OF THE NORTHWEST. 73 
bed of the St. Peter’s is there formed by ledges of soft brown sandstone (F. 1, /) ; 
and from this up to White Rock, eighty miles up the river, sandstones of F. 1, and 
magnesian limestone (F. 2), alone compose the bluffs,—the latter usually of buff 
and salmon colours, containing casts of Hwomphalus, besides a few other Lower 
Silurian fossils, which will be found in the list in the Appendix. This is the “ fawn- 
coloured carboniferous limestone” of Mr. Featherstonhaugh. 
SECTION IT. 
ITS PALEONTOLOGY. 
Tue St. Peter's Limestone is rich in organic remains. The most commonly 
occurring species will be seen by consulting the tables, the Appendix, and details 
of this Report. 
Many species, found both by Dr. Shumard and myself, in the lower shell limestone 
of the Upper Mississippi, are identical with forms occurring both in the substratum 
of gray limestone at Eagle Point, in the Dubuque District—figured and described 
in my Report of 1839—and in the blue limestone of the Ohio Valley. Those of 
the upper division resemble rather the species found in the inferior beds of the 
Upper Magnesian Limestone of that District. But all, so far as our examinations 
have yet extended, are of a Lower Silurian type. 
SECTION III. 
ITS MINERAL CONTENTS. 
SomE specimens of copper ore are reported to have been found in the vicinity of 
the Falls of St. Anthony. If they have, it is not likely that they originated in 
veins traversing this limestone formation, since neither it nor the underlying sand- 
stone bear marks of being metalliferous. Probably they were erratic pieces trans- 
ported from some copper locality lying to the north. The thickness, too, of these 
calcareous beds is so inconsiderable, that even if they did contain metallic lodes, 
these could not extend to any great depth, before they would dwindle in the 
incoherent sandstones beneath. But the schistose structure of the rock itself is 
altogether unfavourable to its metalliferous character. 
SECTION IV. 
ITS PHYSICAL AND AGRICULTURAL CHARACTER. 
Hien up on Turkey River, near the site of Fort Atkinson and the location of 
the Winnebago Agency, this formation appears in the form of wonderfully symme+ 
trical, mound-like forms, with flat tops, as exhibited by the following illustration. 
10 
