U. S. GEOLOGICAL SURVEY 



MONOGRAPH 55 PLATE IV 



jM-'Of ** * J ^ 



A. EOHIPPUS-CORYPHODON ZONE (LOWER PART OF WASATCH FORMATION, LEVEL BIG HORN B), LITTLE SAND 



COULEE 

 Fir^ appearance of Eohipptis. Am. Mus. negative 18565 



B. PHENACODUS-NOTHODECTES-CORYPHODON ZONE (BASAL PART OF WASATCH FORMATION, LEVEL BIG HORN A), 



ABOUT 4 MILES NORTH OF RALSTON 

 Am. Mus. negative 18563 



LOWER WASATCH STRATA RESTING ON BASAL WASATCH STRATA, CLARK FORK BASIN, 



PARK COUNTY, WYO. 



