9.2 



.CONCHOLOGIA CESTRICA. 



Shell, elongate, arcuate, cylindric-ovate ; anterior end 

 rounded; posterior produced; ligament margin regularly 



Jtfargaritana margaritifera. 



Fig, 189, 



curved, and carinate behind the hinge ; base arcuated ; 

 beaks slightly elevated ; epidermis brownish - black ; 

 nacre whitish, posteriorly iridescent ; teeth stout, 

 grooved. H. 2.25, W. 5, T. 1.5, inches. 



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, 



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



