The type series of Semisulcospira multigranosa Boettger, 1886 was found in the Malacological Collection at the Senckenberg Naturmuseum for the first time ca. 135 years after its original description. The syntypes consisted of 38 specimens that can be classified into four species. The examination of adult shell morphology of these original materials revealed that the current taxonomic account of S. multigranosa should be amended. Therefore, we designate a lectotype for S. multigranosa, and thus describe S. multigranosa auct. as Semisulcospira davisi sp. nov. Semisulcospira davisi can be discriminated from the other congeners by the characteristics of adult and embryonic shells, and radulae morphology. The present study resolves one of the fundamental taxonomic problems remaining in Semisulcospira snails.
Keywords: Freshwater snail; Lake Biwa; Radula morphology; Syntypes; Viviparous.