STRATIGRAPHIC TAXONOMY 651 



Divisions A and B from the overlying beds is scarcely less manifest 

 than it is to the paleontologist and stratigrapher. As A and B (beneath 

 the unconformity) are strictly equivalent to the Little Falls dolomite 

 of the Mohawk Valley, this discrimination may be said to have been 

 carried out already. Finally, as long as we endeavor to draw forma- 

 tional and group boundaries in accordance with the important stages 

 in geological history, the Ozarkian Divisions A and B should be grouped 

 with the underlying Theresa and Potsdam. Indeed, the boundary be- 

 tween B and C is thought to be of such high significance that if it were 

 decided to continue the present division of the pre-Silurian part of the 

 Paleozoic into but two systems instead of the four here advocated the 

 separation of the two should be at this line. 



In consideration of the foregoing facts and arguments, it is proposed 

 to restrict the Beekmantown to the three upper divisions (C, D, and E) 

 of Brainerd and Seeiys Lake Champlain Calciferous. The term is thus 

 made to cover the whole of Canadian deposition in the Champlain trough, 

 which here consists only of more or less magnesian or arenaceous lime- 

 stones. Though divisible into good formational units which can and 

 should be mapped separately in the Champlain Valley, the mass, as a 

 whole, may still be referred to as the Beekmantown limestone group or 

 series. Further, in folded areas like the Mercersburg-Chambersburg 

 quadrangle in Pennsylvania, where cartographic limitations permitted 

 the discrimination of only the well marked basal member (the Stone- 

 henge), the designation of the series simply as the Beekmantown lime- 

 stone seems eminently proper. As I see the matter now, this term is 

 properly applicable throughout the Maryland basin part of the valley. 

 But to the south, in the central Virginia, Tennessee, and Alabama basins, 

 other names are thought desirable. In central Pennsylvania also, where 

 the Canadian is divisible into four mappable formations, the name Beek- 

 mantown should not be used. 



Type sections of the Canadian system. — The exposures which fur- 

 nished the principal part of the information respecting the sediments 

 and faunas on which the Canadian period was originally founded are 

 in the Champlain and Saint Lawrence valleys and in northwestern 

 Newfoundland. The first contains the calcareous facies embraced in the 

 restricted Beekmantown limestone. The beds have been well described 

 by Brainerd and Seely and Logan, and their faunas by Billings, Whit- 

 field, and Ruedemann. The essential parts of this information have 

 been well summarized by Schuchert in his recent paper on Paleogeog- 

 raphy of North America. 



