314 THE CAM3RIAN. [bull. 81. 



six species, viz, Kulorgina prospectensis, Seen ell a connla, Olenoides quadriceps, Olenellus 

 yilberli, 0. iddingsi, Anomocare parvum, and I'tychoparia sp.? 1 



The second formation is the Prospect Mountain limestone. This is a 

 massive limestone crystalline and granular in texture. 



Interstratified in the limestone are irregular beds of shale, lenticular or wedge- 

 shaped bodies, varying greatly in width. Indeed they form a characteristic feature 

 in the limestone, which passes readily from massive to shaly beds. Two of the shale 

 bands are quite prominent to the north, but are lost to the southward. The thick- 

 ness of the beds may be taken at 3,050 feet. 2 



Formation "No. 1, the arenaceous shale, between the quartzite and the 

 limestone on Prospect Peak, is more or less a local formation, but it is 

 apparently the zone of Olenellus, and the limestones above are not 

 known to be characterized either by Olenellus or the typical forms of 

 that fauna. Five hundred feet above the base of the Prospect Moun- 

 tain limestone there occurs in a band of shale Scenella conula, Agnostus 

 inter str ictus f Olenoides quadriceps, Ptyclwparia prospectensis. All but 

 the last are closely related to species from the upper beds of the Geor- 

 gia horizon, in either Vermont or Canada. One other species, Sten- 

 otheca elongata, which is found associated with Olenellus thompsoni, 

 Protypus senectus, etc., at L'Anse au Loup, is found 2,000 feet higher up 

 in the limestone. Another species, Olenoides spinosus, is found in asso- 

 ciation with species characteristic of a lower horizon than the typical 

 Potsdam of Eureka, at Pioche, Nevada. J7 3 



Within a short distance of the summit of this limestone the fauna 

 has the general facies of that of the upper Cambrian or Potsdam hori- 

 zon •, still as a whole it occupies the position of the middle Cambrian 

 fauna as the faunas are now classified. Thatr it sustains this view was 

 pointed out by Dr. W. O, Brogger, in his admirable paper on the "Age 

 of the Olenellus zone in North America." 4 He compares the fauna of 

 the Prospect Mountain limestone with that of the Paradoxides zone of 

 Europe and concludes that with the exception of the lowest part of the 

 Olenellus zone it must correspond most nearly to the middle and upper 

 part of the Paradoxides deposits of Scandinavia. His conclusions are 

 based almost entirely upon the presence of the various species of the 

 genus Agnostus. From the results of my studies since 1886, 1 am pre- 

 pared to accept this view of Dr Brogger's and to consider the Pros- 

 pect Mountain limestone as representing the Middle Cambrian or Para- 

 doxides zone of the Atlantic Coast Province. A list of species pub- 

 lished in 1886 is as follows: 5 



1 Second contribution to the studies of the Cambrian faunas of North America. TJ. S. Geol. Survey, 

 Bull. No. 30, 188G, pp. 30, 32. 



2 Hague, Arnold. Abstract of Report on Geology of the Eureka xMstrict, Nevada. U. S. Geol. 

 Surv., 3d annual report, 1881-'82, 1883, p. 255. 



3 Second Contribution to the studies of the Cambrian faunas of North America. U. S. Geol. Survey, 

 Bull. No. 30, 1886, p. 32. 



4 Om alderen af Olenellus zonen i Nordamerica. (On the age of the Olenellus zone in North 

 America.) Aftryk ur Geol. Foren. i Stockh. Forhan, No. 101, Bd. 8, 1886, pp. 182-213. 



« U. S. GeoL Surv., Bull. No. 30, p. 32. 





