In the above mentioned area 39 Bythinella-populations have been studied, 16 of which anatomically. The knowledge about distribution, anatomy, variability and species delimitation of following species have been completed: B. carinulata from E-France (in Boeters, 1973) and B. pupoides from E-France and W-Switzerland (in Mermod, 1930; in Boeters, 1968). In particular the first anatomical description of B. pupoides from the lo cus typicus is given. Four new taxa are described in this paper: (a) viridis-group: B. vesontiana n. sp., from dpt. Doubs, E-France; B. carinulata viridiformis n. ssp., from dpts. Cote d’Or, Haute Marne, Haute Saone and Vosges (E-France); (b) schmidti-group: B. pupoides phreaticola n. ssp., an eyeless phreatic form from the dpt. Ain. E-France: B. schmidti padana n. ssp., from S-Ticino (Southern Switzerland) and northern Italy (Giusti et Pezzoli, 1977). The anatomi­cal and conchyliological characteristics of the new taxa here described and of the related taxa cited in this paper are shortly tabulated.