l68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



The second section studied was that of the Eureka District of 

 central Nevada in 1880— 1 88 1, the results of which were incorporated 

 in Monographs VIII and XX of the U. S. Geological Survey. This 

 section includes the upper portion of the Lower Cambrian 

 (Georgian), the Middle Cambrian (Acadian), and the Upper Cam- 

 brian (Saratogan). The studies of the Cambrian strata were after- 

 ward continued in the Cordilleran area from time to time as oppor- 

 tunity offered. These included the Highland Range section of 

 Nevada and the Big Cottonwood section of the Wasatch Mountains 

 (see Bulletin U. S. Geol. Survey, No. 30, 1886, pp. 33 and 38). 

 The great House Range section of central western Utah was studied 

 and measured in 1905, the Blacksmith Fork section of the Wasatch 

 Mountains in 1906, and the Mount Bosworth section of British 

 Columbia in 1907. The last three sections are included in this 

 paper. 



The strata of the Lower Cambrian (Georgian) are apparently well 

 developed in the Big Cottonwood section of Utah, and the upper 

 portion in the House Range, Eureka, and Highland Range sections, 

 but it was not until the sections of the Lower Cambrian (Georgian) 

 formations of western Nevada and southeastern California were 

 examined that the fauna was found well developed. These sections 

 are incorporated in this paper. 



Illustrations. — In order that geologists and paleontologists who 

 have not had an opportunity to see the sections may get an idea of 

 the completeness of the exposures of the strata in the Cordilleran 

 area, photographs are introduced in connection with the House 

 Range and Mount Bosworth sections. 



The map of the House Range gives the localities and names used 

 in the section. 



CORRELATION OF SECTIONS 



The object of this preliminary correlation is to show in a broad 

 way the interrelations of the strata and faunas in the North Ameri- 

 can Cordilleran area west of the great continental land area of 

 Lower and much of Middle Cambrian time. The margin of this 

 area was as far westward as the present position of the main range 

 of the Wasatch Mountains in the vicinity of Salt Lake, Utah ; from 

 this point the shoreline trended gradually south-southwest to south- 

 western Utah and into southeastern Nevada. To the north of Salt 

 Lake the trend of the early Cambrian shoreline was north-northeast 

 to western Wyoming, and thence north into IMontana (see Dear- 

 born River section). It passed westward of the Belt [Mountain 



