60 
animal possesses tlie faculty of crawling on tlie surface of tlie water, 
in a reversed position, tlie shell downward. 
G-eyus Lymn^a. — Shells suhovate, ohlong or somewhat taper- 
ing. Aperture entire, longitudinally ohlong, the right lip circu- 
larly joined to the left at the base and folded hack on the pillar. 
LymntEA columella. — Shell thin, fragile, horn-color ; whorls 
four, longitudinally wrinkled. Spire prominent, acute. Suture 
not much impressed. Aperture dilated, ovate. Columella much 
narrowed near the base, so that the view may he extended from the 
base almost to the interior apex of the shell. Length seven-tenths 
of an inch nearly ‘ of the spire one-quarter of an inch. 
Inhabits stagnant waters and miry places. Collection of the 
Academy. 
Animal aquatic, base not so long as the aperture ; dusky, with 
small whitish spots ; tentacula broad, pyramidal, compressed ; eyes 
small, black, placed at the inner base of the tentacula. 
This species is allied to A. catascopium of the American edition 
of Nicholson’s Encyclopedia, but the revolution of the whorls is 
more oblique, the shell thinner, the aperture much more dilated, 
and the columella differently formed. For several specimens of 
this shell I am indebted to Mr. Titian Peale. 
[J. A. N. S. vol. i. p. 124, et seqq., Oct., 1817.] 
Genus Ancylus. — Shell conic, not spiral, concave beneath, 
above with a simple apex. Animal with the eyes placed at the 
inner base of the tentacula. 
Ohs. This genus has been by writers confounded with the 
Patellee. The European species are Patella lacustris and jhiviati” 
Us of Linne. 
Ancylus rivularis.- — Shell corneous, opake, conic-depressed, 
apex obtuse, nearer to, and leaning towards, one side and one end ; 
aperture oval, rather narrower at one end, entire ; within milk- 
white. 
Length one-fourth of an inch. Cabinet of the Academy. 
Common, adhering to stones in rivulets ; the animal resembles 
the inhabitant of shells of the genus L^m'iisea, the tail is very ob- 
tuse, rounded. , 
