64 
This shell has evidently the habit of a Helix, and may probably 
belong more properly to that genus, but having found it only in a 
dried up pond, in company with a vast number of aquatic shells, I 
refer it for the present to this genus. 
Planorbis exacuous*. — Dextral, depressed, with an acute 
edge. 
Inhabits Lake Champlain. Cabinet of the Academy. 
Shell depressed 3 whorls four, striated across, wider than long, 
not elevated above the suture, but a little flattened, sides obliquely 
descending to an acute lateral edge, below the middle ; spire not 
impressed ; suture not profoundly indented ; beneath, body whorl 
flattened, on the inner edge rounded ; umbilicus regular, exhibit- 
ing all the volutions to the apex ; aperture transversely sub-trian- 
gular ; labrum angulated in the middle, arquated near its inferior 
tip, the superior termination just including the acute edge of the 
penultimate whorl. 
Greatest breadth, rather less than \ of an inch. 
This species was found in Lake Champlain by Mr. Augustus 
Jessup, who deposited it in the collection of the Academy. Only 
two specimens occurred. It may be readily distinguished from P. 
parvus, by its more convex form above, the spire not being im- 
pressed, and by its very acute lateral edge. It appears to be pretty 
closely allied to Planorhis nitidus of Europe, but it is larger, 
the umbilicus much more dilated, and the aperture does not em- 
brace the penultimate whorl so profoundly. 
Planorbis campanulatus. — Sinistral; whorls longer than 
wide ; aperture sub-campanulate. 
Inhabits Cayuga Lake. Cabinet of the Academy. 
Shell sinistral, not depressed ; whorls four, slightly striate across, 
longer than wide ; spire hardly concave, often plane ', body whirl 
abruptly dilated near the aperture, and not longer behind the dila- 
tation than the penultimate whirl ; suture indented, well defined 
to the tip, the summits of the volutions being rounded ; aperture 
dilated ; throat narrow abruptly ; umbilicus profound, the view 
extending by a minute foramen to the apex. 
[* It would certainly appear that Mr. Say intended this word to read 
exacutus, as Dr. Gould suggests, — jei the same orthography is retained 
in Long’s Exp. — E d.] 
