PLATE XVIII. 



PAGE 



ALLOBISMA ILLISOIENSIS Worthen 132 



Fig. 1. View of a left valve, natural size. 

 Fig. 1 a. Profile view of the dorsal margin. 



LEPTODOMUS? MAGNUS Worthen 107 



Fig. 2. View of right valve, natural size. 

 Fig. 2 a, Dorsal view of the s me. 



PLEUROPHORUS MONKOENSIS Worthen 125 



Fig. 8. Outline view of left valve, natural size. 

 Fig. 3 o. Same valve enlarged 2X. 



BAKEVELLIA LLLINOIENSIS Worthen 126 



Fig. 4. View of left valve, natural size. 

 Fig. 4 a. Profile view of the same. 



SOLENOMYA MONROENSis Worthen 131 



Fig. 5. View of a left valve, natural size. 

 Fig. 5 a. Dorsal view of the same. 



EDMONDIA ILLINOIENSIS Worthen 122 



Fig. 0. View of an imperfect right valve. 

 Fig. 7. Typical specimen, right valve. 

 Fig. 7 a. Dorsal view of the same. 



SCHIZODUS DEPRESSUS Worthen 10S 



Fig. 8. View of right valve, natural size. 

 Fig. 8 a. Dorsal view of the same. 



