34^ Shell Life 



furnished with an arched and ribbed jaw, and the 

 outer teeth of the well-furnished radula are them- 

 selves toothed — that is, their edges are cut up like 

 the edge of a saw. 



There is no operculum to close the shell in Helix, 

 but to prevent undue evaporation in summer the 

 mouth of the shell has a film of mucus spread across 

 it, and this rapidly hardening keeps the dry air out 

 and the moisture inside. In winter this epip]iragr}i, 

 as it is called, is again produced, but then consists 

 of many layers, because it has to last much longer 

 and exclude cold. At this period the snails have 

 usually retired to some sheltered corner among dead 

 leaves, or in the crevices of walls, where they can sleep 

 through the inclement season secure against wet and 

 frost, and from which they emerge Avith the warm 

 spring rains. Their eggs are roundish and enclosed 

 in tough " shells " — in the case of the Roman Snail it 

 is really a shell containing much lime — which are 

 laid in little heaps, often in burrows excavated by 

 the foot of the snail. We have already mentioned 

 the '•' love darts " of certain species of Zonifes, Avhich 

 connect that genus with Helix, in which the possession 

 of these singular instruments is characteristic of about 

 two-thirds of the native species. 



Twenty-five British species are included in the 

 genus Helix by the principal systematists, but from 

 time to time others have broken off" a few species 

 here and there to make new genera ; and quite 

 recently there has been a tendency on the part of 

 some conchologists to respect all these little genera, 

 with the result that the important genus Helix, as 

 most people know it, is left with only a few species 



