Pvn H,i I'UitlS

PECTEN. 53
much distorted, which were attached by a strong byssus
as well as adhering by the shell. According to Fischer
the foot does not become atrophied or proportionally
smaller in the fixed adult, although it is then quite use-
less for the purpose of locomotion. This fact is opposed
to the general idea that the size of organs is modified
or affected by a change in the habits of an animal. The
present species was first described by
wonted accuracy. Wallace,
in his '
Lister with his
History
Orkneys/ has an ingenious way of accounting
of the
for the
shells being so distorted. He calls them the ' ' twisted
Pectines of Stroma," and says, " I cannot think the odd
strange tumbling
anything to that frame ; yet
in any other place."
the tides make there can contribute
after all I never see them
It is the Ostrea sinuosa of Gmelin and the P. distortus
of Da Costa. In its younger state it is the P. multi-
striatus of Poli, and the P. Isabella of Macgillivray but
not of Lamarck.
2. P. va'rius*, Linne.
Ostrea varia, Linn. Syst. Nat. p. 1146. P. varius, F. & H. ii p 27.3
pi. L. f. 1.
Body pale red, pink, brown, or yellow, sometimes mottled
with white or streaked with purplish-brown : mantle broad-
edged : cirri numerous, of unequal length but mostly long
and slender, arranged in four rows : ocelli about 30, black, and
smaller than in the last species : foot rather large, thick, and
white.
Shell transversely oval, much broader in front than be-
hind, nearly equilateral, rather solid and slightly glossy : sculp-
ture, 25-30 smooth and rounded ribs, which are •
equal-sized
the whole surface is also covered transversely with fine plates
which often form vaulted spines on the crests of the ribs the
j
interstices of the ribs are marked with minute bifurcatino-
* Variegated.