40 Proceedings of the Biological Society of Washington. 



a wing band; greater wing coverts margined with avellaneous and tipped 

 with white, the latter forming a second wing bar; tail brownish black, outer 

 webs of feathers margined with dull pale olive-buff; under surface mainly 

 white; sides paler than pale smoke gray, with a slight wash of cartridge 

 buff; flanks washed with buffy brown. 



Measurements (in milUmeters). — Males (two specimens): Wing 69.9'- 

 70.0, tail 56.2-57.8,' culmen 11.8'-12.2, tarsus 20'-21.2. Female (one 

 specimen) : Wing 64.0, tail 55.2, culmen 12.0, tarsus 20.5. 



Range. — The Chaco region in Formosa, Argentina (Kilometre 182, 

 northwest of Formosa) and Paraguay (west of Puerto Pinasco). 



Remarks. — The present form of the widely spread South American 

 song sparrow in its characters is suggestive of two subspecies that have 

 been previously recognized, namely Brachyspiza c. argentina and B. c. 

 hypoleuca. In the diagnosis sufficient explanation has been made of the 

 manner in which B. c. mellea differs from the form first named, which ranges 

 throughout the Pampan region of Argentina, and adjoins mellea on the 

 south. From B. c. hypoleuca the subspecies here described as new differs 

 in much grayer, less rufescent dorsal surface, and in the distinct space 

 that separates the area of longitudinal stripes from the bright brown 

 collar. In addition mellea is even whiter below than hypoleuca, has the 

 sides of the neck grayer, and the sides and flanks paler, grayer, less bright 

 in color. The two forms under discussion should meet somewhere along 

 the western border of the Chaco. 



iType specimen. 



