THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 341 



to the close of the Pliocene in the following table; they may prove subse- 

 quently to belong rather to the early part of the Pleistocene. 



Middle PHocene 



Fig. 159. — ■ Chief Pliocene and Upper Miocene fossil mammal deposits of western North 

 America. 1. Rattlesnake, Oreg. 2. Blanco, Tex. 3. Ogallala, Kan., Nebr. 4. Snake Creek, 

 Nebr. 5. Virgin Valley, Nev. 6. Loup River, Nebr. (See text for horizons.) 



With these doubts in mind as stimulating to further research, the follow- 

 ing ascending arrangement of the best known formations is set forth 

 provisionally : 



(Peace Creek Formation of Elephasf columhi and Equus 



Upper Pliocene, or J southern Florida, Zone 



Lower Pleistocene j [^Qnp Jiiyer, of eastern Ne- Elephas imperator and Equus 



I braska Zone 



Blanco Formation, Staked Ghjptofheri urn Zone, Rhinoceros 



Plains, or Llano Estacado, extinct or undiscovered 

 of Texas 



Virgin Valley and Thousand Ilingoceros Zone, Rhinoceros 



Creek of Nevada surviving 



S7iake Creek beds, western Neotragocerus Zone, Rhinoceros 



Nebraska surviving 



Rattlesnake Formation, John Aliicamelus Zone, Rhinoceros 



Day Valley, Oregon survi\'ing 



Alachua Clays, northern Flor- Peraccras Zone, Rhinoceros very 



ida. abundant 



■Republican River Formation, Peraceras Zone 

 northern Kansas and Ne- 

 braska. 



Lower Pliocene 



Lower Pliocene, or 

 Upper Miocene 



