RANGE BASE OR REFUGE AREAS 35 



throughout the Glacial Epoch. As a proof of the exist- 

 ence of this Sahara sea at no very remote geological 

 era, I may remark that the remains of species of marine 

 shells, still existing in the Mediterranean, are found 

 scattered over the desert, both in the valleys and up to 

 elevations of 900 feet; whilst at least one species offish 

 has been found in the salt lakes of that region, south of 

 Algeria, which is also an inhabitant of the Gulf of 

 Guinea, nearly 2000 miles to the south ! The large 

 quantities of salt so characteristic of the whole region, 

 as I can testify from experience, may also be safely re- 

 garded as direct proof of the recent existence of a vast 

 salt-water area. 



I hope I have succeeded in making it tolerably plain 

 to the reader that the great exit from tropical and South 

 Africa for species increasing their northern range was in 

 the north-east, down the valley of the Nile ; and it is by 

 this route, and this route alone, that we trace the ancient 

 range contraction of such species that had penetrated 

 far into the Palaearctic region. Even this area is now, 

 as it undoubtedly was during Pleistocene time, not very 

 favourable to the emigration northwards of Ethiopian 

 mammals and plants. There can be little doubt that 

 the Glacial Epoch was the cause of the extermination 

 of all or nearly all the great, varied, and dominant 

 mammalian fauna that roamed in that vast Euro-Asiatic 

 continent during Miocene and Pliocene ages ; and the 

 utter absence of the remains of the great pachyderms 

 and carnivores from Post-Glacial deposits in Europe 

 (with the one doubtful exception of the mammoth) must 

 not be ascribed to the submergence of the land passages 

 between North-west Africa and South Europe during 



