60 HELICIDA. 
half. As in the last species the epidermis is raised into 
ridges in the line of growth, but in this shell the ridges are 
exaggerated into points. 
This is a beautiful object under a lens. It is pretty 
generally distributed, and is found among moss and 
dead leaves in moist shady situations. It may often 
be passed over as a small lump of dirt owing to its 
colour and shape. 
Var. albida. Colourless. 
3. H. pomAria (operculate). 
Globose, solid, cream-colour banded with red, coarsely 
striated in the line of growth; wmbilicus narrow. 
This fine shell is the largest of our snails. Though 
common on the Continent, it is only sparingly met 
with in a few localities in the south of England. It 
derives its name from a Greek word (poma) signify- 
ing an operculum, on account of the thick epiphragm 
which it makes on retiring into winter quarters. This 
epiphragm is formed by a secretion of the animal, and 
hardens on exposure to the air like plaster-of-Paris. 
When this thick plate closes the entrance, the animal 
retires deeper into the shell, and fortifies itself still 
further against the cold by a succession of thin films. 
The notion that this shell was introduced by the 
