A CHAT WITH PEOF. COPE — CONTINUED. 363 



the base, although many of the canyons are exca- 

 vated in the yellow rock exclusively. The bluffs of 

 the upper portion of Butte Creek, Fox, and Fossil 

 Spring (five miles south) canyons, are of yellow 

 chalk, and report of several persons stated that those 

 of Beaver Creek, eight miles south of Fossil Spring, 

 are exclusively of this material. Those near the 

 mouth of Beaver Creek, on the Smoky, are of con- 

 siderable height, and appear at a distance to be of 

 the same yellow chalk. 



I found these two strata to be about equally fossil- 

 liferous, and I am unable to establish any palaeonto- 

 logical difference between them. They pass into each 

 other by gradations in some places, and occasionally 

 present slight laminar alternations at their line of 

 junction. I have specimens of Cimolichthys semian 

 cej)s (Cope), from both the blue and yellow beds, and 

 vertebrae of the Liodon glancliferus (Cope) were found 

 in both. The large fossil of Liodon dyspelor (Cope) 

 was found at the junction of the bed, and the caudal 

 portion was excavated from the blue stratum ex- 

 clusively. Portions of it were brought East in blocks 

 of this material, and these have become yellow and 

 yellowish on many of the exposed surfaces. The 

 matrix adherent to all the bones has become yellow. 

 A second incomplete specimen, undistinguishable 

 from this species, was taken from the yellow bed. 



As to mineral contents, the yellow stratum is re- 

 markably uniform in its character. The blue shale, 

 on the contrary, frequently contains numerous con- 

 cretions, and great abundance of thin layers of 

 gypsum and crystals of the same. Near Sheridan 



