Q2 CON CHOL OG VA CE SiR C Ay; 
Shell, elongate, arcuate, cylindric-ovate; anterior end 
rounded; postericr produced; ligament margin regularly 
Margaritana margaritifera. 
Fig, 189, 

curved, and carinate behind the hinge; base arcuated; 
beaks slightly elevated; epidermis brownish - black; 
nacre whitish, posteriorly iridescent; teeth stout, 
srooved. El. 225, W. 5 4.15, 1mehes: 
Station, creeks and ponds. White Clay Creek, Ches- 
ter County ; not common. 
M. undulata, Say. 
Unio undulata, Say, Nich. Encyc., 1st Amer. Ed., 1816. 
M, undulata. 
Fig. 190, 
2x8 

Shell, convex, elongate-oval, olivaceous, with obtuse, 
