_General Remarks._--This genus is intimately related, as has been remarked by Professor Macgillivray,[36] to Lepas: if we look to the body of the animal, which from being less exposed to external influences must, in the Cirripedia, offer the most trustworthy characters, we find that in Conchoderma there are additional filamentary appendages attached to the cirri, that there are no caudal appendages, that the teeth of the mandibles are finely pectinated, and that the ovarian tubes run higher up round the sack; in every other respect, there is the closest similarity, even to the arrangement of the bristles on the cirri. In the capitulum, the difference consists chiefly, though not exclusively, in the less development of the valves, and their consequent wide separation: the scuta, however, in Conchoderma, are added to beneath their umbones, or original centres of growth, which is never the case, or only to a very slight degree, in Lepas. Conchoderma has no very close affinity to any other genus. As the majority of authors have ranked the two common species under two distinct genera (Otion and Cineras), I may observe, that there is no good ground for this separation; in the above few specified points in which Conchoderma differs from the genus most closely allied to it, the two species essentially agree together. If we take the nearest varieties of _C. virgata_ and _C. aurita_, there is but a very slight difference even in the form of their valves, and these hold the same relative positions to each other; the carina, however, is always less developed in _C. aurita_; even the colouring in both tends to follow the same arrangement. The only obvious distinction between the two species, are the ear-like appendages of _C. aurita_, which, however, are not developed in its early age, are subject to considerable variation, are of no high functional signification, and are indicated in _C. virgata_ by two prominences on the same exact spots. On these grounds I conclude, that the generic separation of the two species is quite inadmissible. [36] Remarks on the Cirripedia, &c.; ‘Edin. New Phil. Journal,’ vol. xxxix, p. 171. 1. CONCHODERMA AURITA. Pl. III, fig. 4. LEPAS AURITA. _Linn._[37] Systema Naturæ, 1767. OTION CUVIERANUS (!) BLAINVILLIANUS (!) BELLIANUS (!) DUMERILLIANUS (!) RISSOANUS. _Leach._ Encyclop. Brit., vol. iii, Supp., 1824, and Zoological Journal, vol. ii, p. 208, July 1825. OTION DEPRESSA et SACCUTIFERA. _Coates._ Journal Acad. Nat. Sci. of Philadelphia, vol. vi, p. 132, 1829. OTION AURITUS. _Macgillivray._ Edinburgh New Phil. Journal, vol. xxxviii, 1845. LEPAS LEPORINA. _Poli._ Test. utriusq. Sicil., pl. vi, fig. 21, 1795. LEPAS CORNUTA. _Montagu._ Linn. Trans., vol. xi, p. 179, 1815. CONCHODERMA AURITUM et LEPORINUM. _Olfers._ Magaz. der Gesell. Freunde zu Berlin, 3d Quartel., p. 177, 1814.