Lastly, we come to _var. d'Orbignii_ (Pl. 1, fig. _l_): until quite recently I did not even suspect that this form was only a variety of _B. tintinnabulum_: I have examined a great number of specimens in Mr. Stutchbury's collection, which had come attached on a vessel from Java, and likewise a few other specimens in other collections. They all closely resemble each other in shape, and even in size, and differ only in tint of colour, and in the surface being either very smooth, or longitudinally ribbed, sometimes with rugged, sharp points. From this circumstance--from the peculiarity of the tint, with the tips of the parietes and one side of the radii perfectly white--and from the obliquity of the summits of the radii, I was led to think this form specifically distinct. But the colour does not differ from that of some other varieties of _B. tintinnabulum_; the circumstance of the colour being uniform or not striped, is common to the sub-varieties of several varieties, and the white tips to the parietes, and the white borders to the radii, result simply from the shell, whilst young, having been wholly white, and this is not rarely the case with _var. communis_. Dismissing, therefore, colour, it will be found that hardly any other characters remain by which this form can be separated from _var. occator_; in both the summits of the radii are oblique, in both the sheath is coloured in nearly the same manner, in both the opercular valves, especially the terga (Pl. 2, figs. 1 _m_, 1 _n_), resemble each other; the scuta, however, are smooth in _var. d'Orbignii_ and rough in _var. occator_. This latter form, certainly, cannot be specifically separated from _var. intermedius_, and this assuredly is only a variety of _B. tintinnabulum_. Hence I am led to conclude that _Balanus d'Orbignii_ of Chenu, peculiar as its whole aspect is, must be ranked only as a variety of _B. tintinnabulum_; its oblique radii resulting from the same cause, whatever that may be, which has given this structure to _var. intermedius_ and _occator_; and its peculiar colouring to having been exposed (owing probably to having been transported on vessels) to different conditions, whilst young and old. 2. BALANUS TULIPIFORMIS. Pl. 2, fig. 2 _a_-2 _d_. BALANUS TULIPIFORMIS EX CORALLIO RUBRO. _Ellis._[88] Philosoph. Transactions, vol. 50 (1758), tab. 30, fig. 10. LEPAS TULIPA. _Poli._ Test. utriusque Siciliæ, tab. 5, fig. 1. et 6 (1791). BALANUS TINTINNABULUM (_var._) _Chenu._ Illust. Conch., tab. 3, f. 5.