THE EOCENE PERIOD. 221 



possibly with Africa. The basis for these conjectures is found in the 

 distribution of life at that time, as shown by fossils. It has also been 

 thought that Africa and South America were connected across the 

 Pacific from some earlier time until after the beginning of the Eocene. 1 



If these conjectured extensions of land were real, it will be seen that 

 the division of land and water in the northern and southern hemispheres 

 was far less unequal than now, and that the land was massed in high 

 latitudes to a greater extent than at present, while tropical seas were 

 much more extensive. If extensive polar lands were the cause of 

 glacial periods, it would seem that the geographic conditions during 

 the Eocene were favorable in the extreme, if the relations sketched 

 above were the real ones. In spite of this, the climate of the period 

 seems to have been genial, and less markedly zonal than now. 



Close of the Eocene. — During the later part of this period, and at 

 its close, there were some notable deformations in Europe. The initia- 

 tion of the Pyrenees, and of some of the mountains farther east, is 

 assigned to this time, and the distribution of the later formations, when 

 compared with the distribution of the Eocene, shows that changes of a 

 less pronounced type were in progress elsewhere. 



The Eocexe Life. 



I. The Transition from the Mesozoic to the New Era. 



Four salient features marked the transition of life from the Mesozoic 

 to the Cenozoic era: (1) In marine life, nearly or quite all Cretaceous 

 species were replaced by new ones; (2) in the terrestrial plant life so 

 many species lived across the transition interval as to render the plac- 

 ing of the dividing plane between the Mesozoic and Cenozoic in western 

 America one of the most mooted of classificatory questions; (3) the 

 great saurians, from the dinosaurs of the land to the mosasaurs of the 

 sea, disappeared, and most other reptiles showed profound changes, con- 

 stituting a revolution in the animals of the land corresponding to that 

 of the sea, but contrasted with the continuity in the terrestrial vege- 

 tation; and (4) placental mammals appeared in force and promptlv 

 took a dominant position. The combination is unique, in that, while 

 half the land life joined with the sea life in undergoing a profound trans- 

 formation, the other half of the land life did not notably participate 



1 Neumayr, Erdegeschichte Bd. II. 



