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.
34. [BALANUS] ALLIUM. Pl. [7], fig. [7 a]-[7 d].
Shell faintly tinged with purple: radii broad, with their summits not oblique: basis not porose. Scutum with the lines of growth crenated: tergum with the spur extremely short, truncated, broad as half the valve.
Hab.—Raine’s Islet, Barrier Reef, Australia, Mus. Stutchbury. Hab. unknown, attached to and coated by Porites. Mus. Brit.
General Appearance.—Shell conical, smooth, but with the lower part sometimes narrowly ribbed in lines corresponding with the internal longitudinal ribs; tinted pale peach-blossom purple, owing to the sheath being finely so coloured; or wholly white. Radii broad, white, square on the summit, hence orifice entire, ovate passing into rhomboidal. The parietal portion of the carino-lateral compartments extremely narrow, about one eighth of the width of the parietes of the lateral compartments. Basis concave, partially imbedded in the coral. Largest specimen .35 of an inch in diameter.
There are some specimens in Mr. Cuming’s collection which appear to belong to this species, and are certainly very closely allied to it, but not having the opercula, cannot be identified positively; the shell is flatter, with the walls strongly ribbed up to the orifice, which is more rhomboidal: the basis is much more cup-formed and more deeply imbedded in the coral; but these differences by themselves are by no means sufficiently diagnostic.
Scutum: the lines of growth are crenated, causing the surface to be very obscurely striated longitudinally: the articular ridge is very prominent, as can be best seen from the outside, and runs down the whole length of the tergal margin with a very regular curve, and hence differs from the articular ridge in the foregoing species. The adductor ridge is either absent, or very indistinct, and parallel to the articular ridge: there is a deep little pit for the lateral depressor muscle. Tergum ([7 d]), with the apex somewhat produced or beaked, and tinged purple: external surface almost flat, without any longitudinal furrow: scutal margin curved. Spur very short, placed quite close to the basi-scutal angle of the valve; broad as half the valve; lower end square. Internally, the articular ridge is prominent only in the uppermost part of the valve: crests for the depressores very feeble.