120 Contributions to Indian Malacology. [No. 2, 



following genera which are ahsenfc on the western side of the Bay : 

 Megalomastoma, JPupina, Registoma* Raphaulus, Streptaulus, and 

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

 Sydrocena and Pomatias, the last being piobably only an outlier. 

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

 that Ceylon is a generic area by itself. Lastly there are common to 

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

 Gyclotus, JPterocyclos, Leptopoma, Cataulus,f Alycceus and iJiplom- 

 inatina. In the Indian peninsula, properly speaking, not one generic 

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

 exception perhaps of the little shell which we now describe under 

 the name 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 representative in the Himalayan or Burmese 

 areas J Otopoma only occurs in Katiwar, where the climate is different 

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

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

 of Africa. 



We can therefore only conclude that scarcely sufficient is yet 

 known to justify a decided opinion 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 generic distinction does exist between the two 

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

 satisfactorily shewn that Borneo is the generic centre around which 

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



* In the Nicobar Islands. 



f One species in the Nicobar Islands. 



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

 and Mag. for Feb. 1S60, two new genera of operculate land shells from Molmain, 

 and has named them EJiiostoma and Closiophis , The former is allied to Ptero- 

 cyelos, the latter is a minute form, probably allied to Liplommatina and Opisthcs' 

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

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

 other species allied 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 

 areas. 



