WANLESS— LITHOLOGY OF WHITE RIVER SEDIMENTS. 189 



Section C, which also gives the position of a limestone lens in Little 

 Corral Draw and an algal ball level in Quinn Draw. 



The clays above the upper nodular level are generally alternate 

 bands of pale pink and pale green beds with very few channels and 

 nodular layers and no limestone lenses observed. The average thick- 

 ness of this clay series in the Big Badlands is i6o to 170 feet, with 

 a variation of not more than 10 feet in three sections measured 

 20 miles apart. This clay zone is less interesting because of its 

 poorer fossil content and has not as yet been studied in much detail. 

 Around the western and southern ends of Sheep Mountain this clay 

 series is capped by a heavy sandy nodular layer about 50 feet thick, 

 but this layer was not observed elsewhere. 



3. Leptauchenia-Protoceras Series. — A. Protoceras Beds. The 

 name Protoceras beds has often been applied to all of the Upper 

 White River, but should be restricted to the stream channels cutting 

 the so-called Leptauchenia clays, the former alone carrying a Pro- 

 toceras fauna. No channels over 30 feet in thickness have been 

 observed by the writer, and Wortman's figure of 50-75 feet is prob- 

 ably somewhat excessive. The position of these channels is generally 

 at or near the base of the Leptauchenia beds. As the Protoceras 

 sandstones are only formed in stream channels, many sections contain 

 no Protoceras beds at all, the Leptauchenia horizon resting directly 

 on the Upper Oreodon clays. It has been supposed that the Proto- 

 ceras sandstones were deposited right in the stream channels where 

 the current was strong, while the Leptauchenia " clays " were de- 

 posited at the same time in the quieter backwaters. In many samples 

 of Protoceras sandstones, however, water-worn concretions are found, 

 such as are very characteristic of the Leptauchenia beds. These con- 

 cretions were sufficiently consolidated at the time of the Protoceras 

 channels to be preserved as pebbles in the sandstones formed. This 

 shows that the Protoceras channels were actually cut through the 

 Leptauchenia beds and are thus younger than part of the latter zone, 

 older Leptauchenia beds and are thus younger than part of the latter 

 zone. This suggests contemporaneous erosion of the country rock 

 by the channel forming streams. 



B. Leptauchenia Beds. The most complete section of these is in 



