ead state, the aperture of the capitulum seems to be
always gaping, yet I have little doubt, that the living animal can fold
the flexible membrane, like a mantle, round its thorax and cirri, and
thus protect, though feebly compared with most Cirripedes, these organs.
I suspect that the mouth is always exposed.

_Peduncle._--The membrane of the peduncle is thin; the whole surface is
sparingly and quite irregularly studded with minute, much-branched
filaments (Pl. IV, fig. 3, highly magnified); these are occasionally as
much as l/5th of an inch in length; the degree of branching varies much,
but is generally highly complex; the ordinary diameter of the branches
is about 1/200th of an inch; their tips are rounded, and even a little
enlarged, and frequently torn off, as if they had been attached to or
buried in the flesh of the shark, in which the whole peduncle is
imbedded. These filaments are formed of, and are continuous with the
external transparent membrane of the peduncle, and they contain, up to
the tips of every sub-branch, a hollow thread of corium, prolonged from
the layer internally coating the whole peduncle. In all other Lepadidae,
the peduncle increases in length, chiefly at the summit where joined to
the capitulum, and in diameter, throughout nearly its whole length,
except close to the base; but, owing to the constant disintegration of
the outer surface, the old outside coat does not split in defined lines,
like the membrane of the capitulum. In Anelasma, however, owing to the
imbedded position of the peduncle, the old outer coats are preserved,
the lines in which they have split during continued growth being thus
exhibited: those in the uppermost part almost symmetrically surround the
peduncle, showing that here, as in other Lepadidae, has been one regular
line of growth; but in the lower part the lines are extremely irregular;
and what is almost unique, it appears that the blunt basal end is
constantly increasing in length and breadth, and, apparently, at a
greater rate than any other part. I judge of this latter fact, from the
whole bottom of the peduncle being covered with numerous curved, or
nearly circular, lines of natural splitting, the nature of which can be
best understood by examining the much-enlarged drawing (Pl. IV, fig. 3)
of a small portion (taken by chance) of the membrane of the base, seen
from the outside, and bearing some of the simplest branched filaments:
other branches, as may be seen,