288 ZOOLOGICAL GEOGRAPHY. [part m. 



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 faimas 

 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 Palsearctic 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-Palsearctic 

 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 



