112 ILUNOIS BIOLOGICAL MONOGRAPHS [210 



EXPLANATION OF PLATE 



Fig. 16. Salt Fork and mouth of Spoon River. Rowboat marks outlet of Spoon River 

 through bar. September 24, 1920. 



Fig. 17. Valley of Big Vermilion River from crest of bank at Gray's Siding. October 8, 

 1920. 



Fig. 18. Cutting through shale rock covered with glacial deposits. Big Vermilion River 

 one mile below mouth of Middle Fork. Station 30. October 8, 1920. 



