6 
GENERIC CHARACTERS. 
The ventral orifice which is also the common opening to the lungs,, 
is guarded by the flap, ib., 6, p, which interposes between it and the 
surface over which the animal may be moving with the foot extended. 
The lungs lie partly along the back and partly along the left side, ib., 
6, L L. 
The reproductive organs, as in all hermaphrodite Gasteropods with 
reciprocal impregnation, are quite complicated. They are situated on 
the right side near the ventral orifice, and are attached to one of the 
three large muscles, the upper right, ib., 11, w. The combined ovaries 
and testis, ib., 10, ov, enlarged still more at ib., oov, lie on the upper 
surface of the liver, but do not penetrate it. Emerging from the upper 
extremity of this organ, is the sperm duct which is of a remarkable 
length, often three times as long as the shell; see ib., 10, sd; it is coiled 
on the back, beneath the lungs, and terminates on the central portion of 
the intromittent organ, ib., 10, oi, where there is also a greatly enlarged 
view of the posterior portion. This organ is retractile and the retractor 
muscle, ib., 10, im, being attached to the tip and passing over the back, 
is inserted in the thicker portion of the mantle, near the foot on the left 
side. The organ when protruded, is flat but with the sides capable of 
being curved upward, forming a groove in the center. 
The pyriform sperm reservoir, ib., 10, rv, which is a receptacle of the 
spermatozoa of another individual, lies against the combined ovaries and 
testis, its duct, ib., 10, d, enters the common orifice with the oviduct, 
ib., 10, w. Midway between the reservoir and the orifice, or a little nearer 
the former named, a thin, cylindrical organ arises, and passing down- 
ward along the liver, terminates in a blind, sometimes slightly enlarged, 
end in the three last whirls of the abdomen; see ib., 10, m. Special 
mention of this organ will be made under the head of General Conclu- 
sions. 
The principal muscular system may be briefly described as follows: 
The stomach is provided with abroad, flat muscle, which is divided into 
two branches, ib., 11, H, and hh, the latter named of which supports 
the tongue, and terminates in six fascicles ,ib.. 12, ff. This stomachic 
muscle is inserted on one of the two upper foot muscles, the left, ib., 11, 
q; this, with its fellow, ib., 11, w, on the right, have a common origin; 
below them is another, ib., 11, N. All these three muscles are broad, 
the edges only being given in the figures, but as they pass downward 
they become rapidly narrower and are finally reduced to mere threads. 
^ These passing around on the inside of the liver cling to the column, and 
thus enable the animal to retain a given position in the shell, for it has 
no direct attachment to the shell. The eye peduncles and tentacles are 
