52 (lEOLOdV OF THE EUEEKA DISTIIKJT. 



ill the laiiua from the Hamburg hmestone. Many of these genera gi-uhially 

 give way and are replaced by others, until at about 800 or 1,000 feet below 

 the summit the faunal development is shown by a grouping of fossils made 

 at two widely separated areas, which begin to foreshadow the strongly 

 marked fauna at the summit of the epoch. From the east slope of the 

 ridge east of the Hamburg Ridge there were collected — 



Iteceptaculites ellipticus. Maclurea auuulata. 



Cystidiaii plates. Belleroplioii ? 



Ortliis perveta. Ortlioceras (likii O. inulticauioratuni). 



Triplesia calcifera. Cypliaspis brevimarginatus. 



Rapbistoma? Ilbienurus eurekensis. 



Pleurotouiaria loiieiisis. Asapbus? ouriosus. 



And from the long, eastern slope of White Mountain, al)out 800 feet 

 from the top of the mountain and probably nearly the same distance below 

 the summit of the Pogonip, there were collected as follows : 



Monticiiloiira. Pleurotouiaria loueusis. 



Ortbis testudiuaria. Endoceras proteiforme. 



Eapbistoiua nasoni. Ortboceras sp. ? 



Maclurea auuulata. Batbyurus similis. 



Machirea subanuulata. Asapbus caribouensis. 



Throughout the upper 600 feet of the Pogonip, where\-er organic 

 remains have been observed, the association of genera are much the same, 

 the horizon being well determined both by the fauna and the position of 

 the overlying Eureka quartzite. Tn many areas where the Eureka rjuartzite 

 forms the surface rock an underlying- limestone several liuiuh-ed feet in 

 thickness is. frequently exposed, which carries paleontological evidences of 

 the upper Pogonip strata. Two localities in these upper Pogonip beds 

 have furnished a rich and varied fauna. From a dark limestone on the 

 summit of White Mountain tlie following species have been determined : 



Receptaculites ellipticus. Telliuoinya ooutiacta. 



Eeceptaculites elougatus. Helicotoma sp? 



Receptaculites luammillaris. Ortboceras multicameratum. 



Oystidean plates. Endoceras (like B. multitubulatum). 



Stropboiueua ueinea. Leperditia bivia. 



Ortbis perveta. Leperditia sj)? 



Ortbis testudiuaria. Beyricbia sp? 



