116 
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ILLINOIS BIOLOGICAL MONOGRAPHS (214 
EXPLANATION OF PLATE 
Anodonta grandis. 
Anodonta grandis. 
Anodonta grandis. 
Amblema undulata. 
Amblema undulata. 
Amblema undulata. 
Amblema undulata. 
margin of shell. 
Pathologic mussels from Salt Fork. 
Right valve with pearly growths at anterior end. 
Left valve with injured portion folded inward. 
Pearly formation in left valve. 
Right valve uninjured. 
Left valve with large blister inside pallial line. 
Left valve with abnormal pallial line. 
Left valve with pin-head pearls between pallial line and 
