_Peduncle and Attachment._--The peduncle is generally quite smooth: though with a high power its surface may be seen to be studded with minute beads, or larger discs, of yellowish and hard chitine; in the young of _L. australis_, and I suspect of some other species, it is covered with very minute spines. The peduncle in this genus attains its greatest development. The cement-tissue debouches, I believe, only through the functionless larval antennæ, except in one species, _L. fascicularis_, in which a ball of this substance is formed in a most peculiar manner round the peduncle (Pl. I, fig. 6), apparently for the purpose of serving as a float, as will be presently described. _Size and Colour._--The species of this genus are the largest of the Pedunculata, with the exception of some Pollicipes: even in the smallest species (_L. pectinata_), the capitulum sometimes attains a length of about half an inch. The peduncle varies much in length in the same species: in _L. anatifera_, it is occasionally above a foot long. The colours of _L. anatifera_, _L. Hillii_, and _L. anserifera_, are very bright and striking; the membrane bordering the valves and that round the top of peduncle in two of the species, is of the brightest scarlet-orange; the valves, owing to the underlying corium, are pale blueish-grey, and the interspaces between them dark leaden-purple. The cirri and trophi are generally dark purple or lead-colour. _Filamentary Appendages._--These are attached to beneath the basal articulation of first pair of cirri; they vary in the several species, from one to five or six on each side, the lowest being always the longest. Several of them are occupied by testes. In _L. pectinata_, generally, not even one is developed. They are subject to great variation in their proportional lengths, and in number, in the same species. These organs have generally been considered to serve as branchiæ; I see no reason to believe that they are more especially designed for this end, than is the general surface of the body. _Mouth._--The labrum is moderately bullate, the longitudinal diameter of this part equalling about one third, or half of that of the rest of the mouth. The palpi are moderately developed. The mandibles (Pl. X, fig. 5) have five teeth with the inferior point either broad, or very narrow and tooth-like. The maxillæ are step-formed (Pl. X, fig. 9); the first step is sometimes indistinct and curved; and in _L. pectinata_, all the steps vary much, and are more or less blended together. The outer maxillæ (like those at Pl. X, fig. 16), are internally clothed continuously with spines. The olfactory orifices are not at all prominent.