526 DESCRIPTIVE GEOLOGY. 



eastward, with a strike of north 10° west. From them were obtained the 

 following Coal-Measure fossils : 



Spirifer cameratus. 

 Sjpirifer Kentuckensis. 

 Athyris, subtilita. 

 Bhynchonella, sp.? 

 Pseudomonotis radialis. 

 Pseudomonotis, sp. ? 

 Dentalium Meekianum. 

 Bellerophon carhonarius. 

 Chcetetes. 

 Fenestella. 

 Trematojpora. 



The general aspect of these fossils, taken as a whole, together with 

 the lithological character of their beds, shows that they doubtless represent 

 the extreme upper portion of the Wahsatch limestone. Their relative posi- 

 tion with regard to the Devonian beds exposed at the Hot Springs must be 

 explained by a rather complicated system of faulting, which the character 

 of the country and the limited time at our disposal did not permit us to 

 work out in detail. 



Tulasco Peak itself and the hills to the southeast and west, though 

 showing few outcrops, are evidently occupied by beds of the Weber Quartz- 

 ite, associated with which in the southern end are some flows of a brecciated 

 rhyolite. In some cases, these peculiar quartzitic sandstones are so full of 

 limpid quartz that they may be almost confounded with the rhyolite. They 

 are, in general, the same reddish, rough-feeling rocks observed in the Fount- 

 ain Head Hills, in which the proportion of granular matrix and of enclosed 

 cherty fragments is very variable. The pores generally contain a great 

 deal of brown hydrated oxide of iron, to which the color of the rock is some- 

 what due. In the neighborhood of the rhyolite outflows are found rocks 

 which are made up largely of the same cherty fragments of black and green 

 colors, in which the rock has a more compact and almost felsitic structure, 

 its granular character having disappeared, and there being a more consid- 



