104. LAND AND FRESH-WATER MOLLUSKS. 
and Suecinea, smooth, with a more or less pro- 
minent beak in the middle 
of its lower edge (see fig. 
18, which represents the 
Up 
horny jaw or buccal plate 
of the cellar snail). 
When the animal crawls, the shell is balanced 
nearly horizontally on its back. The tentacles 
are protruded and withdrawn with surprising 
quickness. The species feed on vegetable sub- 
stances, and inhabit damp or shady places, as 
under stones, or among grass or moss. 
The species are very difficult to distinguish ; 
I have given therefore full descriptions of each. 
The following analytical table may be found 
useful :— 
Fig.18. 
l Shell depressed, umbilicus apparent... ... ... 2 
; » trochiform, umbilicus minute ... ... H. fulva 
2. § Opacity around the umbilicus... ... ... ... .«. 3 
(No opacity jive sed oleae 
peer large ; very cloned Coleen Hl. cellaria 
3. « Upper surface more convex, dull... ... H. nitidula 
Shell smaller, surface shining... ... ... H. alliaria 
4. Shelli white ;. 4... 0 0.00 sec, ase es aes 
ie horn-coloured :.,.... .... s+ «+s ee 
5, Whorls not rapidly aeibe wae. A. crystallina 
Last whorl capacious «4... ... 0.) ths | ee eee 
6. Umbilicus very large... ... ... ... HL. excawata 
Umbilicus moderate eres 
. {Surface radiately striated ... ... ... H. radiatula 
a ) », transversely wrinkled... ... ... HH. niteda 
Ne ee 
