30 CLASS GASTEROPODA. 
recurved in the adult, and assumes an uregular and plaited 
form. (H. ringens, Chemn.) 
VITRINA, Drap. HeEttico-Limax, Feérus., 
Are snails with a very thin flatted shell, no umbilicus, large 
aperture, and margin not swelled. The body is too large to 
be withdrawn entirely into the shell. The mantle has a dou- 
ble border; the upper one, which is divided into several lobes, 
may extend considerably beyond the shell, and fold back on it 
to rub and polish it. 
Those which are known in Europe live in humid places, and 
are very small. (Helix pellucida, &c.) 
There are larger ones in the hot climates. 
We should approximate to these some snails, which, with- 
out having the double border, do find some difficulty in with- 
drawing into their shell. (Helix rufa et brevipes, Féruss.) 
When the crescent of the aperture is higher than it is wide, 
a disposition which always obtains when the spire is oblong 
or elongated, it constitutes the 
BuLIMUS TERRESTRIS, Brug., 
Which requires a still further sub-division : as follows. 
BULIMUS (proper), Lam. 
Margin of the aperture tumid in the adult, but without den- 
ticulations. . 
Hot climates produce large and beautiful species; some of 
these are remarkable for the size of their eggs, the shell of 
which is of a stony hardness; others for their awkward-look- 
ing shell. 
Several moderate sized or small species are found in France, 
one of which (Helix decollata, Gm.) Chemn. cxxxvi. 1254— 
1257, has the singular habit of successively fracturing the 
whorls of the top of the spire. ‘This is the example referred | 
