THE EOCENE OF EUROPE AND NORTH AMERICA 83 



Even these dots may give an exaggerated idea of our knowledge, because 

 the remains which have been discovered consist largely of teeth and im- 

 perfect jaws. The conditions which so favored the preservation of the 

 records of reptilian life were singularly unfavorable to the recording of mam- 

 malian life. Exactly the reverse conditions, namely, of extensive terrestrial 

 and freshwater formations, prevailed during the Age of Mammals, so that the 

 mammalian records are far more complete than those of the reptiles, amphib- 

 ians, or fishes. 



Palceogeography of Eocene Europe 



During a considerable part of the Eocene epoch Europe was a small, 

 isolated land area, peninsular and sometimes insular. Seas are known to 

 have extended over the region of the Pyrenees, over Switzerland, southward 

 over a large part of Africa, and eastward to China. In these seas the shells 

 of Foraminifera, called nummulites, accumulated as ' nummulitic ' limestones 

 to the extent of 10,000 feet, especially in the areas which now represent the 

 summits of the Alps and Apennines. 



Despite the broad areas of depression which correspond with the present 

 mountain ranges of the Pyrenees and Alps, the continent of Europe was 

 beginning to assume its present outlines and conformation. To the north 

 France was broadly united with Great Britain. The interior of France was 

 mostly above water. Throughout the Eocene period there were two areas of 

 continental depression and elevation. The first, along the northeast coast 

 bordering Belgium; the second, along the southwest coast bordering the Gulf 

 of Gascogne, in the region of the Pyrenees. It is chiefly in these areas that 

 the great life zones were preserved. The succession of stages which succes- 

 sively record the geographic and life changes in the country now known as 

 France are as follows: 



In the Basal Eocene, or Thanetian, France was 

 Upper Eocene (6) Ludian indented by great northern and southern gulfs. 



Middle Eocene(5) Bartonian ^^"^^ *^^ ^o™^^ ^^^^ *^^ mammaliferous de- 



posits of Cernay and La Fere. In the Lower 

 (4) Lutetian Eocene, or Sparnacian, there was a great northern 



Lower Eocene (3) Ypresian gulf bordered by lagoons. In the Ypresian 



(2) Sparnacian ^'^"'^ '^^' separated from Spain. In the 



Middle Eocene or Lutetian, France and western 



Basal Eocene (1) Thanetian Europe formed a great island separated by a 



broad channel from Eurasia and Asia. 



These disturbed conditions of the shorelines and of the regions which 

 now constitute the great river basins of France explain the great variety of 

 deposits in which the remains of fossil mammals are found, namely, the suc- 

 cession of marine, fluvio-marine, littoral, estuarine, lagoon, and swamp 

 deposits throughout the entire Eocene period in France and England. Con- 



