The species of this group are spread over the whole world, tropical regions having the greatest variety of forms and number of species. The _Strigidæ_ are cosmopolitan, most of the genera belonging to both continents. The _Falconidæ_ are also found the world over, but each continent has subfamilies peculiar to it. The _Cathartidæ_ are peculiar to America, having analogous representatives in the Old World in the subfamily _Vulturinæ_ belonging to the _Falconidæ_, The _Gypogeranidæ_ are found only in South Africa, where a single species, _Gypogeranus serpentarius_ (GMEL.), sole representative of the family, is found. As regards the comparative number of species of this order in the two continents, the Old World is considerably ahead of the New World, which might be expected from its far greater land area. 581 species are given in Gray’s Hand List,[6] of which certainly not more than 500, probably not more than 450, are valid species, the others ranking as geographical races, or are synonymous with others; of this number about 350 nominal species are accredited to the Old World. America, however, possesses the greatest variety of forms, and the great bulk of the Old World Raptorial fauna is made up chiefly by a large array of species of a few genera which are represented in America by but one or two, or at most half a dozen, species. The genera _Aquila_, _Spizætus_, _Accipiter_, _Haliætus_, _Falco_, _Circus_, _Athene_, _Strix_, and _Buteo_, are striking examples. As regards the number of peculiar forms, America is considerably ahead. FAMILY STRIGIDÆ.—THE OWLS. CHAR. Eyes directed forward, and surrounded by a radiating system of feathers, which is bounded, except anteriorly, by a ruff of stiff, compactly webbed, differently formed, and somewhat recurved feathers; loral feathers antrorse, long, and dense. Plumage very soft and lax, of a fine downy texture, the feathers destitute of an after-shaft. Oil-gland without the usual circlet of feathers. Outer webs of the quills with the points of the fibres recurved. Feathers on the sides of the forehead frequently elongated into ear-like tufts; tarsus usually, and toes frequently, densely feathered. Ear-opening very large, sometimes covered by a lappet. Œsophagus destitute of a dilated crop; cœca large. Maxillo-palatines thick and spongy, and encroaching upon the intervening valley; basipterygoid processes always present. Outer toe reversible; posterior toe only about half as long as the outer. Posterior margin of the sternum doubly indented; clavicle weak and nearly cylindrical, about equal in length to the sternum. Anterior process of the coracoid projected forward so as to meet the clavicle, beneath the basal process of the scapula. Eggs variable in shape, usually nearly spherical, always immaculate, pure white.