548 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



ridge; tomia smooth; maxilla and mandible (especially the latter) 

 each with a more or less distinct median lateral groove. Nasal 

 operculum broad and convex posteriorly, the upper basal portion 

 feathered; frontal feathering forming two narrow antiss, extending 

 nearly (sometimes quite) as far forward as anterior end of nasal 

 operculum. Tarsus clothed with short feathers; lateral toes about 

 as long as middle toe, the hallux shorter. Wing three to nearly four 

 times as long as culmen, the outer primary longest. Tail less than 

 half as long as wing to nearly as long as wing in adult males of some 

 species, emarginate or forked in adult males, forked, emarginate, or 

 slightly double-rounded in females, the rectrices straight, the outer 

 ones narrower than middle pair, sometimes much narrower, but 

 always with rounded tip. 



Coloration. — Above metallic green or bronze-green. Adult males 

 brilliant metallic green below, the tail blue-black, green, bronze, or 

 copper-bronze, sometimes with middle rectrices tipped with gray. 

 Females with under parts pale gray or grayish white, middle rectrices 

 greenish (usually blackish terminally or subterminally), the lateral 

 rectrices greenish or gray basally, black terminally or subterminally, 

 the outermost tipped with pale grayish. 



Range. — Southern Mexico to Cayenne, Paraguay, northern Argen- 

 tina, Bolivia, and Peru; one species in Porto Rico. (About twenty- 

 one species, including subspecies.) 



For the present, I follow von Berlepsch and Hartert in uniting 

 Panychlora Cabanis and Heine with this genus. PanycMora seems at 

 first examination to be a very well circumscribed group, the males 

 of all the species having brightly metallic (never blue-black) rectrices, 

 and the tail relatively shorter than in most species of CMorostilhon 

 (not more than half as long as wing) ; but C. prasinus has the tail 

 even shorter (decidedly less than half as long as wing). In short, 

 when all the species of the two groups are carefully compared it 

 is found that there is no character, apparently, that will serve to 

 separate them. 



If Riccordia is to be kept separate from CMorostilhon, as I believe it 

 should, it is necessary to remove R. maugsei from the former and 

 transfer it to the present genus. 



KEY TO THE SPECIES AND SUBSPECIES OF CHLOROSTILBON. 



a. Under parts brilliant metallic green. {Adult males.) 



h. Forehead and crown brilliant metallic green, much brighter than color of back.« 

 c. Bill pale brownish (pinkish or reddish in life) basally, the mandible with at 

 least basal half thus colored; middle rectrices usually tipped, more or less 

 distinctly, with gray. 

 d. Tail nearly as long as to slightly longer than wing. 

 e. Smaller, with relatively smaller bill and longer and more deeply forked 

 tail, the lateral rectrices narrower terminally; wing, 43-44, tail, 38.5-45, 

 middle rectrices, 14-15, culmen, 13-13.5. (Western Mexico.) 



Chlorostilbon auriceps, adult male (p. 551). 



o This character is evident only in fully adult males. 



