LIMNAEA. 103 
19. LIMNASA SMITHSONIANA, Lea. © 
Plate 18, fig. 2. 
Shell fusiform, rather thin, reddish-brown, 
slightly transparent, slightly umbilicate, very 
minutely and transversely striate; spire ob- 
tuse; sutures impressed; whorls six, convex; 
aperture rather large, ovate, brown within the 
margin; outer lip expanded; columella some- 
what thickened and scarcely plicate. 
Length 12, diam. 8 mill. 
Loup Fork of the Platte River. 
Very like L. humilis, Say, but much larger. 
20. LIMNA FERRUGINEA, Haldeman. 
Hald. Monog. 49, t. 13, figs. 19, 20. 
(77) 
