28 Dr. E. C. N. van Hoepen 



was apparently regressing during the Oligocene and it is there- 

 fore possible that land connections between Africa and Eurasia 

 came into existence again. Biological facts demand the presence 

 of such a land bridge at that time and the geological possibility^ 

 is therefore of value. 



Another group of geological evidence is of a tectonic nature. 

 The Karroo Formation in South Africa forms in the main a 

 basin, which is closed along its southern and western sides, 

 and which flattens out towards the north. Its eastern border, 

 however, breaks off abruptly on the south east coast, and this 

 may be regarded as definite proof, that this land deposit once 

 extended further. But there is no proof whatever for a connec- 

 tion with another continent. 



It so happens that some mountain ranges in Africa agree in 

 age and direction with such of the South American continent. 

 This phenomenon has, also recently, been used as proof of former 

 connection between the two continents. Special attention has 

 been drawn to mountain ranges south of Buenos Aires which have 

 a NW.-SE. trend and which are compared vsith mountain ranges 

 practically parallel with our SW. coast and therefore with the 

 same trend. Such phenomena could possibly be explained as 

 the result of identical stresses but never as proof of former con- 

 tinental connection. 



Other evidence is afforded by geomorphological and geo- 

 physical phenomena. The river channel of the Congo continues 

 for nearly a hundred miles over the seabottom and it is quite 

 clear, that the river can only have eroded it on a land surface. 

 This, therefore, gives certain proof, that formerly the African 

 continent at this point extended at least one hundred miles fur- 

 ther v/estward. Similar submerged river channels have also been 

 noticed on our south east coast which furnish further proof of 

 submergence of a portion of our continent in this region. I can- 

 not accept the view of Dr. Matthews, who tentatively explains 

 the undersea channels as having been formed by seaward grow- 

 ing barrier reefs, the channel representing the course of the river, 

 in which the corals could not live. Reefs only grow near the 

 surface. The reefs which formed the channel of the Congo, 



