A RAMBLE OVER THE CHALK. 69 



vicinity of many ancient encampments. Several 

 such sites, moreover, could be named where this 

 large snail is not found ; and, as in Central Italy its 

 place is supplied by another species, Helix lucorum, 

 it is not by any means certain that it was known to 

 the Komans. 



Its large size the mouth alone measuring an 

 inch in diameter and the consistency of its body, 

 will readily distinguish it from all others of the 

 genus to which it belongs. It is furnished with a 

 peculiar epiphragm, or mouth-piece, by" means of 

 which it effectually closes the entrance of its shell, 

 and keeps out the cold and wet while it is hybernat- 

 ing. This lid, as we may term it, exactly fits the 

 mouth of the shell. It is a solid calcareous plate, 

 slightly convex, and is secreted and formed by the 

 mantle, resembling, until it hardens, liquid plaster 

 of Paris. After the animal has hybernated and 

 the fine weather has returned, this covering is 

 no longer needed, and is cast aside. A French 

 naturalist, M. Gaspard, who has paid considerable 

 attention to the structure and economy of this 

 species, says that when the period of hybernation 

 arrives .these snails get indolent, lose their appe- 



