THE COMANCHEAN PERIOD 737 



and is unconformable beneath the Upper Cretaceous, and in South 

 Africa. 1 Marine Lower Cretaceous is wide-spread in the northern 

 part of South America, but not elsewhere east of the Andes. It is 

 generally absent about the borders of the South Atlantic. On 

 the other hand, marine Lower Cretaceous beds occur in many 

 places about the southern Pacific and Indian Oceans. The areas 

 where the system is exposed are, however, mostly small. 



Close of the period. Geographic changes of importance oc- 

 curred in various parts of the earth at the close of the early Creta- 

 ceous period, and are recorded (1) in the unconformities between 

 the Lower and Upper Cretaceous systems, as at some points in 

 Europe, north Africa, Australia, and South America, and (2) in the 

 differences in their distribution, as will appear in the account of the 

 following system. 



Climate. In the aggregate, the known fossils of the Lower 

 Cretaceous of America are not such as to indicate great diversity 

 of climate. Even in Greenland, the climate seems to have been 

 as warm as that of warm temperate regions to-day. 



The fresh-water fossils of those deposits of central Europe 

 which represent the transition from the Jurassic to the Lower Cre- 

 taceous, are, on the whole, of such a character as to indicate a 

 climate far from tropical. So far as they afford a warrant for in- 

 ference, the climate of central Europe would seem to have been 

 comparable with that of the temperate portions of America to-day. 

 The fossils of lower latitudes denote a warmer climate. On the 

 whole, European fossils seem to afford better evidence of the exist- 

 ence of climatic zones than those of America. From them paleon- 

 tologists have thought to find warrant for the hypothesis that the 

 climate underwent more or less fluctuation during the course of the 

 period. 



LIFE 



The terrestrial vegetation. Fossil plants constitute the chief 

 record of the life of the early stages of the Comanchean in America. 

 The earliest flora was akin to that of the Jurassic, in that the cyca- 



1 Ann. Rept. Geol. Com. Cape of Good Hope, 1901, p. 38; Corstorphine, 

 History of Stratigraphical Investigations in South Africa, Kept. S. Af. Assn. 

 for Adv. of Sci., 1904; and Rogers, Geology of Cape Colony, 1905. 



