STRATIGRAPHIC TAXONOMY 641 



found to be less fully and probably somewhat differently represented in 

 the upper Mississippi area than it is in the Ozark region. 



The Shakopee fauna is a well defined association, and although much 

 remains to be done in the way of critical comparisons, sufficient progress 

 has been made to show that its like is found in Missouri only above the 

 Eoubidoux. Possibly the top of the Shakopee, as now understood, locally 

 includes a Canadian fauna. This is suggested by certain species de- 

 scribed by Sardeson which remind strongly of forms in the Beekman- 

 town in N'ew York and in the Yellville in Arkansas and Missouri. How- 

 -ever, taken as a whole, the nearest parallel of the Shakopee known occurs 

 in the Jefferson City dolomite. For the present, then, it seems safe to 

 correlate the New Richmond sandstone and the Shakopee of Minnesota, 

 Iowa, and AA^isconsin with the Eoubidoux and Jefferson City formations 

 in Missouri. 



The Ozarhian in other parts of North America — In the Arbuckle and 

 Wichita uplifts in Oklahoma. — If Ozarkian deposits occur in south cen- 

 tral Oklahoma, they are included in the lower half of the great Arbuckle 

 limestone. The upper half, at least, of the 5,000 to 6,000 feet of lime- 

 stone and dolomite comprising this so-called formation is undoubtedly 

 younger than the top of the Ozarkian in Missouri, and probably no less 

 certainly older than the base of the Saint Peter. It falls, therefore, 

 within the geological interval that it is intended to cover by the term 

 Canadian. Just how much, if any, of the lower half of the Arbuckle is 

 to be assigned to the Ozarkian can not be decided without reexamination 

 of the deposits in the field. The whole formation may prove to be 

 Canadian. On the other hand, the upper and lower parts of the basal 

 700 feet or so contain trilobites that may well be upper Cambrian : and 

 between these trilobite beds lies about 400 feet of pink and white marble 

 interbedded with massive cream-colored, black-weathering dolomite that 

 of the whole section is the most likely to be of Ozarkian age. More prob- 

 ably, however, this 700 feet basal division is to be correlated with the 

 Elvins of Missouri, which would make it late upper Cambrian. N"ext 

 follows a 2,000 feet series of massive interbedded pure and magnesian 

 limestone in which not a sign of organic remains was seen. This great 

 mass may be either Ozarkian or Canadian. However, since it is litho- 

 logically like the. succeeding 2,300 feet, which was arbitrarily marked off 

 at the first appearance of fossils — a species of one of the Canadian types 

 of Maclurea — I incline to the latter view. The overlying 1.000 feet or 

 more, which is thin-bedded to shaly and frequently fossiliferous, is, like 

 the preceding 2,300 feet, all unquestionable Canadian. 



