dorsally curved apex. An embryonic shell (Fol) is often disdnguished from the rest. The animal 

 has a ventral pallial cavity and a dorsal cohimellar muscle. The flexure of the intestine is 

 ventral. The anus situated on the left sidc; in the central nervous system the left portion 

 of the visceral mass is more developed than the right. 



The affinity of the Cavoliniidae with the Limacinidae has been discussed before. 



Three distinct genera can only be admitted among the various species, though formerly 

 a great number of generic titles has been used '). 



These genera are : Clio. Cuvicrina and Cavoliiiia. 



The sfenus Clio inckides four snborenera : 



Creseis^ HyalocyU.\\ Sfv/iohr, Clio fs. sfr.). 



Cuvierina was regarded by Gray ") as a genus, representing a separate family; however, 

 it clearly belongs to the CavoHniidae. 



Cavoliiiia consists of two subgenera : 



Diacria, Cavoliiiia fs. sfr.). 



According to Pelseneer, fourteen species of Clio may be distinguished. However, I cannot 

 regard Clio conica as a distinct form, as I shall explain further on. Munthe has described a 

 new species of Clio (see note i), so that the number of species is fourteen. Six of them were 

 obtained by the Siboga. I cannot discuss the specific distinctness of the species which form the 

 subgenus Clio fs. str.J^ as I could only observe two species. 



As to the genus Cuvierina it includes only a single species. This species was reprssented 

 in the Siboga-material by a few empty shells only. 



The eight species of Cavoliiiia are all included in the Siboga-collection. 



New fornis have not been found. 



Clio Linné. 



1756. Clio Browne, The civil and natural History of Jamaica, p. 386. 



1767. Clio Linné, Systema naturae, ed. 12, vol. I, prt. 2, p. 1094. 



18 10. Cleodora Péron and Lesueur, Histoire de la familie des Mollusques Ptéropodes, Ann. 



Mus. Hist. Nat. Paris, vol. XV, p. 66. 

 1825. Styliola Lesueur, in: DE Blainville, Manuel de Malacologie, p. 655. 

 1828. Crcseis Rang, Notice sur quelques Mollusques nouveaux appartenant au genre Cleodora, 



et établissement et monographie du sous-genre Creseis, Ann. d. Sc. Nat. sér. i, 



vol. XIII, p. 302. 

 1837. Balantniin Benson, Notice on Balantiiiui, a Genus of the Pteropodous MoUusca, Journ. 



Asiat. Soc. Bengal, vol. VI, p. 151. 

 1875. Hyalocylix Fol, Sur Ie développement des Ptéropodes, Arch. d. Zool. Exp., vol. IV, p. 177. 



Subgenus Creseis Rang fs. sfr.J. 



1828. Creseis (part.) Rang, Notice sur quelques Mollusques nouveaux, etc, Ann. d. Sc. Nat. 



sér. I, vol. XIII, p. 302. 

 1828. Styliola (part.) Auctorum. 



i) As to the different generic names, see Pelseneer, Cliall. Rep. LXV, p. 41. 



2) Catalogue of the Mollusca in the collection of the British Museum. Prt. II, Pteropoda, p. 23. 



