Anas obscura rubripes. AN UNDESCRIBED FORM OF THE BLACK DUCK (ANAS OBSCURA). BY WILLIAM BREWSTER. It is a matter of common belief among our more intelligent and observing wild-fowl gunners that two kinds of Black Ducks are found in New England, and certain of the characters by which they are thought to be separable have been mentioned, as well as briefly discussed, by writers on ornithology or field sports. To one, a comparatively small, dark race having a dusky or olivaceous bill and brownish legs, all our local or breeding birds are supposed to belong; the other, a larger, lighter-colored form with clear yel- low bill and bright red legs, is known to occur only during migra- tion or in winter. I have often been struck by these and certain other differences which will be mentioned later, and for the pur- pose of testing their value and significance I have brought together, with the kind assistance of several of my friends, a large series of specimens most of which were obtained in New England in autumn, winter or early spring. Among them are a dozen or more col- lected in late August and early September at Lake Umbagog, which almost certainly represent the form resident in summer throughout New England although I have none from any locality south of the Gulf of St. Lawrence which were taken at the height of the breeding season. Some of my specimens were weighed before being skinned and many of them are accompanied by notes side by side they may be separated at a glance. The larger bird usually has the entire bill (excepting the nail) yellow, varying from