184 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



erate to rather large, strongly curved, acute, that of the hallux 

 decidedly shorter than the digit. 



Coloration. — Wings and tail (usually pileum also) cinnamon-rufous 

 rest of upper parts plain brown; under parts plain pale brownish 

 gray, light grayish brown, or dull buffy. Sexes ahke. 



Range. — Costa Rica to Ecuador (at least) .^ (Many species.)"* 



KEY TO THE SPECIES OF ACRORCHILUS. 



a. Pileum, at least, rufous. (Adults.) 



b. Loral, orbital, auricular, and malar regions rufous; crown without black streaks 

 {Acrorchilus erythrops.) 

 c. Middle pair of rectrices russet-brown. (Ecuador.) 



Acrorchilus erythrops erythrops (extralimital).^ 

 cc. Middle pair of rectrices bright cinnamon-rufous, like rest of tail. 

 d. Rufous of head less extended, the occiput and nape brown, like back; chest 

 and lower throat light buffy olive. (Costa Rica and Panamd.) 



Acrorchilus erythrops rufigenis, adults (p. 185). 

 dd. Rufous of head more extended, invohdng occiput and nape; chest mouse 

 gray fading into nearly ash gray on throat. (Northwestern Colombia.) 



Acrorchilus erythrops griseigularis (extralimital).c 



bb. Loral, orbital, auricular, and malar regions buffy brownish, the superciliary 



region narrowly streaked with whitish; forehead and crown streaked with 



black. (Colombia to Ecvfador.) Acrorchilus antisiensis (extralimital).** 



aa. Pileum without rufous Acrorchilus erythrops rufigenis, young (p. 185). 



ACRORCHILUS ERYTHROPS RUFIGENIS (Lawrence). 



LAWRENCE'S SPINETAIL. 



Similar to A. e. erythrops Sclater,« of Ecuador, but middle pair of 

 rectrices bright cinnamon-rufous (hke other rectrices), instead of 

 russet brown, cinnamon-rufous of head deeper and more extended 

 (occupying whole of auricular and greater part of malar regions, as 

 well as orbital, loral, superciliary, and supra-auricular regions as well 

 as forehead and crown), general coloration darker, and size larger. 



a On account of the very poor representation of species referred to the genus Siptomis. 

 by Dr. Sclater and other recent authorities, in the material which I have been able to 

 examine, I can not give a very definite statement of the number of species or extent of 

 the geographic range of this genus, which is so exceedingly distinct, structurally, from 

 Siptomis that it is difficult to imagine why the fact has not sooner been realized. The 

 only species examined by me in this connection are the following: A. erythrops 

 (Sclater), A. hellmayri (Bangs), and A. pallida (Maximilian). 



iSynallaxis erythrops Sclater, Proc. Zool. Soc. Lond., pt. xxviii, pt. i. May, 1860, 66 

 (Pallatanga, w. Ecuador; coll. P. L. Sclater). Siptomis erythrops Sclater, Cat. Birds 

 Brit. Mus., XV, 1890, 60, i>&rt. —A[crorchilus] erythrops erythrops Ridgway, Proc. Biol. 

 Soc. Wash., xxii, April 17, 1909, 72, in text. 



c Acrorchilus erythrops griseigularis Ridgway, Proc. Biol. Soc. Wash., xxii, April 17, 

 1909, 72 (San Antonio, Rio Call, n. w. Colombia; coll. E. A. and 0. Bangs). 



dSynallaxis antisiensis Sclater, Proc. Zool. Soc. Lond., 1859, 457 (Cuenca, Ecuador; 

 coll. P. L. Sclater).— /Siptorms antisiensis Sclater, Cat. Birds Brit. Mus., xv, 1890, 59. 



e See Key to the Species, this page. 



