246 



TEN YEARS PROGRESS IX VERTEBRATE PALEONTOLOGY 



Upper Niobrara River of the great plains of western Nebraska (see 

 figure 10), with a substantiall}' similar group of mammals, containing 

 no new migrants, but all slightly more advanced specific or mutative 

 stages, we feel assured that we are again in the same pure endemic or 

 American faunal period. 



o 

 o 



J 



lij 



z 



ki 

 O 

 O 

 O 



_J 



o 

 q: 



UJ 

 Q. 



a 



250- 

 300' 



River lava 

 flow, 2000 feet) 



Forest on top of ashes 

 . Camelidae 



J^roTnerycochcerus zone 

 (loiA/est level) 



)'(^Y.''^,^X'\'^y/':'^^)<'V.-A''>'<~\^ hy dJItTcT lo vv_ 



Anchither/um 



Moropus 



Enteloclon 



Paratylopus 



Eporeodon 



Hyp ertragu I us 



MIohippus 

 Protapirus 



Moropus 



^^^^£I^:ZE^5^ Dicevatheri.znn Eporeodon 



zone Agriochderus 



(fossils, numerous) Nothocyon 

 Temnocyon 

 Lepus 

 Steneofiber 



^^-- , , Remains of Meniscomys 



^:-C'=^^"'5=^-^=="A. forest /n the 

 tuff deposits 



)^:^i.'Vi;':>^X\vf;^^rr;^)kRKyoiitic^vf iovv 



-=~=Z,eptaiichenia 



CHICO 



CRETACEO 



/////// 



Dlcerather/'/nae, 



Elother/'um, 

 ^ Oreodon 

 ossils, scarce) 



Figure 9. — Oligocene and Loicer Miocene of John Day Basin, Oregon 



(Modified after Merriam) 



Upper: Promerycochocrus Zone 

 Middle : DiceratJieriuni Zone 

 Lower : Leptauchenia Zone 



Quite arbitrarily, because we have no exact means of close comparison 

 with the Lower Miocene of France, which must be taken as our standard, 

 this Promerycochcerus fauna, together with the giant Dinohyus and 



