The Danian molluscan fauna from the Paris Basin presents a chronological interest of first importance for the understanding of the diversification of European marine ecosystems at the beginning of the Cenozoic. The method consisting in the study of all external prints of molluscs from silicone rubber casts reveals an unexpected faunal diversity. The systematics of 23 species of Patellogastropoda and Vetigastropoda (pro parte) from the Danian perireefal limestone of Vigny (Val-d’Oise, France) and other Danian localities of the Paris Basin are presented here. This study will be completed by further papers in which the Danian molluscan fauna will be revised. Ten new species are described and included in the families Acmaeidae (Scurria dysporista n. sp., Scurriopsis deretrana n. sp.), Fissurellidae (Emarginula (s.s.) horrida n. sp., E. (s.s.) minacis n. sp., E. (s.s.) eucosmia n. sp., E. (s.s.) cavernosa n. sp., Entomella necopinata n. sp., Hemitoma (Montfortia) davincii n. sp., Clypidina (Montfortula) celinae n. sp.) and Pleurotomariidae (Leptomaria meyeri n. sp.). Nine species are reported for the first time from the Danian of Paris Basin (Acmaea simplex, Patella vincenti, Proscutum montense n. comb., Emarginula (s.s.) coralliora, E. (s.s.) montensis, Diodora corneti, D. dolloi, D. concentrica, Praescissurella corneti). Emarginula cretacea d’Orbigny, 1850 is considered a nomen dubium. A new species from the Thanetian of Biouès (Haute- Garonne, France), Emarginula (s.s.) villattae n. sp., is introduced and Emarginula (s.s.) jagti n. nom. is proposed as a replacement name for Emarginula radiata Binkhorst, 1861 non Adams, 1851.
Mollusca, Gastropoda, Patellogastropoda, Vetigastropoda, Lower Paleocene, Danian, France, systematic revision, new species