Pvn H,i I'UitlS

CARDIUM. 289
soft, the shell is thinner, and the posterior side has a
tendency to become elongated and more wedge-like
than usual. In exposed and rough seas, where the
ground is harder, the shell is thick and globular. In
certain localities the inside is of a rich purple colour.
The largest specimens I have seen came from Unst
and Stornoway, and the next in size from Appledore
in North Devon and the Scillv Isles. Some of these
t/
examples measure 2 J
inches in breadth. Distortions
are not unfrequently met with. The most remarkable
are as follows :— inequivalve, the left valve being much
smaller than the right, and nearly flat ; divided into
two lobes by a constriction in front ; resembling a
Cardissa, the anterior side being squeezed in and show-
ing a large lunule; and one shell piled on another,
and apparently growing out of it. Irregular pearls are
occasionally formed. A specimen of C. edule in Mr.
Norman's cabinet, found bv Mr. Cocks at Falmouth,
contains a massive secretion of this kind, which occu-
pies nearly one-half of the inside. It proceeds from
under the beak, and looks like a huge wen. The animal
seems to have suffered no further inconvenience from
the excrescence than being obliged to extend its shell
in front, so as to make up for the space lost at the back.
I have likewise a large button- shaped livercolour pearl
which was taken from a common cockle in the act of
being eaten at breakfast. Young shells are frequently
round, or longer than broad, and are indistinctly angular
on each side. In a still earlier stage of growth they are
very prettily variegated,
C. fasciatum ;
and liable to be mistaken for
but they never have the oblique contour
or the polished ribs of that species.
I hope I shall not be accused of undignified trifling,
or of venting platitudes, if I say a little more about the
o