MOLLUSCA. 



larges the shell by successive additions to its outer 

 edge. It is also by the same medium that acci- 

 dental injuries to the shelly covering are repaired. 

 Mr. Bell observes, "I have at different times cracked 

 the shell, removed small portions, and drilled holes 

 through it at different parts ; and I have found that 

 if the injury were within the reach of the edge of 

 the mantle, it was always drawn up to repair it. 

 I drilled a hole in the shell of Helix Pomatia in 

 the last whorl but one, thinking that it could not 

 draw the edge of the mantle high enough to repair 

 it in the usual way ; however, it effected this imme- 

 diately by protruding the foot to make room for 

 the mantle being drawn high up into the shell, and 

 as soon as the edge came in contact with the injured 

 part, it was passed repeatedly over the hole, leaving 

 a layer of calcareous matter each time until it be- 

 came opaque ; and in a day or two, on examining 

 it, I found the newly-formed part apparently as 

 strong as the rest of the shell." * 



lanthina^ the Violet Snail. 



Though belonging to a different order, the shell of 

 this Gasteropod much resembles that of the Snail ; 

 the animal, however, which is marine, differs mate- 

 rially. It has no operculum, but the under surface 

 of its foot is furnished with what appears to be a 

 mass of foam-bubbles, but composed of a solid sub- 



* Zool. Jour. vol. i. p. 93. "f- 'lavAvoj, ianthinos, purple. 



