376 C. D. Walcott — Position of the Olenellus Fauna. 



Second Contribution to the Studies on the Cambrian faunas of 

 North America,* there was given a description of the typical 

 geologic sections of the Cambrian System, and the order of 

 succession of the faunas contained in their strata as then known. 

 A diagramf was introduced to show the correlation of the sec- 

 tions and the order of successions of the three sub-faunas into 

 which the Cambrian fauna was divided. The first and oldest 

 was the Lower Cambrian or Paradoxides fauna ; the second, 

 the Middle Cambrian or Olenellus fauna, and the third, the 

 Upper Cambrian or Dicellocephalus fauna. Each fauna was 

 designated by the most characteristic genus of trilobite con- 

 tained in it. It was stated;}: that "the conditions that de- 

 veloped the Middle Cambrian (or Olenellus) fauna appeared to 

 have been largely peculiar to the American Continent ;" also 

 that (119) " there does not appear to be an equivalent fauna in 

 the Cambrian System of Europe, either in Bohemia, the Scan- 

 dinavian area, or in Wales. The nearest approach to it is on 

 the Island of Sardinia." 



At the time the introduction was written (1885) there was 

 no satisfactory evidence that " Paradoxides Kjerulji" of the 

 lowest Cambrian strata of Sweden, was not a true Paradoxides ; 

 nor that it was an Olenellus, similar in type to Olenellus asa- 

 phoides of the American " Middle Cambrian." Brogger's ex- 

 cellent paper on the Age of the Olenellus Zone in ISTorth 

 America§ had not appeared ; nor had the beautiful memoir of 

 Holm's on Olenellus Kjerulfi.\ The latter proved conclusively 

 that the genus occurs in the lowest fossiliferous bed of Sweden, 

 beneath the horizon of the genus Paradoxides. Still more re- 

 cently F. Schmidt has published an account of the finding of 

 Olenellus in Estoria, in the Cambrian blue clay, and he states 

 that he must concur with Brogger in his view that the Olenellus 

 fauna is beneath, and older than, the Paradoxides fauna. *[ 



From the evidenee given by Brogger, Holm and Schmidt, 

 there appeared to be no doubt that the Olenellus zone in Eu 

 rope was beneath the Paradoxides zone. In America it had 

 been regarded by Billings, Logan, Ford, Matthew, Walcott, 

 and Winchell** as above the Paradoxides and subjacent to the 

 Dicellocephalus zone. Brogger analyzed the evidence upon 

 which this view was based and concluded that, in the face of 

 the direct stratigraphic proof of the position of the Olenellus 



* Bull. U. S. Geol. Survey, No. 30, 1886. f Loc. cit., p. 44. 



i Loc. cit., p. 57, par. 120. 



§ Aftryck ur Geol. Foren Stockholm, Forhandl., vol. viii, Haft. 3, 1886. 



I Ibid., vol. ix, Haft. 7. 1887. 



T[ Mem. Acad. Imp. Sci. St. Petersburg, VII, vol. xxxvi, No. 2. TJber eine 

 Neuentdeckte Untercambrische Fauna in Estland, 1888, pp. 1-27, pi. i-ii. 



** As reporter of American opinion, Cong. Geol. International 4 me. Session 

 Londres; Res. Rep. Sous. Com. Americans, 1888, p. 9. 



