The Shell-Collector’s Handbook. 25 
and the greater portion of the visceral'mass. It is 
divided into two chambers by the base of the gills, 
one larger and more ventral taking the name of the 
branchial chamber; the other, the smaller and more 
dorsal, the name of the supra-branchial chamber. The 
hinder of the supra-branchial chamber forms the 
cloacal chamber. 
The foot protrudes through the anterior end of the 
cleft between the mantle-lobes, and the inhalent and 
exhalent siphons protrude through the posterior end. » 
The inhalent will be distinguished from the exhalent 
aperture by possessing tentacular fringes. A current 
of water sets in through the inhalent aperture, 
circulates through the pallial chamber, and returns by 
the exhalent aperture, bearing with it the excretory 
products of the body. 
_ Tse Atimentary System.—The mouth is situated 
between the anterior adductor and the anterior border 
of the foot. It is bounded by two triangular pro- 
cesses—the labial palps—and passes back by a short 
and straight cesophagus into a dilated chamber, or 
stomach, which lies in the substance of the digestive 
gland, the duct of which opens into it near its 
anterior end. The intestine takes a convoluted course, 
becomes into intimate relation with the generative 
gland, pierces the anterior end of the pericardium, 
and running back horizontally as a straight tube 
(rectum) passes through the ventricle of the heart 
and finally ends by an opening—the anus—on 
the dorsal side of the cloacal chamber. 
The rectum has a well-marked safalitee of its 
inner wall—the typhosole—the function of which 
