Order XIV. ANSERES.
As noted under the previous Order the only birds now included in the Anseres are the true Swans, Geese and Ducks, though it is possible that eventually the Flamingo and Ducks will have to be relegated to the rank of suborders under the one order, Chenomorphae.
In this Order the three anterior toes are united by webs, extending, except in one Australian genus Anseranas, to the ends of the digits; the hind toe is always present, though it is short and joined to the tarsus on a higher plane than the front toes; the bill, except in the Merging is depressed and flattened and is covered with a soft membrane, except on the dertrum, or nail, which forms the tip of the upper mandible; both mandibles are fringed inside with tomiae, or edges, with lamellae., which are variously developed in different genera.
The skull is desmognathous and holorhinal; basipterygoid processes are represented by oval facets, articulating with the pterygoids close to their anterior extremity, as in the Gallinae; the angle or posterior extremity of the lower jaw is produced backwards beyond the articulation with the quadrate and is curved upwards ; the nostrils are pervious but vary in shape; the furcula is U-shaped and strong; the posterior border of the sternum is furnished with a notch, represented in some genera by a foramen on each side of the keel; there are two carotids of equal size; the caeca are large; there is a tufted oil-gland; the wings are aquincubital with eleven primaries; the aftershaft to the body-feathers is rudimentary or wanting; there are no apteria on the neck; the ambiens, femoro-caudal, a very large accessory femoro-caudal and semi-tendinosus muscles present; as in most swimming birds the accessory semi-tendinosus is absent; the flexor longus hallucis sends off a slip to the hallux and then fuses with the flexor perforans digitorum, which supplies the three anterior digits; the tongue is large and fleshy, denticulated at the sides to At in with the lamellae; the males have a large spiral intromittent organ.
The young are hatched covered with down and are able to run and swim as soon as this dries. In moulting most of the species of this family shed all their quill-feathers at once and are consequently, for a time, unable to fly.
There is but one family, which is cosmopolitan.