SEA-FISHERIES LABORATORY, 7 385 
of waste products, and the only parts of the gills 
performing any really important duty in respiration are 
the branchial expansions of the principal filaments. 
ALIMENTARY CANAL AND DIGESTIVE GLAND. 
The Alimentary Canal of Pecten is comparatively 
simple, and there are no complicated convolutions in the 
visceral mass as in Cardium. The total length is about 
twice that of the longest antero-posterior diameter of 
the body. 
In order to examine the alimentary canal, it is 
necessary to remove the mantle and gills from the right 
side, and it will be easier if the specimen has been left for 
a day or so in 5 per cent. aqueous solution of formol. 
The course of the alimentary canal in the visceral 
mass can be best made out by shaving off slices parallel 
to the surface. Sections will also best show the shape 
and position of the stomach. 
The mouth (fig. 39, J/.) is situated between the lips 
which are conspicuous dorsal to the foot (fig. 39, Lp. u., 
Lp.l.). It is hidden completely by them, and _ food 
particles pass into 1t by being carried forward at each 
side of the visceral mass and foot between the labial palps. 
The Labial Palps (figs. 1 and 39, L. p.e. and L. p.t.) 
consist of an inner and an outer broad flap on each side of 
the visceral mass at the points where the gill lamellae 
terminate dorsally. The outer is a continuation of the 
upper lip, and the inner palp of the lower lip. They are 
pigmented yellow-brown, but are very thin and somewhat 
transparent. The inner palp is rectangular in shape, and 
is attached to the visceral mass along the inner long edge 
and the short ventral edge. The attachment is, however, 
confined to these two edges, and the whole area is 
