BIRDS — CTGNINAE. 



767 



Sub-Family CYGNINAE. 



CYGNUS, Linnaeus. 



Cy^-ims, Linnaeus, Syst. Nat. 1735. Type ^Jias olor, Graelin. (Gray.) 



Ch. — Neck very long. Bill longer than the head, (commissure longer than the tarsus,) the basal portion covered by a soft skin 

 extending to the anterior half of the eye, the plane of the upper outline from eye to eye horizontal ; the lateral outline extending 

 nearly straight to the commissure, or even sometimes widening sliglitly ; not half the width of tlie bill at tip. Nostrils situated 

 in the middle portion of the bill. Lower portion of tibia bare ; the tarsus much shorter than the foot, much compressed,' covered 

 with he.\agnnal scales, which become smaller on the sides and behind. Hind toe small, much elevated ; the lobe narrow. Tail 

 of 20 or more featliers, rounded, or wedgc-sliaped. Sexes similarly colored. 



As North America possesses only one genus of Cygninae, I have combined the sub-family 

 characters with the generic in the preceding diagnosis. By Wagler the peculiarities of the bill 

 have been made the basis of sub-divisions of the old Linnaean genus Cijgnus, as follows : 



Cygnus. — Bill with a swollen fleshy tubercle at the base of culmen. Teeth of the edge of 

 bill projecting and visible from the side. 



Olor, Wagler. — No tubercle at the base of bill. Teeth of the edges of bill not projecting. 



Other members of Cygninae are Chenopis, embracing the Australian black swan, and 

 Coscoroba, a South American white sj)ecies with feathered lores. The black-necked swan of 

 South America belongs to the sub-genus Cygnus. 



There are certain peculiarities of trachea and sternum which distinguish the genus and its 

 species in a marked degree. 



The two North American species of swan belong to Olor as restricted, with the following 

 diagnoses : 



Tail feathers 20. Bill as long as the head. The anterior end of nostrils considerably beyond 

 the middle of commissure. Black naked skin at base of bill, with a reddish spot anterior to the 

 eye C. amerieanus. 



Tail feathers 24. Bill longer than head. Anterior end of nostril opposite the middle of 

 commissure. Skin at base of bill entirely black C. buccinator. 



Comparative measurements of species. 



