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Show 164 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, which the leading modification-the development of the wing-has carried with it, in its special varieties, the rest of the body, subjecting everything else to its domination, is well seen in the difference between Steatornis on the one hand, and the Swifts and Humming:- birds on the other. The latter are " Macrochires ;" their manus is of inordinate length and strength, and the humerus is very short and strong, like that of a Mole. But in Steatornis the manus is short, the humerus long and slender, and the cubitus is extremely long : this bird is thus an isomorph in this respect of the aquatic " Longipennes." This great development of the wing, in both cases, has caused a peculiar modification from that of the shorter-winged arboreal types, viz. the ordinary Passeres, and such Cuculines as the Woodpecker, Toucan, and Kingfisher. In all these latter types there is a complete bridge over the top part of the interosseous space, formed by one of the intercalary metacarpals-that between the normal 2nd and 3rd; in the embryo of these types another remnant appears on the ulnar side of the 3rd, this is a small 4th metacarpal. Now in birds that habitually flit from tree to tree, having only wings of moderate size, the remains of the primordial fore paw, not wanted in the wing, have a better chance of developing to some extent. Thus the remnant of the intercalary metacarpal fused with the functional bars is really large in the adults of these shorter-winged birds. But in Steatornis, the Cypselidae, and the Trochilidae, the great development of the functional bars has aborted these archaic, non-functional, parts much more. The same thing occurs in other families ; in the terrestrial Gallinaceous types the wing is like that of a Sparrow, a Finch, or Crow. In the Swans, Geese, Ducks, Gulls, & c , that is in all birds with long and powerful wings, the intercalary parts are very small, although nearly always demonstrable in the early young or in the embryo. The modification of the legs, and with them of the pelvis, follows that of the wings and shoulder-girdle ; they are not so much modified from a primordial condition as the fore limbs ; but they have undergone, nevertheless, a marvellous amount of change. When degeneration of the wings takes place, then the legs become dominant, as in the Ratitae ; that partial descent from a higher platform is correlated with an arrest of the brain. A very near relationship of Steatornis to the Goatsuckers (Capri-mulgidce) is rendered somewhat doubtful by the great differences to be seen in certain parts of its structure; its skull and dorsal vertebrae are as unlike as can well be. I suspect that the adaptation of this type to its nocturnal habits has made it much more like the Owls and Fem-Owls than can be accounted for on any theory of descent. If this bird should turn out to be a waif from the ancient tribes of the Caprimulgidae, and if Podargus and its allies belong to the same group, then the true Schizognathous Goatsuckers (of the genus Caprimulgus) must be considered as a culminating family, in which the whole skull and face has been lightened and refined to a remarkable degree, to give perfection to these crepuscular Moth-Hawks. Nitzsch's term for them, namely " Cuculinae noc- |