Explanation of Plates I. and II. 



Pirate I. Exposure of St. Peter sandstone northeast of Hesper, Iowa, 

 looking north. Prunus pumila grows on its summit. (See p. 226.) 



Plate II. Same exposure, but looking east. The shrub on the left 

 side of the ledge is Aroiiia nigra. (See p. 226). 



