PHOLAS. 171 
with an exsertile tubular hyaline process; the latter is encir- 
cled 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 of the body a pair of pale reddish-brown 
elongated suboval branchiz, the upper one being much the 
smallest, which are finely striated on the outer surfaces ; their 
posterior 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 pomts; these are 
more striated than the branchiz. The body is centrally sub- 
globose, but tapers posteally and anteally to a blunt terminus, 
and the whole of it presents, 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 im the centre 
of the anterior extremity. With regard to the foot, as I have 
already observed, not a trace is visible, having vanished for 
reasons to be spoken of below. 
P. PAPYRACEA, Juv., nobis. 
Pholadidea papyracea, Brit. Moll. i. p. 123, pl. 5. f. 3, 4, 5, 6; pl. 2. 
f. 1;.(animal) pl. E. f. 4. 
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 produced posteally and anteally to an obtuse 
point, and it is generally of a bluish-hyaline colour, with some 
fine anastomosing lnes throughout its surface, but has nothing 
of the mottled appearance of Pholadidea papyracea ; the shape 
of the branchize is the same as in its congener, but their strize 
are more delicate and colour of the palest yellow; these are 
the mere variations of adolescence, and generally prevail where 
specific identity cannot be doubted, and they are deposited 
partially as in its congener, in the branchial tube: the palpi 
and liver exhibit no variation. 
