From Eocene to Recent Time 



243 



a warm-temperate climate existed even in Greenland. Such, 

 succeeded by colder conditions, would stimulate to organ- 

 ismal modification and evolution. Extensive rivers and 

 lakes existed in north, in central, and in south Europe, in 

 Africa, where Tanganyika was a persistent feature from 

 late Cretaceous times probably (p. 482) ; in North America 

 where thick lacustrine and eolian deposits — interspersed 

 at times by heavy deposits of volcanic dust and ash — gave 

 rise to the White River Formation. 



One of the most extensive and informing deposits of 

 Lower Oligocene age in Europe, is the Tongrian or Upper 

 Flysch series of marine rocks, that can be traced from East 

 France, the Voges, Glarus, N. Italy, and Vienna northward 

 through Bavarian, Swabian and Danubian territory to 

 Moravia and Galicia on the east. Much if not all of this 

 region was a marine expanse, over which deposits were 

 made to a depth of from 1000 to 6000 feet, and while as 

 yet the greater part of the Alps was not in existence. But 

 simultaneous with these deposits, according to the writings 

 of Heer, extensive lakes and swamps in central and north 

 Germany were accumulating freshwater deposits which 

 closely resembled those described below for Switzerland. 



The above marine rocks, as studied by Hauer {181: 

 104), Suess (7^2:87), Paul, and Fuchs amongst others, 

 are divisible into a lower and upper zone. The former 

 is known as the "amphisyle" zone, for the most conspicuous 



Fig. 36. Amphisyle heinrichi. A specially abundant and highly 

 modified fish of the marine Oligocene rocks from Alsace to Baku. 

 Enlarged nearly twice nat. size. (After Heckel). 



Fig. 37. Amphisyle scutata, an East Indian marine fish of 

 near affinity with the above, but somewhat larger. (After Day). 



