A new Ancylus and a new genus of Hydrobiidae from the Ohrid Lake basin (Mollusca: Gastropoda) Author Glöer, Peter Schulstrasse 3, D- 25491 Hetlingen, Germany. E-mail: gloeer @ malaco. de Author Pešić, Vladimir Department of Biology, Faculty of Sciences, University of Montenegro, Cetinjski put b. b., 81000 Podgorica, Montenegro. E-mail: vladopesic @ gmail. com, https: // orcid. org / 0000 - 0002 - 9724 - 345 X text Ecologica Montenegrina 2023 2023-07-11 64 185 190 http://dx.doi.org/10.37828/em.2023.64.2 journal article 10.37828/em.2023.64.2 2336-9744 13246869 urn:lsid:zoobank.org:pub:C6640452-261E-4893-9A1C-D68A6F0D8A4D Ancylus naumiensis n. sp. https://zoobank.org/ urn:lsid:zoobank.org:act: 2CCBEB51-BA20-4BC4-85F8-E7254717E9A5 Figs. 2 A-D Ancylus sp. D – Albrecht et al . 2006 . Type series — Holotype ( ZMH 141503 ): Shell height 2.66 mm , shell width 6.07 mm ; NORTH MACEDONIA , Ohrid Lake area , the springs of the Black Drim near Monastery of St. Naum , 40°54'36.04"N , 20°44'51.14"E , 13.09.2019 leg. Pešić. Paratypes : 6 ex. ZMH 141504 , 3 ex. in coll. Glöer , same data as the holotype . Type locality — North Macedonia , Ohrid Lake region , the springs of the Black Drim near Monastery of St. Naum , 40°54'36.04"N , 20°44'51.14"E . Etymology — Named after the Monastery of Saint Naum in whose vicinity the new species was collected. Description — The shell is broad oval. The shell is 2.7 mm high and 6.0 mm long. The apex does not reach the border of the shell from apical view. Upper side of apex straight and not convex and the tip not bent down. Figure 2 . Ancylus naumiensis n. sp. , holotype (A-B): A = shell, lateral view; B = shell, apical view; C-D = apex. Differential diagnosis — Four species of the genus Ancylus are known from the Ohrid Lake basin ( Albrecht et al . 2006 ). Ancylus tapirulus Poliński, 1929 is characterized by a sharp apex, while A. scalariformis Stanković & Radoman, 1953 is differentiated by a characteristic shape of the shell, with a number of concentric eaves-like projections. The both species live in the “shell zone” ( 18-35 m ), mainly on the zebra mussel Dreissena stankovici . The third species, Ancylus lapicidus Hubendick, 1960 , resembles A. scalariformis in possessing comarginal ribss ( Hubendick 1960 ) and is restricted to the littoral zone, inhabiting the rocky substrate on the eastern side of Lake Ohrid . Fourth species, putatively named as Ancylus sp. D was separated by Albrecht et al . (2006) based on DNA data from two mitochondrial genes (COI, LSU rDNA), and includes specimens collected from springs near the southeastern edge of the lake (St. Naum in North Macedonia and near Tušemišta in Albania ). The latter species, here described as A. naumiensis n. sp . is diiferentiated by the shape of the apex. All four species, as shown by Albrecht et al . (2006) form a monophyletic group that probably evolved in the Ohrid Lake Basin, also supported by the morphological similarity of the species of this group sharing a very characteristic appearance of the radula with solid teeth without cusplets ( Albrecht et al . 2006 ). Habitat — Springs; crenobiontic. Albrecht et al . (2006) mentioned that despite an extensive search, they were unable to find this taxon in the lake. Distribution — Known from the St. Naum springs in North Macedonia and Tusemista spring in Albania ( Albrecht et al . 2006 ).