BOTANY OP FERTiTAlJfDO NOEONHA. 17 



There is another group which is unprovided with means of 

 traversing the ocean, and not carried about by man. This in- 

 cludes the Amphisbcena, Skiuk, the freshwater and terrestrial 

 Mollusca, and perhaps some of the feebler-winged and apterous 

 insects, the endemic ostracod, <^c. 



The Planorlis, Gammarus, and Ostracod, all (?) endemic species, 

 it is quite conceivable may have been brought over on the feet 

 of Waders, which seem to migrate here. 



The remainder are more difficult to account for. The Mollusca 

 are almost all peculiar, and the two that are not so are West- 

 Indian. The Amphislcena and Skiuk are endemic, and allied 

 not to Brazilian but to West-Indian forms. 



It is commonly said that reptiles and terrestrial mollusks find 

 their way across the ocean by secreting themselves or their eggs 

 in floating trees, which are drifted to islands ; and though for 

 several reasons this does not seem a satisfactory explanation of 

 their distribution, yet the distribution of these animals here 

 points to this as the means by which they have arrived. As I 

 have said, they are West-Indian in facies, and correlated with 

 this is the striking fact that the marine fauna and flora, and 

 at least one of the plants whose seeds are known, supposed 

 to be constantly drifted about the sea, and to be thus carried 

 from place to place, is only known also from the West Indies 

 (Ipomoea Tuba). Another fact of interest in connection with these 

 sea-travelling fauna, if I may use the expression, is the fact that 

 almost all occur on all the islands suited for their existence. 

 Thus, on Eat Island the Bulimus Rldleyi, the Amphishcena, and 

 Skink are common on St. Michael's Mount ; the Skink is a large 

 species, but the island, being a mere rocky j)eak, is unsuited for 

 the Amphisbcena. 



On Platform Island the lizard and several terrestrial Mollusca 

 were fouud, while at the same time almost all tke animals of a 

 more recent introduction were absent from these localities, just 

 as is the case in the distribution of the plants. I believe, in 

 fact, that this part of the fauna and flora was established on the 

 island before it was broken up into the little archipelago of rocks 

 and islets of which Fernando Noronha now consists *. Perhaps 



* On reference to A. Vespucci's description of the place, it will be found 

 that he speaks of it as one island, so the breaking-up into an archipelago may 

 only have taken place within the last 400 years. 



LINTS^. JOTJKN. — BOTANY, VOL. XXVII. C 



