walcott.] SUMMARY UTAH AND NEVADA. 317 



Modiolopsis, Maclurea, Crytolites, Orthoceras, Endoceras, Coleoprion, Leperditia, 

 Beyrichia, Amphion, Ceranrus, and Asaphus give it a facies approaching that of the 

 Lower Trenton and indicating a horizon that is considered to be in a measure the 

 equivalent of that of the Chazy formatiou of New York and Canada. The fauna of 

 the lower portion of the Pogonip group corresponds in the same manner to that of 

 the Calciferous sand-rock of the same region. The largo number of individuals of 

 the species of Receptaculites, B. mammillaris especially, gives the fauna of the upper 

 beds a character that this horizon has not hitherto had. This, united with several of 

 the Trenton species, viz, Orthis testudinaria, O. tricenaria, 0. perveta, Tellinomya con- 

 tractu, two species of Modiolopsis allied to Trenton forms, and Eaphisloma nasoni, 

 strongly foreshadows the opening of the Trenton period. 1 



The section of the Highland Range, 125 miles south of the Eureka 

 section, gives a greater variation of sedimentation in the lower portion 

 and less in the upper as compared with the Eureka section. The High- 

 land Range has a more abundant and more varied fauna in the lower 

 1,500 feet above the quartzite, while in the Enreka section the upper 

 or Potsdam fauna is much larger than in the Highland section. In each 

 instance a massive limestone has replaced a succession of limestoues 

 and shales. The Highland Range section measuring from the base is as 

 follows : 2 



Feet. 



(1) Dark reddish brown quartzite, evenly bedded, and ripple-marked in some 



places . 350 



(2) Bluish gray limestone 35 



Fossils: Olenellus gilberti. 



(3) Buff argillaceous and arenaceous shales, more or less solid near the base 



and lami nated in the upper portions 80 



Fossils : Annelid trails and fragments of Olenellus in the lower part. 

 Higher up the heads of Olenellus gilberti and 0. iddingsi occur in 

 abundance. 



(4) Light-colored gray limestone and bluish black limestone _ 16 



(5) Sandy, buff-colored shale 40 



Fossils: Annelid trails, Cruzianasp. ? 



(6) Dark bluish black limestone 46 



(7) Finely laminated buff argillaceous shale 80 



Fossils : Hyolithcs billing si and Ptychoparia piochensis. 



(8) Gray to bluish black compact limestone 18 



(9) Buff arenaceous shales 64 



(10) Compact cherty limestone 50 



(11) Compact shaly sandstonein massive layers 40 



(12) Hard siliceous gray limestone, almost quartz at base 12 



( 13) Yellow to buff, sandy shale 70 



(14) Bluish black limestone , 16 



(15) Yellow to buff sandy shales 40 



(16) Bluish black, hard, compact limestone 12 



Fragments of fossils. 



(17) Shaly sandstone in massive layers.---. ..... 52 



(18) Gray arenaceous limestone 2 



1 Walcott, C. D. : Paleontology of the Eureka District. TJ. S. Geol.Surv., Monograph, vol. 8, 1884, 

 pp. 3, 4. 



2 Walcott, C. D. : Second contribution to the studies of the Cambrian faunas of North America. U 

 S. Geol. Surv., Bull. No. 30, 1886, pp. 33, 34. 



