Identity of Pholadidea papyracea and Pholas lamellata. 7 
except in the Anomie, Ostree and Pectinide, in which, as the 
foot is reduced almost to nothing, the mass of the body is the 
only point d’apput; but when the dome of the shell of the Pho- 
ladidea papyracea is removed, the dark basal point of the stylet 
presents itself in the centre of the mottled belly, precisely where 
the foot is placed in the group of the Pholades, and im this case 
it appears to act as a substitute. 
The siphonal apparatus consists of a long elastic sheath, 
which is often protruded to double the length of the shell, but 
in a state of half-extension it becomes highly corrugated ; ‘it is 
clothed with a dull red-brown epidermis, under which it is 
bluish white ; the margin of its terminus is finely frmged with 
short white colon within the sheath are the anal and Hnantehihl 
tubes, the former with the margin quite plain, but exserts a tu- 
bular hyaline process; the latter is encircled by about twenty 
white cirrhi of different lengths. 
The liver is green, and situated as usual on the dorsal range. 
There are on each side the body a pair of pale reddish brown 
elongated suboval branchie, the upper one being much the 
smallest, which are finely striated on the outer surfaces ; their pos- 
terior extremities suddenly become linear, and are then deposited 
in the branchial tube ; there are also two long flat linear palpi on 
each side, with lanceolate points; these are more striated than 
the branchize. The body is centrally subglobose, but tapers pos- 
teally and anteally to a blunt terminus, and the whole of it pre- 
sents, especially in the genial season, a mottled mass of flaky 
white subrotund spots or dots, with one of the termini of the 
elastic appendage appearing in the centre of the anterior extre- 
mity. With regard to the foot, as I have already observed, not 
a trace is visible, having vanished for reasons to be spoken of in 
another place. 
Pholadidea papyracea, Brit. Moll. 
Pholas lamellata, auctorum. 
Animal nearly of the form we have just described; mantle 
closed, except a large aperture for the passage of the foot, which 
in this form of the P. papyracea is most apparent. The branchial 
processes and siphonal tubes are, in the most minute points, 
similar to those organs in the form styled Pholadidea papyracea 
to which we refer; the body, as in it, is subglobose, and pro- 
duced posteally and anteally to an obtuse point, and it is gene- 
rally of a bluish hyaline colour, with some fine anastomosing 
lines throughout its surface, but has nothing of the mottled ap- 
pearance of Pholadidea papyracea; the shape of the branchiz is 
the same as in its congener, but their striz are more delicate and 
colour of the palest yellow ; these are the mere variations of ado- 
lescence, and generally prevail where specific identity cannot be 
