24 



rilESH-WATEE SHELLS. 



hence, perhaps, the scientific name applied to the family in 

 which they are mostly included — Limncbidce, which, like limti — ■ 

 to paint, agrees with the Trench cnlmniner. These molkisks 

 are found in rivers, streams, ditches, and moist marshy places. 

 Like those which live wholly on land, they breathe through 

 lungs, and therefore cannot exist without air; which accounts 

 for their frequently coming to the surface, when under Avater. 

 In brooks, as well as in stagnant pools, which abound with 

 aquatic plants, they may be found in vast numbers, feeding 

 U2>oii the moist vegetation. 



-^ 



The Common Limnea, (L. stagnalisj is mostly an inhabitant 

 of stagnant waters, where it is often seen floating with the 

 shell reversed, as in a boat; this shell, like most of those 

 of the Fresh- water Mollusks, is thin, and easily broken; the 

 shape it will be seen, is peculiarly elegant, the sj^ire being 

 slender and pointed — very different from that of the Spreading 

 Limnea, called by naturalists, L. auricularia, from aurus — 

 the ear, to which the broad apei^ture, or opening of the shell, 

 may be compared; this resembles the other species in its habits. 



The Horny Planorbis, in Latin 

 P. cornens, from cornu — a horn. 

 The shape, you will see, is flat, 

 the whorls rolling upon each 

 other like the folds of a bugle 

 horn ; this shape would be termed 

 orbicular, from orlis — a sphere, 

 or circular body. This is the 

 largest European species of Fresh- 

 water Shells so constructed; it is 



