INTRODUCTION 81 



Submergence of the coast during Oligocene and Lower Miocene times was 

 succeeded by a reemergence, known as the post-Kenai revolution, in late 

 Miocene or Early Pliocene times. The mammalian life of Europe and 

 North America similarly shows intermittent intervals of close correspondence 

 and similarity and of separation or divergence. The very close similarity 

 between the mammals living at the present time on either side of the Beh- 

 ring Straits is strong evidence that up to late Pleistocene times there was free 

 migration between the two continents. 



The Great Antilles, West Indies, and South America. — This region was 

 another area of emergence and submergence, which is of deep interest because 

 of the apparent faunal connection between North and South America late 

 in the Age of Reptiles and early in the Age of Mammals, followed by a pro- 

 longed and absolute separation or divergence of the mammalian life of the 

 two countries, which was again succeeded by a sudden renewal of relations 

 in the Middle Pliocene. The results obtained by Hill (1899) ^ as to the 

 movements of the Antilles are summarized by Matthew as follows: "The 

 Eocene strata of the Antilles bear evidence of the preexistence of extensive 

 areas of land during the latter part of the Age of Reptiles (Cretaceous) . Late 

 in Eocene time there was a profound submergence including all but the 

 highest tips of the Antilles, which lasted into early Oligocene times. Li Oligo- 

 cene or Miocene times there was a great upward movement whereby many 

 of the islands were connected with each other and possibly with the insular 

 southern portion of Florida, but land connections between the North and 

 South American continents were not established at this time. During 

 Miocene and Pliocene times the islands were again separated by partial 

 submergence into their present outlines, which have been since retained 

 with only slight modifications. In Pliocene and Pleistocene times there have 

 been intermittent periods of elevation, but none so great as those in the latter 

 part of the Oligocene." 



These conclusions on the whole leave the question of the period of connec- 

 tion between North and South America entirely an open one ; yet this period 

 seems to be pretty firmly established as of Pliocene Age through the over- 

 whelming testimony of the interchange of large terrestrial mammals l:)etween 

 North and South America at this time. 



' Hill, R. T., Geological Reconnoissance of Jamaica. BuU. Mas. Conip. Zool., Vol. 

 XXXIV, 1899, pp. 1-226. 



