BIRDS OF NORTH AND MIDDLE AMERICA. 303 



being that first one color, then the other, is flashed forth as the 

 bird changes shghtly its position. 



Note to Trochilid.e.— (1) In descriptions of some of the species certain positions 

 of the bird with reference to the eye and the angle of light are designated as "posi- 

 tion 0," etc.« These positions may be described as follows: 



(2) The vernacular names are mostly taken, with or without niodilication, from 

 Gould's "Monograph of The Trochilidii?." In some cases it has seemed desirable, 

 for the sake of greater brevity or euphony, to change or modify the names bestowed 

 by Gould, while in the case of forms described since the publication of that magnifi- 

 cent work it has, of course, been necessary to invent new ones. At the best, however, 

 it must be said that (as in the case of other groups of birds) many of these vernacular 

 names are more or less fanciful and of slight utility. 



KEY TO THE NORTH AND MIDDLE AMERICAN AND MORE CLOSELY RELATED SOUTH 

 AMERICAN GENERA OF TROCHILID.E. 



a. Nasal oj^erculum well-developed (though sometimes concealed by frontal feather- 

 ing); no white or buffy band across rump; adult males with outer w^eb of ninth 

 primary normal. 

 h. Nasal operculum higher, the lower edge of the posterior portion about midway 

 between culmen and tomia, or nearer to the former. {Phcclhornithinx .) 

 c. Bill excessively decurved, forming about one-third of a circle; feet very stout; 



under parts conspicuously streaked Eutoxeres (p. 310). 



cc. Bill only moderately or slightly decurved; feet much weaker; under parts not 

 streaked. 

 d. Nasal operculum decumbent, with lower edge distinctly convex, at least 

 posteriorly; bill more slender, compressed. 

 e. Tail graduated for at least half its length, with middle pair of rectrices 



more or less elongated PhcEthornis (p. 314). 



ee. Tail graduated for less than half its length, with middle rectrices not 



elongated Glaucis (p. 329). 



(Id. Nasal operculum excmTent, its lower edge more or less concave or arched; 



bill stouter, depressed Threnetes (p. 336). 



hb. Nasal operculum lower, the lower edge of its posterior portion much nearer to 

 tomia than to culmen. {TrocJiilinx .) 

 c. Nasal operculum partly exposed. 



d. Outermost (tenth) i)rimary distinctly shorter than ninth; adult male with 

 next to outer pair of rectrices greatly elongated and head with a double 



occipital crest Aitliurus (j). 338). 



dd. Outermost (tenth") primary ecjual to or longer than ninth (or else with tips 

 attenuated). 

 e. Frontal feathering extending as far forward as that of chin; exposed culmen 

 at least as long as tail, the bill very slender, faintly recurved terminally. 



Hemistephania (p. 342). 



« These positions, it should be stated, do not correspond with those similarly 

 numbered by Gadow in his article on the color of feathers in Proc. Zool. Soc. Lond., 

 1882, 409-421 (see especially diagram on p. 420), which, so far as metallic coloring 

 is concerned is based chiefly on sun-birds (Nectarinidce) and other non-Trochiline 

 forms, which seem to require more or less different positions. 



(a) The eye between bird and light, bird's bill toward eye, bird nearly horizontal. 



(b) Eye directly above bird, the latter's bill toward light, and position of its body 

 nearly horizontal. 



(c) Same as position a, but bird reversed (tail, instead of bill, toward eye). 



(d) Bird between eye and light, tail toward eye, body inclined, with bill point- 

 ing upward. 



