C. D. Walcott — Position of the Olenellus .Faitna. 377 



zone in Sweden, the American geologists and paleontologists 

 had mistaken the order of succession. 



It was stated in 1886* that the only locality known in Amer- 

 ica where the two faunas (Paradoxides and Olenellus) occur in 

 the same geographic area is about Conception Bay, Newfound- 

 land. The evidence given by Logan of the order of succession 

 was unsatisfactory, but it was all that was available and I con- 

 tinued to use the scheme given by him in 1865. Even after 

 reading Brogger's paper I did not feel warranted in changing the 

 table without stronger evidence than that there given. Compar- 

 ing the two faunas zoologically, it appeared to me that in time 

 the Olenellus fauna should follow the Paradoxides fauna. In 

 May, 1888,f I reprinted Logan's scheme, stating that the table 

 was tentative and expressive of my present knowledge and 

 opinion, requesting that ail who use it should decide individ- 

 ually upon the value of its correlations. 



Such was the condition of our knowledge in the spring of 

 1888, when I began an investigation to determine, if possible, 

 the actual stratigraphic succession of the Cambrian faunas of 

 North America. I first re-examined the section of Cambrian 

 strata in Eastern New York, as some evidence was known to me 

 there of the presence of the Paradoxides fauna. One of the 

 results of this study was the discovery of entire specimens of 

 Olenellus asaphoides that showed it to be generically identical 

 with Olenellus Kjerulfi of Sweden, and Olenellus Mickwitzi 

 of the East Baltic region of Russia, as described by Schmidt. 

 Also that the genus Mesonacis, based on Olenellus Vermontana, 

 included Olenellus asphoides, 0. Kjerulfi, and 0. Mickwitzi, 

 in having a similar type of pygidium. Knowing that 0. {Meson- 

 acis) Vermontana was associated in the same stratum of rock 

 with O. Thompsoni, and that the same type occurred beneath 

 the Paradoxides zone in Sweden, Norway and Russia, I fully 

 believed that the stratigraphic position of the faunas would 

 be found to be the same in America as in Europe. I also 

 found at the base of the great Berlin sandstone in Rens- 

 selaer County, N. Y., several species of fossils that appear to 

 be more closely allied to the species occurring in the Para- 

 doxides fauna than to any known elsewhere in the Olenellus 

 fauna, notably, Linnarssonia Taconica, Agnostus desideratus, 

 n. sp., Agnostus like A. pisiformis, Microdiseus connexus and 

 Zacanthoides Eatoni, n. sp. These species occur in the upper 

 portion of the shales that in their middle and lower parts con- 

 tain only the Olenellus fauna 



* Bull. U. S. Geol. Survey, No. 30, 1886, pp. 49-50, par. 97. Distributed in 

 January, 1887. 



f This Journal, III, vol. xxxv, 1 888, p. 399. 



