65 
Grreatest length of the body whirl, one-fourth of an inch Breadth 
from tip of the labmm, one half of an inch ; at right angles to the 
last, two-fifths of an inch. 
This shell abounds in some of the small streams, which discharge 
into Cayuga lake, where it was collected by Mr. J essup, who pre- 
sented specimens to the Academy, and to me. It is readily dis- 
tinguished from our other species, by the sudden dilatation of the 
outer whirl, near the aperture in the adult shell, forming a large 
oval chamber. The summit of the outer whirl, behind the dilated 
portion, is not, or hardly elevated above the summits of the other 
volutions. 
Lymneus elongates. — Shell horn color, tinged with reddish- 
brown ; spire elongated, tapering, acute ; whirls six or seven, 
slightly convex, wrinkled across ; body whirl, measured at the 
back, more than half the total length • suture moderately indented ; 
aperture less than half the length of the shell ; labium with calca- 
reous deposit. 
Length, one inch and three-tenths. 
Inhabits in considerable numbers, the ponds and tranquil waters 
of the Upper Missouri. It is very distinct from L. catascopmm.y 
by the much greater proportional length of the spire. 
Lymneus columellus. — (Jour. Acad. Nat. Sciences, vol. i. 
p. 14.) Var. a. Small, black — from Cold water creek of the Mis- 
souri. This is most probably a distinct species ; we obtained but a 
single specimen of it. 
Lymneus reflexes. — Shell fragile, very much elongated, nar- 
row, honey-yellow, tinctured with brownish, translucent, slightly 
reflected from the middle ; volutions six, oblique, wrinkled trans- 
versely ; spire more than one and an half times the length of the 
aperture, acute, two or three terminal whirls vitreous ; body whirl 
very little dilated ; aperture rather narrow , labrum with a pale 
margin, and dusky red or blackish sub-margin. 
Inhabits Lakes Erie and Superior. Total length, 13-10 — of the 
aperture 11-20 of an inch. 
This shell is remarkable for its narrow and elongated form, and 
for the consequent, very oblique revolution of its whirls. When 
viewed in profile, it has a slightly reflected appearance. It was 
kindly sent to me for examination by my friends Messrs. S. B’. 
