276 Annals of the Carnegie Museum. 



to the southeast of this locality. I judge that they are nearly as thick 

 as the Judith River deposits. 



Pierre Formation : Bearpaw Shales. 



Fish Creek Area. — Overlying the Fish Creek -beds in the Fish 

 Creek section, are the Pierre (Bearpaw) shales. These, according to 

 Hatcher and Stanton, do not differ in lithological characters from the 

 typical Pierre, but they are much thinner than in the typical locality 

 and in the region farther south, where their deposition was probably in 

 part contemporaneous with that of a portion of the beds, which under- 

 lie the Bearpaw shales in Montana. The invertebrate fauna is prac- 

 tically the same as that of the typical Pierre ; but, in addition to this, 

 the deposits contain vertebrates such as mosasaurs, Trachodon, and other 

 dinosaurs. In excavating for dinosaurs, thin films of coal and plant 

 remains, including leaves oi Sequoia, were found. The occurrence of 

 ihe reptilian remains is very different from that in the Judith River. 

 In the latter whole bones and fragments are very numerous, sometimes 

 a few bones of the skeleton being associated. In the Pierre shales 

 skeletal remains are not numerous, but when found it often appears that 

 nearly the whole animal had originally been buried. There are, how- 

 ever, some isolated bones in the Pierre. Several large portions of 

 skeletons were found by Mr. Silberling and the present writer. These 

 were secured for the Princeton Museum and the University of Montana. 

 In searching for fossils in these beds one must violate, to a certain 

 extent, the usual rules. The shales weather into low flats, low rounded 

 hills and shallow ravines. The bones may be found among the grass 

 roots on the sides or tops of the hills, or along the little ravines. 

 Most of the country can be reached with horses and wagon, and nearly 

 all of it on horseback, yet one may easily overlook a good skeleton 

 which shows nothing on the surface except a few fragments of bones. 



The general trend of the outcrop of the Pierre in this region is 

 northwest and southeast. It weathers into depressions between the 

 ridges formed by the Eagle, Claggett, and Judith River beds on the 

 one side, and the Fox Hills (?) and Laramie on the other. In some 

 places the depression is narrow, where the dip of the rock is greater, 

 but it broadens into flats and undulating prairies, where it is more 

 nearly horizontal. I have traced these beds from near the upper 

 branches of .Fish Creek to the Lake Basin, a distance of forty or fifty 

 miles. 



