FOSSIL ELEPHANTS IN AMERICA 
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 in 
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. 
