The freshwater snails (Gastropoda) of Iran, with descriptions of two new genera and eight new species Author Gloeer, Peter Biodiversity Research Laboratory, Schulstrasse 3, D- 25491 Hetlingen, Germany Author Pesic, Vladimir Department of Biology, Faculty of Sciences, University of Montenegro, Cetinjski put b. b., 81000 Podgorica, Montenegro text ZooKeys 2012 2012-09-04 219 11 61 http://dx.doi.org/10.3897/zookeys.219.3406 journal article http://dx.doi.org/10.3897/zookeys.219.3406 1313-2970-219-11 35A0EBEF815740B5BE499DBD7B273918 FFE7FFDBAA3AFF8BF81AFFD7FFCDFF87 577535 Family Neritidae Rafinesque, 1815 Remarks. Theodoxus and Neritina are distinguished from each other by their ontogeny ( Bandel 2001 ). While the Theodoxus species hatch from the spawn as miniature adult, Nertina species leave their spawn as planktotrophic larva that will float in the sea for a more or less extended period before its metamorphosis to a crawling young. However, at the adult stage the taxonomic separation of species of the genera Theodoxus and Neritina is not always easy. As most of the Neritina spp. are marine species and usually have a denticulate border of the columella and two apophysis of the operculum, most species of the genus Theodoxus are limnic and have a smooth border of the columella and one apophysis (the "rib" ); some also have a small apophysis, the peg, on the operculum ( Gloeer 2002 ). Further, in Neritina the peg is thick and strong, while in Theodoxus it is, if exists at all, small and weak. A revision of this family, particularly its subdivion in clearly defined genera is needed.