338 



RELATION OF THE MASCARENES TO INDIA 



CHAP. 



A 



Fig. 225. — Characteristic Mauritian 

 land shells : A, Gihhuspalanga Fer. ; 

 A', young of same; B, Gibbus lyone- 

 tianus Pall. 



has 27 sp. in Mauritius, 8 in Bourbon, 4 in Rodriguez ; in the 

 Seychelles, it is replaced by Edentulina and Streptostele. The 



principal link with Madagascar 

 is found in a part of the oper- 

 culate land fauna. Cyclostoma 

 is present (with Otopoma) in 

 several fine living forms, and the 

 number of sub-fossil species is a 

 clear indication that this group 

 was, not long ago, much more 

 abundant, for of the 16 Cyclo- 

 stoma known from Mauritius 10 

 are sub-fossil. The operculates 

 form a decided feature of the 

 land fauna ; thus in Mauritius 

 there are 32 species, or more than 28 per cent of the whole. 



Indian and Australasian affinities are unmistakably present. 

 Thus Oynphalotropis^ a genus characteristic of small islands, is 

 profusely represented, but it does not occur in Madagascar or 

 Africa. Two Helieina (Mauritius and Seychelles) and a single 

 Leptopoma (possibly a Leptopomoides') are also of eastern rela- 

 tionship. Cyclotopsis^ Cyathopoma^ and G-eostilbia are markedly 

 Indian genera. Microcystis, Patula, and Tornatellina are Poly- 

 nesian. Hyalimax — and this is a very striking fact — occurs 

 nowhere else but in the Andamans and Nicobars, and on the 

 Aracan coast. The nearest relation to the Seychelles Mariaella 

 appears to be the Cingalese Tennentia. Not a single repre- 

 sentative of these eleven genera has been found even in Mada- 

 gascar. 



The fresh-water Mollusca (omitting the Neritidae) are : 

 Mauritius 9 species, Bourbon 5, Rodriguez 4, Seychelles 6, with 

 only 15 species in all. The one Planorhis and the Vivipara, 

 the Paludo7nus and two of the Melania are of Indian types. The 

 Lantzia (peculiar to Bourbon) is probably allied to the Indian 

 Camptonyx. Owing to the paucity of permanent streams, no 

 fresh-water bivalves occur. Among the Neritidae is a single 

 Septaria, a genus which, though occurring in Madagascar, is 

 entirely strange to Africa, and is abundant in the Oriental and 

 Australasian regions. 



It would seem probable that when the closer connexion which 



