440 SJTPPOSED ATLANTIC CONTINENT. CIIAP. xxii. 



being already detected in the tertiary and post-tertiary form- 

 ations of the United States.* 



Professors Ungerf and IIeer;j; have advocated, on botanical 

 grounds, the former existence of an AtUxntic continent during 

 some part of the tertiary period, as affording the only plausi- 

 ble explanation that can be imagined of the analogy between 

 the Miocene flora of Central Europe and the existing flora of 

 Eastern America. Professor Oliver, on the other hand, after 

 showing how many of the American types found fossil in 

 Europe are common to Japan, inclines to the theory, first 

 advanced by Dr. Asa Gray, that the migration of species, to 

 which the community of types in the Eastern States of North 

 America and the Miocene flora of Europe is due, took place 

 when there was an overland communication from America to 

 Eastern Asia between the fiftieth and sixtieth parallels of 

 latitude, or south of Behring's Straits, following the direction 

 of the A^utian Islands. § By this course they may have 

 made their way, at any epoch, Miocene, Pliocene, or Post- 

 pliocene, antecedent!}' to the Glacial epoch, to Amoorland, on 

 the east coast of Northern Asia. 



We have already seen (p. 158) that the living quadrupeds 

 of Amoorland are nOAV nearly all specifically identical with 

 those at present inhabiting the continent of ^Yestern Europe 

 and the British Isles. 



A monograph on the hippopotamus, bear, ox, stag, or any 

 other genus of mammalia common in the European drift or 

 caverns, might equally well illustrate the defective state of 

 the materials at present at our command. We are rarely in 

 possession of one perfect skeleton of any extinct sjiecies, 

 still less of skeletons of both sexes, and of different ages. 



* Proceedings of Academy of Natu- J Flora tortiaria Helvetia). 



ral Science, Philadelphia, for 1858, § Oliver, Lecture at the Royal In- 



p. 89. stitution, March 7, 18G2. 



f Die versunkcne Inscl Atlantis. 



