172 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
KEY TO THE SPECIES OF XENOPS.@ 
a, Breast plain brown, brownish gray, or grayish olive. (Xenops genibarbis.) 
b. Basal portion of rectrices more extensively black. (Tropical South America.) 
Xenops genibarbis genibarbis (extralimital).d 
bb. Basal portion of rectrices less extensively black. (Southern Mexico to Panama.) 
Xenops genibarbis mexicanus ¢ (p. 172.) 
aa. Breast conspicuously streaked with whitish. (Xenops rutilus.) 
6. Under parts more broadly streaked; back, etc., brighter rufous-brown. (Brazil, 
Ob ncn oneudteasedicd ope abt hanayasele Xenops rutilus rutilus (extralimital).¢@ 
bb. Under parts more narrowly streaked; back, etc., duller rufous-brown. (Costa 
Rica to Colombia, Venezuela, Trinidad, and Peru.) 
Xenops rutilus heterurus (p. 175). 
XENOPS GENIBARBIS MEXICANUS (Sclater). 
MEXICAN XENOPS. 
Similar to X. g. genibarbis ¢ but with much less of black on basal 
portion of lateral rectrices. 
Adults (sexes alike)—Pileum brown (nearly bister), the feathers 
sometimes with very indistinct shaft-streaks of paler (these usually 
@ Both species of Xenops almost certainly require further subdivision than is here 
made, but from want of sufficient material, especially of X. rutilus and South American 
representatives of X. genibarbis, I must leave a satisfactory treatment of the genus 
to some one who has both more material and time. (See, however, Hellmayr, in 
Novit. Zool., xiv, 1907, 54, 55, whose paper I did not, unfortunately, see in time 
to utilize it in this work.) 
b Xenops genibarbis Iliger, Prodromus Orn., 1811, 213 (Cameta, Brazil); Sclater, 
Cat. Birds Brit. Mus., xv, 1890, 110.—Neops ruficaudus Vieillot, Analyse, 1816, 68 
(Guiana).—(?)Xenops littoralis Sclater, Proc. Zool. Soc. Lond., 1861, 879 (Esmeral- 
das, w. Ecuador; coll. P. L. Sclater).—(?)Xenops approximaus Pelzeln, Sitz. Akad. 
Wien, xxxiv, 1859, 113. 
In the paper referred to above Hellmayr (than whom there is no better authority), 
divides X. genibarbis into three subspecies (besides X. g. mexicanus), as follows: 
(1) Xenops genibarbis genibarbis (Colombia to Cayenne and Amazon Valley); (2) 
Xenops genibarbis littoralis (western Ecuador); (3) Xenops genibarbis pelzelni (south- 
eastern Brazil, from Bahia to S. Paulo; new subspecies, described on p. 55, the type, 
in coll. Vienna Mus., being from Ypanema, S. Paulo). 
¢ This probably separable into about three subspecies. (See p. 174, footnote.) 
@ X[enops] rutilus Lichtenstein, Verz. Doubl., 1823, 17 (Bahia, Brazil; coll. Berlin 
Mus.); Sclater, Cat. Birds Brit. Mus., xv, 1890, 111, part.—Xenops rutilus rutilus 
Hellmayr, Novit. Zool., xiii, 1906, 29 (Trinidad; crit.); xv, 1908, 62 (Goiaz, etc., 
Brazil; crit.).—Xenops rutilans Temminck, Pl. Col., livr., 12, July, 1821, pl. 72, 
fig. 2.—Xenops affinis Swainson, Anim. in Menag., pt. iii, Jan. 1, 1838, 352 (Brazil; 
coll, W. Swainson).—Xenops argyobronchus Bertoni, Aves Nuevas del Paraguay, 
Jan , 1901, 75 (Djaguarasap4, lat. 26° 53’, upper Rio Paran4, Paraguay; coll. A. de W. 
Bertoni; see Arribdélzaga, An. Mus. Nac. Buenos Aires, vii, 1902, 352, 358 and Iher- 
ing, Rev. Mus. Paulista, vi, 1904, 328). 
¢ See p. 172, 
