3o6 THE MIGRATION OF BRITISH BIRDS 



The recent discovery of sub-fossil remains of an extinct 

 hippopotamus in Madagascar^ is an event of profound 

 and far-reaching importance. The presence of this huge 

 mammal in Madagascar clearly proves that the southern 

 emigration of the higher forms of life into the Ethiopian 

 region could never have taken place at the date Dr. 

 Wallace ascribes to it, and further proves that these 

 large mammalia must have had an equatorial or southern 

 base to survive the climatic vicissitudes of the Ice Age, 

 as I have already insisted. As Dr. Wallace writes 

 {Island Life, p. 448), " the most striking and character- 

 istic groups of animals now inhabiting Africa are entirely 

 wanting in Madagascar. Let us first deal with this fact, 

 of the absence of so many of the most dominant African 

 groups. The explanation of this deficiency is by no 

 means difficult, for the rich deposits of fossil mammals 

 of Miocene or Pliocene Age in France, Germany, Greece, 

 and North-west India, have demonstrated the fact that 

 all the great African mammals then inhabited Europe 

 and temperate Asia. We also know that a little earlier 

 (in Eocene times) tropical Africa was cut off from 

 Europe and Asia by a sea stretching from the Atlantic 

 to the Bay of Bengal, at which time Africa must have 

 formed a detached island-continent such as Australia is 

 now, and probably, like it, very poor in the higher forms 

 of life. Coupling these two facts, the inference seems 

 clear, that all the higher types of mammalia were 

 developed in the great Euro-Asiatic continent (which 

 then included Northern Africa), and that they only 

 migrated into tropical Africa when the two continents 



* Conf. Ileilprin, Geographical and Geological Distrib. of Animals, 

 p. 373 ; and Nature, January 24, 1895, p. 311. 



