Pvn H,i I'UitlS

302 CYPRINID.E.
taken four or more days before they were brought to
me exhibited on dissection the following curious appearance
:—On removing the mantle from the surface
of the shelly a considerable quantity of shelly matter of
the consistence of thick cream, or like moistened plaster
of Paris, was discovered ; on a nearer inspection, the
interior layers of its shelly covering were found to be
deeply corroded in parallel furrows, in some spots so
deeply that the brown or outer layers
of the shell were
laid bare. This shelly matter had undergone no change
but that of trituration. To what cause is this appear-
ance to be attributed ? Are the animals of this species
when in a state of starvation, as these probably were,
capable of absorbing a portion of their shell (the gluten),
and converting it into nourishment ? Or do the animals,
when languid and unhealthy, secrete a medium that
destroys the cohesion of the particles of which their
habitations are formed? In none of the living specimens
that I had an opportunity of examining did I
detect any parasite ;
while in nine out of ten specimens
of the Cyprina Islandica from the same neighbourhood,
I found a small Hirudo lurking under the mantle of
each ; and in very many specimens of a Modiola from
the shallow water of the same coast, a small Crab (Pisa)
shared the habitation with the animal." Mr. Bulwer
also remarked that the /. cor of the Mediterranean
appeared to differ considerably from that of the Irish
Sea in respect of the animal, judging from the descrip-
tion and anatomical drawings of Poli ; but the differ-
ences he has noticed are probably varietal. Mediter-
ranean specimens are smaller. Linne indulged in some
rather fanciful similitudes with regard to the shell, de-
Systema
Naturae '
e
scribing it in the tenth edition of the
as Cardium humanum, and in the twelfth edition com-