PLATE C. 



EXPLANATION. 



Figure 1. Dolomite from Lanesboro p. 155 



Magnified forty diameters. No. 16 of the systematic table. 

 Figure 2. Dolomitic limestone from Red Wing p. 164 



Magnified forty diameters. No. 17 of the systematic table. 

 Figure 3. Dolomitic limestone from Minneapolis, from the upper beds of the 



Trenton '. p. 165 



Magnified forty diameters. No. 22 of the systematic table. 

 Figure 4. Argillaceous limestone, St. Paul p. 172 



Magnified forty diameters. No. 28 of the systematic table. 

 Figure 5. Pinkish-yellow sandrock, from Hinckley p. 177 



Magnified 40 diameters. No. 30 of the systematic table. 

 Figure 6. The same between crossed Nicols. 



