The smooth-shelled Neritidae Rafinesque, 1815 (Mollusca,Gastropoda) from the Ypresian of the Paris Basin, with the introduction of three new species.

This paper discusses the smooth-shelled species of Neritidae present (or supposedly present) in the Ypresian of the Paris Basin. These species have been previously assigned to the genera Neritina Lamarck, 1816, Clithon (Pictoneritina) Iredale 1936, Theodoxus (Vittoclithon) H. B. Baker, 1923, Neritodryas Von Martens 1869 and Neritoplica Oppenheim, 1892. This study is based on a simplified and homogeneous approach to the identification of the various species of this family of gastropods, based on a limited number of distinguishing criteria. Examination of more than 250 specimens from public institutions and private collections, including the types of most of the taxa considered, allowed the compilation of a clear reference iconography and the introduction of three new taxa: Clithon (Pictoneritina) coeuvrensis nov. sp., Clithon (Pictoneritina) tigrinus nov. sp. and Clithon (Pictoneritina) occultatus nov. sp. A key based on shell characters is given to facilitate the identification of the species.