THE MIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 289 



belong to the peculiarly American family of Miocene and Pliocene mery- 

 codonts, allied in skeletal but not in horn structure to the modern prong- 

 horned antelopes or antilocaprids. 



The appearance of these modernized selenodont artiodactyls or Pecora 

 must have effected a change in the external aspect of the fauna only less 

 marked than that caused by mastodons and bulky rhinoceroses. Other 

 new elements of Eurasiatic origin appear. Among the artiodactyls appears 

 a bovine or antelopine form somewhat similar to the characteristic Protra- 

 gocerus of the Middle Miocene of Europe, an animal (Dromomeryx) whose 

 zoologic position is still uncertain; it presents certain resemblances to the 

 Antilocapridae. There are also carnivores resembling the amphicyons, and 

 among the Mustelidse the otters appear (Potamotherium) , animals which 

 are first recorded in the Upper Oligocene or Aquitanian of Europe. A 

 felid similar to the characteristic Lower Miocene Pseudcelurus also occurs. 



Probably of native or North American origin, because related to the 

 haplodontids or sewellels, is a very peculiar family of mylagaulid rodents 

 with short, deep skulls, but which depart from all other rodents in develop- 

 ing horns. 



Most surprising is the evidence of the existence of true edentates of 

 Megalonyx type in the Mascall beds of Oregon.^ The extinction of several 

 mammals characteristic of the Lower Miocene or Pr ornery cochoerus Zone, 

 and the occurrence of more advanced stages in the evolution of the horses 

 and camels, especially mark this stage as intermediate or halfway between 

 Lower and Upper Miocene. 



Formations. — The Deep River, or Ticholeptus Zone of Oregon was dis- 

 covered by Grinnell and Dana in 1875, and divided into two levels by Cope 

 in 1879, namely, the Ticholeptus and Procamelus beds (Upper Miocene) 

 which he rightly recognized as quite distinct in age. In 1893 Scott first fully 

 characterized the mammals of these beds, and concluded that the nearest 

 European equivalent is the fauna of Sansan and Simorre," which we now 

 determine as Middle Miocene. 



The Pawnee Creek horizon of Colorado was first explored by Cope in 

 1873. The American Museum parties entered these beds in 1898, and re- 

 turned in 1 901 , under Matthew, who first distinguished the horizon from 

 the 'Loup Fork,' or Upper Miocene, to which all previous writers had 

 referred it.^ In 1903 Douglass * made known the mammals of the Flint 

 Creek Formation in Montana, which proved to be of similar age, or transi- 



' Sinclair, W. J., Some Edentate-like Remains from the Mascall Beds of Oregon. Univ. 

 Cat., Bull. Dept. Geot., Vol. V, no. 2, 1906, pp. 65-66. 



^ Scott, W. B., The Mammalia of the Deep River Beds. Trans. Amer. Philos. Soc, n.s., 

 Vol. XVIII, 1895, no. 2, p. 182. 



' Matthew, W. D., Fossil Mammals of the Tertiary of Northeastern Colorado. Amer. 

 Mus. Nat. Hist., Mem. I, Pt. 7, Nov., 1901, pp. 358-.374. 



* Douglass, E., The Neocene Lake Beds of Western Montana, and Descriptions of Some 

 Vertebrates from the Loup Fork. Univ. Montana, thesis, June, 1899. 

 U 



