_General Remarks._--I have very great doubts whether I have acted rightly in considering this as a species; but as there were many specimens, old and young, all differing remarkably from the common species, this form anyhow deserves description. The points by which it can be distinguished from _C. virgata_, are--the almost rectangular manner in which the upper portion of the tergum is bent outwards and along the orifice of the sack--the narrowness of all the valves, and especially of the lateral lobes of the scuta,--and lastly, the greater curvature of the carina, which in some specimens runs up far between the terga; had this last character been constant, it would have been an important one, but such is far from being the case. Great as are these differences in the valves, and though common to many specimens, they are not sufficient to convince me that it is a true species, and I should not be at all surprised at varieties, intermediate between it and the common form, being hereafter found;--had a name not been already attached to it, I should not have given one. In the monstrous variety described, we see to what an extent the valves may vary. The _C. Hunteri_ approaches nearest to the var. of _C. virgata_, called by Leach _Cineras chelonophilus_, for in both, the top of the capitulum is bluntly pointed and the terga are solid within; in the _Var. chelonophilus_, the terga and carina are minute, whereas here, though very narrow, they are much elongated. Certainly _C. chelonophilus_ has almost as strong a claim to rank as a species as _C. Hunteri_; but, in the former, by the aid of other varieties, the differences were almost reduced to the peculiarities in the terga--the valves, the most subject to variation. In _C. Hunteri_ we have other differences, and the form of the terga is even still more peculiar. I have, therefore, provisionally attached to it the specific name by which it is designated in the Museum of the College of Surgeons. From having been long kept in spirits, all aid from colour is lost. _Genus_--ALEPAS. Pl. III. ALEPAS. _Sander Rang._ Manuel des Mollusques, 1829. ANATIFA. _Quoy_ et _Gaimard_. Voyage de l’Astrolabe, 1834. TRITON. _Lesson._ Voyage de la Coquille, 1830. CINERAS. _Lesson._ Secundum Sander Rang. _Capitulum aut sine valvis, aut scutis corneis, pæne abditis._ Capitulum without valves,[41] or with horny, almost hidden, scuta. [41] Any one not attending to the characters derived from the softer parts of the Balanidæ and Lepadidæ, might easily confound with Alepas the genus Siphonicella (genus nov.), which, undoubtedly, though having the external appearance of a pedunculated cirripede, belongs to the Balaninæ, and is closely related to Coronula. Filaments seated beneath the basal articulations of the first pair of cirri; mandibles, with two or three teeth; maxillæ notched, with the lower part irregular, projecting; caudal appendages multi-articulate.