170 PHOLADID&. 
appear that only one species exists; but that malacologists 
may judge, we give specific descriptions of the two phases, the 
one being called Pholas papyracea, the other, P. lamellata. 
PHOLAS, Linneus. 
P. papyracea, Solander et Auct. 
P. papyracea, Brit. Moll. i. p. 123, pl. 5. f. 3, 4, 5, 6, and pl. 2. f. 1; 
(animal) pl. F. f. 4. 
Animal elongated, subcylindrical; mantle closed, except a 
small rayed aperture for the foot, as long as one exists, and 
which corresponds in position with a similar aperture in the 
membrane connecting the doming of the shell, and is styled 
by Dr. Turton a “spiracle,’ but which may perhaps in this 
species, the only one of the Pholades that has it, be for the 
purpose of a partial issue, or rather protrusion, without the 
solution of continuity of the ventral membrane of the animal, 
of the hyaline cylindrical appendage which exists in all 
bivalves, to secure for it a pomt of support when the foot 
becomes so much diminished as not to afford one. In all 
other bivalves this stylet is not visible, bemg imbedded in the 
body and upper part of the pedicle of the foot, which is the 
leaning-stock or poimt of resistance, 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 dappui; 
but when the dome of the shell of the Pholadidea 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 ; or the fissure may be, for 
flux and reflux of the water for branchial purposes. 
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 fringed 
with short white cirrhi; within the sheath are the anal and 
branchial tubes, the former with the margin quite plain, but 
