170 ORIGIN OF LIFE IN AMERICA 



the tropical flora had gained admission to southern Florida 

 during its supposed land connection with the West Indies 

 in lower Pleistocene times, it would have been all destroyed 

 again subsequently. If Dr. Spencer's theory were substan- 

 tiated, the tropical flora of Florida should owe its origin to 

 accidental transport. 



When Dr. E. A. Smith * visited Florida in 1880 he made 

 some geological notes on the peninsula which do not bear out 

 Dr. Spencer's views. He maintains that Florida was elevated 

 nearly to its present height above sea-level after the deposi- 

 tion of the Vicksburg limestone, that is to say, after the 

 Eocene Period, and that this elevation persisted until the 

 Pleistocene, when the country was partly submerged. 



No one, however, has done more practical geological work 

 on the peninsula than Dr. Dall,f who, in his monumental 

 treatises on the Tertiary fauna of Florida, presented us with 

 a masterly survey of the past life of that portion of the United 

 States. His opinion on the geological history of Florida 

 deserves, therefore, most serious consideration, and it may be 

 stated at oncte that he is strongly opposed to Dr. Spencer's 

 views, declaring them to be " incompatible with every geologic 

 and palaeontologic fact of South Florida which has come to 

 my knowledge." 



As the result of his researches Dr. Dall expresses the 

 opinion that the peninsula of Florida, together with the larger 

 Antillean Islands and the Middle American highlands, were 

 uplifted, and the two Americas thus united in Oligocene 

 times, that is to say, during the early part of the Tertiary 

 Era. 



Professor Gregory J had a similar idea, except that he did 

 not specify any geological period. 



When Florida again became disconnected from this Antil- 

 lean continent is not clearly stated, but Dr. Dall thought 

 that it formed a peninsula of the southern continent as it 

 does now of the northern. Florida, according to the same 

 author, became definitely united to North America towards 



* Smith, E. A., "Geology of Florida," p. 306. 



t Dall, W. H., "Tertiary Fauna of Florida," IV., p. 1546. 



I Gregory, J. W., "Geology of West Indies," p. 305. 



