130 GEOLOGY. 



on the whole, of such a character, particularly as to size, as to indi- 

 cate a climate which was far from tropical. So far as they afford a 

 warrant for inference, 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. 



Close of the period. — Geographic changes of importance occurred 

 in various parts of the earth at the close of the Early Cretaceous period, 

 and are recorded (1) in the unconformities between the Lower and Upper 

 Cretaceous systems, and (2) in the differences in their distribution. 

 Unconformity between the two systems is recorded at some points 

 in Europe, in North Africa, in Australia, where it is great, and in South 

 America. The differences in distribution between the two systems 

 will appear in the account of the following system. 



THE LIFE OF THE COMANCKEAN PERIOD. 



The terrestrial vegetation. — Fossil plants constitute the chief record 

 of the life of the opening epoch of the Comanchean. The very earliest 

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

 deans, conifers, ferns, and horsetails were the dominant forms. In 

 Europe, where the Jurassic grades into the Cretaceous through the Pur- 

 beck and Wealden (and their continental equivalents), this rather 

 monotonous group continued to hold possession of the land throughout 

 the Lower Cretaceous, except in Portugal, where angiosperms appeared. 

 The members of this group continued their slow modernization, but did 

 not undergo any radical change in Europe during this period. So far 

 as known, the same was true of Asia, Africa, and Australia, but data 

 relative to these regions are scanty. The same appears also to have 

 been true of northwestern America, where (in Shastan and Kootenay 

 series) these groups made up the recorded flora and formed beds of 

 coal. 



The introduction of angiosperms. — But in the central and eastern 

 American region representatives of the present reigning dynasty of plants, 

 the angiosperms, including both monocotyledons * and dicotyledons, 

 appeared in the Lower Potomac, and developed strongly during the 

 period, so that by the opening of the (Upper) Cretaceous they seem 



1 Monocotyledons have been reported earlier, but the identification is not beyond 

 question. 



