64 MYTILIDZ. 
duck’s stomach, shot in Northumberland, sud fide Kingii, is 
considered by him of doubtful British origm. We have the 
specimen. 
PINNA, Linnezus. 
P. pectinata, Ibid. 
P. pectinata, Brit. Moll. ii. p. 255, pl. 43. f. 1,2, and pl. 53. f. 8. 
P. ingens and P. papyracea, Auct. 
Animal elongated, body large; mantle open, of delicate tex- 
ture except at the margin, which is furnished at the posterior 
end with two rows of tentacular cirrhi, but only one at its 
anterior portion. There are on each side a pair of large 
branchize of nearly equal size and crescent-shaped, united by 
two wide labia, foliaceous on the internal surface, which fall 
on each side the body, connected with the buccal orifice and 
a pair of short, narrow, lanceolate palpi, which appear dispro- 
portionate for so large an animal. The mantle forms neither 
siphons nor even sessile orifices. The foot is conically sub- 
cylindrical, not long, with a byssal groove at the posterior bend, 
from which a large fine silky byssus of attachment issues ; 
this the animal has the power to discard when it wishes to 
change place, and can refix itself by spmning in a very short 
time a new one. 
Having only seen very young examples alive, we have for 
descriptive assistance had recourse to M. Poh, ‘ Test. Sicil.’ 
AVICULA, Lamarck. 
A. TARENTINA, Ibid. 
A. tarentina, Brit. Moll. 11. p. 25], pl. 42. f. 1,2, 3, and (animal) pL. 
f. 4. 
Animal suboval compressed; mantle entirely open, having 
the margin frmged, as in Pinna, with tentacular filaments ; 
there are no siphons nor orifices. The dorsal range of the 
shell usually forms a slender lnear posterior elongation, which 
is led by a fold of the mantle. On each side of the body there 
are a pair of nearly similar-formed branchiz of crescent shape, 
