67 
tliaiQi the spire ; labium, calcareous depo-sit copious, not perfectly 
oppressed at base, but leaving a very small umbilical aperture. 
Inhabits Cayuga Lake. Length 7-10 of an inch.* 
-Found by Mr. Augustus J essup. It is closely allied to L. ehdeSj 
but the whirls are more convex, one less in number, and the two 
terminal ones are proportionally smaller ; the callus of the labium, 
also, near its inferior termination, is applied still more closely to 
the surface of the body whirl. 
Lymneus macrostomus. — Shell suboval; whirls five, body 
whirl somewhat reticulated ; suture not profoundly indented ; spire 
about two-thirds of the length of the aperture, acute ; aperture 
much dilated ; labrum not thickened on the inner sub-margin. 
Inhabits Cayuga Lake. Length one half of an inch, and up- 
wards. 
Imperfect specimens of this shell were found on the shore of 
Cayuga Lake, by Mr. A. J essup, but they are sufficiently entire, 
to exhibit considerable similarity to some varieties of L. auricu- 
larius of Europe. It may readily be distinguished from L. catas- 
copium, by its much more dilated aperture. 
Lymneus emarginatus. — Shell rather thin, translucent; volu- 
tions four, very convex; body whirl large; suture deeply im- 
pressed ; spire somewhat eroded ; mouth two-thirds of the length 
of the shell. 
Length nearly 4-5 of an inch ; of the mouth, half inch. 
Inhabits Lakes of Maine. This species was discovered by Mr- 
Aaron Stone. 
It is a rather larger and considerably wider shell than L. catas- 
copium, and the emargination visible on a profile view of the 
umbilical groove is far more profound. 
Physa gyrina. — Shell heterostrophe, oblong ; whirls five or 
six, gradually acuminating to an acute apex ; suture slightly im- 
pressed ; aperture more than one half, but less than two-thirds of 
the length of the shell ; labrum a little thickened on the inner 
margin. 
Length rather less than one inch. 
Inhabits waters of the Missouri. 
[* 'Tlie text gives 7-20ths, wkicli is corrected by Mr. (Say in. tbe remarks 
on L. humilis.—ED,~\ 
