No. XV. GEOLOG5 . 339 



out in the magnificenl volumes published by the U. S. Geo- 

 logical Survey of the Territories, containing the researches of 

 Professors Leo Lesquereux, Meek, Mndge, I) rs . Hayden and 

 Newberry, and others. 



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

 Dakota group, has much in common with the Greenland 

 Upper Cretaceous Flora, some of the twenty-eighi 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 

 beino; common to the Greenland and Mackenzie rocks of that 

 age, and some of them reappearing in the plant-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 Onoclen, sensibllis (Felieites hebridicus 

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



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