14 GBOGKAPHICAL DISTEIBUTION. 



while the type-forms represented on the opposing shores might have 

 been alike, the species would have almost undoubtedly differed. 

 Equally positive proof in this direction is furnished by the similari- 

 ties presented in the reptile and amphibian faunas. The shallow- 

 ness of the channel separating Spain from Morocco renders it prac- 

 tically certain that one such connecting land-mass occupied the 

 position of the present Straits of Gibraltar. On the other hand, the 

 finding of remains of several species of elephant in Sicily and Malta 

 is almost proof positive of a second connection having been formed 

 between Italy and Tunis. An elevation of the present bed of the 

 sea a few hundred fathoms would bring about this result. The 

 Mediterranean would then consist of two land-locked basins. But, 

 doubtless, many of the other islands besides Sicily and Malta were 

 united with the mainland, for otherwise it would be impossible to 

 explain the distribution of several modern animals, the moufilon, 

 for example, which is found in Sardinia, Corsica, Crete, and the 

 mountains of Greece. 



Granting this connection between Africa and Europe, it appears 

 more than likely that the principal disturbing element which reacted 

 upon the Post-Pliocene European fauna, the great northern ice-sheet 

 and the accompanying cold of the glacial period, rather than caus- 

 ing the complete or sudden extermination of the receding fauna, 

 compelled it to migrate over into regions of a more congenial cli- 

 mate. That such was the fate of many of the forms there can be 

 no reasonable doubt. The African continent thus became stocked 

 with its existing fauna largely from the more temperate northern 

 regions. But there is every reason to believe that these same south- 

 ward retreating forms were in great part primarily introduced into 

 Europe from Africa, and over the same routes by which the later 

 southerly migration was effected. Concerning the origin of the 

 African fauna itself we possess little precise information. The 

 paleontology and geology of the region are so imperfectly known 

 that we possess as yet no basis for satisfactory deductions. The 

 absence of sufficient data naturally renders uncertain all speculation 

 relating to the late European fauna as well. It may be considered 

 highly probable, however, that many of its characteristic elements 

 have been derived from the region about India, where a considerable 

 antiquity, extending back to the Miocene or early Pliocene period 

 is proved for at least a number of the more prominent types. Seve- 



