TABLE I. 



B. 



SPECIMENS CONTAINING LINGULA, OBOLHS, AND ORBICUtA, FKOM NEAR TUB BASE OE THE LOWEST PItOTOZOIC 



SANDSTONES OF WISCONSIN AND MINNESOTA. 



Medul-ru]<?d on Steel iVoni ihe Original Specimens. 



Tab. I. B, Fig. 1. Slab, containing several species of Lingiilas and Orbiciilas, from the Falls of St. Croix. This engraving 

 illustrates beautifully not only the capabilities of the inedal-niling process lot such subjects, but the 

 highly fossiliferoiis character of these beds, near the base of a formation at one time supposed to be 

 nearly barren or entirely destitute of organic remains. 

 " Figs. 2, 7, 10. Slabs, conVdining Lingida antiqita and Lingula prima (Y), in F. 1, b, from the Falls of St. Croix. No 

 essential difference has been discovered between some of the Lingulas in these slabs and those of 

 Lingula aniiqua and prima of the Potsdam Sandstone of the State of Nevi' York, except in size ; the 

 Sr. Croix specimens being usually much larger. 





Figs. 



4, 



0, S. Lingula pinna/ormis (N. S.) In F. 1, Ik Falls of St. Croix. 





Figs. 



3i 



14. Slabs of Obolus grits, from the banks of the Mississippi, nearly opposite, ihe old mouth of Black 









River. 





Figs. 





12. Lingula arnpla (N. S.) From the Lingula grits, member c, of F. 1, Upper Mississippi River, near 









Mountain Island. 



It 



Figs. 



0, 



11, 15, 20. Obobis [Appolinus f) . From member i, of the grits below Movjntain Island, nearly opposite 









the old mouth of Black River. 





Figs. 



i; 



:!, I'i, 17, 18 (?), 19, and middle figure in 8. Orbicula prima (N. S.) From the lowest layers at the Falls 









of St. Croix. 



> 



