406 



Illinois Natural History Survey Bulletin Vol. 26, Art. 5 



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Fig. 19. — Part of the clitf at Principia, near Elsah, Jersey County, with sharp rock salients 

 that project beyond the spur frnnts above. 



Im 



Fig. 20. — An upper slope of a cove of Principia hill prairie with a mixture of prairie plants. 

 R/ius glabra, and small oaks. 



