Genus-level revision of the Alycaeidae (Gastropoda, Cyclophoroidea), with an annotated species catalogue Author Pall-Gergely, Barna Plant Protection Institute, Centre for Agricultural Research, Herman Otto ut 15, Budapest, H- 1022, Hungary https://orcid.org/0000-0002-6167-7221 pallgergely2@gmail.com Author Sajan, Sheikh Zoological Survey of India, Prani Vigyan Bhawan, M Block, New Alipore, Kolkata 700053, West Bengal, India & Wildlife Institute of India, Chandrabani, Dehradun 248 002, Uttarakhand, India https://orcid.org/0000-0002-2785-6824 Author Tripathy, Basudev Zoological Survey of India, Prani Vigyan Bhawan, M Block, New Alipore, Kolkata 700053, West Bengal, India Author Meng, Kaibaryer National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing, China Author Asami, Takahiro Department of Biology, Shinshu University, Matsumoto 390 - 8621, Japan https://orcid.org/0000-0001-5706-0272 Author Ablett, Jonathan D. Mollusca Section, Invertebrates Division, Department of Life Sciences, The Natural History Museums, London SW 7 5 BD, United Kingdom text ZooKeys 2020 981 1 220 http://dx.doi.org/10.3897/zookeys.981.53583 journal article http://dx.doi.org/10.3897/zookeys.981.53583 1313-2970-981-1 5194AAC86B8A473F8A41470A60182A0B 7C44C797C4125A71BAE032A55E6FA5DC Genus Dioryx Benson, 1859 Dioryx Benson, 1859: 177. [section (subgenus) of Alycaeus ] Dioryx - Kobelt and Moellendorff 1897 : 146; Gude 1921 : 198; Thiele 1929 : 107; Wenz 1938: 477; Egorov 2013 : 34. Type species. Alycaeus amphora Benson, 1856 (Fig. 26 ), SD Gude (1921 : 198). Diagnosis. Shell small to very large (3.5-9 mm), globose, sometimes the body whorl is angled or keeled; protoconch smooth, not spirally striated; R1 usually very finely reticulated due to fine radial ribs and fine spiral striation, or smooth; R2 short to long, usually without ribs (superficially smooth, with alternating lighter and darker stripes); R3 practically absent (the inner opening of the sutural tube is situated close to the aperture). Operculum thin, usually proteinaceous ( "horny" ), in some species can be thicker, calcified. Central tooth with 5-7 cusps, broad, central cusp blunt. Differential diagnosis. The combination of the globular shell, the reduced sculpture (only very fine spiral and radial lines are present), and the absence of the R2 region characteristic for the vast majority of alycaeid species make Dioryx species distinguishable from other alycaeid genera. Distribution. Dioryx is distributed from the southeastern Himalayan region to Taiwan in the east, and down to the northern part of the Malay Peninsula and southern Vietnam in the south (Fig. 7 ). Remarks. Dioryx is primarily classified based on the reduced R3. This character state is found in other genera of the Alycaeidae as well, such as in Alycaeus conformis , Chamalycaeus microconus , and in Awalycaeus (treated as a synonym of Dicharax ). Even presuming that similar morphology has appeared multiple times in the Alycaeidae , we can reasonably assume the monophyly of Dioryx due to the uniform, simple sculpture across all species, and the generally globose shell.