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. 91 



AN ANNOTATED SYNOPSIS OF PALEOZOIC FOSSIL SPORES 



AND 



THE DEFINITION OF GENERIC GROUPS 



BY 



J. M. ScHOPF, L. R. Wilson, and Ray Bentall 



Prepared in collaboration with the Department of Geology, 

 Coe College, and the Tennessee State Division of Geology 



PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS 



URBANA, ILLINOIS 



19 4 4 



