402 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
primary longest. Tail half as long as wing (E. cupreiceps) to more 
than half as long (#. chionura), emarginate, double-rounded, or 
rounded (in female of E. cupreiceps), the rectrices rather broad and 
soft. 
Coloration. Above metallic green, bronze-green or (in FE. cuprei- 
ceps) bronze passing into purple or copper bronze on head and upper 
tail-coverts; lateral rectrices white, tipped with black or grayish or 
(in females) crossed by a subterminal band of the same. Adult males 
with under parts bright metallic green, the under tail-coverts (ab- 
domen also in £. chionura) white; adult females grayish white beneath, 
spotted or spangled with metallic green. 
Range.—Costa Rica and western Panamé. (Two species.) 
The two species which, so far as known, constitute this group are 
quite different in certain structural details, and are scarcely strictly 
congeneric. Except for its green and dusky (instead of cinnamon- 
rufous) secondaries and emarginate (instead of truncate or slightly 
rounded) tail and absence of minute serrations on maxillary tomium 
E. chionura might well be placed in Eupherusa. E. cupreiceps, on 
the other hand, has a distinctly decurved as well as much more slender 
bill, and the tail is relatively shorter (not more than half as long as 
wing). 
KEY TO THE SPECIES OF ELVIRA. 
a. Bill very slightly if at all decurved; lateral rectrices broadly tipped with black 
(male) or crossed by a broad subterminal band of black (female); adult male 
with pileum metallic grass-green, the lower abdomen and hinder flanks white; 
adult female with lateral under parts more extensively green. (Western Panamé, 
and southwestern Costa Rica.)..............-2-2.--+-- Elvira chionura (p. 402). 
aa. Bill strongly decurved; lateral rectrices tipped with pale gray (male) or crossed 
by a narrow subterminal bar of dusky (female); adult male with pileum coppery 
bronze, the lower abdomen and hinder flanks metallic green; adult female 
with lateral under parts less extensively green. (Costa Rica.) 
Elvira cupreiceps (p. 404). 
ELVIRA CHIONURA (Gould). 
WHITE-TAILED EMERALD. 
Adult male-—Above metallic bronze-green, the upper tail-coverts 
and middle rectrices usually more bronzy; three outer rectrices (on 
each side) pure white, broadly (for about 5-7 mm. on outermost) and 
abruptly tipped with black (passing into dull bronzy terminally); 
remiges purplish slaty brown, the secondaries tinged with chestnut, 
the innermost ones more or less green; chin, throat, chest, breast 
(except medially), sides, and flanks bright metallic green (more 
yellowish green anteriorly), the feathers pale gray or dull grayish 
white beneath surface, becoming darker grayish basally; abdomen, 
middle line of lower breast, anal region, and under tail-coverts pure 
white, the shorter lateral under tail-coverts sometimes spotted with 
