[27] Professor Macgillivray does not consider the species, which he has described under _L. nauta_, and which I cannot doubt is the same with the present species, as the _L. anserifera_ of Linnæus; but I find it so named in all old collections, and it seems to agree very well with Linnæus’s description. There has been much groundless confusion about this species; I have no hesitation in giving _A. striata_, of Brugière, as a synonym, though I have received from Paris the _Lepas pectinata_ of this volume, named as the _A. striata_; and on the other hand, Poli has incorrectly called a common variety of _L. pectinata_ by the name of _L. anserifera_. _L. valvis approximatis leviter sulcatis (tergis præcipuè); scuto dextro dente forti interno umbonali, lævo aut dente exiguo, aut merâ cristâ instructo; margine occludente arcuato, prominente: pedunculi parte superiore aurantiacâ._ Valves approximate, slightly furrowed, especially the terga; right-hand scutum with a strong internal umbonal tooth; left-hand with a small tooth, or mere ridge; occludent margin arched, protuberant: uppermost part of peduncle orange-coloured. Filaments five or six on each side. Var. (_dilatata_, young); valves rather thin, finely furrowed, often strongly pectinated; scuta broad, with the occludent margins much arched, making the space wide between this margin and the ridge connecting the umbo and the apex: carina often barbed. Common on ships’ bottoms from the Mediterranean, West Indies, South America, Mauritius, Coast of Africa and the East-Indian Archipelago. Central Pacific Ocean. China Sea. Chusan. Sydney. Attached to pumice, various species of fuci, Janthinæ, Spirulæ; often associated with _L. anatifera_ and _L. Hillii_, and, in a young state, with _L. fascicularis_. _General Appearance._--Capitulum more or less elongated relatively to its breadth; in two specimens, with scuta of equal width, one was longer than the other by the whole of the occludent margin of the terga. Valves white, thick, (in young specimens sometimes diaphanous and thin,) closely approximate to each other; surfaces furrowed to a very variable amount. Terga generally more plainly furrowed than the scuta, of which the basal portion is generally less furrowed than the upper part; ridges, often rough, generally much narrower than the furrows: in half-grown specimens (var., _dilatata_ of Leach,) the ridges are frequently denticulated, and there is even sometimes a row of bead-like teeth along the basal margins of the scuta. The ridges vary much, sometimes alternately wide and narrow; in two specimens of equal size, there were, in one, thirty-two ridges, and in the other only eighteen, on the scutum.