I looked in vain for cement, or for the cement-glands, (but the specimen was in an extremely unfavorable state for finding the latter) or for the prehensile antennæ of the larva. No doubt this Cirripede at first becomes attached in the same way as others, but after early life, I suspect it is retained in its place, by being so deeply imbedded in the shark’s body, and perhaps by the root-like branched filaments. The irregular growth and splitting of the membrane at the base of the peduncle, where the prehensile antennæ of the larva must originally have been situated, would account for not finding them.

The inside of the peduncle ([fig. 2 g]) was gorged, in the specimen examined by me, with immature ova. The innermost muscular layer consists of longitudinal bundles of unusual size, but placed rather far apart from each other; these do not extend to the very base of the peduncle, and at the upper end they curve inwards, almost to the middle of the under side of the diaphragm, separating the peduncle and capitulum. Outside these longitudinal muscles, there are delicate transverse ones, but apparently there are no oblique muscles in the upper part of the peduncle, as in other Lepadidæ; near the bottom, the transverse muscles form a thicker layer with many of the bundles running in oblique lines.

Mouth.—uLovén has not described this part quite accurately, owing to his not having used high enough magnifying powers. He states that the trophi are soft and functionless, which is far from the case. The whole mouth ([fig. 2 d]), is unusually small; it is, to a certain extent, probosciformed, and being curved a little downwards, projects slightly over the adductor muscle, to which it is closely placed. The labrum does not project more beyond the general surface of the body, than in many other Cirripedes, but the probosciformed structure is caused by the elongation of the surface fronting the thorax. The summit of the mouth stands above the level of the top of the pedicels of the first pair of cirri. The labrum is slightly hollowed out in the middle of its upper margin; it can scarcely be called bullate, in which it differs from all other Lepadidæ; on the other hand, the outer and inner folds of the labrum are not so close together as in Balanus. On each upper corner, there is, as usual, a small rounded prominence, close to which there is a second slight, rounded, spineless swelling; these latter represent the quite rudimentary Palpi.

The Mandibles ([figs. 4, 5]) are more highly developed than the other trophi; they are, however, very minute, the toothed edge being only about 16/1000th of an inch in length, measured in its longest direction; the edge is unusually thick, with the teeth placed rather on one side; this organ, when viewed on the labrum side ([fig. 5]), shows two large teeth placed low down, with the inferior angle pectinated and broadly truncated; but when viewed on the other or maxillæ side ([fig. 4]), several large and small teeth, placed alternately and irregularly in pairs, are seen extending along the whole edge. The mandibles are furnished, as usual, with three principal sets of muscles attached to the basal fold of the mouth.

The Maxillæ ([fig. 7]) are still smaller than the mandibles; the spinose edge being only the 1/100th of an inch in length; the edge, instead of being square, and furnished with a double row of long spines, as in all other Cirripedes, is rounded, thick, club-shaped, and with the side facing the mandibles, thinly and irregularly strewed with short, thick, very minute spines; there is a large broad apodeme (a), in the usual place, but it is much more transparent and flexible than common: there are also the usual muscles. In other cirripedes, the mandibles alone seem to force the prey down the œsophagus; but here, the mandibles and maxillæ equally stand over the orifice, and their adjoining spinose faces and edges, seem excellently adapted to force, by their united action, any minute living creature down the passage.

The Outer Maxillæ are almost in as rudimentary a condition as the palpi; they are quite spineless; viewed externally, they appear like two smooth, blunt, very minute projecting points; but viewed internally, the membrane forming the supra-œsophageal hollow seems to be united actually to their tips, so that they do not project at all. I was surprised to find that the longitudinal muscles going to these organs were developed, in proportion to the other muscles, quite as fully as in ordinary cirripedes: hence, these two little outer maxillæ, no doubt, serve as an under lip, and possess the usual backward and forward movement.

The surface of the probosciformed mouth facing the first pair of cirri, has a deep central longitudinal fold, and rather more than half-way down, a transverse fold; just above this latter fold, and therefore quite below the outer maxillæ themselves, the two olfactory orifices are seated; these are unusually large, and the sack into which they lead, is most unusually large and deep. In this Cirripede, I was first enabled to observe that the membrane lining the sack is tubular, and open at the bottom.

Cirri.—There are, as usual, six pair, and not of very small size; they have a shapeless and rudimentary appearance; they are coloured, like the rest of the body, blackish purple: they are quite spineless, and not articulated, but their anterior faces are either obscurely or very plainly lobed, so that in some (for instance in the third pair, [Pl. IV], [fig. 6]), nine or ten prominent steps could be counted, manifestly representing so many segments. The rami are equal in length in the first pair, and slightly unequal in the second and third pair; these two latter are longer than either the first or three posterior pair. There is a small interspace as usual between the first and second pair of cirri. Internally, the cirri are occupied, even up to their tips, by delicate striæ-less muscles. The external membrane of the thorax and limbs, when examined under a very high power, is seen to be covered with minute toothed scales, as in most Cirripedes.

The thorax is articulated as usual: the posterior part, however, is smaller, and tapers more suddenly than in other species, and this corresponds with the smaller size and more rudimentary condition, of the three posterior pair of cirri, compared with the anterior pair. The prosoma is hardly at all developed. The orifice ([Pl. IV], [fig. 2 e]) of the acoustic (?) sack, beneath the first cirrus, is unusually large.

There are no filamentary appendages.