636 E. W. BERRY CENOZOIC FLORAS OF EQUATORIAL AMERICA 



permanency of ocean basins, as developed by Matthew in ^^Climate and 

 evolution/' ^^ seems nnqiiestionably sound in the present state of our 

 knowledge of isostatic compensation. Whether the latter was always as 

 complete as it seems to be at present may well be doubted — certainly we 

 know of remarkably great epeirogenic changes, and, furthermore, a rather 

 good case can be made out for the theorem advanced by Walther and 

 others, that the deep seas are post-Mesozoic in age. Be this as it may and 

 while its acceptance does not directly oppose Matthew's contention, the 

 present continental scarps can not be regarded in all cases as the metes 

 and bounds of the continents in past times, and a very strong case can be 

 made out for Suess's sunken block theory in a large number of areas, 

 and especially in the Caribbean region. 



It seems to me, as I review the various lines of evidence, that the long 

 region of weakness extending from Graham Land to the Antilles may 

 well indicate that the Antilles were once a part of South America, and 

 that the latter continent was connected with Antarctica. I have recently 

 shown that the change of elevation of the great central plateau of Bolivia 

 and the eastern Andes in that region has amounted to a minimum of 2% 

 miles since the Pliocene,^* and the weight of this argument is not dis- 

 posed of by calling these changes orogenic instead of epeirogenic. I am 

 therefore the more inclined to believe that comparable changes of level 

 have taken place in the Caribbean region during the Tertiary. 



In all discussions of paleogeography based on the distribution of the 

 mammals it should be constantly borne in mind that the facts, in so far 

 as they contribute toward an understanding of the relations between 

 N"orth and South America, are derived almost entirely from the region 

 of the Great Plains and Eocky Mountains in North America and from 

 Argentina in South America — regions which were separated, at least 

 during the Eocene and the Oligocene, as they are today, by the greatest 

 extent of tropical rain forest on the globe. The fact that the edge of this 

 equatorial American rain forest appears to have covered the southern 

 shores of the United States during the first half of the Tertiary renders 

 it obvious why the Artiodactyla and Perissodactyla of our western plains 

 were not exchanged for the typotheres and litopterns of Patagonia. 



13 W. D. Matthew : Annals N. Y. Acad. Sci., vol. 24, 1915, pp. 171-318. 

 " E. W. Berry : Proc. U. S. Natl. Mus., op. cit. 



