155 
LYMNJSA. 
Gen. Char. 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. 
i he 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. 
LYMNiEA fusiformis. 
TAB. CLXIX.— Fig. 2 and 3. 
Spec. Char. Subfusiform, smooth ; sides of the 
spire nearly straight ; aperture narrow, half 
the length of the sheik 
The narrowness of the mouth of this makes the two ends 
almost equally taper ; the spire is pointed ; the stri® ©f 
growth are tolerably sharp, between them the surface is 
VOL. II, 
