100 



TITANOTHEHBS OF ANCIENT WYOMING, DAKOTA, AND NEBEASKA 



under Granger and N. H. Brown, who discovered this 

 fauna in 1908, is as follows: 



Oreodon zone = Brule for 



Summit of lower Oligocene 



mation 



Base of lower Oligocene, Titanotherium zone=Chadron 

 formation 



Upper Eocene, Diplacodon zone = Uinta(?) formation — 



Middle Eocene (?), unfossiliferous = Bridger (?) forma- 

 tion 



Lower Eocene, Lamhdotherium zone = upper part of 

 Wind River formation 



Feet 

 540 



O/'eodoTL zone 



A single tooth of either Diplacodon or Protitano- 

 therium has been found at Beaver Divide, Wyo. 

 The correlation with Uinta C rests upon Camelodon 

 arapahovius Granger, a species somewhat more pro- 

 gressive than Protylopus of Uinta C and somewhat 

 more simple than Leptotragulus , characteristics that 

 combine to place it among ancestral camels, in the 

 Camelidae. In certain characters it agrees with Lep- 

 totragulus profedus of the Titanotlierium zone of Pipe- 

 stone Springs, Mont. The Amy- 

 nodon found here agrees with the 

 species A. antiquus, originally 

 determined in Washakie B 

 ( = Uinta B). Two specimens 

 of Protoreodon are referable to 

 P. parvus, from the base of Uin- 

 ta C or the summit of Uinta B. 

 Above this Diplacodon (?) 

 level is a very marked erosional 

 unconformity between the up- 

 per Eocene and the lower Oli- 

 gocene; broad, shallow valleys 

 (Sinclair and Granger, 1911.1, 

 p. 99), indicating fairly mature 

 topography, were excavated in 

 the sediments of the Diplaco- 

 don(1) zone. After these val- 

 leys were cut the first deposits 

 laid down were fine-grained 

 buff-colored tuffaceous shales. 

 In this tuff the American Mu- 

 seum exploring party of 1909 

 found a skull of Menodus heJoce- 

 ras, which belongs to the lower 

 level of the Titanotherium zone, 

 corresponding with Chadron A. 

 The volcanic ash comprising 

 the sediments of the Oreodon 

 titanothere zone, a few feet 

 thick, is covered with a mud 

 flow of volcanic material 46 feet 

 thick, above which lies 540 feet 

 of fine, wind-blown buff ash and 

 dust. No clays have been found 

 at this middle Oligocene horizon , 

 which corresponds in age with 

 the Brule formation of the 

 White River group — only wind- 

 laid ash and coarse gravel, 

 perhaps deposited by torrents 

 during occasional heavy rains. 

 None of these sediments ap- 

 pear to have been much dis- 

 turbed by water, and Sinclair 

 Diagrammatic section of deposits at Green Cove, Beaver Divide, Wyo. ^^^ Grander (1911.1 p. 114) 



Oreodon 

 Cyllndrodon 

 Caenopus 

 Ischyromys 

 Poebro therlum 



Menodus he/oceras 



? DiplcLcodoTz zone 



Amynodon ? anfiquus 

 Protoreodon 

 Camelodon 

 Pro titan o ttierium 



Lamhdotherium zone 



Lambdotherium 

 Coryphodon, PlienacoduSj 

 hieptodon , Eohippus 



Figure 67 ^^^ ^^„„ „ ^„ , 



(No. 6, fig. 35), from the Lambdotherntm zone (Wind River) to the Oreodon zone """ .""'"""" t"*h lie e that 



they accumulated under a drier 



(White River) at the summit 



Chiefly after Granger (1910.1). 



