MAMMALIAN FOSSILS FROM DEVIL'S GULCH 183 



Dutch Creek, large banks of Pierre shale are exposed. The very 

 topmost layer, some 50 feet in thickness, is a bright ochre-yellow 

 color, instead of the customary dull, slate color. There are 

 certain thin, flinty, nodular bands, traces of which are found as 

 far as Sioux County. This bed has been traced to the west and to 

 the north, well into South Dakota, especially around the Rosebud 

 Agency. To the southwest, in Furnas County, near Beaver City, 

 the ochreous, flinty, nodular layers are very pronounced. The 

 character of this 5o-foot bed seems constant, and we made free in 

 our field notes to call it the Ainsworth formation. Above the 

 Pierre occurs the well known Oligocene bad lands, which in cer- 

 tain exposures shows a thickness of about 100 feet. Immediately 

 overlying this come 225 feet of sandy beds belonging to the " Loup 

 Fork." In our field notes, we have called this the Devil's Gulch 

 stage. 



As to the geological horizon, the faunal evidence suggests 

 Pliocene equivalent to the Snake Creek beds of southern Sioux 

 County. Possibly some Pleistocene may be represented. Further 

 study will be necessary to determine accurately the geologic posi- 

 tion of this newly explored fossil field. Faunal comparisons show 

 this bed to be much earlier than that of Hay Springs, and later 

 than that of the famous Agate Springs Quarries. It will not be 

 far wrong to call the Devil's Gulch deposits, Pliocene. The upper 

 part may merge into Pleistocene. Unlike the beds at Agate 

 Springs, which are sufficiently lithified to make the chisel and pick 

 necessary, the beds at Devil's Gulch are so loose and sandy, that 

 work is greatly facilitated. Only occasionally are mineralized or 

 concretionary patches encountered. 



The bones, \vhen freshly exhumed, are of a light brown color, 

 changing to whitish on continued exposure to sunlight. The bones 

 near the base of the canyon seem to be harder and more enduring 

 than those near the top which are soft and perishable to the last 

 degree, demanding skillful treatment. 



TWO NEW MASTODONS FROM DEVIL'S GULCH 



The discovery of two new mastodon skulls, with mandibles, and 

 certain skeletal parts, is of special interest, and constitutes the 



