254 Trans. Acad. Sci. of St. Louis. 



Lampsilis gracilis Barnes. 

 Common. 



Obovaria ellipsis, Lea. 



Common. Fifty per cent of this species bore pearly secre- 

 tions ; one specimen contained two pearls in the umbonal 

 cavity. 



Plagiola securis Lea. 



Not common. Pearly secretions rare. 



Plagiola elegans Lea. 



Common. No specimens were seen with pearly secretions. 



Tritogonia tuberculata Barnes. 



Common. Fifty per cent bore pearly secretions. Only 

 onejspecimen was distorted. 



Obliquaria reflexa Rafinesque. 



Common. Seventy-five per cent contained pearly secre- 

 tions. 



Strophitus edentulus Say. 



Common. Pearly secretions rare. Nacre pure white to 

 brilliant salmon. Distortions rare. 



Anodonta grandis Say. 

 Common. 



Anodonta grandis Say, Var. gigantea Lea. 

 Common. 



Anodonta corpdlenta Cooper. 



Common. Diseased shells frequent. 



Arcidens confragosus Say. 



Common. Pearly secretions rare. Twenty-five per cent 

 of this species were distorted. 



Symphynota costata Rafinesque. 



Common. Nacre varying from white to salmon. No 

 pearly secretions. 



