256 Trans. Acad. Sci. of St. Louis. 



variety which this species exhibit in the pustulosity of its 

 shell, the extremes being perfectly smooth and densely pustu- 

 lose. Distortions rare. 



QUADRULA PUSTULATA Lea. 



Not common. 25 per cent contained pearly secretions. 



QUADRULA TRIGONA Lea. 



Very common. The nacre of the specimens from this lo- 

 cality varies from white to salmon-pink. Pearly secretions 

 are common, at least 70 per cent containing abnormal pearly 

 matter. One specimen contained an erect, sharp piece of 

 pearly matter extending across the middle of the anterior 

 muscle scar. 



Quadrula obliqua Lamarck. 



Very rare. Only one specimen secured. 



Quadrula ebena Lea. 



Very common. This is the pearl shell par excellence to 

 the mussel fishermen. Of those secured, 25 per cent con- 

 tained pearly secretions and one specimen had the left valve 

 badly diseased. Distortions rare. 



Quadrula granifera Lea. 



Apparently rare. Only two specimens were obtained. 

 The nacre is of a peculiar deep copper color. 



Class GASTROPODA. 



Family Viviparidae. 



VlVIPARA INTERTEXTA Say. 



Common in the Mississippi River. 



Vivipara subpurpurea Say. 

 Common. 



Campeloma integrum De Kay. 

 Common. 



