Mesozoic and Cfpnozoic Geology and Palceorttology. 239 



Wyoming, high on hills from the river, Ceanothus cinnamomoides, 

 now Zizyphiis cinnamomoides ; from the Bridger Group at Washakie 

 station, near Bridger's Pass, Bhamnus intermedms, Liquidambar 

 gracile, now Aralia gracilis, and Quercus cemulans; and from Barrell's 

 Springs, Equisetum haydeni. 



After reviewing the state of the knowledge of the Tertiary and Cre- 

 taceous flora of this country, he arrived at the following conclusions, 

 to- wit: 



1. The Tertiary flora of North America is, by its types, intimately 

 related to the Cretaceous flora of the same country. 



2. All the essential types of our present arborescent flora are al- 

 ready marked in the Cretaceous of our continent, and become more 

 distinct and more numerous in the Tertiary- therefore the origin of our 

 actual flora is, like \i^ fades, truly North American. 



3. Some types of the North American Tertiary and Cretaceous 

 flora appear already in the same formations of Greenland, Spitzbergen, 

 and Iceland; the derivation of these types is, therefore, apparently, 

 from the arctic regions. 



4. The relation of the North American Tertiary flora witli that of the 

 same formation of Europe, is marked only for North American types, 

 but does not exist at all for those which are not represented in the 

 living flora of this continent. Therefore, the European Tertiary flora 

 partly originates from North American types, either directly from our 

 continent, or derived from the arctic regions. 



5. The relation of the Tertiary flora of Greenland and Spitzber- 

 gen with ours indicates, at the Tertiary and Cretaceous epochs, 

 land connection of the northern islands with our continent. 



6. The species of plants common to the Cretaceous and Tertiary 

 formations of the arctic regions, and of our continent, indicate, in the 

 mean temperature, influencing geographical distribution of vegetation, 

 a difference, in -|-, equal to about 5° of latitude for the Tertiary and 

 Cretaceous epochs. 



7. The same kind of observation on the geographical distribution of 

 vegetable species, shows at the Tertiary and Cretaceous times, differ- 

 ences of temperatui'e according to latitude, analagous to what is re- 

 marked at our time, by the characters of the southern and northern 

 vegetation. 



Prof E. D. Cope* referred the Bridger Group to the Eocene, and de- 

 scribed, from Cottonwood creek, Wyoming, M^onyx ohtusidens^ Triaco- 



* Pal. Bull., No. 1, and Proe. Am. Phil. Soc, vol. xii. 



