In the Picariæ, we have first, the toucans (Rhamphastidæ); an extraordinary and beautiful family, whose enormous gaily-coloured bills and long feathered tongues, separate them widely from all other birds. The Galbulidæ or jacamars, the motmots (Momotidæ), and the curious little todies (Todidæ) of the Antilles, are also isolated groups. But most remarkable of all is the wonderful family of the humming-birds, which ranges over all America from Tierra del Fuego to Sitka, and from the level plains of the Amazon to above the snow-line on the Andes; which abounds both in genera, species, and individuals, and is yet strictly confined to this continent alone! How vast must have been the time required to develop those beautiful and {9}highly specialized forms out of some ancestral swift-like type; how complete and long continued the isolation of their birthplace to have allowed of their modification and adaptation to such divergent climates and conditions, yet never to have permitted them to establish themselves in the other continents. No naturalist can study in detail this single family of birds, without being profoundly impressed with the vast antiquity of the South American continent, its long isolation from the rest of the land surface of the globe, and the persistence through countless ages of all the conditions requisite for the development and increase of varied forms of animal life. Passing on to the parrot tribe, we find the peculiar family of the Conuridæ, of which the macaws are the highest development, very largely represented. It is in the gallinaceous birds however that we again meet with wholly isolated groups. The Cracidæ, including the curassows and guans, have no immediate relations with any of the Old World families. Professor Huxley considers them to approach nearest to (though still very remote from) the Australian megapodes; and here, as in the case of the marsupials, we probably have divergent modifications of an ancient type once widely distributed, not a direct communication between the southern continents. The Tinamidæ or tinamous, point to a still more remote antiquity, since their nearest allies are believed to be the Struthiones or ostrich tribe, of which a few representatives are scattered widely over the globe. The hoazin of Guiana (Opisthocomus) is another isolated form, not only the type of a family, but perhaps of an extinct order of birds. Passing on to the waders, we have a number of peculiar family types, all indicative of antiquity and isolation. The _Cariama_ of the plains of Brazil, a bird somewhat intermediate between a bustard and a hawk, is one of these; the elegant _Psophia_ or trumpeter of the Amazonian forests; the beautiful little sun-bittern of the river banks (_Eurypyga_); and the horned screamers (_Palamedea_), all form distinct and isolated families of birds, to which the Old World offers nothing directly comparable.