476 



MB. H. N. RIDLEY ON THE 



i have said, tbey are West-Iudiau in their affinities, and it is a 

 striking fact that the marine fixuna and flora are mainly West- 

 Indian, while at least one of the plants {Ipomoea Tuba) whose 

 seeds are known to be constantly drifted about at sea, and 

 thus carried from place to place, is also only known from the 

 West Indies. Another fact of interest in connection with 

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

 almost all the species noted occur on all the islands suitable for 

 their existence. Thus, on Rat Island the BiUimus Ridleyi, the 

 Amphisbcena, and Skink are common on St. Michael's Mount ; the 

 Skiuk is a large species, but the island, being a mere rocky peak, 

 is unsuited for the AnipJiisbceiia. 



On Platform Island the lizard and several terrestrial Mollusca 

 were found, while at the same time almost all the animals of 

 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 

 even this portion of the fauna and flora was introduced previously 

 to the deposition of the basalt over the masses of phonolite 

 which form as it were the skeleton outline of tlie island. 



MAMMALIA. 



No indigenous Mammals are to be found on these islands, and 

 notwithstanding their proximity to the mainland, where Bats 

 are abundant, no Bat of any species was observed by us, nor 

 had the convicts ever seen any. Eats and Mice are exceed- 

 ingly common. The Rat (Mus rattus) is here much paler 

 than usual, and generally of a grey colour, wliile albinos are 

 sometimes met with. It frequents the melon-fields and the 

 tops of the cocoanut-trees, and is very destructive. The com- 

 mon House-Mouse, M. muscuhis, is even more abundant, and 

 has suggested the name Rat Island (Ilha do Ratta), where it is 



* Oil 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 au archipelago can 

 only have Uvken place within the last 400 years. 



