No. XV. GEOLOGY. 339 



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Out in the magnificent volumes published by the U. S. Geo- 

 logical Survey of the Territories, containing the researches of 

 Professors Leo Lesquereux, Meek, Mudge, Drs. Hay den and 

 Newberry, and others. 



The flora of the base of the Cretaceous of America, the 

 Dakota group, has much in common with the Greenland 

 Upper Cretaceous Flora, some of the twenty-eight species 

 determined by Prof. Heer being identical. The vast extent 

 and homogeneousness of the formation in America point to a 

 marine deposit, formed during a period of subsidence, followed 

 by a long stationary era, experiencing a land climate dry, 

 and proportionally cold. 



The marine forms, which occur in the Dakota group, and 

 which have so large a development in the overlying beds, are 

 absent in the Greenland beds, and the Lower Cretaceous flora 

 appears to be unrepresented in North America, pointing to a 

 long and unbroken continental epoch in the Arctic Circle, 

 ranging through the entire Cretaceous and Tertiary eras. In 

 the overlying American Eocenes occur types of plants, oc- 

 curring in the European Miocenes, and still living, proving 

 the truth of Professor Lesquereux's postulate that the plant 

 types appear in America a stage in advance of their advent 

 in Europe. These plants point to a far higher mean tem- 

 perature than those of the Dakota group, to a dense atmo- 

 sphere of vapour, and a luxuriance of ferns and palms. The 

 subtropical flora of the Eocene Tertiary lignitic group is 

 absent in the Arctic lands, though a certain amount of mingling 

 of temperate forms occurs ; these, however, come in great 

 force in.the overlying Lower Miocene beds, many of the species 

 being common to the Greenland and Mackenzie rocks of that 

 age, and some of them reappearing in the plants-bearing shales 

 of Grinnell Land ; the successive Miocene deposits pointing 

 to a gradual lowering of the mean temperature. 



The American origin of the Miocene flora of Europe, as 

 Dr. Newberry points out, is strongly supported by the occur- 

 rence of the plant Onoclea sensibilis (Felicites hebridicus 

 of Forbes), discovered long ago by the Duke of Argyll in the 



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