CONTRIBUTIONS TO PAL^ONTOLOGT. 215 



Potsdam sandstone, on the north shore of Lake Huron ; and alo 

 that this sandstone of St.Mary's river (which is now regarded 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 William Logan that this sandstone represents the 

 Upper sandstone, or fills the place of the Chazy formation in the 

 East, the limestone being absent ; and that it is this arenaceous 

 deposit, greatly augmented, which gives the Sandstone formation 

 of the south shore of Lake Superior*. 



In 1846, Mr. C. C. Douglass discovered a fossiliferous magnesian 

 limestone resting upon sandstone on the south side of Keweena 

 point, in a line between the head of the Bay and the mouth of 

 Misery river. In 1848 or 1849, Messrs. J. W. Foster and J. D. 

 Whitney brought from this locality several species of fossils, 

 which were submitted to the examination of the writer. The 

 geologists of Michigan represent that the same sandstone, at 

 Grand island, is succeeded by a fossiliferous limestone, which is 

 doubtless the same as that of Keweena point. 



The character of the fossils from the locality on Keweena point 

 is such as to leave no doubt that the limestone is equivalent to the 

 Buff limestone of Wisconsin; holding the identical fossils, and 

 representing the Birdseye and Black-river limestones. The order 

 of sequence in Central and Western Wisconsin, and in Iowa and 

 Minnesota, is that already given, viz : 



Buff limestone = Birdseye & Black-river ; 

 St. Peters sandstone ; 

 Lower Magnesian limestone. 



Now the beds of Buff limestone at Keweena point rest upon a 

 sandstone which has a much greater thickness than the St. Peters 

 sandstone is known to have in any of its western localities ; nor 

 has the Lower Magnesian limestone been seen below that sand- 

 stone, so far as we now know ; unless the magnesian limestone 

 seen by Mr. Murray, of the Canadian Survey, at the mouth of 

 Dead river, beneath the sandstone of the south shore of Lake 

 Superior, be the true Lower Magnesian limestone or "Calciferous 

 sandrock"f. 



* Geology of Canada, 1863, pp. 83-86. 



t On this [the south] coast at the mouth of the Dead river, north of Marquette, 

 there is a mass of very ferruginous dolomite, of which the stratification is not very 

 distinct ; but it is overlaid by the sandstone, which fills up the inequalities in the 



