384 
ORIGIN OP LIFE IN AMERICA 
to Africa, whereas I favour the theory that such a connec¬ 
tion could only have persisted indirectly by way of the Antilles 
and southern Europe. 
It has been urged that if a land bridge had once existed 
between Brazil and west Africa we ought to find some traces 
of sedimentary rocks on the few islands that are scattered 
about in the intermediate area, like Fernando de Noronha, St. 
Paul’s, St. Helena, Ascension and Tristan da Cunha, whereas 
all these are believed to be composed of volcanic rocks. Pro¬ 
fessor Schwarz,* nevertheless, affirms that although Ascen¬ 
sion consists of volcanic rock the substratum is granitic. St. 
Paul’s island, he thinks, is mainly metamorphic in structure, 
and there are signs of its Raving been subjected to considerable 
earth movements. Continental types of rocks occur on Tristan 
da Cunha. Consequently Professor Schwarz concludes that 
these Atlantic islands furnish some geological testimony for 
the belief in a Mesozoic Continent in the position of the 
southern Atlantic lasting until the beginning of the Tertiary 
Era. 
The island of Fernando de Noronha lies about two hundred 
miles east of Cape San Roque on the coast of Brazil. Since 
its discovery in 1503 both the original fauna and flora of the 
island have been laid waste by early settlers, so that only 
vestiges of these are left. The splendid trees that once clothed 
the island are gone and with them probably the greater part 
of the fauna. A mammal, at any rate, existed on Fernando de 
Noronha when it was discovered, but it has quite vanished. 
Mr. Ridley, who visited Fernando de Noronha in 1887, noticed 
that quite a number of species of animals and plants had evi¬ 
dently been introduced by human agency. Many others, he 
thinks, have been transported to the island from the main¬ 
land by winds, although he noted that the smaller birds and 
a large proportion of the smaller insects are endemic. A few, 
he remarks, may possibly have been brought over on the feet 
of wading birds. There still remains a small group of indi¬ 
genous species which are difficult to account for, on the hypo¬ 
thesis of accidental distribution. The subterranean lizard 
* Schwarz, E. H. L., “Land-connection between Africa and Tilth 
America,” pp. SI — 90. 
