624 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



brachiopods have been studied sufficiently by Walcott to insure safety in 

 comparisons. Of the 14 species of brachiopods, listed from the upper 

 Cambrian Eeagan formation in Oklahoma, and chiefly from the cal- 

 careous upper part, for which the name Honey Creek member is proposed, 

 8 species are found in Texas, 6 in Wyoming, 5 in Missouri, 4 in the upper 

 Mississippi Valley, and 2 in Tennessee and Alabama. Of 19 species col- 

 lected from central Texas, 7 occur in Wyoming, 7 in Missouri, 2 in the 

 upper Mississippi Valley, and 2 in east Tennessee. 



While the faunal similarities above noted are believed to be sufficient 

 to' establish the general contemporaneity of the formations in the widely 

 separated areas mentioned, the more or less striking dissimilarities 

 suggest impeded communication between the several areas. It is not 

 improbable, further, that oscillation and shifting of seas occurred, with 

 deposition going on in one place while slight emergence prevailed at 

 another, so that none of the fossiliferous beds in certain of the areas is 

 strictly synchronous with richly fossiliferous beds in any of the others. 

 If oscillation of this kind obtained during the upper Cambrian we should 

 expect to see it manifested, especially on comparing the sequence of 

 faunas and deposits in the Appalachian and Cordilleran provinces with 

 those in the interior continental provinces. Here in fact is where the 

 greatest discrepancies are encountered. Comparing the interior areas 

 with each other decided community of species is observed. It is strongest 

 between Texas, Oklahoma, Colorado, and Wyoming, good between these 

 and Missouri on the south and the upper Mississippi area on the north, 

 and surprisingly weak between Missouri and the upper Mississippi 

 localities. Evidently, there was no direct communication between the 

 latter two areas. 



Correlation of Eopaleozoic beds in the Appalachian and interior 

 provinces with those in the Atlantic province is but seldom entirely 

 satisfactory. The principal exceptions are those carrying graptolite 

 faunas, which were occasionably swept into the continental troughs and 

 basins by favorable marine currents. The Bretonian of Matthew, which 

 is commonly referred to as upper Cambrian, contains one of these 

 graptolite zones. This is the Dictyonema flabelliforme zone, the type 

 species of which, together with two or three associated graptolites, is 

 widely distributed in eastern America and western Europe. It affords a 

 basis on which we may correlate with reasonable confidence. For reasons 

 that will be brought out in discussing the Canadian system, the Dicty- 

 onema flebelliforme zone is regarded as post-Ozarkian, hence as much 

 younger than the upper Cambrian as here defined. In fact, all of the 

 Bretonian seems to me younger than the Ozarkian. On the other hand. 



