BIEDS OF NORTH AND MIDDLE AMERICA. 715 



■ i. Wing averaging 48.4, tail 52.4; more white on lateral rectrices. 

 (Eastern Brazil.) 



Polioptila leucogastra, adult male (extralimitaD <* 

 I , CO. Head without any hlack. '' 



d. Gray of pileum not darkening toward auricular region. 

 e. No white superciliary stripe; tail longer (averaging more than 43). 

 /. Auricular region with at least upper half pale gray, not conspicuously 

 different from darker gray of occiput, and fading gradually into paler 

 gray or grayish white of lower portion. 

 g. Bill smaller (exposed cuhnen averaging less than 10.5); outermost 

 primary much smaller, much less than half as long as next (ninth). 

 h. Larger, with smaller bill (wing averaging more than 50, exposed' 

 culmen less than 10). 

 i. Black at base of lateral rectrices more restricted; gray of upper 

 parts clearer,' white of under parts less grayish. 



Polioptila caerulea cserulea adult female (p. 717) 

 17. Black at base of lateral rectrices more extended; gray of upper 

 parts duller, white of under parts grayer. 



Polioptila caerulea obscura, adult female (p. 720) 

 hh. Smaller, with larger bill (wing averaging less than 48, culmen 

 averaging 10 or more). 

 i. Smaller and paler (in coloration like P. c. cserulea); wing averag- 

 ing 45.3, tail 43.5; tarsus 16.5. 



^ Polioptila caerulea mexioana, adult female (p. 722) 



ii. Larger and darker; wing averaging 47 or more, tail more than 



50, tarsus 17 or more. 



j. Upper parts bluer slate-gray; under parts pale bluish gray 



( white only on abdomen, anal region, and under tail-coverts) . 



Polioptila caerulea caesiogastra, adult female (p. 723) 



jj. Upper parts duller slate-gray; under parts white medially. 



Polioptila nelsoni, adult female (p. 724) 

 gg. Bill larger (exposed culmen averaging more than 11) ; outermost 

 primary much larger, at least half as long as the next (ninth) . 



Polioptila nigriceps, adult female (p. 729) 

 ff. Auricular region white, or grayish white, abruptly and strongly con- 

 trasted with a dusky postocular streak, above which is a narrow 

 white or whitish streak. 



"Slylvia] leucogastra Maximilian, Beitr. Naturg. Bras., iii, pt. 2, 1831, 710 (Province 

 of j5ahia, e. prazil; type in coll. Am. Mus. Nat. Hist.). — Polioptila leucogastra Sclater, 

 Proc. Zool. Soc. Lond., 1855, 12, part (BaHia; Montevideo?); Sharpe, Cat. Birds 

 Brit. Mus., X, 1885, 446 (Bahia and Pernambuco, Brazil). — PloliojMla'] leucogastra 

 Eidgway, Proc. U. S. Nat. Mus., v, 1882, 387, 388, 389, part (Bahia; crit.); Hell- 

 raayr, Novit. Zool., vii, 1900, 536, in text (crit); viii, 1901, 360 (diagnosis); Tier- 

 reich, 18 Lief., 1903, 25. — Culicivora (itricapilla Swainspn, Zool. Illustr., new ser., ii, 

 1831, pi. 57 (no locality mentioned). — lOulicivora] dumicola (not Sylvia dumicola 

 Vieillot) Bonaparte, Consp. Av., i, 1850, 316, part; Clulicivora'j dumicola Cabanis 

 Mus. Hein., i, 1850, 34. 



6 In the adult females of P. leucogastra and P. 2>lumbiceps (probably also P. anteocu- 

 laris, which, however, I have not seen) the deep slate-gray or slate color of the 

 pileum gradually darkens into nearly black on the upper portion of the auricular 

 region: but there is no distinct, sharply defined black mark or "hood" as in section c. 



