462 



AVES. 



bant down in the middle, cove red 'with soft membrane, with horny lamel- 

 lae at the sides, maxilla very rnoveable ; hallux reduced or absent, toes 

 fully webbed. Eocene to present. Phoenicopterus L., India, Afr., trop. 

 Amsr., S. Amer. Palaelodus M. Edw., extinct, Miocene. 



Tribe 6. ANSERIFORMES. 



Aquatic birds with desmognathous skull, basipterygoid processes, with 

 two pairs of sterno-tracheal muscles, an evaginable penis, without or with 

 rudimentary aftershaft. The beak is covered by a soft sensitive mem- 

 brane and edged both above and below with horny lamellae. The young 

 leave the nest early. From the Oligocene onwards. 



Fam. Palamedeidae. Without uncinate processes and syrinx muscles. 

 Pneumiticity very highly developed, air-cavities extending beneath the 



FIG. 253. Chauna chavaria (R6gne animal). 



skin and even into the fingers and toes. With two sharp spurs 011 the 

 wings. Chauna chavaria 111., the crested screamer or chaja (Fig. '253). 

 Paraguay and Brazil, can be domesticated and used to herd flocks of 

 fowls and geese in S. Amer. Palamedea cornuta L., the horned screamer. 

 Fam. Anatidae. Swans, geese, and ducks. Beak usually broad and 

 depressed. The anterior toes usually fully webbed, hallux short and 

 elevated. Neck unusually developed with extra vertebrae in the swans. 

 Trachea often with elongations and dilatations especially in the male. 

 Usually good flyers, but a few forms flightless (Nesonetta, Tachyeres). 

 Good swimmers, frequenting either sea or fresh-waters. Cosmopolitan. 

 About 150 living species. From the Eocen iwards. Cygnus L., swans 



