PLATE rv 



1. Platyceras ? vetulum n. sp. Apical view. 



2 and 3. Lingula morsii N. H. Winchell. Outline of a cast (2) and of a 



shell (3). Both specimens are under the average size. 

 4. Orthis cf. perveta Conrad. From an imperfect cast of a ventral valve. 

 5 and 6. Rau fella fucoida n. sp. 



7. Modiolopsis fountainensis n. sp. Cast of right valve. 



8. Modiolopsis postica n. sp. 



9. Transition from Saint Peter to Trenton near Fountain. 



a. Coarse sand and small ferruginous pebbles and argillaceous shale. 



b. Coarse light yellow sand ; 3 feet 6 inches, variable. 



c. Argilaceous shale, mixed with sand and lime at the top and bot- 

 tom ; 4 feet. 



d. Coarse sand. 



e. Firmer ferruginous laminae. 



The formations above and below these strata are characteristic Trenton and 

 Saint Peter. 



10. Contact of Shakopec and Saint Peter formations near Pickett Station , 

 Wisconsin. 



a. Saint Peter. 



b. Green shale laminae. 



c. Dolomite, much folded, exposed in elevation about 20 feet, 

 a b c. Illinois Central railway track. 



