GEOLOGIC HORTZONS AND LIFE ZONES. 



19 



Pawnee Creek, Northwestern Colorado. 



This important and thoroughly explored region has yielded through the successive explorations of Cope, Matthew, 

 and Thomson, the following important types of described species, which are regarded as typical Middle Miocene. 



Type of Parahippus pawniensis Gidley, 1907.1. Type of Merychippus sejunctus Cope, 1874.3. 



" " " coloradensis Gidley, 1907.2. " " « sphenodus Cope, 1889.2. 

 " " Merychippus paniensis Cope, 1S74.1. " " " campestris Gidley, 1907. 



" " " labrosus Cope, 1874.2. " " Hypohippus osborni Gidley, 1907. 



SCALE OF MILES 



SUFPOSED UPPER PAWNEE CREEK HORIZON AT SAND CANYON 

 AND EAST OF GROVER, POSTULATED ON FAUNAL EVIDENCE 



Fig. 10a. Oligocene (Cedar Creek), Middle Miocene (Pawnee Creek), and Lower Pliocene (Upper Pawnee Creek) 

 exposures of northwestern Colorado. Areas explored by the American Museum of Natural History in 1898, 1901, 1902, 

 by Messrs. Matthew, Brown, and Thomson. 



The American Museum party of 1898 worked westward under Matthew to the head of Cedar (or Clear) Creek, 

 (Brown) the character of the beds changing and the division lines breaking down. In 1901 the section near Pawnee Buttes 

 was worked, showing the Pawnee Creek series above (Ticholeptus-Merychippus zone), directly overlying the Upper Oreo- 

 don zone. The Pawnee series appears to include two levels, as follows : 



Typical " Pawnee Creek," 



True Merychippus Zone, upper Middle 

 Miocene. 



Merychippus sejunctus ref. 



" paniensis " 



" sphenodus " 



" campestris " 



" eoplacidus type 



" proparvulus " 



" eohipparion " 



" Upper Pawnee Creek," Sand Canon, also localities west 

 of Grover, Col. Protohippus-Hipparion zone, Lower 

 Pliocene. 



Protohippus proplacidus, type 

 Pliohippus ref. 

 Hipparion ref. 



