BIRDS OF NORTH AND MIDDLE AMERICA. 307 
p. Lateral pair of rectrices not longer than middle 
pair; wing not less than 50 mm. 
Polyerata (p. 522). 
pp. Lateral pair of rectrices longer than middle pair, 
or else (Chlorostilbon, female, part) wing less 
than 45 mm. 
q. Bill relatively broader, distinctly depressed in 
middle portion, deeper subterminally; tail 
forked for much less than one-fourth its 
length, the rectrices relatively much broader; 
adult male with whole head dark metallic 
DINO veasecc tude Saeed Cyanophaia (p. 526). 
qq. Bill narrower, not at all depressed in middle 
portion, not deeper subterminally; tail forked 
for at least one-fourth its length or else 
(Chlorostilbon, part) the bill not as in q. 
r, Nasal operculum with only the edge exposed; 
adult males with under parts of body at 
least partly blue or violet, or else pileum 
WOletzec2 oss sesemceest Thalurania (p. 530)- 
rr. Nasal operculum with much more than edge 
exposed; adult males with under parts of 
body never partly blue or violet, the 
pileum always green. 
s. Bill slightly decurved, the exposed culmen 
more than half as long as tail; tail nearly 
to quite two-thirds as long as wing, 
forked for not more than five-sevenths its 
length esesg ss secened Lepidopyga (p. 537). 
ss. Bill straight, the exposed culmen less than 
half as long as tail and tail forked for 
more than five-sevenths its length, or 
else (Chiorostilbon, part) the tail much 
less than two-thirds as long as wing. 
t. Frontal feathering not extending much 
beyond middle of nasal operculum; 
adult male with tail more than two- 
thirds as long as wing, forked for at least 
two-fifths its length, the lateral rectrices 
not narrowing terminally; a small white 
postocular spot. ...-. Riccordia (p. 542). 
tt. Frontal feathering extending nearly if not 
quite to middle of nasal operculum; 
adult male with tail less than two-thirds 
as long as wing and forked for less than 
two-fifths its length, or else lateral rec- 
trices narrowing terminally; no white 
postocular spot..Chlorostilbon (p. 547). 
ce. Nasal operculum entirely concealed by closely appressed frontal feathering. 
d. Base of maxilla less extensively feathered, the distance from frontal antiz 
to tip of maxilla more than twice (usually several times) the distance 
from the same point to base of nasal operculum. 
e. Bill excessively compressed anteriorly (acutely wedge-shaped in vertical 
profile); tomia distinctly serrate terminally....... Heliothryx (p. 561). 
