112 ILLINOIS BIOLOGICAL MONOGRAPHS {210 
EXPLANATION OF PLATE 
Fic. 16. Salt Fork and mouth of Spoon River. Rowboat marks outlet of Spoon River 
through bar. September 24, 1920. 
Fic. 17. Valley of Big Vermilion River from crest of bank at Gray’s Siding. October 8, 
1920. 
Fic. 18. Cutting through shale rock covered with glacial deposits. Big Vermilion River 
one mile below mouth of Middle Fork. Station 30. October 8, 1920. 
