130 



Cincinnati Society of Natural History. 



lent of the sandstones in Wisconsin and Minnesota, which are 

 generally ranged in the horizon of the Potsdam of New York. 

 As the uplift of Keweenaw Point has tilted the sandstones on 

 the west, while those on the east have retained their horizon- 

 tally, there is reason for supposing that the eastern strata are 

 of more recent origin. It may, nevertheless, be true that the 

 sandstones on both sides of the Point are of the same age, 

 though those on the eastern side were not permanently tilted 

 by the convulsion which upheaved the others. As we find 

 apparently superincumbent strata, which answer to the Cal- 

 ciferous, we shall continue to parallelize the Lake Superior 

 sandstone, presumptively, with the Potsdam." 



Dr. Rominger, in 1873,"!" also considers the Chazy and Cal- 

 ciferous under one head. In his description he says: " Below 

 the well-characterized Trenton strata, and reposing on the 

 Lake Superior sandstones, we find over the whole extent of 

 the Peninsula a series of calcareous or arenaceo-calcarecus 

 beds which hold the place of the Chazy limestone and the 

 calciferous formation of the Eastern States. We can not dis- 

 tinguish two different formations with different faunas in the 

 West, where all the fossils ever found are three or four 

 species of shells, and those generally in imperfect condition. 

 Bat we can see a plainly expressed typical similarity between 

 the fossils of the eastern and western localities. Also the 

 lithological characters of the compared rocks are in perfect 

 general correspondence, so that we can safely consider our 

 western strata as the equivalents of the two named groups 

 of the New York system. The greatest observed thickness 

 of the formation within the district is near 100 feet, but 

 usually it is not found in so large a development." Worthen, 

 in 1866,+ considered the St. Peter's to form the upper portion 

 of the Calciferous series of New York, while in 1874, Broad- 

 head|| makes the Saccharoidal sandstone equal to the St. 

 Peter's and also to the Calciferous. 



In 1883 Prof. Chamberlin^ gave a resume of the knowledge 

 of the formation. It is stated to repose on the billow T y sur- 



/ 



■Ibid, pp. 43-44- 



jMiehigan Geological Survey. Paheozoic Rocks, 1873, p. 71. 

 ^Geological Survey of Illinois, Vol. I, 1866, p. 149. 

 Report of the Geological Survey of Missouri; field work, 1S73-1S74; 1^74, 

 chart oppo. p. iS, and p. 29. 



^Geology of Wisconsin, Survey of 1S7 3-1879, Vol. I, 1883, pp. 145-150. 



