The Bythinella spp. of Greece (Gastropoda: Hydrobioidea: Bythinelliidae) Author Glöer, Peter Schulstrasse 3, D- 25491 Hetlingen, Germany; e-mail: gloeer @ malaco. de Author Reuselaars, Robert Traverse 33, 9408 MG Assen, The Netherlands; e-mail: f 2 hreuselaa @ hetnet. nl text Ecologica Montenegrina 2020 2020-03-14 29 2020 20 33 http://dx.doi.org/10.37828/em.2020.29.3 journal article 10.37828/em.2020.29.3 2336-9744 12808255 urn:lsid:zoobank.org:pub:873D27C2-1693-4E93-8313-D00B72F82B82 Bythinella petrosensis n. sp. [fig. 2.8] Material examined: Holotype ( RMNH .MOL.340508) and 1 paratype ( RMNH .MOL.340509) from type locality. Holotype : 2.9 mm high, 1.8 mm broad from type locality. Paratypes : 1 paratype from type locality, 2.0 mm high and 1.3 mm broad, 4 (dry) in coll. Robert Reuselaars (no. 682). Locus typicus: Spring 5-6 km Se of Aghios Petros , Parnon mountains , Peleponnesos , Greece at 1.105 meters altitude ( Figure 10 ), 37° 17' 36.115787'' N 22° 35' 30.35337'' E , 24.09.2010 Robert Reuselaars leg. Habitat: This species occupies an area of only less than 0, 15 m 2 in an artificial basin of a slow running spring Etymology: Named after Aghios Petros town. Description: The shell is elongated ovate with 3-4.5 convex whorls which are separated by a deep suture. The aperture is ovate. The peristome is thickened at the columella. The umbilicus is closed. The body whorl takes 0.8 of shell height. The aperture is 0.8 mm high and 0.7 mm broad. The ratio of shell height to shell width is 1.6. The shell is 2.0- 2.2 mm high and 1.3 mm broad. Differentiating characters: This species is much smaller than B. liandinaensis n.sp. and much smaller than B. atypicos as well. Distribution: Only known from type locality.