264 MOLLUSCA, 
flap can be reflected over to the left and the true dorsal 
surface of the body or diaphragm exposed. The pulmonary 
chamber is then seen to be triangular in shape, bounded by 
the collar in front, the vascular mantle above and the 
diaphragm below. Along its outer edge, emerging at the 
Fig. 185.—First DissEcTION OF SNAIL (Helix pomatia). 
. (Ad nat.) 
Ocular Tentacle. 
Pulmonary 
Aperture. 
* Excretory 
Diaphragm. 
Rectum 
Visceral Hump. 
Auricle of 
Heart. 
Kidney. 
The snail is pinned out on its ventral surface, and the mantle is cut free from the 
body by a cut along the collar and round the spiral. Note the pulmonary veins in 
the mantle leading to the auricle of the heart, which passes to the ventricle and thence 
by an aorta to the body. 
* The excretory pore is really within the pulmonary aperture. 
