of the two valves almost
touch each other under the middle of the carina; main growth towards the
infra-median latera and upwards; umbones projecting not above one fifth
of the entire length of the valve.

_Peduncle_, much flattened, rarely as long as the capitulum, with the
upper end nearly as wide as it; the lower end is either blunt, or tapers
to a very fine point. The calcareous scales are transversely elongated,
and are about four times as wide as high; their internal surfaces are
slightly concave, and their external, convex; the two ends are pointed.
Viewed internally, the scales approach in shape to rhomboids. There are,
in a medium-sized specimen, about twenty scales in each whorl, their
tips overlapping each other: the whorls are placed not very near each
other and at rather unequal distances, except round the uppermost part,
where, being in process of formation, they are packed closely together.
The membrane uniting the scales, supports numerous transverse rows of
articulated spines, varying from 1/100th to 1/500th of an inch in
length, and each furnished with a long sinuous tubulus, 1/10,000th of an
inch in diameter, running through the membrane to the underlying corium.

_Attachment._--Specimens are attached to various horny corallines, and
occasionally to the peduncles of each other.[51] In both cases,
supposing the coralline to be erect, the capitulum is placed upwards,
with its orifice towards the branch to which it is attached, and
consequently with its carina outwards. Where several are crowded in a
group, their peduncles often become twisted and their positions
irregular, with their orifices facing in any direction. This uniform
position is simply the consequence of the larva attaching itself
head-downwards, and from the position of the prehensile antennae,
necessarily with its sternal surface parallel and close to the branch of
the coralline; hence the dorsal surface, which afterwards is converted
into the carina, faces outwards. The peduncle, as already stated, often
tapers, at its basal extremity, to a sharp point. In very young
specimens, for instance in one with a capitulum only 1/20th of an inch
in length, the method of attachment is the same as in Lepas and many
other genera, namely, by cement proceeding exclusively from the antennae
of the larva; but in older and full-grown specimens, instead of the
whole bottom of the peduncle becoming flattened and broadly attached,
which would be here impo