The two taxa formerly considered formae of one species are separated as distinct species, D. trispinosa and D. major, as sympatric occurrence in time and space is evident. The shell size studied proves that a statistical difference exists between the shells of animals in the minute stage and animals in the adult stage, which is another indication for the fact that the minute stages are distinct and natural stages in the life cycle of the two species and in all probability also in most other Cavoliniidae.