From Eocene to Recent Time 253 



We would decidedly question the correctness in de- 

 termination of the genus Podocys^ regarding which Wood- 

 ward {180: ^i()) observes "too imperfectly known for 

 discussion." 



All of the above lists emphasize the fact that alike in 

 freshwaters as in the sea, the families of European fishes 

 were the same as those that still are found in like environ- 

 ment. Also, the families as well as the genera that inhabit 

 the two media, are largely different from each other, while 

 the freshwater types are of more primitive character and 

 are least modified, those of marine habitat are often highly 

 modified in structure. 



The earliest Miocene (Oligocene) deposits of North 

 America are poorly developed in the eastern as compared 

 with the western part, and in the east they are largely 

 marine. But the White River and the John Day beds 

 that spread over a wide extent of South Dakota, Utah, 

 Colorado, Wyoming, Idaho, and westward to Northern 

 California and Oregon at least, seem to have been very 

 largely deposited in extensive lakes, that were a continua- 

 tion of one — the Wasatch Lake — or possibly of several 

 lakes of Eocene age. Cope says: "great lakes or seas 

 occupied the centre of the continent during Miocene time, 

 when the ranges were still higher. Vast forests of vegeta- 

 tion and a rich population of animal life, point to a humid 

 climate during the entire period that has elapsed, since 

 the great elevation of the Rocky Mountains in the beginning 

 of the Eocene epoch to within comparatively recent times." 

 When the fossil fish fauna of these lakes, that Cope in 

 part elucidated, has been properly studied, the results 

 will aid in many problems of distribution. As yet com- 

 paratively little has been done. 



But some deposits — and notably those of Florissant — 

 are of exceptional interest. For they suggest striking cor- 

 relation in physical and biological features with the Oenin- 

 gian or Tortonian beds of Switzerland, though the former 

 are of lower Oligocene, the latter of uppermost Miocene 

 age. Thus Scudder has described about 800 species of 

 insects, the fishes also were very abundant and are beauti- 

 fully preserved, as are the insects, in a pale fissile limestone 



