T. W. Stanton — Fox Hills Sandstone. 175 



All except the basal member of the section belong to the 

 Fox Hills. 



The hard sandstones of Nos. 1 and 3 are merely local indura- 

 tions which in some places are seen to pass hoi-izontally into 

 soft friable sandstone. Other exposures in the neighborhood 

 especially on the north side of Grand River show that the 

 upper sandstone, No. 1, is very near the top of the Fox Hills. 

 About a mile northwest of the mouth of Dirt Lodge Creek 

 and not more than two or three miles from the section just 

 described the upper sandstone is represented by a few feet of 

 sandy shale which pass upward into similar sandy shale about 

 4 feet thick, which is tilled with brackish-water fossils includ- 

 ing Ostrea glabra M. & H., 0. subtrigonalis E. & S., Anomia 

 micronema Meek, and Corbicula subdliptica var. nioreauensis 

 M. & H. Immediately above this brackish-water bed without 

 any apparent stratigraphic break are shales, soft sandstones and 

 carbonaceous beds, weathering into badlands, and locally con- 

 taining abundant remains of Triceratops, Traehodon, turtles 

 and other members of the Lance formation fauna. 



About 3 miles east of the mouth of Dirt Lodge Creek in 

 section 12, T. 20 JST., R. 22 E., the oyster bed at the top of 

 the Fox Hills is again exposed with the basal portion of the 

 Lance formation above it. Vertebrate fossils of the types just 

 mentioned are here abundant about 30 or 40 feet above the 

 oyster bed. 



A few miles farther east on Grand River near the mouth 

 of Fire-steel Creek the contact of the oyster bed with the 

 underlying sandstone shows an irregular surface suggesting an 

 unconformit}', but facts to be recorded on subsequent pages 

 will show that the oyster bed actually belongs to the Fox 

 Hills sandstone as proved by its fauna. 



Another instructive section in T. 15 N., R. 18 E., on Thun- 

 der Butte Creek about 30 miles south of Grand River, is as 

 follows : 



Section on Thunder Butte Creek. 



Feet 



1. Friable gray and yellow sandstone with many large 



indurated masses locally containing an oyster bed with 

 an abundant brackish- water fauna mingled with many 

 specimens of marine Fox Hills species (see list on p. 180). 

 borne evidence of channeling and erosion at base of 

 oyster bed 20 



2. Banded shale and shaly sandstone _ 50 



3. Dark, somewhat sandy, shale referred to the Pierre with 



Avicula linguiforniis E. & S., Mactra warrenana 

 M. & H., etc. Exposed 30 



