118 ILLINOIS BIOLOGICAL MONOGRAPHS [216 



EXPLANATION OF PLATE 



Fig. 29. Amblema undulaia. Left valve with channel due to injury. 



Fig. 30. Amblema undidata. Right valve with ridge due to same injury. 



Fig. 31. Strophitus edentidus. Right valve with pearl near posterior end. 



Fig. 32. Strophitus edentidus. Left valve with distomid discoloration. 



Fig. 33. Lasmigona costata. Right valve with repaired injury near posterior end. 



Fig. 34. Amblema undulata. Spoon River form with rounded shell. 



Fig. 35. Lampsilis ventricosa. Left valve with injured postero-ventral margin. 



Pathologic mussels from Salt Fork. 



