The greater number of the species of the Balanidæ have wide ranges, as might be inferred from the fact of between one third and one fourth of the total number inhabiting both the torrid and temperate zones; but it should not be overlooked, that those species, as _Balanus tintinnabulum_, _amphitrite_, _improvisus_, and, in a lesser degree, _B. trigonus_ and _Tetraclita radiata_, which seem to range over nearly the whole world (excepting the colder seas), are species which are habitually attached to ships, and which could hardly fail to be widely transported. Indeed, it appears to me surprising, that such species as _Balanus psittacus_ and _eburneus_, which often become attached to vessels, should still be confined, the one to Southern, and the other to Northern America. But some other Cirripedes, which I have never seen attached to vessels, have likewise immense ranges: thus _Tetraclita porosa_ is found in every tropical and warmer sea, and _Chthamalus stellatus_ ranges round the world in the northern hemisphere, and, along the eastern side of America, far south of the equator: _Balanus spongicola_, and _Acasta spongites_, extend from the shores of Britain to the Cape of Good Hope: _Balanus lævis_ ranges from Tierra del Fuego to California. I may further remark, that the only two other species of Balanus, and the one Chthamalus, inhabiting Tierra del Fuego, are, also, found on the shores of Peru. But to show the powers of endurance in some species, I may specify the case of _Balanus improvisus_, which flourishes on the coast of Nova Scotia, amongst the West Indian Islands, in Southern Patagonia, and near Guayaquil. Even more striking is the case of _B. crenatus_, of which I have seen specimens from latitude 74° 48′ north, from the West Indies, and the Cape of Good Hope! In these two latter localities, however, it seems to be rare, and may have been first transported to them from the shores of Europe, on the bottoms of vessels, to which it sometimes adheres.