138 THE CHICAGO ACADEMY OF SCIENCES, 
SUBCLASS ANISOPLEURA. 
Gastropoda in which the head and feet are bilaterally sym 
metrical, but the visceral dome and mantle-fiap, with all the 
containing organs, have been subjected to a rotation, bringing 
the anus from its posterior position to a point above the right 
side of the animal’s neck, thus causing the shell to incline to 
the right side of the animal. Asa result of this torsion the 
organs of one side become atrophied. 
Superorder Euthyneura. 
Gastropoda anisopleura in which the nervous loop of the 
viscera, being sunk below the body-wall, is not affected by the 
torsion of the visceral hump, but remains straight. 
ORDER PULMONATA. 
Gastropoda with a well-developed foot and (usually) a 
large, spiral shell, inoperculate (Amphibola excepted), capable 
of containing the entire animal; some forms, however, are with- 
out an external shell; the lungs are simple, being a pouch lined 
with a network of respiratory vessels; respiratory orifice small; 
sexes united in the same individual, but reciprocal union neces- 
sary; the genital orifices may be contiguous or distant. The 
lingual membrane is very variable, being in some forms short 
and broad and in others long and narrow; the mouth is further 
armed with one or more horny jaws. The Pulmonata are prin- 
cipally terrestrial; but several large groups are aquatic, inhab- 
iting fresh water, while some (Auriculidz) live in the neigh- 
borhood of the sea and follow the ebb and flow of the tide. 
The pulmonates are typically vegetable feeders, although 
some few genera are carnivorous (Circinnaria, Glandina). They 
thrive best in warm, humid localities, and in desert countries 
are stunted in size and few in number. 
The life history of a pulmonate gastropod is as follows: In 
May or June they lay their eggs, to the number of forty or 
more, in a moist locality, sheltered from the sun’s rays, under 
old leaves or by the side of logsorstones. After about twenty 
or thirty days the young mollusk appears. It takes two or 
three years for a snail to reach maturity. In October or No- 
vember the snail ceases to become active and prepares to hiber- 
nate. This it does by secreting a membrane and placing it 
