164 THE CAMBRIAN. [bull. m. 



geology. One of these refers to the finding of a specimen of Ptychopa- 

 ria oweni M. and H. on the Cascade River in debris brought down from 

 the mountain, indicating the presence of the Cambrian in the Cascade 

 Mountains. 1 



An admirable map accompanies Dr. Dawson's report, and includes 

 the region between latitude 49° and 50° 30'. The geographic distribu- 

 tion of the Cambrian quartzite series and its relations to the superja- 

 cent Carboniferous and Devonian rocks is delineated, and their strati- 

 graphic position is shown in an accompanying diagrammatic section. 



When exploring the Yukon district in 1887 Dr. Dawson 2 discovered 

 that the country north of Dease Lake had a granitic nucleus with Paleo- 

 zoic rocks on its flanks, ranging from the Cambrian to the Carboniferous. 

 No details are given. 



The detailed exploration of the Paleozoic rocks west of the great 

 Archean area, near the border of British Columbia and Alberta, was 

 undertaken by Mr. R. (x. McConnell, and his results are presented 

 in the annual report of the Canadian Survey for 1886. The Castle 

 Mountain group, a great limestone formation, has a known minimum 

 thickness of 7,700 feet. The lower portion is of Cambrian age, and the 

 upper part forms the base of the Lower Silurian (Ordovician). Beneath 

 the Castle Mountain group the Bow Eiver series forms a great thick- 

 ness of dark colored argillites, associated with some sandstones, quartz- 

 ites, and conglomerates. The portion exposed has an estimated thick- 

 ness of 10,000 feet, and in the upper part of it occur the fossils men- 

 by Dr. Dawson, Olenellus gilberti, etc. 3 The occurrence of fossils of 

 Cambrian age in the lower portion of the Castle Mountain group is 

 noted on page 28D of the report. 



The fauna from the slates or shales at the base of the Castle Moun- 

 tain group, in the Mount Stephen section, was described by Dr. C. 

 Rominger in 1887, 4 and reviewed by Mr. C. D. Walcott in the following 

 year. 5 



In noticing the two papers just mentioned Mr. R. G. McConnell gives 

 a resume* of the section at Mount Stephen. He states that no fossils 

 have been detected in the lower part of the Bow River series, but speci- 

 mens of Olenellus gilberti were found by Dr. Dawson in 1884 about 2,000 

 feet below the top of the formation. The next fossiliferous zone occurs 

 near the junction of Bow River and Castle Mountain groups, where 

 Paradoxides was found ; and a third zone, between 3,000 and 4,000 feet 

 higher up, carries the fauna described by Dr. Rominger. 6 



1 Op. cit., p. 143B. 



2 Notes on exploration in Yukon District. Science, vol. 10, 1887, p. 165. 



'Report on the Geological Structure of a portion of the Rocky Mountains, with a section. GeoL 

 Surv. Canada, Ann. Report, new ser., vol.2, 1887, pp. 24-30 D. 



4 Description of Primordial fossils from Mount Stephens, Northwest Territory of Canada. Phil*. 

 Acad. Sci. Proc, 1888, pp. 12-19, PL I. 



'Cambrian fossils from Mount Stephens, Am. Jour. Sci., 3d ser., vol. 36, 1888, pp. 161-166. 



6 Notes on the geology of Mount Stephen, British Columbia. American Geologist, vol. 3, 1889, pp. 

 23-25. 



