_Shell pinkish-purple or white, clothed by an orange-coloured membrane;
radii represented by mere fissures; basis solid. Scutum, with a sharp,
curved adductor ridge; with crests for the lateral depressor muscle:
tergum, with the spur short, truncated, one third of width of valve._
_Hab._--New Zealand, New South Wales, Mus. Brit. and Stutchbury;
attached to shells.
_General Appearance._--Shape conical, often steeply conical; orifice
small; radii not developed, represented by mere fissures. The walls
are smooth, or slightly, or strongly ribbed longitudinally. The shell
itself is of a fine peach-blossom pink, or nearly white, but it is
generally covered by a thick yellow or brownish-orange epidermis.
Opercular valves pinkish, but similarly covered. Basal diameter of
largest specimen .7 of an inch.
_Scuta_, with the lines of growth closely approximate; surface
somewhat convex. Internally, the articular ridge is very little
prominent, but runs far down the tergal margin; in some specimens,
however, it is shorter and more prominent. The adductor ridge is
strongly prominent, is curved towards the rostral angle, and runs
down nearly to the basal margin. The rostral depressor muscle is
lodged in a small cavity, formed, as usual, by the overlapping of
the occludent margin; within this cavity there are either tolerably
distinct little crests, or merely traces of them, for the attachment
of the muscle. The lateral depressor muscle is attached to several
quite distinct crests, seated in a concavity beneath the adductor
ridge. _Tergum_ rather narrow, with the apex produced or beaked; the
beak is purplish and flat. There is a slight rounded longitudinal
furrow, or depression. The spur is fully one third of the width of
the valve: it is short, with the end truncated, and placed close to
the basi-scutal angle; the basal margin on the carinal side slopes
gently towards the spur. Internally, the scutal margin is scarcely at
all inflected, and the articular ridge is very little prominent: the
crests for the tergal depressores are pretty well developed.
From the points here enumerated, it is clear that the opercular
valves are articulated together much less strongly than is usual with
most species, excepting _B. allium_ and its allies. It is remarkable
that in this species the terga are united to the sheath, not, as is
usual, by a single opercular membrane, but by five or six, one above
the other, the upper membranes not having been exuviated as each new
lower one was formed. The minute spines on the membrane lining the
sheath are rather larger and more numerous than is usual, and to the
base of each spine a tubulus of unusual diameter runs, imbedded in
the shell.
The _Walls_, internally, have unusually numerous, narrow,
approximate, strongly prominent, longitudinal ribs, denticulated at
their bases, and inserted into the furrows on the borders of the
basis: in old specimens these internal ribs die out in the upper
part of the walls. The _Radii_ are not developed in any of the many
specimens which I have seen, and the edges of the compartments on
both sides of each suture are equally marked by slight, irregular
ridges or knobs, answering to the septa and their recipient furrows,
in the species with ordinarily developed radii. There is very little
diametric growth, the orifice being gradually enlarged by the
disintegration of the upper ends of the walls; the _alæ_, however,
in some specimens, do grow a little along their lateral or sutural
edges, so that some little diametric growth must be effected. The
summits of the alæ are very oblique; their sutural edges are plainly
crenated. The sheath descends about half way down the walls. The
_Basis_ is flat, not permeated by pores, but deeply furrowed in lines
radiating from the centre.
_Mouth_: labrum sometimes with no teeth, sometimes with four minute
teeth; mandibles with four teeth, of which the third is blunt and
rather large; the fourth is a mere knob. Maxillæ; there is, as usual,
an upper pair of large spines (beneath which there is sometimes
a small notch), but all the lower spines, instead of standing as
usual in pairs, form a single row. _Cirri_; first pair with the rami
remarkably unequal in length, one ramus having twenty-two segments,
and being more than twice the length of the other, having only nine
segments: these segments, and likewise those of the second and third
pairs, have an inverted conical shape; and they are all less thickly
clothed with spines than is usual. The second pair is short, about as
long as the shorter ramus of the first pair, and has ten or twelve
segments. The third pair is above twice as long as the second pair,
and contains twenty-four segments: this very unusual length is owing
to the presence of numerous thin tapering upper segments, unlike
those generally found in _Balanus_, in the third pair of cirri, and
apparently serving as feelers. These upper tapering segments are
of an inverted conical shape, and support on their upper margins
two very small tufts of spines, one behind and one in front: on the
segments lower down these tufts increase in size, and the spines are
more spread out, so that in the basal segments, the tufts in front
form on the upper margin two or three crowded rows of bristles. The
three posterior pairs of cirri have elongated segments, which bear
on their upper half three pairs of spines; of these the lowest pair
is minute, and the middle pair is only one third of the length of
the upper pair. The sixth cirrus, in the same individual as before,
contained twenty-seven segments in each ramus, that is only three
more than in the third cirrus! I must observe, that the cirri in
all the specimens were irregular, often distorted and monstrous;
and therefore, probably, there is considerable variation in the
proportional numbers of the segments in the cirri.
At the base of the penis there is a minute, knife-edged, triangular
projection. The branchiæ are rather narrow, pointed, and not very
large.
_Affinities._--This is a very distinct species, as shown by the
peculiarities in the cirri, by the absence of radii to the shell,
and by the presence of crests for the attachment of the lateral
scutal depressores. With the exception of this latter character, the
opercular valves clearly show, that _B. vestitus_ is allied to _B.
allium_, _cepa_, and _quadrivittatus_. In some respects this species
manifests an affinity to _B. imperator_, which latter has its third
pair of cirri nearly similar to those of _B. vestitus_.