IV CONTENTS 



Chaptek II — Continued. 



Section 2 — Continued. Page 



Second f aunal phase (lower Eocene) 64 



Transitional basal Eocene faunas 64 



Zone 5: Phenacodus-Nothodectes-Coryphodon zone (base of Wasatch formation of Big Horn Basin, first 



Wasatch Ufe zone, Big Horn A; Cernaysian of Europe) 64 



Early Eocene time 65 



Lower Eocene faunal zones 68 



Zone 6: Eohippus-Coryphodon zone (second Wasatch life zone, Big Horn B; lower Sparnacian of 



Europe) 68 



Zone 7: Systemodon-Coryphodon-Eohippus zone (third Wasatch life zone, Big Horn C; upper 



Sparnacian of Europe) 69 



Zone 8: Heptodon-Coryphodon-Eohippics zone (fourth Wasatch life zpne, Big Horn D and Wind 



River A; lower Ypresian of Europe) 69 



Zone 9: Lambdotherium-Eotitanops-Coryphodon zc*ne (fifth Wasatch life zone. Big Horn E, Wind 



River B, and Huerfano A; upper Ypresian of Europe) 69 



Transitional lower to middle Eocene deposits 74 



Huerfano formation of Colorado 74 



Wind River beds and their fauna 74 



Third faunal phase (middle and upper Eocene) 77 



Correlation of American zones with European stages 77 



Typical Bridger formation 78 



Zone 10: Eometarhinus-Trogosus-Palaeosyops fontinalis zone (Bridger A and Huerfano B; lower 



Lutetian of Europe) ^ 82 



Zone 11: Palaeosyops paludosus-Orohippus zone (Bridger B; upper Lutetian of Europe) 84 



Zone 12: Uintatherium-Manteoceras-Mesatirhinus zone (Bridger C and D, Washakie A, and Uinta 



A; part of Bartonian of Europe) 84 



Washakie Basin, Wyo 85 



Stratigraphy of the basin 85 



Zones 13 and 14: Metarlmius zone and Eobasileus-Dolichorhinus zone (Uinta B 1 and Washakie B 1; 



Uinta B 2) 89 



Uinta Basin, Utah 91 



Physiographic, climatic, and volcanic conditions in the Uinta Basin during middle (?) and later Eocene 



time 91 



Geologic horizons in the Uinta Basin 91 



Uinta B 1 (Metar/iinus zone = zone 13) 94 



Uinta B 2 {Eobasileus-Dolichorhinus zone = zone 14) 94 



Zone 15: Diplacodon-Protiianotherium-Epihippus zone (Uinta C 1; Ludian of Europe) 94 



Summary of faunas of Uinta B and C 97 



Adaptive radiation of the titanotheres in the Uinta Basin 97 



Genera and species represented 97 



Adaptive radiation of phyla 98 



Fauna unrepresented 99 



Zone 16: Theoretic Uinta C 2 99 



Composite Eocene and lower Oligocene section at Beaver Divide 99 



Fourth faunal phase (lower Oligocene) 101 



Lower Oligocene mammals 101 



Correlation of European and American forms 101 



Zone 17: Titanotheriuni-Mesohippus zone (Chadron A, B, and C; Sannoisian of Europe) 101 



Oligocene flood-plain sedimentation in the western Great Plains region 103 



Conditions of deposition 103 



South Dakota in Titanotherium time : 106 



Rapid fluviatile sedimentation in the Cypress Hills, Saskatchewan 109 



Slow sedimentation in South Dakota 109 



Geographic distribution of the Chadron formation 110 



Comparison of basins in western United States with the flood plain of the Nile 112 



Faunal divisions in the Chadron formation 113 



Three f aunistic levels determined 113 



Stratigraphic distribution of species of Oligocene titanotheres 113 



Hatcher's coUections, 1886-1888 115 



Sources of error in determining stratigraphic levels 116 



Mammalian life of the lower Oligocene Titanotherium zone 117 



Notes on the habitat of the fauna of the clay and sandstone as a whole 120 



Section 3. Adaptive radiation, primary and secondary, through change of environment a cause of diversification of the 



titanotheres 121 



Habitat of the ungulates 121 



Polyphyly among hoofed mammals ' ; 121 



The titanotheres and other extinct forms 121 



The existing African antelopes 124 



