150 CORBULID AL. 
SPHAINIA, Turton. 
S. Brneuamt, Turton. 
S. Binghami, Brit. Moll. i. p. 190, pl. 9. f. 1, 2, 3. 
Animal elongated, compressed, pale yellowish-white ; mantle 
closed, except a passage anteally for a small, narrow, sub- 
cylindrical foot, of a bluish transparent colour, with a 
byssus of coarse filaments, and another for the anal and 
branchial tubes. The anal siphon is short, but the longest of 
the two; it is encircled by 5-6 rough white cirrhi, and emits 
a large, subhyaline, delicately frosted valve, which, on each 
step of the animal in advance, is considerably exserted, and 
then suddenly withdrawn; the branchial siphon is little more 
than a sessile orifice, but in connection with the anal one, 
and, like it, furnished with 5-6 rough white cirrhi. The 
branchize are of a pale brown, the under one being the largest, 
and runs horizontally ; the upper is much smaller, and laps on 
the other obliquely ; the branchial vessels are so minute as to 
give the lamine the appearance of smoothness ; there is, on each 
side, at least one subtriangular, pointed, well-striated palpum, 
and it is probable there is a second that has escaped detection. 
This animal has great affinity to Saxicava, besides alliances 
with Corbula and Mya; indeed the genus Sphenia is almost 
unnecessary, as its animal is nearly identical with Savicava 
arctica, and the structure of the hinge and the other hard 
parts have much the same generalities. In our dubiety 
whether this animal ought to be deposited in Sphenia or 
Saxicava, we have cut the Gordian knot, by adopting, con- 
trary to our particular views, an almost superfluous genus, 
being in some measure stimulated to this resolve by the 
respect we entertain for the memory of our old talented 
friend Dr. Turton, its founder, whose numerous works are so 
highly valued by conchologists. 
PANDORA, Lamarck. 
P. optusa, Leach et Auctorum. 
P. obtusa, Brit. Moll. i. p. 210, pl. 8. f. 5; (animal) pl. G. f. 10. 
Animal suboval, somewhat elongated ; the left side is more 
