872 HISTOEICAL GEOLOGY. 



Great Britain, 1885, American, 1894, 



Etheridge R. P.AVhitfield 



Corals 76 27 



Echinoderms 201 G5 



Brachiopods 106 28 



Lamellibranchs 476 1329 



Gastropods 298 839 



Ammonoids 206 224 



Nautiloids 20 12 



Belemnites 14 19 



Crustaceans 110 17 



The contrast is equally great with the marine fauna of the Parisian and 

 Mediterranean basins in Europe. It will be noted that the American 

 species are from all North America. The species are, it is true, but imper- 

 fectly studied ; yet the contrast, if all were known, would be strong. Great 

 Britain leads in species of clear seas, and those of moderately deep water — 

 Corals, Echinoderms, and Brachiopods ; and if the comparison were confined 

 to the Atlantic border of ISTorth America, immensely so in Ammonoids and 

 Nautiloids. The number of both groups from this border is only 24, and 

 that of Echinoderms less than 15. 



But in number of species of Reptiles America is far ahead of Britain and 

 Europe ; and probably because its broad Western Interior had a vast extent 

 of shallow sea-borders and emerging lands, and thus afforded them especially 

 favorable conditions for existence. 



CLEMATE. 



During the Cretaceous period, a warm climate still prevailed over the 

 earth even to the poles, but with some cooling during the closing part of 

 the period ; and in North America with a great Central Interior Sea, to the 

 end of the period, the climate was moist. The Cycads and associated species 

 of plants in the lower Cretaceous beds of Greenland indicate, according to 

 Heer, a mean temperate of 21° C. to 22° C, or about 70° F. to 72° F. This 

 temperature is that of Cuba. The facts prove that a somewhat similar tem- 

 perature prevailed at the same time over Spitzbergen and in Alaska, where 

 the same flora existed ; even along the Atlantic border at least as far north as 

 Long Island ; in the region of the Kootanie beds in Montana and the neigh- 

 boring part of British America ; and over more western North America 

 to Alaska. The Gulf Stream of the Atlantic may account in part for the 

 extension of so high a temperature to Greenland; and a like stream over 

 the Pacific, for that to Alaska. 



The plants of the Vancouver coal-beds, and those of the Patoot beds in 

 Greenland, which Dawson refers to the age of the Montana series, he com- 

 pares with those of Georgia at the present time, where the mean tempera- 

 ture, he states, is about 65° F. The Dakota plants of Kansas and elsewhere^ 

 with those of the Mill Creek group, Canada, and the Atane of Greenland^ 



