_Hab._--Warmer temperate and tropical seas; extremely common; Mediterranean, Smyrna, Sicily, Coast of Portugal; West Coast of Africa, River Gambia, West Indies, Demerara, Natal, Madagascar, Red Sea, Mouth of the Indus, Ceylon, Philippine Archipelago, East Indian Archipelago, Pacific Ocean, east coast of Australia, New Zealand; extremely common on ships' bottoms; often attached to floating timber, canes, &c.; often associated with _B. tintinnabulum_; attached to pebbles and various shells. With respect to the nomenclature of this extremely common species, which is widely distributed in all the warmer seas (excepting, as far as I have seen, on the west coast of America), there is some difficulty. I have no doubt that it is the _Lepas radiata_ of Wood (1815), but Bruguière, in 1789, gave this same name to a Balanus which he had not seen, but which is figured in Chemnitz, Tab. 59, fig. 842. I should have thought that this also had been the present species, but Spengler, in describing (Skrifter af Naturhist. Selskabet i, B. 1790) this individual specimen, which he calls _L. purpurea_, states that it is 13 lines in basal diameter; now this is a size which is never acquired by _B. amphitrite_; and the description, habits, and size, would apply equally well to the species which I have called _B. amaryllis_; but when no notice is taken of such points of importance, as whether the walls are permeated by pores, whether the radii are smooth-edged, whether the scuta are striated, it is impossible to identify with any approach to certainty sessile Cirripedes; and the names given ought, in my opinion, to carry little weight with them. With respect to Lamarck's _Balanus radiatus_ (1818), the synonyms quoted exhibit some great and inextricable confusion. The _B. radiatus_, again, of Risso, is a fossil and apparently distinct species. There can be no doubt that the present species is the _Lepas balanoides_ of Poli, (and of several authors who have followed him), and equally little doubt that the present species is not the true _L. balanoides_ of Linnæus, which has a membranous basis, and which I have not seen from the Mediterranean. Under these circumstances I have concluded that less confusion would be caused by giving a new name to this species than by taking that of Wood, which ought not to have been used by him, considering Bruguière's previous adoption of it.