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.