164 MR. W. K. PARKER ON STEATORNIS CA.RIPENSIS. [Apr. 2, 



which the leadinff mollification — 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 be- 

 tween Steatornis on the one hand, and the Swifts and Humiiiing- 

 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 oi&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 chauce 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 

 Trochilidse, the great development of the functional bars has aborted 

 these archaic, non-functional, parts nnich 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 leys, 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 uu- 

 dergone, nevertheless, a marvellous amount of change. 



When deyeneration of the wings takes place, then the legs be- 

 come 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 ver- 

 tebrae are as unlike as can well be. I suspect tliat the adaptation 

 of this type to its nocturnal habits has made it much more like the 

 Owls and Fern-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 Caprimulgidse, and if Podargus and its allies belong to 

 the same group, then the true Schizognathous Goatsuckers (of the 

 genus Caprimulyus) must be considered as a culminating family, 

 in which the whole skull aud face has been lightened and refined 

 to a remarkable degree, to give perfection to these crepuscular 

 Moth-Hawks. Nitzsch's term for them, namely " CuculiuBe noc- 



