724 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



POLIOPTILA NELSONI Ridgway. 

 NELSON'S GNATOATCHER. 



Similar to P. caevulea csesiogastra, but much larger and very much 

 darker in coloration. 



Adult male in simvmer. — Pileum dark bluish slate color, becoming 

 blue-black and distinctly glossed on forehead, but showing in certain 

 lights a more positively black U-shaped mark bounding frontal region 

 as in the forms of P. cserulea; hindneck, back, scapulars, lesser wing- 

 coverts, and rump, uniform bluish slate color; wings (except lesser 

 coverts) brownish slate color, with slate-colored or slate-gray edgings;" 

 upper tail-coverts and tail black, the outermost rectrix with outer web 

 white, except basally, the inner web with about terminal half white, 

 the second rectrix with considerably less of white, the third white for 

 about 10 mm. from tip; a narrow white orbital ring, the sides of the 

 head otherwise, including lores, bluish slate color or bluish slate-gray; 

 under parts pale bluish gray (nearly cinereous) becoming white on 

 abdomen and anal region; bill black, the mandible indistinctly paler 

 (more grayish) basally; legs and feet brownish black (in dried skin); 

 length (skin), 107; wing, 49; tail (decidely worn at tip), 50; exposed 

 culmen, 11; tarsus, 16; middle toe, 8.5. 



Adult female in winter. — Pileum and hindneck plain slate color; 

 back, scapulars, wing-coverts, and rump slightly paler (between slate 

 color and slate-gray); remiges dark brownish slate with pale-gray 

 edgings, the tertails broadly edged with dull whitish; upper tail- 

 coverts and tail black, the outermost rectrix mostly white (inner web 

 with basal third, or more, black), next with about terminal half of 

 inner web, considerably more of outer web, white, third with outer 

 web broadly tipped -and edged for most of its length with white, the 

 fourth with a small white tip; sides of head paler gray than upper 

 parts, i-elieved by a conspicuous white orbital ring; under parts white 

 medially, pale bluish gray laterally, the chest faintly shaded with pale 

 bluish gray; maxilla black; mandible blackish terminally, the basal 

 half, or more, pale grayish; legs and feet grayish black (in dried 

 skins); length (skin), 108; wing, 47.5; tail, 52; exposed culmen, 10; 

 tarsus, 17; middle toe, 9.* 



States of Oaxaca(Oaxaca City) and Chiapas (Comitlan), southeastern 

 Mexico. 



Polioptila nelsoni Eidgway, Proc. Biol. Soc. Wash., xvi, Sept. 30, 1903, 109 (Oaxaca 

 City, Oaxaca; coll. U. S. Nat. Mus. ) 



o Tertials are much worn, so that any white or pale-colored edgings which may- 

 have existed in fresh plumage have quite disappeared. 



^Description and measurements from no. 142692, coll. U. S. Nat. Mus. (Biological 

 Survey collection), Comitlan, Chiapas, Dec. 10, 1895; Nelson and Goldman. This 

 specimen I am unable to refer to any other form, and therefore place it here, though 

 with some doubt. It was identified as P. cserulea mexicana by Mr. Nelson, but is 

 much too large for that form and besides is too dark in coloration of the upper parts. 



