190 PLANORBIS. 
2. PLANORBIS HORNII, Tryon. 
Plate 5, fig. 3, 4. 
Shell large, consisting of three convex volu- 
tions; aperture almost orbicular, not oblique, 
nor extending above or below the plane of the 
whorls; labrum slightly reflected, thickened 
within, its ends converging so as nearly to 
connect on the parietal wall; lines of growth 
fine and close. Color light horn. 
Diameter 21, alt. 7 mill. 
Fort Simpson, British America. Dr. Geo. 
H. Horn. 
Grant’s Lake, California. W. M. Gabb. 
Not so depressed as the preceding, smoother, 
the growth lines being much closer and but 
little elevated, and very different in the form 
of the aperture. 
(37) 
