ENVIEONMENT OF THE TITANOTHEEES 



101 



climate than that which prevailed in Eocene time. 

 These upper sediments contain a true Oreodon zone 

 fauna. 



FOURTH FAUNAI PHASE (LOWER OLIGOCENE) 



LOWER OLIGOCENE MAMMALS 



COERELATION OF EUROPEAN AND AMEEICAN FORMS 



The lower Oligocene mammals represented by the 

 fossils thus far discovered are listed below. 

 Peculiar to Europe: 



Paleotheres. 



Anoplotheres. 



Oenotheras. 



Gelooids. 



Amphicyonids. 



Viverrids. 



Cricetines (hamsters). 



Theridomyids. 



Sirenians (Hahtherium). 



(Horses not recorded.) 

 Common to Europe and North America: 



Titanotheres (central Europe). 



Chalicotheres. 



Rhinoceroses (aceratheres and diceratheres) . 



Amynodonts. 



Anthracotheres. 



Suillines. 



Entelodonts. 



Opossums. 



Hyaenodonts. 



Canids (dogs). 



Mustelids (martens). 



Machaerodonts (saber-tooth cats). 

 Peculiar to North America: 



Horses. 



Hyracodonts (rhinoceroses) . 



Oreodonts. 



Camelids. 



Hypertragulids. 



Leptiotids. 



Chrysochlorids? (inseotivores) . 



Ischyromyids (rodents). 



Leporids (hares). 



ZONE 17: TITANOTHERIUM-MESOHIPPUS ZONE 

 [Chadron A, B, and C; Sannoisian of Europe] 



The forms that constituted this rich world of lower 

 Oligocene mammalian life were distributed through 

 the Rocky Mountain basin region, but the sediments 

 that contained the fossils have been eroded away 

 except in a few isolated areas, such as those along 

 Pipestone Creek, Mont.; at Beaver Divide, Wyo., 

 south of the Wind River Basin; and at Bates Hole, 

 Wyo. The areas in which these sediments were 

 deposited lie east of the Rocky Mountains, in Sas- 

 katchewan, North Dakota, South Dakota, and Colo- 

 rado. The chief fossil-bearing sediments exposed are 

 in the localities shown below. 



Recorded thickness of the Titanotherium zone in thirteen exposures 

 of lower Oligocene deposits 



Feet 



1. Cypress Hills, Saskatchewan (Lambe, 1908) 50-500 



2. Pipestone Creek, Jefferson County, Mont. 



(Douglass, 1903) 300 + 



3. White Butte, N. Dak. (Douglass, 1903) 120 



4. Big Badlands, S. Dak. (Hatcher, Darton) (typical 



area of Titanotherium zone) 180 



5. Goshen Hole (Scotts Bluff), southeastern Wyoming 



(Darton), maximum thickness 200 



6. Hat Creek, South Fork, Cheyenne River, Dawes 



County, Nebr 100 ± 



