34 THE MIGRATION OF BRITISH BIRDS 



exceedingly limited one ; it was also singularly ill-adapted 

 to the requirements of such hordes of mighty beasts. 

 North-west Africa possesses no large rivers in which the 

 rhinoceros and the hippopotamus could find congenial 

 haunts ; no vast forests and wild fertile areas suitable 

 for the elephant, the sabre-toothed tiger, and the mam- 

 moth. That many of these larger mammals inhabited 

 North-west Africa during the Pleistocene Period, when 

 the area was continuous with northern continental land, 

 we have abundant proof in the remains which have 

 been discovered in the caves of Algeria of Eqims, Bos, 

 Anti/ope, Hippopotanuis, RJiinoceros, Ursns, Camis, and 

 Hycena ; but how few of these have left descendants, 

 and succeeded in preserving their species or their types 

 in that area when it became isolated ! 



It is generally presumed that these large mammals 

 retreated south in Africa to the haunts in which they 

 live now, and which were then occupied by many of the 

 same species, coming north again with the return of 

 milder climatal conditions. But there can be little 

 doubt that many of these animals dwelt in the vast 

 Euro- Asiatic continent which then included North-west 

 Africa, over which they were widely dispersed as a 

 dominant fauna, the range of at least some species ex- 

 tending northwards from tropical Africa, as that area was 

 united to the northern continent b}^ the upheaval of part 

 of the bed (from Egypt and Abyssinia to the delta of 

 the Ganges) of that primeval ocean which then extended 

 from the Atlantic to the Bay of Bengal, this event 

 taking place in late Miocene or early Pliocene time. As 

 we have already seen, the western portion of that ancient 

 ocean perhaps endured across what is now the Sahara 



