372 



DE. K. W. SHUFELDt's MORPHOLOGICAL 



humeri in Clicetura pelagica are pneumatic, but the bone is 

 shaped upon the same plan as the humerus of Micropus, and the 

 pneumatic fossa is, as in Passeres, on the ulnar side. From 

 what has gone before, we now know that in general form, and 

 other particulars, Micropus is nearer the Swallows than is such 

 a Swift as Chwtura, and this last fact, with respect to the arm- 

 bones, points still more strongly to the truth of such a state- 

 ment. Even at this moment I am not acquainted with any other 

 bird in the Class that has the pneumatic fossa of its humerus 

 situated on the radial side of the bone, as the Trochili have. 

 This fact alone, and surely when taken in connection with the 

 otherwise vastly different form of the bone itself, is sufficient to 

 show that in their wing-structure Swifts and Humming-birds 

 widely differ. 



Further, in the papers above alluded to I have already 

 pointed out how in the bones of the antibrachium, in Tro- 

 chilus and Micropus, the radius is actually bent to a bow in the 

 former, while it is as absolutely straight as any bone can be in 

 the Swift. The ulna, too, in these birds differs in its general 

 form. Moreover, we find sesamoids present in the carpus of 

 Humming-birds which do not exist in Cypseli, although, since 

 writing my first memoir on this subject, I have found a sesamoid 

 at the elbow in Clicetura and Micropus, such as the Swallows have. 



Coming next to the carpo-metacarpus we find one great 

 and principal difference, in addition to minor ones — in the Hum- 

 ming-birds the middle metacarpal in this compound bone is 

 longer than the index metacarpal, the reverse condition obtain- 

 ing among the Swifts. This is enough to show that the bones 

 are essentially unlike in their most important character. The 

 proximal phalanx of the index finger is altogether a differently 

 formed bone from the corresponding segment in the manus 

 of the Swift, as any one may see by a comparison either of the 

 bones themselves or my drawings (P. Z. S. 1885, pi. Ixi. figs. 3 

 and 4i,j»"). 



To briefly recapitulate, then, the absolutely essential and 

 fundamental characters in the wing-structure of a Swift and a 

 Humming-bird, I find that : — 1. The parts markedly differ in 

 their external characters, inasmuch as they do not possess the 

 same number of secondary quill-feathers ; Swifts have a very 

 peculiar pigmented (deep black) area of the skin centrally located 

 on both sides of the hand, while Trochili have not; the character 



