558 



PATAGONIAN EXPEDITIONS I ZOOLOGY. 



The sexes do not vary in size; there is much individual variation 

 however. 



Color. — Adult male cited above. Adults of either sex are alike when 

 in adult plumage. 



Polybonis plancus, adult male. P. U. O. C. 7894. About one-fourth natural size. 



Head : A crested cap reaching from the base of the bill, above the eyes 

 backward to the occiput, where the feathers are elongated, dark seal-brown ; 

 region in front of the eyes, and sides of the face pale isabelline, sometimes 

 almost buffy white. 



Neck : Pale isabelline or buffy white ; immaculate on the throat, and 

 barred with dark seal-brown barring elsewhere, the barring giving more 

 prominence to the dark than to the light color. 



