Family XXXIX. ANATINAE. DUCKS.
GENUS III. CYGNUS, Meyer. SWAN
Bill longer than the head, higher than broad at the base, depressed, and a little widened toward the end, rounded; upper mandible with the dorsal line sloping, the ridge very broad at the base, with a large depression; narrowed between the nostrils, convex toward the end, the sides nearly erect at the base, gradually becoming more horizontal and convex toward the end, the sides soft and thin, with numerous transverse little elevated internal lamellae, the unguis obovate; nasal groove elliptical, sub-basal, covered by the soft membrane of the bill; lower mandible flattened, with the angle very long, and rather narrow, the sides convex, the edges with numerous transverse lamellae. Nostrils submedial, longitudinal, placed near the ridge, elliptical. Head of moderate size, oblong, compressed; neck extremely long and slender; body very large, compact, depressed. Feet short, stout, placed a little behind the centre of the body; tibia bare for a very small space; tarsus short, a little compressed, covered all round with angular scales; hind toe extremely small, with a very narrow membrane; third longest, fourth very little shorter; anterior toes covered with angular scales for nearly half their length, then scutellate, and connected by broad reticulated entire membranes. Claws rather small, strong, arched, compressed, rather obtuse. Space between the bill and eye bare; plumage dense and soft. Wings long, broad; primaries curved, stiff, the second longest. Tail very short, graduated, of twenty or more feathers. OEsophagus very slender, at the lower part of the neck a little dilated; stomach transversely elliptical, with the lateral muscles extremely large, the epithelium dense, with two concave grinding surfaces; intestine long, and of moderate width; coeca rather large, narrow; cloaca globular. Trachea generally enters a cavity in the sternum, whence it is reflected, before it passes into the thorax; no inferior laryngeal muscles.