232 Annals of the Carnegie Museum. 



a long period of erosion has reduced the greater portion of the surface 

 to a lower level, leaving isolated buttes both of Early Tertiary and 

 Oligocene age.' (4) Later the Little Missouri River has cut deeper 

 into the strata and is now beginning to broaden its valley. If other 

 neighboring streams were doing the same work that the Little Missouri 

 is doing, the whole region might after a vast lapse of time be reduced 

 to a plain on the same level as the bottom of its valley, three hundred 

 feet or more below the present plain and six hundred feet or more be- 

 low the ancient level. 



The buttes are now, as they have been for ages in the past, under- 

 going disintegration and reduction in size. We see them now in all 

 stages. Some are large with approximately flat tops and sides scored 

 by ravines. Some of these ravines have worked backward until the 

 capping-rock is dissecte'l. In other places this rock has been worn 

 away and has left the softer portions as isolated conical buttes, which 

 year by year by the action of the winds and rains are vanishing away. 

 Of the conical mounds we can see every stage, from high symmetrical 

 buttes, through smaller, lower elevations, to low mounds or hills, which 

 are fading away into the great plain. 



During this trip I did not collect many fossils, as the time was 

 limited, but returned to Medora by stage, and went to Dickinson by 

 rail. Here I employed a man and team to take me to the Little Bad- 

 lands (not the Little Missouri Bad-lands). From the accounts of 

 Mr. and Mrs. T. F. Roberts and others it seemed probable that these 

 were also composed of White River deposits. This proved to be the 

 case, and they were found to be more fossiliferous than the beds at 

 White Butte. In November, when returning from the trip into Idaho 

 and Montana, I made my headquartes at Mr. Roberts' ranch while 

 collecting at White Butte and vicinity ; I then went to the Little Bad- 

 lands for two weeks and made a considerable collection of fossil 

 mammals. 



Trip from White Butte to Dickinson in November. 



The " H. T. Road," over which I traveled from Mr. Roberts' 

 ranch to the Little Bad-lands, keeps outside the "breaks" of the 

 Little Missouri River and on the undulating prairie. There are no very 



' Dr. A. G. Leonard has written me that the Oligocene at White Butte rests on a 

 massive sandstone, which is undoubtedly the same as that capping Black Butte, and 

 that the sandstone at the latter butte dips sufficiently to carry it under the Oligocene 

 at White BuUe. 



