STRATIGRAPHIC TAXONOMY 625 



I agree with Walcott in seeing nothing but middle Cambrian in Mat- 

 thew's Johannian (Divisions C 2 a, h, c), and thence down in the section 

 to the base of the Protolenus zone. If these views are well founded, then 

 there are neither upper Cambrian nor Ozarkian deposits in the New 

 Brunswick sections described by Matthew. 



Taxonomic relations of the loiver Catnhrian to tJie middle and upper 

 Camhrian. — In his great work on "Paleogeography of Xorth America," 

 Schuchert separates the "Acadic or Middle Cambrian" as a distinct 

 system from the "Georgic or Lower Cambrian system." The grounds 

 for this separation are not very clear. As near as I can make them out, 

 the fact chiefly relied on is that 



"Toward the close of the Georgic the eastern lands are known to have 

 moved, and apparently this elevation drained the entire trough from Labrador 

 to Alabama. This movement is of great significance in the subsequent distri- 

 bution of the faunas, for it is seen that when the seas again invaded the 

 region of this fold the descendants of the former universal Pacific Olenellus 

 faunas were prevented from mixing with those of the northern Atlantic. On 

 the west of this protaxis of "Middle Cambric" time were the Olenoides faunas 

 of the Pacific realm, while to the east are the Atlantic Paradoxides biotas. 

 Here occurred, therefore, the birth of the Appalachian protaxis of Dana and 

 the Chilhovvee-Oreen Mountain barrier of Ulrich and Schuchert. In the Cor- 

 dilleran region the seas are continuous." (Op. cit., p. 483.) 



Apparently another important part of the evidence that induced this 

 author to divide the Cambrian into two systems is the "Saint Croix 

 transgression . . . the duration of which embraced all the Middle 

 Cambric and some of the Upper Cambric as generally defined." I 

 regret that I can not accept this age assignment of the Saint Croixan. 

 My dissent is based primarily on stratigraphic and diastrophic grounds ; 

 and certainly there is very little about the Saint Croxian fauna as de- 

 veloped in the Mississippi Valley and in Tennessee, Missouri, Oklahoma, 

 and Texas that is closely comparable with the middle Cambrian faunas 

 collected by Walcott in the Cordilleran basin, or again with the typical 

 "Acadian" fauna of the north Atlantic province. The Saint Croixan 

 transgression succeeded the deposition of thousands af feet of middle 

 Cambrian ])eds, and, as stated a few pages back, the diastrophic and sedi- 

 mentary record of this transgression makes an admirable closing epoch 

 for the Cambrian period. 



Regarding the diastrophic movements which separated the middle 

 Cambrian from the lower Cambrian, they are no more important than 

 those which preceded the upper Cambrian. Indeed, movements, similar 

 in kind and order of magnitude, took place two or more times in each 



