188C.] TROCHILI, CAPRIMULGI, AND CYPSELID.E. 503 



Be this as it may, tlie oversight has been kindly pointe 1 out to ine 

 by Mr. F. A. Lucas, the osteologist of the United States Natioiiai 

 Museum, and it devolves upon me to set the matter right. 



The only changes it demands in the text of my article is, that on 

 p. 908, in describing the humerus of Trochiliis, the sentence reading 

 " but the radial crest is represented by a strong and gracefully 

 curved hook" should state, instead of the " radial crest," the ulnar 

 tuberosity. Again, in the description of this figure on p. 915, it 

 should say the right humerus instead of the left ; and here as else- 

 where in the paper take into consideration the changes that result 

 therefrom. 



Now as a correct comparison of these bones is of such high import- 

 ance, and as 1 fully intend to carry my comparisons of the structure 

 of these groups still further, I have redrawn, increasing iu size and 

 presenting two views, the humeri of the forms under discussion, and 

 offer these drawings here as illustrations to the present article. 



From an examination of figures 1 and 2, it must be evident, to any 

 one familiar with the ordinary form of the avian humerus, that in 

 the Swallow the bone departs to some extent from the more common 

 shape it wears among the Passeres. The principal departure, 

 however, consists in a marked shortening of the shaft, and perhaps 

 a comparatively more conspicuous radial crest. The bone is likewise 

 non-pneumatic. This also we find to be the case in the Swift, where, 

 too, the radial crest is drawn out into an upturned hook, and the 

 ulnar tuberosity is simply drawn out further and consequently more 

 hook-like. 



Now turning to the Humming-bird (figs. 5 and 6), we find a 

 humerus that, so far as my knowledge extends, has not its counter- 

 part among living birds. In the first place, the extraordinary position 

 of its pneumatic fossa, being on the radial side of the bone, is an 

 exception to every general definition of a bird's humerus that the 

 writer has ever met with. Of the peculiar method of insertion of 

 the pectoralis major muscle in this bird I shall have sometliing to 

 say in a future contribution. As will be seen from the figures, 

 the ulnar tuberosity is a prominent decnrved process, and one of the 

 most striking features of this curiously twisted bone. It would be 

 superfluous on my part to point out in the figures the manifest 

 differences existing between the humerus of this Hummer and the 

 Swift ; they are even greater than I thought them to be, before I 

 made the oversight above quoted. In addition to its general form, 

 the humerus is highly pneumatic in Trochilus, which, as I have said, 

 is not the case among the Cypselidae, these latter agreeing with the 

 Swallows in this particular in having nou-pnenmatic humeri. 



