304 



CEYLON AND SOUTHERN INDIA 



decisively separating that island from India, Bvirinah, and 

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

 tribution. Eurystoma, with a single species (-£'. vittata Mlill.), 

 is also peculiar. 



As usual when Helix gains ascendancy, the Naninidae retrogress, 

 Durgella, Austenia, and Girasia are absent altogether, while 

 MacTochlamys, Sitala, Kaliella, 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 Philojwtamis is peculiar, but for one 



Fig. 20i.— Helix {Aca- 

 ims) Waltoni 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 which do not 

 occur in the rest of India proper. Two {Aulopoma and Cataulus) 

 are quite peculiar, while the other nine are represented in 

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

 the other hand, I)iplommati7ia 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. 



Genera and Subgenera occurring in tJie Cingcdese District, 

 hut not in K. and Centred India 



The district consisting of U2J2^er Burmah, Pegu, Tenasserim, 



