GALLERY.] NATURAL HISTORY. 129 
the Testacella are peculiar for having the mantle and the 
ear-shaped shell on the posterior extremity of the body. 
This animal also has the power of extending the edge of the 
mantle, so that it can cover up the whole of the contracted 
body, and thus protect it from drought; its lips are cylindri¬ 
cal and retractile, like the tentacles: they live, the greater 
part of their time, in holes under the ground, where they 
feed on earth-worms. In all the other genera the mantle 
and shell are on the central part of the foot, and the lips 
are short and rounded, and sometimes serrated or torn be¬ 
neath. As the animals of the different genera are so simi¬ 
lar, it is necessary to divide them into sections, according to 
the form of the shell. The first section, which have been 
generally called Snails, have the whorls twisted round a 
short axis into a subglobose shell, with a crescent-shaped 
mouth, formed by the projection of the last whorl but 
one into its cavity. The animal has a distinct and 
variously divided vesicula multi/Ida. The true Helices , 
Helicodonta , &c., have the peristoma of the shell thick¬ 
ened, while the Helicophanta, Epistylium, and Proser¬ 
pina have it thin and sharp. The second group chiefly 
differ in the whorls being on a longer axis, so that the shell 
is oblong. These animals have no vesicula multijida , and 
the mouth of the shell is longer than it is broad. This 
group is again subdivided into those that have the mouth of 
the shell continued without interruption into the pillar lip. 
The axis of their shell is generally perforated, especially 
in the young state, for the animal, as it grows, sometimes 
covers the perforation with the reflexed portion of the inner 
lip; and the eyes are placed, as in the snails, on the tips of 
the blunt tentacles. The genera of this section, as in the 
snails, is distinguished by the modifications that the mouth 
of the shell assumes when the animal has arrived at its per¬ 
fect state; for during their growth they all have the same 
thin, simple lips. Thus the Bulimi have simple, thick¬ 
ened, reflexed lips, and gradually enlarging whorls. 
The Pupce have one or more solid teeth formed by the 
thickening of the inner edge of the lips, and the 
whorls enlarge in diameter so gradually (after the very 
early age of the animal) that the shell generally assumes 
a cylindrical form. The Chondri chiefly differ from the 
former in the mouth being armed with long plaits, formed 
g 3 
