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Phillips, The American Black Ducks. 



rAuk 

 LJuly 



First let us glance briefly at the ten specimens before us and in 

 a general way give the main points of sexual difference. Of the 

 six males, four are correctly sexed, one is unsexed, and one has been 

 sexed both as a male and a female and then had both marks crossed 

 out. There is, however, no question about the sex of either of 

 these two. All six males present the characteristic V-shaped 

 markings on the breast (see plate) thickly streaked throat and 

 cheeks, nearly black pileum, sometimes mixed with iridescent 

 green towards the neck; wand except in one case evidence of sex 

 feathers in the tail. In this one case (Nat. Mus. No. 113448) the 

 middle tail feathers are lacking, probably moulted out as the date 

 is May. The sex feathers appear to be typically three in number, 

 but they may be four. They are not so well developed as in the 

 Mallard. 



Of the four females all are correctly sexed. They all have the 

 streaked under parts characteristic of A. diazi (see plate), im- 

 maculate throats and absence of sex feathers. 



The table of measurements below shows the size difference in 

 the two sexes. This is small and about comparable with that seen 

 in A. diazi. 



Males. 



We must now turn to Dr. Stejneger's account of the species. 

 He first describes the two males, U. S. N. M., No. 113447 and No. 

 113449, and shows several points of difference between them, 

 especially in the color of the bill, in the anterior white wing band 

 and in the under wing-coverts and under tail-coverts. 



