FOSSIL ELEPHANTS IN AMEEICA 359 



todon called Trilophodon on account of the three transverse 

 rows of cusps on its intermediate grinding teeth. Now Trilo- 

 phodon arrived in Europe and in North America at about the 

 same time during the Miocene Period. Professor Osborn 

 assumes that these mammals came from Asia, although we 

 possess no evidence of their having reached the northern or 

 eastern parts of that continent. We might be tempted to 

 invoke a direct land connection between Africa and South 

 America in Oligocene times, but, as we shall see later on, that 

 connection must have disappeared at a still earlier period. 

 However, these and other problems will be considered in the 

 next chapter. 



Several important zoogeographical features of western and 

 northern South America still remain to be considered. Special 

 researches among the Cretaceous rocks and their fossils in 

 Peru have shown that during Lower Cretaceous time, that is to 

 say, towards the latter part of the Mesozoic Era, the greater 

 part of the country was buried deeply beneath the ocean. 

 From Bolivia and Chile, even as far south as the Strait of 

 Magellan, Lower Cretaceous deposits have been discovered. 

 North of Peru they occur in Colombia and Venezuela. The 

 most surprising circumstance connected with these South 

 American beds, however, is the great number of species that 

 are either identical with or closely allied to, such as occur iq 

 the Cretaceous deposits of north Africa, the south of France, 

 Switzerland and the neighbouring countries.* More than 

 sixty years ago D'Orbigny already drew attention to this fact, 

 and argued from it that a land connection across the mid- 

 Atlantic must have enabled species to cross the ocean by 

 travelling along a continuous shore-line. On the other hand, 

 scarcely any affinity exists between the Cretaceous of Vene- 

 zuela and that of Mexico or Texas, thus clearly implying the 

 presence of a land barrier between these two areas. The old 

 highland of Guiana east of Venezuela was long ago a penin- 

 sula of the archaean highlands of Brazil in the south. There 

 is reason to believe that the great mountain chain of the 

 Andes gradually emerged out of this sea. During this process 

 some of the newly-formed islands probably became attached 



* Paulcke, W., " Kreideformation in Sudamerika," pp. 305 308. 



