Introduction 



and the Sudan and northern equatorial zone, we arc obhged 

 to assume that in prehistoric, but not very distant times, 

 much of the Sahara and Libyan deserts were covered by a 

 wide expanse of shallow sea, or by fresh-water lakes many 

 times larger in area than the Victoria Nyanza and Lake Chad. 

 There is some local evidence to support this assumption. 



Along the Eastern route, from Syria and Arabia, through 

 Egypt and Abyssinia we may surmise justifiably that the 

 anthropoid apes came to east equatorial Africa, and thence 

 crossed the continent in the forms of the chimpanzi, to extend 

 their range through its vast western forests. The gorilla, 

 perhaps arriving later, only penetrated westward to the 

 proximity of the Niger delta. 



The okapi likewise passed from Egypt (its nearest relations 

 are found fossil in Greece and Asia Minor) to the north- 

 eastern Congo forests, but has not — as has the Hylochcrrus 

 genus of swine — been found west of the Mubangi affluent of 

 the Congo. 



The fossil remains of an equine like the zebra have been 

 found in Algeria, but no wild ass or zebra has been located in 

 the Sahara or Libyan deserts ; or anywhere west of the main 

 Nile, as far south as the Semliki River and the north end of 

 Tanganyika. The range of the zebra, in two or more species, 

 skirts the south end of Tanganyika and in general the southern 

 limits of the Congo basin, and penetrates into Angola, south 

 of the Kwanza River. The range of the rhinoceroses in the 

 southern half of Africa is very much that of the zebras except, 

 of course, that within the last hundred years the white 

 rhinoceros has been virtually exterminated in Trans-Zambezian 

 Africa by the Britisli-Boer wliite man. But nortJi of the 

 equator both forms of the rhinoceros may be found west 



XX xi 



