4 



CONTENTS. 



Chapter III. Western American Cenozoic horizons — Continued. Page. 

 Eocene — Continued . 



III. Third faunal phase — Continued. 



Mddle Eocene (etages Lutetien superieur, Bartonien) 50 



5. Bridger formation; OroMjopiis and Uintatherium zones 50 



Middle to upper Eocene (etage Bartonien) 53 



Later Eocene deposits of Washakie basin; Uintatherium and 



Eobasileus zones 53 



Upper Eocene (etages Bartonien in part, Ludien (Ligurien) in 



part) 54 



7. Later Eocene deposits of Uinta basin; Uintatherium, 

 Eobasileus, and Diplacodon zones 54 



Oligocene 57 



IV. Fourth faunal phase. 57 



Lower Oligocene, White River group of Hayden (etage Sannoisien 



[Tongrien inferieur]) 60 



8. Chadron formation; Titanotheriuvi zone 60 



Middle Oligocene (etage Stampien [Tongrien superieur]) 62 



9. Lower part of Brule clay; Oreodon zone and " Metamynodon 

 sandstones" 62 



Upper Oligocene, first phase 63 



10. Upper part of Brule clay; Leptauchenia zone and " Pro- 



iocer as sandstones" 63 



Oregon Cenozoic formations 64 



Resume of the Oregon deposits as a whole 64 



John Day formation 64 



Upper Oligocene, second phase 67 



11. Middle part of John Day formation; Diceratherium zone 

 (also upper part of John Day, transitional) 67 



Upper Oligocene, latest phase 68 



12 . Upper part of John Day formation ; Promerycochoerus zone . . 68 

 Miocene 70 



IV. Fourth faunal phase — Continued 70 



Lower Miocene (etages Aquitanien, Burdigalien) 70 



13. Arikaree formation; Promerycochoerus zone 70 



General features 70 



Westerly section 73 



A . Lower division 73 



(a) Gering formation 73 



(6) Monroe Creek formation 73 



(c) Harrison formation, Hatcher 73 



(d) Harrison formation. Agate Spring quarry 74 



B. Upper division 74 



(e) Upper part of Harrison formation 74 



Easterly section 74 



A. Lower part of Rosebud 75 



B. Upper part of Rosebud 75 



V. Fifth faunal phase 76 



Middle Miocene (etages Helvetien, Sarmatien, Tortonien) 76 



Faunal changes 76 



14. Deep River sequence; TichoJe plus zone 76 



Upper Miocene (etage Pontien) 79 



15. Ogalalla formation (in part); Procamelus zone 79 



