120 Contributions lo Indian Malacology. [No. 2, 



following genera which are absent on íhe western side of the Bay : 

 Ilegal omastoma, Pupina, Begistoma* IiapJiauIus, Slreptaulus, and 

 Hybocystis (all of which are closely allied genera and of one type) 

 Jíydrocena and Pomatias, the last being probably only an outlier. 

 In Ceylon there is one peculiar genus, Aidopoma, but it is evident 

 that Ceylon is a generie área by itself. Lastly there are comrnon to 

 both sides of the Bay of Bengal or of the Ganges valley Cyclophorus, 

 Cyclotus, Pterocyclos, Leptopoma, Cataulus,f Alycmus and Diplom- 

 inatina. In the Indian península, properly speaking, not one gern ric 

 form exists, which is wanting in Trans-gangetic countries, witfa the 

 exception perhaps of the little shell which we novv describe under 

 the ñame of Opistlwstoma : but even assuming this genus to be 

 decidedly operculate, it would be premature to assert that so minute 

 a shell has no specific representativo in the Himalayan or Burmese 

 áreas J Otopoma only occurs in Katiwar, where the climate is diffcrent 

 from that of India proper, and where all organic nature shews an 

 intermixture of Indian forms with those of South- western Asia and 

 of África. 



We can therefore only conduele that scarcely sufficient is yet 

 known to justify a decided opinión as to the distribution of the land 

 shells of India and the adjoining countries. So far as the most recent 

 discoveries enable us to form a judgment, we agree with Mr. Benson 

 in considering that a generie distinction does exist between the two 

 áreas of Cis and Trans-gangetic India, but we doubt whether it is 

 satisfactorily shewn that Borneo is the generie centre around whicli 

 all the forms of South-western Asia and the Indian Archipelago are 



* In the Nicobar Islán ds. 



f One species in the Nicobar Islands. 



J Since these remarks were written, Mr. Benson has describec!, in the Ann. 

 and Mag. for Feb. 1860, two new genera of operculate land shells from Molmain, 

 and has named thera Ehiostoma and Closíophis. The former is allied to Fiero- 

 cyelos, the latter is a minute form, probably allied to DipJommaüna and Opisthos- 

 toma. Like the latter it is separated from the former on account of peculiarities 

 in the last whorl, which, in Closíophis, is free and descending. It is possible that 

 other species alhed to these new forms may hereafter be discovered, and the two 

 types be found to represent and replace each other in the Indian and Burmese 

 a rea 3. 





