In the present paper, Auris bilabiata melanostoma (Moricand, 1836), is described based on alive specimens from Estado do Rio de Janeiro, Brazil. Genital organs, pallial chamber and radula are described, as well as variations of the shells from several localities. The author emphasizes the importance of the study of soft parts to come to a definitive conclusion about the validity of the two sub-species (bilabiata s.st. and melanostoma).