210 DOUGLASS — CKETACEOUS AND LOWER TERTIARY. LApril 3, 



ramii small Baculiies and other Mollusca, all of Benton types. 

 These shales weather into ravines between the sandstones of the 

 Dakota below and the Niobrara above. 



Niobrara. 



In the Niobrara gray sandstones predominate, though there are 

 beds of shale. This differs from the usual character of this forma- 

 tion in most other regions where it has been observed. It has 

 usually been described as being composed principally of limestone 

 and marl, though sometimes containing considerable sand. The 

 sandstones here are very much like some of those of the Laramie, 

 and near the middle portion are seams of coal. In two or three 

 places I looked in vain for any well-preserved plant remains in the 

 carbonaceous shales and in the sandstones above and below the 

 coal, and followed ravines cutting through the prominent sandstone 

 ridges without finding any good fossils. However, about twenty 

 miles to the southeastward a few plant impressions were found — the 

 best of which was apparently a Sequoia — in beds which I take to be 

 Niobrara. Undoubtedly, by careful, continued search, a fair col- 

 lection could be obtained. 



In one place, where Mud Creek cuts through the formation, the 

 beds approach near to a vertical position. I should not estimate 

 the thickness to be less than 700 or 800 feet here. It may be 

 more. The sandstones form a prominent ridge where they are 

 much inclined. These ridges are sometimes wooded, though the 

 trees are usually not very large or numerous. 



Fisii Creek Beds. 



Above the Niobrara are beds which I believe to belong to the 

 Belly River formation, but until they are certainly correlated with 

 the latter I give them the above name. 



They are best exposed between Fish Creek and Mud Creek, only 

 a few miles from where the latter empties into the Musselshell 

 River. Here they are nearly horizontal, while the underlying 

 Niobrara dips at a considerable angle to the southward. Farther to 

 the east and west I did not notice any unconformity between the 

 two formations. In the above-mentioned locality, where they are 

 horizontal, they weather into *'bad land " forms. The material is 

 principally rather soft sandy clay, with hard, almost black concre- 



