P. Dumrongrojwattana leg). Type locality. Thailand , Khao Maka Cave Temple , Mueang Sakaeo district , Sakaeo Province ; 13 ° 47 ' 16.6 " N , 101 ° 56 ' 53.7 " E . Etymology. The specific designation “ sagitta ” for the prominent oval indentation resembling a target in archery. Diagnosis. Shell minute, ovately conical, orangish, protoconch round to slightly ellipsoid and mix of rounded, ellipsoidal to irregular sculpture with oval indentation. Body whorl peripherally rounded with 8–9 spiral lirae. Aperture semi-rounded. Umbilicus closed. Operculum corneous with apophysis, paucispiral, opaque white, and semi-rounded. Description. Shell minute, dextral, orangish to brownish, ovately conical with 4.25–4.5 whorls (Fig. 2 C ). Protoconch orange consists of 1 whorl, round to slightly ellipsoid, covered with mix of rounded, ellipsoidal to irregular sculpture and a large oval indentation present (Figs 4 J , 4 K ). Teleconch orange, consists of 3.25–3.5 whorls. Peripherally rounded, sculptured with 8–9 prominent lirae on the body whorl, crossed with weak oblique growth lines. Basal part of the body whorl, there are more densely spaced spiral cords, approximately 7–8 cords (Figs 2 C , 4 I ). Suture incised. Aperture semi-rounded. Peristome thin, sharp, unexpanded or thickened, not reflected. Umbilicus closed. Operculum paucispiral, nucleus submarginal, corneous, opaque white, semi-rounded, thin, smooth outside surface with apophysis, inside surface with an arched peg arising from base (Fig. 4 L ). Radula. Ribbon-like, slender, longer and delicate towards the outside, rhipidoglossate (Fig. 5 I – L ). Central tooth five small teeth, trapezoid shape. Lateral teeth five teeth, claw-like with 7–13 alternately long and short denticles decreasing in size from the first lateral tooth toward the 5 th lateral tooth. Marginal teeth two teeth, claw-like with 12–14 equal size denticles. Radula formula 2: 5: 1 + 1 + 1 + 1 + 1 + 1: 5: 2. Differential diagnosis. Georissa sagitta sp. nov. resembles G. monterosatiana Godwin-Austen & Neville, 1879 . Georissa monterosatiana differs in having more convex body whorl, smooth protoconch, and more lirae (9–11 instead of 8–9 lirae).