Three new hydrobiid species from Thassos Island (Greece) with a re-description of Amnicola charpentieri Roth, 1855 Author Georgiev, Dilian Department of Ecology and Nature Conservation, Faculty of Biology, Paisii Hilendarski University of Plovdiv, 24 Tsar Assen Str., 4000 Plovdiv, Bulgaria Author Glöer, Peter Biodiversity Research Laboratory, Schulstrasse 3, D- 25491 Hetlingen, Germany Corresponding author. E-mail: diliangeorgiev @ abv. bg text Ecologica Montenegrina 2020 2020-10-22 35 129 137 http://dx.doi.org/10.37828/em.2020.35.10 journal article 10.37828/em.2020.35.10 2336-9744 13232490 urn:lsid:zoobank.org:pub:F63DAA57-8D7A-4EC7-9FA0-602943FED1FB Bythinella rachonica n. sp. ( Figs. 2 , 22-25 ) https://zoobank.org/ urn:lsid:zoobank.org:act: DD058BE9-160A-4CA0-8ECB-7F5E642420DC Materials studied: Holotype : shell height 3.1 mm , width 1.75 mm , from type locality ( ZMH 140795 ). Paratypes : 3 specimens in ethanol ( ZMH 140796 ) , 1 specimen in coll. Glöer. Type locality: Greece , Thassos Island , North Aegean , a big spring in the yard of the church of Rachoni village , N40 45 29.6 E24 38 17.3 , 107 m a.s.l. ( Fig. 4 ) . Etymology: Named after village of Rachoni where the new species was found. Description: Shell ivory, cylindrical with 4.5 whorls, separated by a deep suture. Surface silky and finely striated. Apex obtuse, umbilicus closed. Aperture oval, with a sharp peristome, angled at the top. Shell height 2.9-3.1 mm , width 1.8 mm . Penial appendix twice longer than the penis, tubular gland medium-sized, with 5 half loops, tapering from distal to proximal part ( Fig. 5 ). Differentiating features: From this region no Bythinella spp. are known ( Glöer & Hirschfelder 2020 , Glöer & Reuselaars 2020a , b, c), except from the neighbouring Samothrake Island, from where Reischütz described Bythinella charpentieri cabirius P.L. Reischütz 1988 (considered as a separate species by Glöer & Georgiev 2012), which is a small and slim species ( 2.5-2.7 mm high and 1.2-1.3 mm broad) ( Glöer & Georgiev 2012 ) and in this way different from Bythinella rachonica n. sp. Figures 22-25. Bythinella rachonica n. sp. , 22 : shell, 23 : penis in situ, 24 : penis with penial appendix, 25 : tubular gland. Distribution: Known only from the type locality. The spring at the Agora of Limenas was checked but no living snails were found. Some empty, eroded shells of a Bythinella species were found by D. Georgiev in sand deposits in a spring below Panagia village ( N40 43 56.8 E24 44 26.6 , 49 m a.s.l.) but it is not clear if they belong to Bythinella rachonica n. sp. Habitat: Found in a spring (captured under the church of Rachoni, with a concrete bed) on stones and submerged mosses.