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 antie, 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. Panychlora 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 Chlorostilbon 
(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 Chlorostilbon, as I believe it 
should, it is necessary to remove R. maugxi 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.) 
b. 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). 
@ This character is evident only in fully adult males, 
