A new species of Spixia is described in the context of a revision of the genus. Spixia cuezzae is distributed in the mountain area of Punilla political department, Córdoba, Argentina. The shell is characterised by its fusiform shape sculptured with tall thin ribs separated by narrow intervals and a sub-oval to sub-circular aperture. A large and muscular pen ial sheath is observed internally. In Spixia, the sculpture of the penis wall is important for differentiation of the species. Spixia cuezzae is characterized by a muscle group forming an inverted V-shape in penial area I. Penial area III exhibits zigzag folds which form a transition and are continuous with penial area IV where the folds straighten longitudinally towards the distal part of the penis. This kind of sculpture has not been observed in other species of the genus. Spixia cuezzae was compared with its most similar species, S. costelilifer (Haas 1936) and S. philippii (Doering 1874). Spixia cuezzae differs from them not only in the shell shape, size and teleoconch sculpture but also in some genital characters such as penial sheath length and thickness as well as sculpture of the penial wall.
shell ultra structure