LIMN^AD^. 



197 



The following Table respecting the eggs of Lim- 

 nceadcB is drawn up from M. Bouchard's observations, 

 the first column giving the form of the masses of 

 eggs, the second the number of eggs in each mass, 

 the third the number of days after they are laid 

 before they hatch. 



Limnea auricularia 

 . ovata - 



peregra 



stagnalis 



palustris 



fossaria 



Amphipeplea glutinosa 

 Physa hypnorum 



fontinalis 



Velletia lacustris 

 Planorbis contortus - 



corneus 



albus 



imbricatus 



vortex 



marginatus 



carinatus - 



nitidus 



elliptical 



cylindrical 

 rounded 



round or oval 

 roundish 

 orbicular 



It had been supposed that the shells of fluviatile 

 Mollusca could be distinguished from those of the 

 terrestrial kind, by the edge of the mouth of the 

 shell never being furnished with a thickened in- 

 ternal rib, and not being in the slightest degree 

 reflexed, and that the animal never closes it with an 

 epiphragm ; however, further examination has shown 

 that when the Pond-snails and the Whirl-shells are 

 left nearly dry by the evaporation of the water, 

 o 3 



