AUGUST, 1915. NOTES ON SOUTH AMERICAN BIRDS CORY. 329 



Wing (of the single specimen examined), 166; tail (badly worn), 

 115; tail band, 24mm. 



Distinguishing characters: The very pale and unspotted under 

 parts of C. s. isabellina will at once distinguish it from other forms, 

 with the exception of C. s. distincta from which it apparently differs* 

 in having the crown darker (less ashy) ; the wing and tail somewhat shor- 

 ter; and in the white marking of the inner webs of the outer primaries. 

 In isabellina (and in most other races) the inner webs of the outer pri- 

 maries have seven or eight white bars, the dark bars which separate 

 them reaching nearly or quite to the edge of the web on the greater 

 portion, and on some of the feathers the two distal white patches often 

 being confluent. In distincta, however, the greater portion of the inner 

 web is white, the dark bars being much shorter and more irregular, often 

 (especially on the basal half of the feather) not extending beyond the 

 middle of the web so that the white areas are correspondingly increased. 

 From C. s. margaritensis it may be separated by its paler under parts 

 (less distinctly tinged with ochraceous cinnamon) ; paler abdomen and 

 flanks; and the absence of distinct white spots on the outer web of the 

 second outer primary. 



Specimens examined: British Guiana, i d" (U. S. Nat. Mus., No. 

 90160). 



Remarks: Judging from published descriptions and the very few 

 specimens I have seen from British Guiana, I am forced to believe that 

 two small forms of Cerchneis inhabit that region: one (isabellina') a pale 

 form which occurs on the higher savanas of the interior, and the other 

 (perplexa) a dark form probably inhabiting the low country bordering 

 the rivers and in the valleys nearer the coast. Swainson's original 

 description of the type (/. c.) gives the "breast and body beneath, 

 isabella, unspotted." Wing, 6 3-10 in. and tail 5 in. Penard and 

 Penard (Vogels von Guyana, I, 1908, p. 437) describe C. s. isabellina 

 as having the throat white, passing into light brown or yellowish white 

 on the breast; wing 175 mm. Sharpe, who had access to Swainson's 

 type and other specimens from British Guiana (obtained by Schomburgk 

 and preserved in the British Museum), gives the coloration of the under 

 parts of the body as "pale fawn shading into buffy white on the flanks 

 and thighs" (Cat. Bds. Brit. Mus., I, 1874, p. 441). We must, there- 

 fore, assume that the bird described as isabellina by Swainson is a pale 

 form closely approaching distincta in the coloration of the under parts. 



A specimen in the collection of the United States National Museum 



* The single specimen of isabellina I have seen from British Guiana is faded and 

 worn and the measurements evidently below the average. A good series may prove 

 the supposed characters separating it from C. s. distincta to be inconstant. 



