42 GEOLOGY OF THE EtTEEKA DISTRICT. 



Prospect Peak, near the summit of the ridge, there may be traced for over 

 a mile a red areuaceous and calcareous shale, which is lost to the southward, 

 but which, followed to the northward, may be seen to pass gradually into a 

 dark gray shaly limestone. This arenaceous shale may be taken at 100 feet 

 in thickness, and, from the organic remains which it carries and from its 

 paleontological and geological importance, has been designated the OleneUus 

 shale. From this horizon the following species have been obtained : 



Kutorgiua iirospectensis. Olenellus gilberti. 



Ptyclioparia .sp. ! ' Oleuellus iddingsi. 



Abo\it one-half mile northward of this locality, and in a bed of lime- 

 stone 100 feet in thickness, tmderlying the fossiliferous arenaceous shale, 

 and, in the same manner, resting directly upon the quartzites, species indi- 

 cating an identical geological horizon were found, as follows : 



Oleuellus gilbeiti. Oleuoides quadriceps. 



Olenellus iddlugsi. Seenella conula. 



Auomocare iiarAOim. 



These two groupings represent all that have as yet been identified 

 from this lower horizon. 



The Olenenus shales pasc upward into a great thickness of bluish gray 

 limestone, with an occasional thin band of interstratified shale. The beds, 

 however, yield no well defined organic remains for nearly 500 feet, but at 

 that hoi'izou they furnish foiTQs which might belong both to the OleneUiis shales 

 below and the next fossiliferous strata above. Although localities yielding- 

 well defined fossils from this second horizon are seldom met with, indistinct 

 traces of life are seen in the limestone underneath the Mountain shale. The 

 best known locality is foimd at the head of New York Canyon on the long 

 sloping ridge south of the Fom-th of July mine. Here were obtained the 

 following : 



Oleuoides quadriceps. Agnostus interstrictus. 



SceneUa conula. Ptychoparia prosiiectensis. 



The species of PtycJioparia prospectensis has not as yet been found at 

 a higher horizon. Above this horizon the limestone is much metamoiiDhosed 

 and altered to marble, and is so broken up that well defined beds favorable 



