30 The Badland Formations of the Black Hills Region 



lier of the Arikaree. No hones were found to throw light on 

 this question."* 



Little attempt has heen made north of the Hills to separate 

 the Oligocene from the rocks of later Tertiary age, if such be 

 present. The lithologic conditions seem too changeable and in- 

 definite to be of positive service alone and there has been almost 

 no opportunity for paleontologic investigation. Prof. Todd 

 mentions the finding of Titanothere remains near Short Pine 

 Hills, hence Oligocene strata must be present. Certain structur- 

 al disturbances in some of the lower beds together with the 

 character of the over-lying beds in certain places, particularly 

 in Slim Buttes, seem to give some fair ground for division into 

 Oligocene and Miocene, and Prof. Todd has indicated this in 

 his paper. Corroborative proof of the accuracy of this division 

 must, it seems, await the rinding of fossils characteristic of the 

 various formations. 



Three small areas in the southwestern part of North Da- 

 kota are known to contain Oligocene strata, and one of these, 

 White Butte, only thirty-five miles from Cave Hills, has af- 

 forded important fossils sufficient for detailed correlation. 

 White Butte is beyond the boundaries of the accompanying map, 

 but in view of its important bearing on the deposits in north- 

 western South Dakota, its seems proper to briefly describe it. 

 The butte seems to have been first studied by Prof. Cope, who 

 collected some fossils there in 1883. Mr. Earl Douglas, of the 

 Carnegie Museum, spent some time in the locality in 1905, at 

 which time he made a detailed section and collected many fossils. 

 Among these were the remains of many rhinoceroses, including 

 a number of complete skulls and several three-toed horses. Re- 

 mains of crocodiles were also found. The rhinoceroses belong 

 to the species Aceratherium tridactylum Osborn, and the horses 

 to the two species Mesohippus bairdi (Leidy) and Mesohippus 

 br achy stylus Osborn. 



Prof. A. G. Leonard, State Geologist of North Dakota, 

 visited the locality in 1907 for further study, t The following 

 is a section measured by Prof. Leonard : 



* Bar ton, N. H. Geology and Water Resources of the Northern 

 Portion of the Black Hills and Adjoining Regions in South Bakota 

 and Wyoming. U. iS. Geol. iSurv., Prof. Papers No. 65, 1909, p. 59. 



TLeonara, A. G. North Bakota Geol. Surv. Fifth Biennial Kept. 

 1908, p. 67. 



