288 
ZOOLOGICAL GEOGRAPHY. 
[part hi. 
ancestral type may have been a bird capable of flight, and that 
it spread from one of the three southern continents to the others 
at the period of their near approach, and more or less completely 
lost the power of flight owing to the long continued absence 
of enemies. 
During the period we have been considering, the ancestors of 
existing apes and monkeys flourished (as we have seen in 
Chapter VI.) along the whole southern shores of the old Palae- 
arctic continent ; and it seems likely that they first entered 
Africa by means of a land connection indicated by the extensive 
and lofty plateaus of the Sahara, situated to the south-east of Tunis 
and reaching to a little north-west of Lake Tchad; and at the same 
time the elephant and rhinoceros type may have entered. This 
will account for the curious similarity between the higher faunas 
of West Africa and the Indo-Malay sub-region, for owing to the 
present distribution of land and sea and the narrowing of the 
tropical zone since Miocene times, these are now the only 
lowland, equatorial, forest-clad countries, which were in connec- 
tion with the southern shores of the old Pal ie arctic continent at 
the time of its greatest luxuriance and development. This 
western connection did not probably last long, the junction that 
led to the greatest incursion of new forms, and the complete 
change in the character of the African fauna, having apparently 
been effected by way of Syria and the shores of the Red Sea at 
a somewhat later date. By this route the old South-Palmarctic 
fauna, indicated by the fossils of Pikermi and the Siwalik Hills, 
poured into Africa; and finding there a new and favourable 
country, almost wholly unoccupied by large Mammalia, increased 
to an enormous extent, developed into new forms, and finally 
overran the whole continent. 
Before this occurred, however, a great change had taken place 
in the geography of Africa. It had gradually diminished on the 
south and east ; Madagascar had been left isolated ; while a 
number of small islands, banks, and coral reefs in the Indian 
Ocean alone remained to indicate the position of a once extensive 
equatorial land. The Mascarene Islands appear to represent 
the portion which separated earliest, before any carnivora had 
