114 DISTRIBUTION OF EXTINCT ANIMALS. [part ii. 



with almost all the forms now living, produced a rich and varied 

 fauna such as we now see only in the open country of tropical 

 Africa. During all this period we have no reason to believe that 

 the climate or other physical conditions of Europe were more 

 favourable to the existence of these animals than now. We must 

 look upon them, therefore, as true indigenes of the country, and 

 their comparatively recent extinction or banishment as a remark- 

 able phenomenon for which there must have been some adequate 

 cause. What this cause was we can only conjecture ; but it 

 seems most probable that it was due to the combined action of 

 the Glacial period, and the subsidence of large areas of land once 

 connecting Europe with Africa. The existence, in the small 

 island of Malta, of no less than three extinct species of elephant 

 (two of very small stature), of a gigantic dormouse, an extinct 

 hippopotamus, and other mammalia, together with the occurrence 

 of remains of hippopotamus in the caves of Gibraltar, indicate 

 very clearly that during the Pliocene epoch, and perhaps during 

 a considerable part of the Post-Pliocene, a connection existed 

 between South Europe and North Africa in at least these two 

 localities. At the same time we have every reason to believe 

 that Britain was united to the Continent, what is now the German 

 Ocean constituting a great river-valley. During the height of 

 the Glacial epoch, these large animals would probably retire into 

 this Mediterranean land and into North Africa, making annual 

 migrations northwards during the summer. But as the connect- 

 ing land sank and became narrower and narrower, the migrating 

 herds would diminish, and at last cease altogether ; and when the 

 glacial cold had passed away would be altogether prevented from 

 returning to their former haunts. 



Miocene Peeiod, 



We now come to a period which was wonderfully rich in all 

 forms of life, and of which the geological record is exceptionally 

 complete. Various lacustrine, estuarine, and other deposits in 

 Europe, North India, and North America, have furnished such a 



