CORRELATION AND PALEOGEOGRAPIIY 



249 



kota, Colorado, Montana, New Mexico, and Texas (Gidley, 1903) /» 

 Geologic studies and sections are also greatly needed in this period. 



Porcupine Butte 

 Volcanic ash layer 



MerycocTicerus 



ZOTW 



Blastomeryx . 



Parahlppus 



Cynodesmus 



Phlaocyon 



Oligobunis' 



Megalictis 



Oxydactylus 



Desmathyus 



Protomeryx 



Merycochoerus 



Merychyus (abundant) 



Aelurocyon 



Arctoryctis 



£ntoptychus 



Lepus 



Ca[cm*eo us_s ha|y 

 imestone layers 



Projnery- 

 cochoems 



Promerycochoerus 

 ([/ery abundant 

 and characteristic) 



Dicera therium 

 EJotherium 

 Steneo fiber 

 /iy pert rag u/us 

 Parafiippus (small sp) 

 Leptauchenia 

 (near base) 



Nimrai^us 

 Moropus 

 Dinohyus 

 fVlesoreodon 



BRULE '=^^^^:^^^^^r^:^-:r^^-:^Leptxnic7xeTi7a zone 



Figure 11. — Oliyocene and Lower Miocene of South Dakota 



(After Matthew and Thompson) 



Upper : Merycochariis Zone 

 • Middle : Promerycocharus Zone 



Lower : Leptauchenia Zone 



Pliocene 



The beginning, the succession, and the close of the Pliocene still await 

 correlation and definition. It will be observed that as we progress from 



18 J. W. Gidley : The Fresh-water Tertiary of Northwestern Texas. Bulletin of the 

 American Museum of Natural History, vol. xix, art. xxvl, November 21, lOO:?, pp. 017- 

 635. 



