252 Trans. Acad. Sct. of St. Louis. 
those that contained none, or only traces of pearly secre- 
tions. 
Pearl abundant. Pearl absent. 
Lampsilis ventricosa. Lampsilis ligamentina. 
Symphynota 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. Woodruff 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 
ridge one and one-fourth inches long near the muscle scar. 
