462 



GEOLOGICAL SUEVEY OF THE TEREITOEIES. 



The important differences are the ^tresence of Artiodactyla with seleno- 

 dont molar teeth in the French Eocene ; I allude to the Anoplotheriidm 

 and HyopotamidcB, which are entirely wanting in the Wyoming beds. 

 On the part of the latter, the presence of the JEobasiliidce, Bathmodontidw, 

 and Anchippodontidw constitute a marked peculiarity. On the whole, 

 the evidence is in favor of ascribing the priority of age to the Wyoming 

 Eocene. 



The appearance of selenodont artiodactyles, including great numbers 

 of Tragulidce, with horses and rhinoceroses in the White Eiver beds, 

 clearly mark the advent of the Miocene, while the presence of Eyopo- 

 tamus and jE7Zot/tenMW indicate a nearer relation to the Lower than to the 

 Upper Miocene of Europe. The family of OreodontidcB is the peculiar 

 feature which distinguishes the American from the European beds, while 

 the latter contain numerous viverrine carnivora not known from Amer- 

 ica. The Loup Fork beds, from the greater proportion of existing ge- 

 nera which they contain, display a resemblance to the European Plio- 

 cene ; but they differ strikingly in the greater number of horses and 

 camels which they contain. The smaller percentage of existing genera 

 in the Loup Fork beds, with the persistence of an oreodont, {Merychyus,) 

 indicates that these also should be placed anterior to the Pliocene of 

 France. 



The species enumerated in the following pages are distributed in their 

 orders as follows. I add a list of the species enumerated by Dr. Leidy, 

 as occurring in the White River beds of Dakota and Nebraska, with the 

 number common to them and the Colorado beds. I add also a column, 

 indicating the number not yet identified out of Colorado. 





ffl 



cS 



o 



^g 





oi. 



P . 



a 6 



^ 2 





Ms 



c3 cS 



0=^ 





a1 





2 3 







ll^ 





O 



o o 





o p o 





pin© 



2^ 



?^,- 



0)^0 





OQ 



OQ 



m 



<J1 



Insectivora , - 



11 



2 







11 





10 

 16 



5 

 6 



4 

 4 



6 



Perissodactyla 



11 



Artiodactyla 



10 



20 



4 



6 



Garni vora 



10 

 1 



8 

 (?)1 

 1 

 

 



3 







7 



Quadrumana 



1 



Testudiuata 



5 



8 

 5 



1 











4 



Lacertilia 



8 



Ophidia 



5 







Total , 



75 



43 



16 



59 







The difference between the Dakota and Colorado faunas is more appar- 

 ent than real. The presence of numerous small reptiles and insectivor- 

 ous and rodent. mammals in the latter is chiefly due to local advantages 

 for preservation and subsequent discovery. This is indicated partly by 

 the fact that the more abundant rodents of Colorado are those which 

 have been already discovered in Dakota. Other differences are not so 

 readily accounted for. Thus, the poverty in species of Oreodontidce in 

 the midst of most abundant individual remains is a peculiarity of the 

 Colorado formation, while the Tragulidw of the latter are more abun- 

 dant in both individuals and species than in the Dakota fauna. While 

 there is but one species in the latter, there are five species of four ge- 



