Peduncle.—This, as already remarked, cannot be distinctly separated from the capitulum; it is much compressed; it is composed of unusually thin and delicate membrane, transversely wrinkled and thickly clothed with long cylindrical horns or spines of chitine. These horns ([fig. 8 c´]) are not the analogues of the spines which are articulated on the external membranes of many Pedunculated and Sessile Cirripedes, but of the calcified scales on the peduncle of Scalpellum and Pollicipes; for they pass through the membrane (the underlying corium being marked by their bases) and are persistent, being added to, like the valves, during each successive period of growth. Their bases are concave, so that a section of the layers of growth exhibits a series of pointed cones, one within another. Each spine is nearly cylindrical, irregularly curled, and nodose or slightly enlarged at intervals: the apex smooth and pointed; the exterior surface longitudinally and finely ribbed, like the valves. The spines increase irregularly in size from the bottom to the top of the peduncle, those at the carinal and rostral ends being generally the longest; they point upwards and hide the bases of the valves. They are not arranged symmetrically, and new ones are formed over all parts of the peduncle. They are formed of the same substance as the valves, and do not contain any calcareous matter. These horns are yellowish, generally ringed with pale and dark blueish brown, which on pressure becomes slightly opalescent with pale blue and fiery red: sometimes only the upper horns are thus ringed, and in rare instances all are simply yellowish. The muscles of the peduncle run up to the bases of the four valves.

Surface of Attachment.—The cement appears to proceed from only two points. In some specimens, a considerable length of one side of the peduncle was fastened to the surface of attachment, the horns or spines being enveloped in the cement. The prehensile antennæ of the larva will presently be described under the male.

The length of an average specimen, including the peduncle and valves, is about half an inch, and the width across the widest part one fifth of an inch. Mr. Cuming has one specimen an inch in length, but this is owing to the peduncle being unusually tapering. In a specimen kept some years in spirits, the cirri, trophi, caudal appendages, and corium under the membrane between the scuta, were all dark purple; the sack and corium of peduncle clouded with purple, and the prosoma pale-coloured.

The Body ([Pl. IV], [fig. 8 a´]) is small compared with the capitulum and peduncle; it is much flattened; the prosoma is of a very peculiar shape, being square, the sides of equal length, and, in an average-sized specimen, 75/1000th of an inch long. The peculiar shape arises from the great distance between the first and second cirrus—from the mouth being far removed from the adductor scutorum muscle—and lastly, from the lower part of the prosoma being not at all protuberant. The thorax which supports the cirri is also unusually small, plainly articulated, and separated from the prosoma by a deep fold. The thin membrane of the prosoma is studded with some fine, pointed hairs, about 3/400ths in length, and articulated on little circular discs.

Mouth, placed at a considerable distance from the adductor, and directed in an unusual manner towards the ventral surface of the thorax: the trophi are arranged, in a curved line, facing the thorax (see [Pl. V], [fig. 2], for this part in the male), and therefore less laterally than is usual.

Labrum ([Pl. IV], [fig. 8 a´ opposite c]) highly bullate; the upper part produced into a blunt point: on its crest there are no teeth.

Palpi ([fig. 8 a´ opposite d]) small, blunt and rounded at their ends; inner margins slightly concave.

Mandibles ([Pl. X], [fig. 4]), with three teeth, of which the first is much larger than the second and third, and distant from them: inferior angle produced and pectinated; upper edges of the second and third teeth finely pectinated.

Maxillæ ([Pl. X], [fig. 11]) small, slightly but distinctly indented by two notches, supporting, besides the three upper great spines, three pairs of moderately long spines and some finer ones: apodeme short, thick.

Outer Maxillæ, unusually pointed, with the inner bristles not very numerous, continuously arranged; externally, the bristles are longer. Olfactory orifices, tubular, projecting, flattened, square on the summit, smooth: they point upwards and obliquely towards each other: they arise more laterally than in the other genera, namely outside the bases of the outer maxillæ, and between them and the inner maxillæ.