I I 2 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 TacJiyeres ; 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, Dafila, and Harelda ; in Aex, Querquedula, 

 Tadorna, and so forth, it is rounded ; in Chenalopex squarer ; and 

 in Sarcidiornis and Asarcornis more cuneate. In TacJiyeres 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 Eunetta the upper 

 and under tail-coverts exceed the tail itself. 



The formation and disposition of the trachea 1 are of great 

 importance. Cygnus musicus, C. 'buccinator, C. lewicki, and C, 

 colurtibianus have a peculiar cavity in the sternum, while the wind- 

 pipe, entering in front of the clavicles, traverses and' retra verses 

 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, sec A. Newton, Diet. Birds, 1896, pp. 983-985. 



