155 
LYMNAA. 
Gen. Cuar. An oblong subturreted univalve ; the 
aperture entire, longer than wide ; lower part 
of the right lip entering the aperture, and 
forming a very oblique plait along it. 
J ee Helix stagnalis of Linneus, is Lamarck’s type of 
this Genus, and upon a comparison of this with the 
Helix pomatia, the propriety of their separation is im- 
mediately visible. The Lymnea is an elongated pointed 
shell; in general it is smooth, tender, and has to boast 
of very little variety of colour: the recent species are 
known inhabitants of fresh water pools or rivers, and the 
few fossil ones hitherto met with belong, exclusively, to 
the newest depositions. 
The thinness and semi-transparency or horny aspect of 
the shells of this; and many other fresh water Genera, is 
a great help towards distinguishing the fresh water for- 
mations from those of the salt water. 
LYMN A fusiformis. 
TAB. CLXIX.—Fig. 2 and 3. 
Srec. Cuar. Subfusiform, smooth; sides of the 
spire nearly straight ; aperture narrow, half 
the length of the shell. 
EES 
T nz narrowness of the mouth of this makes the two ends 
almost equally taper; the spire is pointed ; the strie of 
erowth are tolerably sharp, between them the surface is 
VOL... /{/7% BY XKA 
