IV ANATIDAE ysis 
to horizontal. -Azseranas shews a double loop in this organ,’ and 
in the males of many Ducks an enlargement is found at its junc- 
tion with the bronchial tubes, consisting of a round bony structure, 
termed the bulla ossea or “labyrinth.” Similar structures have been 
noticed in Chenalopex, Dendrocycna, Chloéphaga, Plectropterus, and 
Sarcidiornis ; and in the Fuligulinae they shew apertures with 
membranous coverings ; Jetopiana peposaca, Mergus merganser, M. 
serrator, Tadorna cornuta, Oedemia fusca, and (doubtfully) Oc. per- 
spicillata are stated to have an additional bulb, but Oe. nigra has 
none. Clangula glaucion and the Merginae have a swelling in 
the middle of the trachea. 
The headquarters of the Family are in the north, while Dr. 
Sclater’s calculations,’ though modified by subsequent discoveries, 
give a good idea of the distribution. He assigns as residents 
about seventy-seven species to the Northern Regions, forty-one to 
the Neotropical, twenty-nine to the Australian, twenty-two to the 
Ethiopian, and twelve to the Indian; twenty Geese out of thirty- 
three, seven Swans out of ten, and twenty-six Sea-Ducks out of 
thirty-one belonging to the first. Polynesia is especially poor. 
The Anatidae are for the most part of similar habits, and 
frequent seas, lakes, rivers, and watery spots generally, being found 
to a great extent in winter on the shore, especially where mud- 
flats are exposed by the ebbing tide, and beds of such food-plants 
as Zostera (grass-wrack) are uncovered. Large flocks, which 
include many migrants, are formed at that season, and in spring 
the ganders and drakes commonly collect into parties while the 
female is incubating, which she does during twenty-one to forty-two 
days. Later in summer the majority of the Family shed their quills 
simultaneously, and conceal themselves until again capable of flight, 
the males then becoming dull in colour for several weeks, and re- 
sembling the other sex.’ J/erganetta is found only on the torrents 
of the Andes; Hymenolaemus and Salvadorina being also residents 
on mountain streams. The noisy flight is extremely powerful, and 
much swifter than it appears, the wedge-shaped formation which 
Geese affect being especially noticeable ; some forms, however, are 
practically flightless, such as Vesonettg and the adult Steamer-Duck 
(Tachyeres). All the Anatidae swim exceptionally well, diving being 
carried to its perfection in the marine Fuligulinae ; while the parti- 
1 W. A. Forbes, P.Z7.S. 1882, p. 350. 
2 P.Z.S. 1880, p. 533. 3 Supra, p. 4. 
VOL. IX I 
