56 THE MAMMALIA OF THE DEEP KIVEK BEDS. 



this region of a Miocene lake basin, which was succeeded by another lake basin in 

 Pliocene time. 



" Camp Baker [the spot marked Logan on the map herewith given] is situated 

 on Deep creek, a stream which flows into the Missouri river above Sun river. It lies 

 about fifty miles due east of Helena. It is surrounded on all sides by mountains, of 

 which the Big Belt range, lying immediately to the south or southwest, is the highest 

 and most conspicuous 



" The Tertiary beds found here consist, for the most part, of homogeneous cream- 

 colored clays, so hard as to be with difficulty cut with a knife. The beds are hori- 

 zontal and rest unconformably upon the upturned red and yellow slates below. The 

 clays of which they are formed resemble closely those found in the Miocene [i. e., 

 White River] beds at Scott's Bluffs, near the North Platte river, in Wyoming. The 

 deposits at Camp Baker have been extensively denuded and nowhere reach any great 

 thickness. At a point about three m\les southeast of the Post, some bluffs were 

 noticed where the Miocene beds attained a thickness of about two hundred feet, and 

 these were capped by fifty feet of the Pliocene clays, both beds containing character- 

 istic fossils. In the underlying Miocene beds were found a species of Rhinoceros, 

 several species of Oreodon Leidy and Eporeodon Marsh, a canine tooth apparently of 

 Elotherium Pomel and remains of Turtles. In the Pliocene beds the principal fossils 

 were a species apparently of Merycliyus Leidy, remains of an equine smaller than 

 the modern horse, and Pliocene Turtles. These fossils have not yet been carefully 

 studied, and for this reason their relations to the remains found in the other lake 

 basins of similar age cannot be stated. 



" We saw the first exposures of these beds a few miles west of the Sulphur 



Springs This point is about six miles southeast of Camp Baker. From here, 



the bed was traced continuously along Deep creek for a distance of fifteen miles, 

 extending quite up to the mountains, on the eastern side at least. Beds of the same 

 character, containing similar fossils, were found on White-Tailed Deer creek, a 

 branch of Deep creek, about seven miles to the north of Camp Baker, as well as on 

 Camas creek, to the southwest of the Post. Traces of this deposit, containing what 

 appear to be remains of Rhinoceros, were also found two miles or more south of Moss 

 Agate Springs and at a considerable elevation above the creek bed. With more time 

 than we had at command, they could no doubt have been traced much farther, 

 although in many places the beds have been washed out or have been covered by the 

 later local drift. 



" These Tertiary beds were all laid down after the elevation of the mountains 

 and the igneous eruptions. They are, as has been said, perfectly horizontal, and are 



