252 Trans. Acad. iSci. of St. Louis. 



those that contained none, or only traces of pearly secre- 

 tions. 



Pearl abundant. Pearl absent. 



Lampsilis ventricosa. Lampsilis ligamentina. 



Syniphynota complanata. Lampsilis recta. 



Quadrula trigona. Plagiola securis. 



Quadrula ebena. Plagiola elegans. 



Unio gibbosus. 

 Quadrula plicata. 

 Quadrula pustulosa. 



The Unio fauna was numerous in individuals but only thirty- 

 five species were secured. It is probable that a more ex- 

 tended study, covering several years, would bring to light 

 many additional species. 



My thanks are due to Mr. A. B. Wolcott for collecting 

 many of the land shells, to Mr. W. H. C. Elwell for several 

 shells and a number of rough pearls, to Mr. Williams and to 

 Mr. W. K. Higley for assistance in collecting small land snails 

 on the hills west of McGregor, and to Mr. F. M. Woodrulf for 

 assistance in collecting the Unionidae. The small land snails, 

 Strobilops, Bifidaria, Helicodiscus and Zonitoides were col- 

 lected near a spring which issued from the shale on the side 

 of a hill about two miles northwest of McGregor, the land 

 belonging to Mr. Williams. 



Catalogue of Species. 

 Class PELECYPODA. 



Family Unionidae. 



Lampsilis ventricosa Barnes. 



Common. Nearly half the specimens of this species con- 

 tained pearly secretions of various sizes ; these were mostly 

 confined to the posterior end and were more abundant about 

 the posterior adductor muscle. One specimen has a knife-like 

 ridsre one and one-fourth inches long near the muscle scar. 



