92 BLYTT. DISPLACEMENT OF BEACH-LINES. [No. 1. 1889]. 



numerous mammalian types common to the East and West, a id 

 telling of a new land-bridge. In respect the later Tertiary period, 

 the similarity between the fauna and flora of China and Western 

 North America, and between the fresh-water fauna of these 

 countries and South Eastern Europe, speaks of a connection 

 across the Behring Strait (or the Alentes). 



The marine Tertiary shells of Atlantic North-America, are, 

 according to Neumayr, not like those of Europe. On the 

 contrary the similarity is greater at the present time than in 

 the Miocene. This tends to show, that the above named land- 

 bridge across the Atlantic, is of later origin than Miocene. 



Therefore I believe, that relatively slight geographical chan- 

 ges, probably aided to some degree by alternations caused by pre- 

 cession under varying eccentricity, might suffice to explain the 

 climatic changes of Tertiary and Quaternary times. And I 

 think, on the whole, that the hypothesis, I have stated, assisted 

 perhaps by the old hypothesis of secular cooling, but probably 

 even without that assistance, is quite sufficient to account for 

 the geological facts. 



