THICKNESS OF POGONIl' BEDS. 123 



comes in a sharp anticline, beyond which the beds dip uniformly to the 

 west. At the western end of this ridge occurs a small knoll or hill of Eureka 

 quartzite, its geological position being determined by the Eeceptaculites fauna 

 immediately underlying it. 



At the eastern end of this ridge, just west of Wood Cone, a fauna was 

 obtained which indicated a horizon not far above the base of the Pogonip, 

 being largely made up of species found near the summit of the Cambrian, 

 associated with others never as yet recognized below the Pogouip. It is a 

 fauna characteristic of the lower portions of the epoch and quite like a 

 grouping found on the east side of Hamburg Ridge. In other words, they 

 may be correlated with the transition beds just above the Hamburg shale. 

 Many of the species also characterize the Pogonip of White Pine. Among 

 the species identified were the following: 



Lingulepis mjra. Orthis hamburgensis. 



Lingula manticula. Triplesia calcifera. 



Leptajna inelita. Bathyurus congeneris. 



Illaenurus eurekeusis. Bathyurus tuberculatus. 



No accurate measurements of the Pogonip along this ridge can be 

 made, owing to the great irregularities of dip and strike, but it is probable 

 that the beds exceed 3,000 feet in thickness. From the fauna obtained 

 just below the Eureka quartzite, and that from the base of the limestone 

 west of Wood Cone, it is evident that the entire development of Pogonip 

 is represented in this ridge. This gives a somewhat greater development 

 for the epoch than has been recognized east of the Prospect Ridge, but, on 

 the other hand, it does not reach the very great thickness found on Pogonip 

 Mountain at White Pine, estimated at 5,000 feet. 



REGION BETWEEN FISH CREEK MOUNTAINS AND PROSPECT RIDGE. 



This region possesses some distinctive features unlike either of the 

 mountain blocks that adjoin it, yet at the same time it shows the influence 

 of the forces that uplifted Prospect Ridge on the northeast and Fish Creek 

 Mountains on the southwest. It is sharply denned from Prospect Ridge in 

 geological structure by the Sierra fault, which brings tin- Silurian up 

 against the lower Cambrian of Prospect Ridge. The anticlinal structure 



