BIVALVES. 
13 
These adductor muscular scars, as they are called, 
are connected by a faintly impressed line following 
the curvature, and near the front of the valve: 
this is the impression left by the attachment of 
the muscles of the mantle. Near to the ad¬ 
ductor muscular scars, but a little further from 
the edge of the shell, are situated the impressions 
of the muscles that move the foot. 
Figure 1 represents the right valve of the 
shell removed so as to disclose the animal. It is 
necessary for all dissections to remove one of the 
valves. This may be readily accomplished by 
first killing the animal by hot water, when the 
valves will gape open. Forcing them now wider 
apart, the muscles which close the valves may be 
then readily seen, as white cords, which must be 
cut with a pair of scissors. The whole body of the 
animal is covered by a thin fleshy envelope, termed 
the mantle , which consists of two lobes, joined at 
the back, but free in front. The disposition of 
the lobes has been well compared to the “ covers 
of a book when it is placed on its edge with the 
back uppermost.-” Each lobe of the mantle 
corresponds with a valve of the shell, and is at¬ 
tached to it in front by a series of muscles, which 
produce the mantle-line of impressions. The 
mantle extends as a free portion beyond the 
muscles to the edge of the shell, which portion is 
much thickened, and secretes the shell. The lobes 
