New Morphological Characterization of (Gastropoda, Veronicellidae), Differential Diagnosis for the Genera and , and Novel Combinations for Species of .

The genera Colosi, 1922 and Colosi, 1922 were originally proposed as "groups" within the genus Ferrussac, 1822, and since their establishment they have been variously considered valid or invalid until they gained the ultimate status of genus. The descriptions of both genera are general and broadly inclusive, and this fact has complicated taxonomic recognition. Additionally, incomplete descriptions and difficult identification of characteristics in the name-bearing type specimens demonstrate the need to revisit the species and revise the two genera. Herein, we broaden the description of Colosi, 1922 with respect to the circulatory system, the radula, the jaw, the position of entry of the ligation duct in the bursa copulatrix in relation to the canal of the bursa, the origin of the muscle of the penial gland, along with the morphometric characteristics of the phallus, the penial gland, the pedal gland, and the bursa copulatrix. We also propose new differential diagnoses for the genera and limited to the essential characteristics that enable taxonomic recognition. Hence, we propose the assignment of the species (Thiele, 1927), (Thiele, 1927), and (Colosi, 1921) to the genus , based on the presence of morphological characteristics attributable to this genus, such as the phallus being short and conical; the bursa copulatrix being sessile or short, and lacking a head; the ligation duct inserted near the canal of the bursa; as well as on the similarity in phallus morphology with Colosi, 1922, the type species of this genus.