_Shell striped or clouded with pinkish-purple, or quite white; radii
narrow, with their oblique summits smooth or arched: basis porose.
Scutum plainly striated longitudinally: tergum with the spur narrow._
_Var._ (_a_):[99] _bright rosy pink, not distinctly banded
longitudinally_. Hab. North-east coast of Australia.
_Var._ (_b_): _snow white, glossy; orifice deeply toothed_.
[99] This variety perhaps is the _B. roseus_ of Lamarck, as
figured in Chenu, 'Illust. Conch.' Tab. 2, fig. 9; but as Lamarck
does not even notice such conspicuous external characters as the
longitudinal striæ on the scuta, and the smooth rounded edges of
the radii, it is impossible to identify his species.
_Hab._--Mouth of the Indus; East Indian Archipelago; Philippine
Archipelago; Moreton Bay, and the north-east coast of Australia.
Attached frequently on ships' bottoms, associated with _B.
tintinnabulum_ and _amphitrite_. Sometimes attached to _Gorgoniæ_
with _B. calceolus_.
_General Appearance._--Shell steeply conical, with the orifice
sub-rhomboidal, moderately large, very slightly, or deeply notched:
surface very smooth: white, longitudinally banded with pinkish or
leaden purple, with sometimes a purplish, sometimes a yellowish tint,
the latter owing to the persistent epidermis; the bands are pale,
and often fade away in the lower, and sometimes in other parts of
the shell; the epidermis is generally more persistent on the narrow
rounded radii than on the parietes, and hence the radii are generally
yellowish. The opercular valves are pale dull purple: the sheath is
darker purple, with the exception of the portions of the alæ added
during the diametric growth, which are of a dead white, and are
externally conspicuous. The scuta are striated longitudinally. I
may remark, that, excepting the narrowness of the radii, with their
quite smooth, rounded and very oblique summits, some specimens are
hardly distinguishable, in external aspect, from varieties of _B.
amphitrite_. If the specimens from the north-east coast of Australia,
of which I have seen many (but unfortunately only one small one had
its opercular valves), form, as I fully believe, merely a variety; it
is characterised by its nearly uniform beautiful rosy pink, without
any _distinct_ longitudinal bands: of these specimens I have seen
one two inches in basal diameter, and three in height: of ordinary
duller-coloured striped specimens, the largest was 1.7 in basal
diameter. Of the perfectly white _var._ (_b_), I have seen several
specimens, the largest being .6 of an inch in diameter: these have
a somewhat peculiar aspect, but I have met with only one specimen
with opercular valves, and that was extremely young: I at first
considered this form as specifically distinct; but I can point out,
after careful examination of the whole shell, operculum, and internal
animal of the young specimen, no sufficient diagnostic characters.
_Scutum_, plainly striated longitudinally, with the striæ dividing
the prominent lines of growth into squarish beads: internally, the
upper part of the valve is roughened: the articular ridge is short,
remarkably little prominent, and not reflexed; the adductor ridge
is blunt and little prominent; sometimes it is almost confluent
with the articular ridge: there is a deep but variable depression
for the lateral depressor muscle; and in young specimens of _var._
(_a_) it was almost absent. _Tergum_: the surface exhibits traces of
longitudinal striæ: there is a deep longitudinal furrow, with the
sides folded in and quite closed in full grown specimens: the scutal
margin is considerably curved towards the scutum. The spur is long
and narrow, with the end bluntly pointed, placed at rather above its
own width from the basi-scutal angle; the basal margin slopes but
little towards the spur: the crests for the depressores are feebly
developed.
_Parietes_: their internal surfaces are strongly ribbed
longitudinally, with the basal ends of the ribs coarsely
denticulated, and with the denticuli extending close to the outer
lamina. The radii are generally narrow, but their width varies;
their summits are very oblique, smooth, rounded, and inflected, with
the lines of growth, in the uppermost part, curving inwards; their
sutural edges, in the upper inflected portion, are quite smooth,
without septa; in the lower and larger portion, the edge is crenated
with excessively fine teeth or septa, not denticulated: the radii,
like the parietes, have no inner lamina: the recipient grooves in
the opposed compartments are smooth, and are in the lower part of
the shell of unusual depth. The _alæ_, differently from the radii,
generally have their summits very slightly oblique, but sometimes
they are highly oblique: their sutural edges are most finely
crenated. The _basis_ is generally flat, sometimes cup-formed; it is
permeated by pores, crossed by transverse septa; and sometimes there
is an underlying cancellated layer.
_Mouth_: labrum with either six very small teeth, or with none.
_Mandibles_ (Pl. 26, fig. 5), with the third tooth a little thicker
than the first; fourth and fifth teeth small, but quite distinct.
_Maxillæ_ (Pl. 26, fig. 7), with the inferior part forming a square
step-formed projection, bearing, one behind the other, two spines
as long as the upper pair; in a young specimen of _var._ (_a_) this
step-formed projection was absent.
_Cirri_: first pair with the rami unequal by about four segments: the
shorter ramus has the segments very protuberant in front, thickly
clothed with strongly serrated spines; the second cirrus has segments
moderately produced; the third has them produced only in a slight
degree. The pedicels of the second and third cirri have dorsal tufts
of spines, but not a hairy plate prolonged over the thorax. The
posterior cirri have segments broader than long, bearing only two
pairs of nearly equally long spines; and between each pair there is a
small intermediate tuft. The penis has the usual basi-dorsal point.
_B. amaryllis_ is a distinct and well-defined species, more nearly
related to _B. Hameri_ than to any other form.