Me IEA ANSERIFORMES CHAP. 
the jaws are closed in many cases, and are comparable to the 
similar formations in Prion (Procellariidae) and the Phoenicopte- 
ridae. They act no doubt as a sifting apparatus, but may 
assist in nipping off herbage and gripping fish, the piscivorous 
Mergansers having them directed backwards. The metatarsus 
is normally short or moderate, though occasionally long, as in 
Plectropterus and Dendrocycna ; it may be stout and roundish, 
as in Anser’, or laterally compressed, as in Fuligula ; and is usually 
reticulated with transverse scutellae in front, though wholly 
reticulated in the Cygninae, Anserinae, and Dendrocycna. The 
anterior toes are fully webbed, Anseranas and Cereopsis alone 
having the foot semi-palmated; the hallux is short and elevated 
—except in the former species, where it is long and incumbent 
and possesses a broad membranous lobe in the Merginae, Mer- 
ganettinae, Erismaturinae, and Fuligulinae, while a very narrow 
membrane may be observed in the Anatinae and Chenonettinae. 
The claws are as a rule small and curved, but are long and sharp 
in Anseranas, Dendrocycna, Nettopus, and Plectropterus. The 
wings vary considerably, but are usually ample and rather long, 
though short in Cosmonetta, Erismatura, and Tachyeres; the 
number of primaries is eleven, and of secondaries from fifteen to 
twenty-eight, a horny spur being developed on the pollex, or even on 
the index, in Plectropterus, Sarcidiornis, Chenalopex, and Merganetta. 
The tail is, generally speaking, short, and may be narrow and 
pointed, as in Anas, Dajila, and Harelda ; in Aex, Querquedula, 
Tadorna, and so forth, 1t is rounded; in Chenalopex squarer ; and 
in Sarcidiornis and Asarcornis more cuneate. In Tachyeres the 
two median rectrices are long and recurved, and in the males of 
Harelda and Dafila they are inordinately produced; while all 
the feathers have spiny shafts and narrow webs in the Erisma- 
turinae and Merganettinae. The number varies from twelve to 
twenty-four, with even more in Swans. In Hunetta the upper 
and under tail-coverts exceed the tail itself. 
The formation and disposition of the trachea’ are of great 
importance. Cygnus musicus, C. buccinator, C. bewicki, and C. 
columbianus have a peculiar cavity in the sternum, while the wind- 
pipe, entering in front of the clavicles, traverses and retraverses 
the swollen keel, which in old birds it penetrates to its furthest 
extremity, the direction being changed in the two last from vertical 
1 For a general account, see A. Newton, Dict. Birds, 1896, pp. 983-985. 
