SPECIAL ANATOMY. 237 
by an inflection of the muscular layer of the integument 
of the body. The renal organ is placed to the right of 
the heart, and at its posterior part is perforated by the 
aorta. 
Vaginulus. The pulmonary cavity is situated be- 
tween the muscular peritoneum and the integument of 
the body. Its principal portion is placed upon the right 
side, anterior to the middle, but extends to the left side, 
over the back, and along the right side to the pulmonary 
aperture, between the tail and posterior extremity of the 
podal disc. The heart is placed in the anterior portion 
of the cavity. The auricle receives a vein from the right 
and another from the left side. The renal organ is 
placed posterior to the heart, between the passage lead- 
ing from the pulmonary cavity to its orifice, and the 
course of the rectum. 
Helix. In this genus, as is also the case in all the 
testaceous genera under examination, the pulmonary 
chamber is comparatively very large, for reasons already 
stated, and occupies a position on the outside of the 
lower one or two whorls of the turbinated mass of the 
viscera. In front, it is bounded by the collar, in the 
right side of which is the pulmonary orifice. The floor 
of the cavity is formed, as in slugs generally, by the 
muscular peritoneum. The roof, or outer wall, is occu- 
pied on the right side by the rectum, posteriorly by the 
heart and renal organ, and anteriorly by the pulmonary 
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