ANATID.E — THE SWANS. 



421 



1. Sthenelus, Stejneger, 1882. 



c^. Inner webs of outer three (jriniaries and outer webs of the secoml, third, and fourth 

 sinuated ; the young with the down on the sides of the bill teriuinatiug far back of 

 the nostrils ; webs of the feet straight, not scalloped. 



•2. Cygnus, Bechst., 1803. 



b-. Tail rounded ; the young with llie down on the sides of the bill forming very distinct loral 

 antise. 



3. Olor, Wagl., 1832. 



a-. Predominant color of the adults blackisli ; the young with naked lores ; tertiaries and scapu- 

 lars crisp ; tail shovter than the middle toe with cluw. 



4. Chenopis, Wagl. 1832. 



" Geof/riip/i !(■/'/ Distribution. 



" The Cijgninm appear both in the northern and tlie southern heunspheres as extra-tropical birds, 

 no representatives of these large Lamdlirostres being found within the tropics. They are conse- 

 quently wanting both in the Indo-African Tropical — they do not at all breed in Africa — and in 

 the American Tropical Region, only one species being met with in the South American Temperate 

 and one in the Austi'alian Region. The remaining seven species occur in the Arctic and the 

 North Temperate Regions, tlio greatest number, viz., five, being found in the Old World, and here 

 tliey only extend their winter migrations to the two southern provinces, the Mediterranean and 

 the Manchurian, without breeding there. The two North American species only breed within the 

 American division of the Arctic Region. 



" The following table gives a synopsis of their distribution : — 



Of the genera, as defined above, only the tliird (Olur) belongs to North America, the remainder 

 being distributed as follows : — 



The first, Sthenelus (new genus, Pr. U. S. Nat. Mus., Vol. b, .July 25, 1882, p. 183), includes 

 only the Black-necked Swan (.-hio.^ mdancorijfhn, Mol., Cygnus niyricollis, Adct. ex Gsiel.) of 

 Cliili and other parts of Southern South America ; Cygnus proper contains tliree species (one of 

 tliem the common domestic species), all of them peculiar to the Pahcarctic Region ; Clienopis, in- 

 cluding only the Black Swan of Australia {Anas atrata, Lath., Cygnus atratus, Auct.), is confined 

 to Southern Australia. 



As before remarked, the Coscoroba Swan (Anas coscoroba, Mol., Cygnus coscoroba, Adct., Aiiser 

 candidus, ViElLL., Coscoroba Candida, Stejn.) of South America, wliile resembling the true Swans 

 in its large size and pure white color, agrees in structure with the Uucks, and can properly be 

 considered only as a gigantic member of that sub-family. 



