LYMN.^ANA. 167 



roiir genera pertain to the family LymncEana : — Planor- 

 his, Lf/mncea, Physa, Ancylus. No further particuhars of 

 interest are recorded concerning this family ; but the mind 

 is naturally directed to that inexplicable faculty, by means 

 of which these apparently insignificant creatures are enabled 

 so to use their breathing-organs, or else by internal me- 

 chanism readily to separate from the water so much air as 

 suffices to preserve them when completely overflowed. 



The lungs of land animals bear a relation to the air, as 

 a permanently elastic fluid, and by such relationship they 

 live and move ; they cannot breathe in water, neither is it 

 necessary — they have an important mission to fulfil on land : 

 with the family of Lymnceana the case is different. As yet, 

 nothing is ascertained concerning the purpose which they 

 are designed to effect in the economy of nature ; though, 

 doubtless, there is a purpose ; why else the power of sus- 

 pending the action of their breathing-organs, by which 

 the breath of life is preserved in them ? 



Shells of the Lymncnaiia are rather thin and smooth ; the 

 aperture is generally large, with a simple, acute, but never 

 reflected margin. 



