The operculate micro land snail genus Dicharax Kobelt & Moellendorff, 1900 (Caenogastropoda, Alycaeidae) in Thailand, with description of new species Author Jirapatrasilp, Parin https://orcid.org/0000-0002-5591-6724 Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand Author Pall-Gergely, Barna https://orcid.org/0000-0002-6167-7221 Plant Protection Institute, Centre for Agricultural Research, Herman Otto ut 15, H- 1022 Budapest, Hungary Author Sutcharit, Chirasak Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand Author Tongkerd, Piyoros https://orcid.org/0000-0001-9221-9293 Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand piyorose@hotmail.com text Zoosystematics and Evolution 2021 2021-01-05 97 1 1 20 http://dx.doi.org/10.3897/zse.97.59143 journal article http://dx.doi.org/10.3897/zse.97.59143 1860-0743-1-1 1D5553BA24894F2C9527B7E46B9B432B BD006A3AD2C6516AB596CDA05E0F375D Dicharax pongrati Jirapatrasilp & Tongkerd sp. nov. Figs 6D , 7C , 12D Type material. Holotype CUMZ 7430/1 (Fig. 12D ), paratypes CUMZ 7430/2 (56 shells; Figs 6D , 7C ), HNHM (2 shells), NHMUK 20200328 (2 shells) and SMF (2 shells) from Doi Chiang Dao, Chiang Mai Province, Thailand, 19°14'26.7"N , 98°52'49.8"E , 24-28 May 1997, coll. S. Panha, J.B. Burch, P. Dumrongrojwattana. Diagnosis. Shell medium-sized (SH up to 2.3 mm, SW up to 4.4 mm), lenticular, depressed-conical. Spire ca. 1/4 of shell height. R1 with regular, thread-like ribs; R2 three times longer than R3; R2 with ca. 76 ribs. R3 strongly reduced, without swelling. Aperture round. Inner peristome with two shallow indentations. Outer peristome expanded, slightly reflected. Umbilicus elliptical. Operculum multispiral, with or without elevated lamella. Description. Shell medium-sized (SH up to 2.3 mm, SW up to 4.4 mm), lenticular, depressed-conical, solid, translucent, yellowish to pale orange. Shell outline oval in apical view, spire ca. 1/4 of shell height. Whorls ca. 4 and 1/8. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 13/4 whorls with fine, regular, thread-like ribs; with ca. 17 ribs in 1/4 whorl adjoining R2, ribs more elevated and sharper near suture and flatter near umbilicus and at the edge of body whorl. Boundary between R1 and R2 distinct as R2 contains denser and thicker ribs than R1; R2 with ca. 76 ribs that are curved towards aperture; R2 ca. 1/3 whorl, three times longer than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 strongly reduced, without swelling, practically the constriction continues directly to outer peristome. Aperture round; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome slim, slightly protruding, with two shallow indentations. Outer peristome thickened, expanded, slightly reflected, multilayered (visible in lateral view). Umbilicus elliptical, open, approximately one third of shell width. Operculum either thin with low lamella or thick with elevated lamella. Etymology. In honor of Pongrat Dumrongrojwattana, a Thai malacologist who has studied micro land snails of Thailand and was one of the collectors of this new species. Distribution. The new species is known only from the type locality in Chiang Mai Province, Thailand. Remarks. Differs from the sympatric and similar depressed-conical D. pratatensis in having a wider and more depressed shell, a much longer R2, a shorter R3 without a swelling and two shallow indentations at the inner peristome.