338 



RELATION OF THE MASCARENES TO INDIA 



27 sp. ill Mauritius, 8 in Bourbon, 4 in Eodriguez ; in the 

 Seychelles it is replaced by Edentidina and Streptostde. The 



principal link with Madagascar is 

 found in a -part of the operculate 

 land fauna. Cyclostoma is present 

 (with Oto2)ovut) in several fine 

 living forms, and the number of 

 suli-fossil species is a clear indi- 

 cation that this group was, not 

 long ago, niucli more abundant, 

 lor of the 16 Cyclostoma known 

 from Mauritius 10 are sub-fossil. 

 The opercidates form a decided 



A 



Fig. 



225. — Characteristic Mauritian 

 land shells : A, Gibbus palanga Fer.; 



A', young of same ; B, Gibbus lyone- feature of the land fauna ; thus 

 tianusv&w. in Mauritius there are 32 species, 



or more than 28 per cent ot the whole. 



Indian and Australasian affinities are unmistakal)ly present. 

 Thus Omphalotrojns, a genus characteristic of small islands, is 

 profusely represented, but it does not occur in Madagascar or 

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

 Leptopoma (possibly a Leptopomoides) are also of eastern relation- 

 ship. Cyclotopsis, Cyathopoma, and Geostilhia are markedly 

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

 nesian. Hycdimax — 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, Eodriguez 4, Seychelles 6, with 

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

 the Paludornus 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 whicli 



