Anas obscura rubripes. 186 BREWSTER, An Undescribed Form of Black Duck. [Auk Apr. Indeed it would be possible to contend that these aberrant or intermediate specimens are really hybrids, for in the series before me they do not exceed in number the birds (no less than nine) which show unmistakable traces of an infusion of Mallard blood. Since two species so obviously distinct as are the Mallard and Black Duck are connected by intergrades known to be hybrids, why should we not assume that the scarcely more numerous intergrades between the red-legged and brown-legged Black Ducks are also hybrids? Not that I am disposed to seriously press this argument for, however plausible it may seem, my present impression is that the forms of the Black Duck here considered are only sub-specifically distinct. There can be no reasonable doubt that the smaller of the two is the original Anas obscura. This name has remained unchanged in form and uncoupled with any synonym ever since it was instituted, more than one hundred years ago, by Gmelin (Syst. Nat. I, part ii, 1788, 541), who based it on the “Dusky Duck” of Pennant. This is described (Arct. Zool., II, 564) as coming “from the province of New York” and having “a long and narrow dusky bill, tinged with blue: chin white: neck pale brown, streaked downwards with dusky lines.” Pennant adds that the legs in one of his birds were “dusky, in another yellow”; but as the specimens which he examined were evidently dried skins (in the Blasius Museum) this statement, as well as that relating to the color of the bill, loses much of its apparent importance. At Lake Umbagog, where the Black Duck breeds rather plentifully, I have not cared to incur the odium of breaking the game laws and the reproaches of my own conscience by killing birds which were sitting on their eggs or in charge of broods of tender young, but I have shot a few specimens in late August and very many during the month of September. Among these I have found only one example of rubripes, a nearly typical female taken on September 28, 1889. With this single exception I have never met with the red-legged form at this locality before October 8. Soon after that date it becomes common, remaining until the waters of the lake are closed by ice. In Massachusetts, also, the locally bred birds or early migrants from the north, which we kill during September and the first half