224 STRUCTURE AND CLASSIFICATION OF BIRDS 



MACROCHIRES 



Definition. — Eeotrioes, ten ; oil gland nude ; aftersliaft present. Muscle 

 formula of leg, A — . Expansor seoundariorum, sterno-oOraooideus, 

 and biceps sUp absent. Ceeoa absent. Manns very long. Sternum 

 unnotched. 



This group of birds contains two well-marked types — 

 the humming birds and the swifts,' the former confined to 

 America, the latter world-wide in distribution. 



In external characters the generally minute size, the 

 frequently brilliant metallic plumage, and the long slender 

 bill distinguish the Colibris from the swifts. But Dr. 

 Shtjpeldt has found ^ in a nestling humming bird a bill 

 hardly longer than that of a swift. 



The rectrices are ten, and in all these birds the oil 

 gland is nude. There is an aftershaft. In the swifts there 

 are down feathers upon the apteria ; in the humming birds 

 there are not. 



The pterylosis of the group has been chiefly studied by 

 NiTZSCH, to whose account Dr. Shufbldt has added details 

 of value. 



The throat is completely feathered in the swifts, the two 

 ventral tracts, however, becoming distinct at the beginning 

 of the neck. The ventral tracts widen out in the pectoral 

 region, but there is no outer branch or trace of one. The 

 narrow dorsal tract bifurcates between the shoulders and 

 reunites again to enclose a narrowish spinal space. There 

 are well-marked femoral tracts. 



In the humming birds the ventral tract is double up to 

 the symphysis of the mandibles, or nearly so ; the dorsal 

 tracts are very much wider and form a diamond-shaped patch, 

 within which is a very slight dorsal apterion ; there appear 

 to be no femoral tracts, and there is a naked space in the 

 nape of the neck, dividing the dorsal tract. 



' GiEBEL, ' Ueber einige Eigenthumliohkeiten in der Organisation der Koli- 

 bris,' Zeitschr. f. d. ges. Naturw. 1. 1877, p. 322 ; W. K. Pakkee, ' On the Sys- 

 tematic Position of the Swifts,' Zool. (3), xiii. 1889, p. 91. 



'^ ' Studies of the Maoroohires,' &o.. J. Linn. Soc. 1888. 



