14 



E. M. MUSEUM MEMOIRS. 



of both basins, also to the fact that several genera which are common in one 

 basin are rarely or never found in the other. 



The three exposures of the Bridger (Br.) beds are indicated in the map. 

 First, that of the Washakie basin, which has an east and west extension of 

 about twenty-five miles by about sixteen miles north and south. It is sur- 

 rounded by a narrow band of Green River (Gr.) beds. Passing to the south 

 across Vermillion Creek, is another small exposure of much more contracted 

 dimensions. Much larger than either are the beds lying in the Bridger basin, 

 extending east and west about sixty miles with an expansion to the north which 

 has not been surveyed. These beds are largely surrounded by those of the 

 Green River period. At some points, however, they overlap the Vermillion 

 Creek (V.) beds. On the flanks of the Uinta Mountains they come in contact 

 with the still older Mesozoic rocks. If the view advocated above be adopted, 

 they represent two large sheets of water lying east and west of the present bed 

 of the Green River and draining to the south. A low line of hills made up 

 of Vermillion Creek and Green River rocks separated them, and was suf- 

 ficient to account for the variations of the fauna observed in the two basins. 

 It is well to add that there may have been some slight differences in the 

 character and date of their deposition which would attract one group of animals 

 rather than another. 



The comparison of the Suessonian of Europe with the Vermillion Creek 

 or Wahsatch of the American Eocene has been extended by Prof, Cope, with 

 more restrictions, into a further comparison of the Bridger with the Parisian 

 beds. They possess many genera in common — chief among which are HycenO' 

 don, Adapts, Plesiarctomys, Hyrachyus, Tapirulus, ^ioAAnaptomorphus. The Paris- 

 ian beds have, moreover, a large number of Selenodont Artiodactyla of primitive 

 type, but are distinguished by the absence of the Tillodonta and Dinocerata 

 which are so characteristic of the Bridger epoch. 



Wandering on the shores of the Bridger or Washakie lakes were great 

 herds of Palceosyops, the American Palceotherium, and other perissodactyle ani- 

 mals more closely allied to the tapir. There were also primitive horses of 

 the size of the modern fox. Many lemurs and small rodents testify to the 

 presence of wooded vegetation. The Carnivora were represented by several 

 genera of formidable proportions. Dominant in size were the huge Dinoce- 

 rata, LoxolopJiodon, and Uintatherium, standing a little lower than the elephant, 

 but equally long in the body. Crocodiles and many smaller saurians were abun- 

 dant on the shores, and turtles as large as the modem loggerhead floated on the 

 water, and there were many varieties of land and aquatic birds of small size. 

 The fauna was that of a semi-tropical country, and the climate was very moist ; 

 for, alternating with the finer clays, are coarse gravelly beds indicating periods 



