12 



osborn: OLIGOCENE, MIOCENE, PLIOCENE EQUID.E. 



4. Protoceras sandstones, Wortman, 1893, lower levels. Forest and fluviatile fauna. 



5. Brule clays (upper levels of), Darton, 1899. 



6. Martin Canon beds, northeastern Colorado, Matthew, 1901. 



7. White Buttes, North Dakota, Douglass, 1907. 



8. Blacktail Deer Creek, Montana. 



9. (Incertm scdis) Gering formation, western Nebraska, Darton, 1899. Typical horizon at Scott's Bluffs. 



Protoceras Sandstones, River Channel Beds, usually in Middle levels. 



The Protoceras sandstones are equivalent in time to the middle Leptauchenia depositions or begin with the upper 

 Leptauchenia depositions (J. W. G. 1917). 



Type of Miokippus validus Osborn, 1904.3. Type of Miokippus intermedins Osborn and Wortman, 1895. 



" " " gidleyi Osborn, 1904.4. " " " crassicuspis Osborn, 1904.5. 



Leptauchenia-Miohippus Zone (= Upper Level of Brule Clays). 

 Type of Miokippus meteulopkus Osborn, 1904.1. Type of Miokippus brachystylus Osborn, 1904.2. 



DlCERATHERIUM-MlOHIPPUS ZONE, SECOND PHASE OF UPPER OLIGOCENE. AQUITANIAN OF EUROPE. 



1. John Day formation (Middle), Oregon, Marsh, 1875, Cope, Wortman, Merriam, Sinclair. 



2. Diceratherium beds, 500 to 1,000 ft., Wortman, Merriam 1901. 

 3. (Incertee sedis) Monroe Creek formation, western Nebraska, Hatcher, 1902. 



John Day, Middle. 



The geologic level of Cope's types of Miokippus equiceps, M. brachylophus, M. longicristis , also of Marsh's types is 

 inferred from the surrounding green matrix characteristic of Middle John Day; also from the records of "The Cove," a 

 locality exposing principally Middle John Day. 



Type of Miokippus anceps Marsh, 1874.2. Type of Miokippus longicristis Cope, 1878.3. 



" " " equiceps Cope, 1878.1. " "} " primus Osborn, 1918.1. 



" " " brachylopkus Cope, 187S.2. " " " qtiartus Osborn, 1918.2. 



Promerycochcerus-Miohippus Zone, late phase of Upper Oligocene (Aqtjitanian of Europe) or Lower Miocene. 



1. Upper John Day beds, Ore., Cope, Wortman, Merriam, Sinclair. 



2. Promerycochcerus beds of authors. Promerycockoerus, a widely distributed oreodont. 



3. Arikaree formation (in part), western Nebraska, Darton, 1899 (= Gering, Monroe Creek, Harrison, etc.). 



4. (Incertce sedis) Munroe Creek, western Nebraska, Hatcher, 1902 (= Lower Arikaree, Darton, probably = Lower 

 Rosebud, Peterson, Thomson). 



5. Fort Logan beds, Mont., Douglass, 1903. 



6. Lower Rosebud, Matthew, Gidley, 1904, Matthew, 1907. 



Upper John Day. 



Chiefly gray matrix, locality Bridge Creek, John Day Basin, Ore. 



Type of Miokippus condoni Leidy, 1871. Type of Kalobatippus prcestans Cope, 1879. 



" " annectens Marsh, 1874.1. " " Miokippus acutidens Sinclair, 1905. 



