The _Lepas anserifera_ can be distinguished by the slight furrows on its valves from all the other species, excepting _L. pectinata_: this latter species can be readily known, by the close proximity in the scuta of the occludent margin, and the ridge extending from the umbo to the apex; by its carina being very narrow above the fork; by the prongs of the fork diverging at an angle of from 135° to 180°; by the thinness of its valves; by the coarseness of the furrows on them; and lastly, by there being at most in _L. pectinata_ only one filamentary appendage beneath the first cirrus. 4. LEPAS PECTINATA. Pl. I, fig. 3. LEPAS PECTINATA. _Spengler._ Skrifter Naturhist. Selbskabet, 2, B. 2, H., 1793, Tab. X, fig. 2. ---- MURICATA (var.) _Poli._ Test. Utriusque Scicil., vol. i, Pl. vi, figs. 23, 29, 1795. LEPAS ANSERIFERA. _Poli._ Test. Utriusque Scicil., vol. i, Pl. vi, figs. 25-27. ---- SULCATA. _Montagu._ Test. Brit., Pl. i, fig. 6, 1803. PENTALASMIS SULCATA. _Leach._ Encyclop. Brit. Suppl., tom. iii, Pl. lvii, 1824. ---- spirulæ (!) (var.) _Leach._ Tuckey’s Congo Expedit. Appendix, 1818. ---- RADULA (var.) et SULCATUS. _Brown._ Illust. of Conchology, Pl. li, figs. 3-6, 1844. ---- INVERSUS. _Chenu._ Illust. Conchy., Pl. i, fig. 14. ANATIFA SULCATA. _Quoy et Gaimard._ Voyage de l’Astrolabe, Pl. xciii, figs. 18, 20.[28] [28] I may add, that I have received many specimens incorrectly labelled _A. striata_, which is properly a synonym of _L. anserifera_. _L. valvis tenuibus, crassè sulcatis, sæpe pectinatis; scutorum cristâ prominente ab umbone ad apicem juxta marginem occludentem pertinente: furcæ carinalis cruribus inter angulos 135° et 180° divergentibus._ Valves thin, coarsely furrowed, often pectinated. Scuta with a prominent ridge extending, from the umbo to the apex, close to the occludent margin; fork of the carina with the prongs diverging at an angle of from 135° to 180°. Filaments absent, or only one on each side. Var. (Pl. I, fig. 3 _a_), upper part of the terga (bounded by the two occludent margins) produced and sharp; surface of all the valves often coarsely pectinated, and with the carina barbed. Atlantic Ocean, from the North of Ireland to off Cape Horn; common, under the tropics; Mediterranean: attached to wood, cork, charcoal, sea-weed, a reed-like leaf, spirulæ, cuttle-fish bones, to a bottle together with _L. anatifera_; to a ship’s bottom, Belfast, (W. Thompson.) Often associated with _L. fascicularis_. Montagu states (‘Test. Brit.,’ p. 18) that this species is sometimes attached to the fixed _Gorgonia flabellum_.