The Marbled Duck has been bandied about from one generic group to another, and has been referred in turn to Dafila, Anas, Querquedula, Chaulelasmus, and even Fuligula, with none of which has it any real affinity. It clearly must be placed in a genus by itself, if only on account of its peculiar dull greyish plumage, without any coloured speculum.
The bill is about equal to the head in length, and shaped as in Nettium—rather narrow, with the two sides parallel, and the nostril near the base. The wings are short and rounded; tail moderately long, pointed, of 14 feathers. Head with a short but full occipital crest, more developed in the drake. Labyrinth of trachea lateral, very similar to those of Anas and Nettium.
A single species.