CONIA ROSEA.[109] _Krauss_ (!). Die Südafrikanischen Mollusken, Tab.
6, fig. 28, 1848.
BALANUS CUMINGII. _Chenu._ Illust. Conch., Tab. 4, fig. 5.
[109] I am greatly indebted to Professor Krauss for having sent
me, for examination, the unique specimen collected by himself in
Algoa Bay. There can be no doubt of the identity of the African and
Australian specimens. It is a singular circumstance that the same
species should occur in these two distant places, and, as far as at
present known, not in the intermediate, more tropical coasts.
_Shell dirty white, tinged with pink; parietes formed by a single row
of large tubes: radii generally narrow: tergum with the spur rather
short and broad._
_Hab._--New South Wales, Moreton Bay in lat. 27°, Port Jackson, and
Twofold Bay; South Africa, Algoa Bay. Attached, in Australia, to
littoral rocks and shells; often associated with _T. purpurascens_,
_Chthamalus antennatus_, and _Catophragmus polymerus_; Mus. Brit.,
Cuming, Krauss, Darwin, Stutchbury.
_General Appearance._--Shell steeply conical, often rather convex;
dirty or brownish white, feebly tinted with pink; external surface
generally much disintegrated, and having in the upper part a pillared
appearance, owing to the exposure of the upfilled, large, square,
parietal tubes, and, in the lower part, a striated (and sometimes
serrated) appearance, from the exposure of the parallel, approximate
plates, with which the outer lamina of the shell is internally
strengthened. In only a few young specimens, the whole outer lamina
of the shell was well preserved; and in these the surface was very
smooth, and even glossy, giving to the specimens a quite different
aspect; even in partially corroded specimens, the lower part of the
shell sometimes is quite smooth. Generally, the radii are developed;
in most specimens they are narrow, but sometimes of moderate width;
their summits are oblique, and their edges often notched or toothed.
The recipient furrow, in each opposed compartment, is often almost
as wide as the radius itself, and is equally notched. In some much
corroded specimens there were no radii. Basal diameter of largest
specimen, 1.1 of an inch.
_Scuta_, generally thick, sometimes very thick, with the external
surface usually much corroded: articular furrow rather wide;
articular ridge not very prominent; adductor ridge prominent. The
rostral depressor muscle is attached in a small oblong pit, sometimes
including little crests; and the lateral depressor muscle is attached
to what may be described either as three or four parallel furrows or
crests.
_Terga_, with the spur placed close to the basi-scutal angle, so that
there is no basal margin on that side; spur short, with its lower end
truncated and rounded; broad, even exceeding, when measured across
the upper part, half the width of the valve. Articular furrow wide.
Apex not beaked.
_Structure of Walls and Radii._--This species differs from all the
others of the genus in having only a single row (fig. 3 _d_) of
parietal tubes; these are large, quadrangular, but elongated in the
ray of the circle. They are not filled up, even at the very top of
the shell, but they become thickly lined all round with compact
shelly matter. When the surface of the shell is disintegrated,
these upfilled tubes greatly affect, as already stated, the
external appearance. The outer lamina near the basis is internally
strengthened by longitudinal, sharp, approximate ridges or plates,
which, also, often affect, after corrosion, the external appearance.
The _radii_ have their sutural edges formed by a set of narrow,
branching ridges or septa; the ends of which, seen externally, often
give a notched outline to this edge; the recipient furrows in the
opposed compartments are deep, and their edges likewise are often
notched: the interspaces between the branching ridges are filled up
solidly. The _alæ_ have their edges coarsely crenated. The lower edge
of the sheath is not free.
The _mouth_ and _cirri_ present no particular characters: the third
cirrus has both its rami elongated, with the terminal segment
tapering. In the three posterior pairs of cirri, the tufts of little
spines between the main pairs are rather large.
_Affinities._--This species has no particular affinity with any
other. The circumstance of there being only a single row of parietal
tubes is not so important a difference as might at first be thought,
inasmuch as in the other species, during their quite early youth, the
walls are formed of only a single row of tubes or pores.