Together they run along the rostral edge, giving out through each orifice a little disc of brownish cement, and finally they enter the larval antennæ. The peduncle, just above the attached portion, where still lined by corium, no doubt increases in diameter at each period of growth, and must, I presume, become pressed against the almost parallel branch of the coralline. The corium, at this same period, shrinks, or is absorbed, and the two cement-ducts come in contact with, and adhere to, the inner surface of the outer membrane of the peduncle; and then, by a process which I do not understand in this or any other Cirripede, apertures are formed both in the ducts and through the membrane, so that the cement passes through, firmly fastening the outer surface of the peduncle with its calcareous scales and spines, to the coralline. [51] Mr. Peach, (Transact. Brit. Assoc., 1845, p. 65,) states that this is sometimes the case in Cornwall; and I have seen a similar instance in a fine group from Naples. The structure of the larval prehensile antennæ will be most conveniently described when we come to the Complemental male; and figures (10-12, Pl. V) will be given. _Size and Colours._--Montagu states (‘Test. Brit.,’ p. 18) that British specimens rarely have a capitulum .62 of an inch in length; I have, however, seen an Irish specimen, .7 long; and several specimens, from the Bay of Naples, .8 long, and including the peduncle, 1.3 in length. The valves in all the specimens are white, and the membrane connecting them either nearly white, or dirty pale yellowish, or purplish-brown. Within the sack the corium under the valves is tinted pale purple, and two very faint bands of the same colour can generally be distinguished running down the two sides of the peduncle. Body, coloured yellowish-white, with the upper segments of the pedicels of the cirri, tinted in front with purple. _Body_, much flattened, the prosoma is very little developed; the mouth placed far from the adductor muscle, and is directed in a remarkable manner towards the ventral surface of the thorax: the first pair of cirri stands far separated from the second pair. _Mouth._--Labrum with the upper part highly bullate, forming an overhanging projection equalling the longitudinal axis of the mouth; basal margin much produced; crest with a row of bead-like teeth. _Palpi_ rather small, with their external margin straight, and internal margin oblique: the bristles on the two palpi just meet each other. _Mandibles_, with five or six teeth, with the second, (or second and third, when there are six teeth,) smaller than the others; in two specimens, there were five teeth on one side and six on the other; inferior angle rather broad and strongly pectinated.