312 The Upper Cretaceous Floras of the World 



after all is known of the real relations of organisms to their environment. 

 In local areas with the concomitant evidence from sediments and asso- 

 ciated faunas it is often possible to be more explicit, but in considering 

 the floras as a whole it can only be said that they unmistakably show more 

 uniform climatic conditions than existing floras. They can be traced 

 from Greenland to Texas with apparently but slight changes; they cross 

 the equator unchanged in both the eastern and western hemispheres. In 

 general they furnish but slight evidence of deciduous habits, but prevail- 

 ing show a character more like existing floras of the warm temperate 

 rain-forest type, less tropical than succeeding Eocene and Oligocene Moras. 



The so-called Mediterranean faunas of both hemispheres, characterized 

 especially by the Chamacea and Itudistacea, have often been supposed to 

 indicate climatic zones but this may justly be doubted. Considering only 

 the North American region it may be noted that the marine faunas of the 

 east coast, as was true of the floras, can be traced from New Jersey to 

 Alabama with scarcely any evidence of climatic influence. On the other 

 hand, the Mediterranean fauna of Mexico and Texas extends northward 

 in the Western Gulf area to about the same latitude that the Atlantic 

 Coast fauna reaches in Alabama in the Eastern Gulf area. It is obvious 

 that distance from the equator was not a factor as is also abundantly 

 proven by the European record. While the effects of warm currents 

 might be considered as of importance in Europe it is difficult to conceive 

 any arrangement of Cretaceous currents that would affect the western 

 and not the eastern shore of the Cretaceous Mississippi Gulf. Both 

 faunas are conspicuously shallow-water, and the one outstanding differ- 

 ence is the character of the sediments — those of the Eastern Gulf and 

 Atlantic Coast being clays and sands, while those of the Western Gulf 

 are limestones of clear waters. It is concluded that the character of the 

 water is the major factor and that the faunas confirm the floras in indicat- 

 ing but feeble if any zonal climatic differentiation. 



No attempt at a detailed correlation of these widely scattered Upper 

 Cretaceous floras that have been enumerated on the preceding pages has 

 been considered feasible in view of their very unequal values. A few of 

 the more important have been brought together and compared with the 

 standard section in the accompanying table. 



