_Rostrum_, not one third of the length of the carina, concave, triangular, with the basal margin slightly protuberant. Of the other valves, including the sub-carina and sub-rostrum, the shape of their inner surfaces is sub-triangular, with the basal margin convex; externally the umbones are pointed, and slightly curled inwards, so as to overlap each other like tiles: the smaller valves, however, of the lower whorls (fig. 1 _a_) are more or less transversely elongated, so as to become almost elliptic instead of triangular. Of the latera, the upper pair, which corresponds to the interspace between the scuta and terga, is the largest, but barely exceeds in size the pair answering to the carinal latera in Scalpellum, which lie between the terga and carina: the next largest pair is the rostral, or that between the scuta and rostrum. Some, however, of the lower latera are of nearly equal size. _Peduncle_, narrower, but generally longer than the capitulum; upper part encased with small calcareous scales, with their apices curved inwards, and overlapping each other. The inner surface of each scale is triangular, with the basal margin protuberant. The scales continue to grow or be added to, only in about the ten upper whorls, which form but a small part of the whole peduncle; in the lower part, the scales become further and further separated from each other. The surface of attachment, in full-grown specimens, is broad; but in two very young specimens, which I removed with great care after the action of potash, I found the peduncle ending in a filiform prolongation, such as often occurs in _Scalpellum vulgare_ and in _Lepas fascicularis_. At the extremity of the pointed peduncle, there were seated the larval prehensile antennæ, of which the following measurements are given to show how minute they are. _Inch._ Length, from apex of disc, to the further edge of the basal articulation 20/6000 Breadth of basal segment, in broadest part 6/6000 Hoof-like disc, length of 6/6000 Ultimate segment, entire length of 6/6000 “ “ breadth, in broadest part 6/20000 The disc resembles a broad, rounded hoof, very little longer than broad, and narrowed in at the heel; the apex is not at all pointed, and bears some minute and thin spines. There is one large spine on the under side of the disc; and another on the basal segment, on the outside, in the usual position. The ultimate segment is long and thin; it has a notch on the inner side (the segment supposed to be stretched forward), bearing two or three long flexuous spines; and there are three or four other spines on the summit: altogether there is a close resemblance with the antennæ in Scalpellum, excepting that the hoof-like disc is not here pointed.