434 ISLAND LIFE tart ii 



Madagascar to tlie Seychelles and subsequent modification, 

 offers no difficulty. The other species is Fnndulus 

 ortlionohts, found also on the east coast of Africa ; and as 

 both belong to the same family — Cyprinodontidae — this 

 may possibly have migrated in a similar manner. 



Land-shells. — The only other group of animals inhabiting 

 the Seychelles which we know with any approach to 

 completeness, are the land and fresh -water mollusca, but 

 they do not furnish any facts of special interest. About 

 forty species are known, and Mr. Geoffrey Nevill, who has 

 studied them, thinks their meagre number is chiefly owing 

 to the destruction of so much of the forests which once 

 covered the islands. Seven of the species — and among 

 them one of the most conspicuous, AcJiaiina fulicct — have 

 almost certainly been introduced ; and the remainder show 

 a mixture of Madagascar and Indian forms, with a prepon- 

 derance of the latter. Five genera — Streptaxis, Cyatho- 

 ponea, Onchidium, Helicina and Paludomus, are mentioned 

 as being especially Indian, while only two — Tropidophora 

 and Gibbus, are found in Madagascar but not in India.^ 

 About two-thirds of the species appear to be peculiar to 

 the islands. 



Mauritius, Bourhon and Eodrigucz. — These three islands 

 are somewliat out of place in this chapter, because they 

 really belong to the oceanic group, being of volcanic 

 formation, surrounded by deep sea, and possessing no 

 indigenous mammals or amphibia. Yet their productions 

 are so closely related to those of Madagascar, to which they 

 may be considered as attendant satellites, that it is 

 absolutely necessary to associate them together if we wish 

 to comprehend and explain their many interesting 

 features. 



Mauritius and Bourbon are lofty volcanic islands, 

 evidently of great antiquity. They are about 100 miles 

 apart, and the sea between them is less than 1,000 fathoms 

 deep, while on each side it sinks rapidly to depths of 2,400 

 and 2,600 fathoms. We have therefore no reason to 

 believe that they have ever been connected with Mada- 



^ "Additional Notes on the Land-sliells of the Seychelles Islands." By 

 Geoffrey Nevill, C.M.Z.S. Proc. ZooJ. Soc. 1869, p. 61. 



