670 GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



was found in a tract of land about six miles long, east and west, and 

 about five miles wide, north and south. Another locality where it is 

 very conspicuous is near the center of Sec. 17, T. 7, R. 4 E. In a 

 ditch by the side of the road, it appears as a very dark-red sandstone, 

 streaked occasionally with yellow, and overlaid by a dark-brown, 

 earthy, ferruginous shale. 



Along the road for some distance above this outcrop, there is a 

 sandstone containing seams of iron ore. The formation appeared to 

 be about sixty feet thick and unfossiliferous. The country here is so 

 deeply covered with fallen rock, from the overlying formations, that 

 it is difficult to determine the precise horizon of the different beds. 

 The same beds were traced out to the K. "W. qr. of Sec. 7, T. 7, R. 4: 

 E., where they present the same appearances. In each of these local- 

 ities, the thickness of the overlying Lower Magnesian does not exceed 

 100 feet. 



From the results of certain experiments instituted upon the shales 

 designated in the section as No. 4, we are inclined to think they 

 would make a tolerable quality of hydraulic lime, although they are 

 not sufficiently quick-setting to make a good hydraulic cement. 



It will be seen from an inspection of the foregoing section, that no 

 sandstone is included in the Lower Magnesian formation which ex- 

 tends to B. Some geologists, however, place the line dividing the 

 two formations between the beds numbered nine and ten under B in 

 the section, p. 668, thus including the Dicellocephalus shales and lime- 

 stones, as well as the upper bed of sandstone, in the Lower Magne- 

 sian formation, and beginning the Potsdam with the bed numbered 

 ten. If this arrangement were adopted, the Lower Magnesian would 

 sum up as follows: Limestone above the sandstone bed No. 3 of the 

 section, full thickness, 250 feet; sandstone, 45 feet; shales and lime- 

 stone, 61 feet, making a total of 356 feet, which is much greater than 

 has heretofore been attributed to the formation. On the whole, it has 

 seemed best, on paleontological grounds, for the sake of "perspicuity, 

 and to avoid confusion in comparison with other reports, to respect 

 the old landmarks, of subdivision, especially as bed No. 4 contains 

 the characteristic Potsdam fossils. 



Paleontology. The fossil remains of this formation seem to bo 

 chiefly confined to the calcareous strata and argillaceous shales, de- 

 scribed under numbers 4 and 6 of the foregoing section, the most 

 productive being those which immediately overlie the limestone 

 quarry rock. All the quarries from Black Earth to Boscobel were 

 examined, and, in all, more or less specimens were found. The re- 

 mains consist chiefly of JLingula aurora and Dicellocephelus Minne- 



