THE EOCENE OF EUROPE AND NORTH AMERICA 141 



France and the consequent recession of the old Northern, or Suessonian 

 Gulf, replaced in the Basin of Paris by a period of great lagoons, the evapo- 

 ration of which caused thick deposits of gypsum. At the same time numer- 

 ous small freshwater lake, river, and swamp deposits (lignites) collected 

 mammal remains over a very wide area, reaching northern Spain, southern 

 England, and Bavaria (Heidenheim) in the east, and giving us prol)al)ly 

 a very true picture of the entire fauna of western Europe. The lagoons 

 were fed l:)y freshwater streams, which brought with them remains of animals 

 from neighboring districts. Those of the Paris gijpse probably communi- 

 cated with the sea by river channels to the north. The bed of the ancient 

 lake of Velay contains a flora of African type, including the sal)al (Sabalites) 

 and the date palms (Phienicites). 



The Mammalian group as compared with that of America. — We first note 

 in the Old World the entire absence of tapirs (Tapiridse), of titanotheres 

 (Titanotheriidifi), and rarity of pro-Carnivora (Miacidse), as well as of 

 many other archaic and modern forms of mammals which have been dis- 

 covered in the American Eocene. The number of European Middle and 

 Upper Eocene families surviving, or having descendants at the present 

 day, is, in fact, very small, including only the horses (Equidse), moles (Tal- 

 pidae), hedgehogs (Erinaceidae), and possibly the aye-ayes (Cheiromyidae). 

 Possibly certain of the Old World dichobunes (Dichobunidse) are ancestral 

 to the modern ruminants. With these exceptions this is truly an ancient 

 fauna, and so it impressed all the early French writers. It is not, however, 

 an archaic fauna in the sense of being a survival from the Age of Reptiles, 

 because the only archaic mammals are the hytenodonts and insectivores. 

 This group represents, therefore, the first adaptive radiation of the higher 

 kinds of placental Herljivora, radiating mostly into hrowsing types, which 

 exhibit a great range of size and speed, and indicate a general prevalence 

 of forested conditions and soft herbage. Without exception the grinding 

 teeth are short-cro^vned or l^rachyodont. No distinctively grazing or 

 hypsodont animals are lvno\\ii in all this assemblage. Stehlin ^ (1904, p. 473) 

 observes: "Thiis the aspect of the European fauna during the second half 

 of the Eocene tends to become ever more homogeneous as our knowledge 

 of it increases. It is a period of comparative calm, during which a num- 

 ber of types (lophiodonts) dominant at first, become extinct, while others 

 (palacotheres) gradually gain in importance." 



Like the mammals which appeared in North America late in Wind River 

 and early Bridger times, this faunal group was destined to monopolize the 

 European world durmg the Middle and Upper Eocene. The first extinc- 

 tions occurred in the Bartonian. The first invasion of any considerable 

 number of new mammals appeared at the very close of the Eocene or 

 Ludian (see p. 145). 



' stehlin, H. G., Sur les Mamniiff^ros des Sables Bartoniens du Castrais. Bull. Soc. Gcol. 

 France, Ser. 4, Vol. IV, May, 1904, pp. 445-475. 



