112 ANSERIFORMES 



the jaws are closed in many cases, and are comparable to the 

 similar formations in Prion (Procellariidae) and the Phoenicopte- 

 ridae. They act no dou]>t 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 Fidigida ; and is usualh' 

 reticulated with transverse scutellae in front, though wholl}' 

 reticulated in the Cygninae, Anserinae, and Dendrocycna. The 

 anterior toes are fully webljed, Ausercmccs 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, Ijut are long and sliarp 

 in Anseranas, Dendrocycna, Nettopus, and Plectropterus. The 

 wings vary considerably, but are usually ample and rather long, 

 though short in Cosmonetta, Erismatara, and Tacky eres ; 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 Plcct7'opter us, Sarcidiornis, CJicnalopex, and Mcryanctta. 

 The tail is, generally speaking, short, and may be narrow and 

 pointed, as in Anas, Dafila, and Harelda ; in Aex, Qucrquedula, 

 Tadorna, and so forth, it is rounded ; in Chenalopcx 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 Eunctta the upper 

 and under tail-coverts exceed the tail itself. 



The formation and disposition of the trachea ^ are of great 

 importance. Cygnus musicus, C. hnccinator, C. heivicki, and C. 

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

 pipe, entering in front of the claA'icles, 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 

 ^ For a general account, see A. Xewton, Did. Birds, lS9t?, ])]i. 98-3-985. 



