This organ is itself a study. Long as it is when extended, it can
be thoroughly drawn within the body; and there it forms two fleshy
cylinders, one within the other, exactly like a stocking half turned
on itself. There are proper muscles attached to its walls, and to
the interior of the head, by extremities which are branched in a
fan-shape, so as greatly to strengthen their insertions; and these,
by contraction, draw the one portion within the other. Then there is
a broad hoop of muscle, which, passing round the inner cylinder, by
contracting pushes it out, and lengthens it. Within the interior of
this latter there is a long narrow ribbon of cartilage, which is armed
with rows of sharp flinty points, turned backwards; and this tongue or
palate, as it is variously called, is the Dog-whelk’s weapon.
We cannot induce the Whelk to attack his prey just when we please; but
he has been detected in the operation, and I will describe it. With his
broad muscular foot he secures a good hold of the bivalve, and having
selected his point of attack, in general near the hinge--a selection
which probably looks more at the superiority of the meat within than
at any peculiar facility in the perforation--he brings the tip of his
extended proboscis to the point, so that the silicious teeth can act
on the shell. Hard as is the calcareous shell, it is not proof against
the flint; for, without any solvent excretion, the aid of which some
physiologists have been ready to suppose, these glassy points, grating
round and round as on a pivot, soon wear away the substance, and
gradually bore the tiny aperture which exposes the sapid morsel.
Continuing our researches, we find, deep in a rocky pool under a tuft
of weed, a shell of a peculiar form, because of the enormous expansion
of its outer lip. It is known as the Pelican’s-foot,[7] from the
resemblance which this lip with its diverging ribs bears to the webbed
toes of a water-fowl. This, too, is a carnivorous species; and though
it is somewhat rare to detect the animal moving, even though kept
alive in captivity, yet by carefully examining this one in its deep
pool, before we disturb its equanimity, we can just see the proboscis
protruding from the wide square notch in the shell, and discern that it
is rather prettily coloured, being marked with spots of opaque white on
a rose-coloured ground.
This species is interesting from the changes of figure which it
undergoes in its progress from youth to maturity. While young the shell
is simple, with no trace of the expanded lip; and it is only at mature
age, and rather suddenly, that the shell makes its remarkable growth
into these far-projecting points and angles, the augmented thickness of
which is, moreover, at least equally conspicuous with the expanse.