98 



GEOLOGY OP THE EUEEKA DISTRICT. 



Orthis pecosi. Spirifera rockymontana. 



Streptorhyuchus creriistria. Athyris subtilita. 



Productus cora. Eetzia mormoiii. 



Productus setnireticulatus. 



They represent a distinctively Coal-measure fauna and are identical 

 with forms collected from beds at Pancake. On the other hand, none of 

 the species obtained at Pancake, indicating the horizon at the base of the 

 Lower Coal-measures, have as yet been found at Bald Mountain. In this 

 grouping at Bald Mountain there is nothing to prevent the horizon from 

 being considered as belonging to the Upper Coal-measures, but it is hardly 

 possible to suppose that the geological position of these beds differs from 

 the position of the coal at Pancake. The geological mode of occurrence 

 at both places and the sections across the beds indicate that the coal comes 

 from near the same horizon, and was deposited under similar conditions, with 

 the probabilities in favor of their having at one time formed a continuous 

 coal area. 



The following analyses of samples of these coals, collected at the time 

 of our visit, are given here for the purpose of showing the character of the 

 deposits. They were made by Dr. W. F. Hillebrand, of the U. S. Geolog- 

 ical Survey. 



The coals do not cake or sinter. 



These coals, while they are of no commercial value, are of geological 

 importance from their exceptional mode of occurrence in the Carboniferous 

 rocks of the Great Basin. A further search would doubtless indicate whether 

 they belong to the base of the Lower Coal-measures or to the middle of 

 the Upper Coal-measures. 



