402 BULLETIN 50, TJlSriTED STATES NATIONAL MUSEUM. 



primary longest. Tail half as long as wing (E. cupreiceps) to more 

 than half as long (E. 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 E, 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 E. chionura) white; adult females grayish white beneath, 

 spotted or spangled with metallic green. 



Range. — Costa Rica and western Panama. (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 SPECIE8 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 Panamd 



and southwestern Costa Rica.) 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 

 wliite 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 



