304 



CEYLON AND SOUTHERN INDIA 



CHAP. 



decisively separating that island from India, Burmah, and 

 Siam, forms a most interesting problem in the history of dis- 

 tribution. Eurystoma^ with a single species {E. vittata MiilL), 

 is also peculiar. 



As usual when Helix gains ascendancy, the Naninidae retro- 

 gress. Durgella^ Austenia^ and Girasia are absent altogether, 

 while Macroclilamys^ Sitala, KalieUa, etc., are present in greatly 

 diminished numbers. The sub-genus Beddomea is peculiar, a 

 form directly related to Amphidromus (Siam and Malacca). 

 The fresh- water operculate Philopotamis is peculiar, but for one 



eml\^^ '/,3 



Fig. 204. — Helix {Aca- 

 V us) Wa Itoni Reeve, 

 Ceylon, showing em- 

 bryonic shell (emb). 



species found in Sumatra; while Tanalia is quite peculiar. But 

 the forms which, next to the Helices^ most emphasise the separa- 

 tion of the Cingalese district are the land operculates. There 

 are eleven genera or subgenera of land operculates whicli do not 

 occur in the rest of India proper. Two (^Aulopoma and Cataidiis') 

 are quite peculiar, while the other nine are represented in 

 Burmah, Siam, and the Malay islands, but not in India. On 

 the other hand, Diplommatina and Alycaeus^ so profusely abun- 

 dant in India, have not yet been discovered in Ceylon. Among 

 the slugs, Tennentia is a peculiar genus, whose nearest relation 

 occurs in the Seychelles. 



G-enera and Subgenera occurring in the Cingalese District^ hut 

 not in N. and Central India 



The district consisting of Upper Burmah^ Pegu^ Tenasserim, 



