OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 183 



that the Middle Eocene sirenians of Europe are more speciahzed than the 

 Upper Eocene sirenians of Africa might be cited as evidence that the sire- 

 nian center of diffusion was hkewise to the northward. 



Geographic changes in Europe. — The early earth movements of the 

 Oligocene caused an invasion of the sea in the north of France, and in Ger- 

 many as far south as Leipzig. This vast northern ocean of Tongrian and 

 Stampian age is believed to have made the northern climate of Europe more 



Fig. 77. — ■ Oligocene. A period of continental elevation and reunion followed by the 

 reestablishmcnt of oomiections between the life of the New and Old Worlds. Central Europe 

 submerged or partly archipelagic. African mammals and birds partly similar to those of 

 Europe. Madagascar united with Africa. South America entirely separated, its mammals 

 developing independently. Australia entirely separated. Closing the Oligocene, another 

 long interval of separation between North America and Europe. Rearranged after 

 W. D. Matthew, 1908. 



temperate. The lignitic flora of south central Germany now includes 

 sequoias, birches (Betula), and palms {Palmacites)} Southern Europe 

 through the rise of the Pyrenees and Swiss Alps was elevated, and conditions 

 were favorable for continental depositions rich in mammalian life both in 

 southern France and in the south of Germany, as shown in Fig. 79. 



In the Aquitanian, or Upper Oligocene stage almost all of Europe had 

 again emerged from the sea; great shallow lakes were scattered over France, 

 Switzerland, Germany, Austria, Italy, and Greece. In southwestern France 

 or Aquitania, from which the stage derives its name, there is a renewed 

 advance of the sea over the land. The freshwater lakes are varied by 



> De Lapparent, A., Traite de Gcologie, 1906, pp. 1547-1549. 



