612 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



top of the Nolichucky in east Tennessee, the top of the Conasauga in 

 Alabama, the top of the Elvins in Missouri, the top of the Saint Croix 

 in Minnesota and Iowa, the top of the Honey Creek member of the 

 Reagan formation in Oklahoma and central Texas, the top of the Bliss 

 sandstone in western Texas and the top of the Deadwood formation in 

 the Black Hills and Big Horn Mountains section in Wyoming. Not 

 having seen the Cordilleran sections, I find it difficult to decide Just 

 where to draw this boundary in, say, Walcott's House Eange section in 

 Utah. Hazarding an opinion, I would say that his Notch Peak forma- 

 tion is Ozarkian and the Orr formation upper Cambrian. 



It may be observed that the Cambrian as here defined accords fairly 

 well with the Cambrian of Walcott as used by him in classifying forma- 

 tions to the west of the Mississippi.'^^ Except that he seems inclined to 

 include a portion of the Knox, it accords, also, with his usage of the term 

 in the Appalachian Valley. The chief difference concerns the New York 

 section, where Walcott embraces the Potsdam sandstone and the Hoyt 

 limestone in a Saratogan series and proceeds to correlate this series with 

 the "upper Cambrian" elsewhere in the country. As recently shown by 

 Ulrich and Cushing,'^^ there is neither a faunal nor a stratigraphic 

 break^^ between the Potsdam and the Little Falls dolomite, of which 

 the Hoyt limestone is merely a locally distinguishable member. It is 

 shown further that the Saratogan, including the Little Falls dolomite, 

 is really the equivalent of middle parts of the Ozarkian section in Mis- 

 souri, and that it is, therefore, much younger than the beds in Missouri, 

 Texas, Oklahoma, and Wyoming, which Walcott formerly and now refers 

 to the upper Cambrian. It is merely a case of mistaken correlation, an 

 error of judgment that in the absence of detailed knowledge respecting 

 the stratigraphy and the faunal and diastrophic history of the late- 

 Cambrian to early Ordovician deposits, he could hardly have escaped. 

 Relying on the New York section, in which he noted (1) the essential 

 continuity of sedimentation from the Potsdam sandstone on through th^ 

 Theresa passage beds into the Hoyt limestone and from this into the 

 supposedly Ordovician dolomite of the Little Falls ("Calciferous") 

 formation, and (2) the apparent Cambrian aspect of the Hoyt fauna, 

 Walcott properly inferred that the Cambro-Ordovician boundary was 

 hidden somewhere in the mass of the Knox dolomite, the lower part of 



"C. D. Walcott: Proc. Washington Acad. Sci., vol. i, 1900, p. 304. 



■^8 E. O. Uli-ich and H. P. Cushing : Age and relations of the Little Falls dolomiie 

 (Calciferous) of the Mohawk Valley. Bull. New York State Mus.. No. 140. 1909. 



^» The conformable relations of the Little Falls dolomite and the Potsdam sandstone 

 have been repeatedly admitted by Walcott. 



