476 
MR. H. N. RIDLEY ON THE 
I Lave said, they are West-Indian in their affinities, and it is a 
striking fact that the marine fauna and flora are mainly West- 
Indian, while at least one of the plants ( Ipomosa 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 Bulimus Itidleyi , the 
Amphisbcena, and Skink are common on St. Michael’s Mount ; the 
Skink is a large species, but the island, being a mere rocky peak, 
is unsuited for the Amphisbcena. 
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 the 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. Rats and Mice are exceed- 
ingly common. The Rat (Mus rattus) is here much paler 
than usual, and generally of a grey colour, while albinos are 
sometimes met with. It frequents the melon-fields and the 
tops of the cocoauut-trees, and is very destructive. The com- 
mon House-Mouse, JSI. musculus , is even more abundant, and 
has suggested the name Rat Island (Ilha do Ratta), where it is 
* 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 can 
only have taken place within the last 400 years. 
