ANSERINE. CYGNUS. 
155 
base and margins, as well as part of the upper surface, 
fringed with tapering horny papillae, the tip thin, horny, 
rounded ; oesophagus extremely long, narrow, dilated a little 
toward the furcula ; proventriculus bulbiform ; stomach an 
extremely developed, oblique, transversely elliptical gizzard, 
of which the lateral muscles are extremely thick, their 
tendons large, the epithelium forming two very thick, con- 
siderably concave, grinding surfaces ; intestine long, rather 
narrow, arranged in sixteen folds ; coeca long, narrow at 
the base, then of moderate width ; cloaca oblong. Trachea 
considerably flattened, a little enlarged below, with the 
syrinx much compressed ; the bronchi wide, enlarged, 
near the end. Nostrils elliptical, medial, near the ridge. 
Eyes small. Aperture of ear small. Legs short, stout, 
placed a little behind the centre of equilibrium ; tibia bare 
for a very short space ; tarsus considerably compressed, 
reticulated ; hind toe very small and elevated, compressed 
beneath ; anterior toes longer than the tarsus, the outer 
two nearly equal ; all scutellate, unless toward the base ; 
membranes full ; claws strong, arched, compressed, rather 
obtuse, that of the third toe expanded and rounded. Plu- 
mage moderately full, close, firm, unless on the head and 
neck ; wings very long, rather broad, convex, of about 
thirty -two quills ; the second and third longest ; tail short, 
rounded, of from eighteen to twenty-four feathers. 
The Swans inhabit chiefly the temperate and cold parts 
of the globe ; breed in the glacial regions, laying numerous 
elliptical, generally greenish-grey eggs. They walk slowly, 
but swim gracefully ; sometimes feed on shore, but usually 
in the water, on the roots and submersed stems of plants, 
which their very long necks enable them to reach. Their 
food consists entirely of vegetable substances. In most of 
the species, the trachea enters the keel of the sternum and 
returns, before proceeding to the thorax. The young are 
generally grey, the adult white ; but one species, the Aus- 
tralian, is black. In the adults is a large bare space at the 
base of the bill, extending to the eyes ; but in the young 
it is covered with very small feathers. 
