TAHLE I I. 



n. 



FOSSILS or THE SIIELL-BEPS (F. III., A) AND OVERLYING LH AD-nEARING BEHS ( I'. III., B) OF THE I'PPER MAONESIAN 



LIMESTONE OF WISCONSIN, IOWA, AND MINNESOTA. 



Medal-rnletl on Sleel, from the Oi'iyiiia! Speciinen.s. 



Tab. II. B., Fig. 1. CyrtoUtcs ornatKS (?), three miles above Fort Snelling. 



" Fig. 2. Pygidium o{ Phaio]}s (N. S. ?) Turkey River, Iowa, associated with Fig. 1, Tab. II. A. 



" Fig. 3. Leptana (N. S.?), near the base of tlie Upper Magnesian Limestone of Wiscon.sin, above Savannah ? 



" Figs. 4, 5. Orthis subjugata (1), three miles above Savannah, in tVie shell-beds at the base of the Upper Magne- 

 sian Limestone of Wisconsin. 

 This fossil may possibly be a new species, as it difi'ers from O. snbjugata in the umbo being more 

 elevated, and in the size and prominence of the ribs, as well as in their mode of bifurcation. 



" Figs. 0, 7, 14, 15. Orihis tesludiiiaria. The specimens here figured are from Ohio; they were selected for 

 representation as being more perfect than those hitherto collected in the Northvifest, to test the appli- 

 cability of the medal-ruling process to fossil shells of this character. 



" Fig. 8. Lingula quadrata ('?), from the lead-bearing beds of the Upper Magnesian Limestone, near Dubuque, 

 Iowa. 



" Fig. 0. Orthis, undetermined, in the shell-beds, F. 3, .A., above Savannah, Wisconsin. 



" Fig. 10. Leplana deltoidea, Falls of St. Anthony, Minnesota, in the shell-beds F. 3, a. 



" Fig. 11. Orthis pcctinella, in the shell-bed F. 3, A, at Prairie du Chien. 



" Fig. 12. Lcpt(?iia sericea (1.), and Orihis (undetermined), from Great Lake Winnipeg. 



" Fig. 13. Scknoides lowensis, (N. S.) Turkey River, Iowa, associated with Figs. 8 and fi, Tab. II. 



" Fig. IG. Lepfcena (N. S.?), in the shell-bed, F. 3, A, at the Big Springs, near the Upper Iowa River. 



Fig. 17. Lingula (nndet.) Lower Fort Garry, Red River of the North. 

 " Fig. 18. Tcrfhratvla {\\\v\eX.) Lower Fort Garry, Red River of the North. 



" Fig. 10. Plcurorhynchus anliqua. This small and delicately-formed Pleurorhynchus is, I believe, the first of the 

 genus that has been discovered in this country in rocks of Lower Silurian date. 



" Fig. 20. Ort/fis (undet.), allied to 0. occidentalis, in the shell-beds, F. 3, A. three miles above Savannah, Wis- 

 consin. 



" Fig. 21. Ltplcena (N. S. ?), allied to deflecla, in the shell-bed, F. 3, A, three miles above Savannah. 



" Fig. 22. Cytherina (undet.), from the outcrops of magnesian limestone, equivalent to F. 3, a, at the Great South 

 Bend of Red River of the North. 



" Fig. 23. Orihis disparilis. Agency, Turkey River, Iowa; shell-beds at the base of the Upper Magnesian Lime- 

 stone. 



