With respect to _var._ 1, _communis_, I have nothing further to remark, except that I have seen specimens identically similar from the Mediterranean, Natal, the Philippine Archipelago, and Sydney; at the latter place it is said to be rare, but in most places it is the commonest variety, and is often attached to ships' bottoms. Of _var._ 2, _venustus_, I have seen specimens from the west coast of Africa, Natal, and Ceylon, in groups by themselves, and associated with _var. communis_; it is much less common than _var._ 1. The third variety, _pallidus_, is not uncommon; I have seen many specimens from the bottoms of ships, from the West Indies, and the west coast of Africa. Of the _var._ 4, _niveus_, I have seen the most perfect graduated series passing into _var._ 1, both from the West Indies, Florida, and the Mediterranean: I have seen other specimens from the Red Sea and Madagascar. Of the _var._ 5, _modestus_, I have seen only one group from an unknown locality; it is only remarkable from its uniform colouring. The _var._ 6, _Stutsburi_, is more remarkable than the foregoing; until quite lately I did not doubt that it was specifically distinct; but as I have seen every character graduate into other varieties, I am now convinced that it is not a true species: all the specimens which I have seen have come on shells, or on ships' bottoms, from West Africa. Of _var._ 7, _obscurus_, I have seen three or four groups of specimens from unknown quarters, both on pebbles, shells, and on cork (probably from the Atlantic ocean); and likewise some specimens taken from the bottom of Her Majesty's ship "Fly," on the east coast of Australia; these latter are intermediate in character with the next _var. variegatus_; from the Australian seas, which I at first ranked as an undoubted species, but I have subsequently failed in discovering any sufficient diagnostic character. Lastly, of _var. cirratus_, I have seen several groups of specimens from India and the Philippine Archipelago, and a group intermediate in character between this and the first and third varieties, from Australia; I retained this variety owing to its peculiar freckled, pale brown colouring and beaded scuta (of which, however, I have seen decided traces in the common variety), as a distinct species, after I had given up all the foregoing forms. I entertain some doubts whether I have now acted right; but when I found some specimens which, I found it impossible to decide, whether to rank as _amphitrite_ or _cirratus_, I determined to take the more prudent course, and sink the latter as a species. This variety, also, seems to connect _B. amphitrite_ and _concavus_ very closely. 20. BALANUS PŒCILUS. Pl. 5, fig. 3 _a_, 3 _b_. _Shell dull red, freckled with white. Scutum internally without an adductor ridge; tergum with the spur, sharply truncated, almost one third of width of valve._