The protoconch in Limacina helicoides, Peraclis moluccensis, Styliola subula, Cavolinia globulosa, C. gibbosa, C. inflexa and C. longirostris are described; finer structures of the shell in these species and Hyalocylis striata, Diacra quadridentata and Cavolinia tridentata are described. The occurrence of a distinct protoconch-I and -II in Cavoliniidae is discussed as well as the taxonomic value of the structure of the ventral ribs in the Cavoliniidae mentioned.