184 



Contributions to Paleontology, 



to expect the final disappearance of the limestone in that 

 direction, and of the sandstone to the southward. Now 

 it happens that to the north of the localities on the Upper 

 Mississippi valley, we have upon Lake Superior, a great 

 development of sandstone, the precise, age of which has 

 for some time been debated, and from which no fossils 

 have been obtained, with the exception of a single species 

 of Lingula 3 . 



In his Report for 1840, Dr. Houghton says : 

 "This Lake Superior sandstone, in its easterly prolongation, rests 

 "against and upon the primary range of the Ste. Marie's river, 

 "before described; while on the south, it is seen to pass beneath 

 "the limestone at the Nebeesh rapids of the boat and canoe chan- 

 nels of that river. The rapids or falls of the Ste. Marie's river 

 "are formed by the passage of the waters over the outcropping edge 

 "of the sandrock, which inclines or dips from this point southerly; 

 "thus passing conformably below the limestone before alluded to." 



So long since as 1845, I had myself observed that the 

 sandstones of the St. Mary's river come out from beneath 

 the Black river and Birdseye limestones ; but the Calcife- 

 rous sandstone was nowhere visible in the immediate 

 neighborhood. The later and more complete investiga- 

 tions of the Canada Geological Survey have proved the 

 absence of the Calciferous sandstone, and of the Potsdam 

 sandstone, on the north shore of Lake Huron ; and also 

 that this sandstone of St. Mary's river (which is now re- 

 garded as identical with that of the south shore of Lake 

 Superior) rises from beneath the Black river and Birdseye 

 limestone, and there is' no evidence of the Calciferous 

 sandstone in that region. It is the opinion of Sir Wil- 

 liam Logan that this sandstone represents the Upper sand- 

 stone, or fills the place of the Chazy formation in the East, 



1 This Lingula I have formerly referred to L. prima of the Potsdam sand- 

 stone ; but a later critical examination of the specimens which have been 

 more carefully separated from the surrounding stone shows it to be more 

 nearly related to a species in the Calciferous sandstone. 



