No one group of birds gives to Australia so tropical and foreign an air as the numerous species of this great family, by which it is tenanted, each and all of which are individually very abundant. Immense flocks of white Cockatoos may be seen perched among the green foliage of the _Eucalypti_; the brilliant scarlet breasts of the Rose-hills blaze forth from the yellow-flowering _Acaciæ_; the _Trichoglossi_ or Honey-eating Parrakeets enliven the flowering branches of the larger _Eucalypti_ with their beauty and their lively actions; the little Grass Parrakeets frequent the plains of the interior and render these solitary spots a world of animation; nay, the very towns, particularly Hobart Town and Adelaide, are constantly visited by flights of this beautiful tribe of birds, which traverse the streets with arrow-like swiftness, and chase each other precisely after the manner the Swifts are seen to do in our own islands. In the public roads of Van Diemen’s Land the beautiful _Platycerci_ may be constantly seen in small companies, performing precisely the same offices as the Sparrow in England. I have also seen flocks of from fifty to a hundred, like tame pigeons, at the barn-doors in the farm-yards of the settlers, to which they descend for the refuse grain thrown out with the straw by the threshers. As might naturally be expected, the agriculturist is often sadly annoyed by the destruction certain species effect among his newly-sown and ripening corn, particularly where the land has been recently cleared and is adjacent to the brushes. Fifty-five well-defined species of this great family are described and figured in the present work. They appear to constitute four great groups, each comprising several genera, nearly the whole of which are strictly and peculiarly Australian; for instance, neither _Calyptorhynchus_, _Platycercus_, _Euphema_, _Psephotus_, _Melopsittacus_, or _Nymphicus_ have been found in any other country; and whether we consider the elegance of their forms or the beauty of their plumage, they may vie with the members of this extensive family from any part of the world. Genus CACATUA, _Briss._ Australia, the Molucca and Philippine Islands and New Guinea are the great nurseries of the members of this genus. They incubate in holes of trees or in rocks, and lay two eggs. 361. Cacatua galerita Vol. V. Pl. 1. There are evidently several varieties or races of this species in Australia, each possessing a modification in the form of the bill doubtless given for some specific purpose; the Van Diemen’s Land bird is the largest, and has the upper mandible attenuated, while the Port Essington bird is altogether smaller, and has a much more arched bill. 362. Cacatua Leadbeaterii Vol. V. Pl. 2.