112 INVERTEBRATE ZOOLOGY 
GASTROPODA 
A PULMONATE GASTROPOD. A LAND SNAIL (Helix pomatia) 
This snail is very common in Europe, in many parts of which 
it is used for food. It is imported into this country for the 
same purpose and may be obtained at small cost in New York 
and Philadelphia. It is especially adapted for dissection, but 
any large Helix may be used instead. The large slug (Limax 
maxima) is very similar to Helix in structure and may also be 
used, but as it has no coiled shell that feature of the dissection 
would be omitted. 
The snail is a terrestrial animal and feeds principally upon 
leaves. It hibernates in the winter under stones and logs after 
having first closed the mouth of its shell with a thin disc of 
calcified slime called the epiphragma. If it is still in winter 
quarters, when obtained, the epiphragma should be removed 
and the animal placed among fresh leaves in a warm room, 
when it will soon come out of its shell and begin to feed. 
Snails are best killed for dissection by drowning. They should 
be placed in a large covered jar of water, when they will die 
expanded in from one to two days. If the air be first boiled 
out of the water the process will be accelerated, but the animal 
should not be placed in water which is still hot. 
Study the external characters of the animal. Its body is 
unsegmented and is covered with a shell, but unlike the shell 
of the pelecypod that of the snail is a univalve. As in 
other mollusks, the shell is the cuticula of the animal charged 
with calcareous salts, and forms an exoskeleton. In shape the 
shell is an elongated cone which has been twisted to the right, 
forming a closely coiled spiral. The tip of the spiral is called 
