94 



Contributions to Palceontology . 



limited time prevented such investigations as would have 

 been desirable. Since that period little has been added 

 to the species before known from New York localities, 

 except a single species of Conocephalites discovered by 

 Mr. Bradley at Keeseville. 



At a later period (1847-50), Dr. D. D. Owen, in his 

 investigations in Wisconsin, Iowa and Minnesota, dis- 

 covered, in the sandstone of the Upper Mississippi valley, 

 a comparatively abundant fauna, which he at first regarded 

 as marking a horizon far below the Potsdam sandstone 

 of New York, having considered the Saint Peters sand- 

 stone as the equivalent of that rock. In pursuing some 

 investigtions in connection with the United States Survey 

 of the Lake Superior region in 1850, I had an opportunity 

 of tracing the formations from Drummond's island and 

 St. Mary's river to the head of Green bay, and thence 

 made a section across the country to the Mississippi river. 

 The position of the sandstone on the St. Mary's admitted 

 of no doubt; and its relative position to the lower lime- 

 stone had before that time been well determined, and 

 the same was likewise ascertained by the several exploring 

 parties along different lines between Lake Superior and 

 Green bay. 



Throughout Wisconsin there is no difficulty in re- 

 cognizing the following sequence : 



Trenton limestone ; 

 Black-river or Buff limestone ; 

 Birdseye limestone; 

 St. Peters sandstone ; 



Lower Magnesian limestone, or Calciferous sandstone; 

 Potsdam sandstone. 



The St. Peters sandstone holds the place of the Chazy 

 limestone of the more eastern localities ; and, with this 

 exception, we have the same sequence that we find in 



