STATE OF ILLINOIS 

 DWIGHT H. GREEN, Governor 

 DEPARTMENT OF REGISTRATION AND EDUCATION 

 FRANK G. THOMPSON, Director 



DIVISION OF THE 



STATE GEOLOGICAL SURVEY 



M. M. LEIGHTON, Chief 

 URBANA 



REPORT OF INVESTIGATIONS — No. 77 



CHESTER OSTRACODES OF ILLINOIS 



BY 



CHALMER L. COOPER 



PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS 



URBANA, ILLINOIS 

 1941 



