1916 ] Miller, Classification of the Scoters. 279 



of Melanitta and Pelionetta the trachea is abruptly enlarged at its 

 upper end and again at a point some distance above its bifurcation 

 into the two bronchi. At least the lower of these two bulbous 

 enlargements is possessed by many other genera of Ducks. Both 

 however, are wholly wanting in true Oidemia, which also differs in 

 having the bronchi somewhat enlarged. After describing the 

 lar}Tix of Oidemia americana, MacGilli\Tay (Birds of America, 

 1843, p. 346) remarks: "It is indeed very remarkable that this 

 species, so nearly allied to the Velvet (White-winged) and Surf 

 Ducks, should present no dilatations, either at the upper larynx, 

 or in the course of the trachea, as are seen in them * * * The 

 trachea of the male of this species merely resembles that of the 

 female of the other species." MacGillivTay states that the trachea 

 of the Surf Scoter " presents the same structure as that of the Velvet 

 Duck," but several differences of specific or subgeneric value are 

 pointed out by William Thompson in the ' Annals of Natural His- 

 tory,' XVIII, 1846, p. 370, and by Herbert Langton in 'The Zoolo- 

 gist' for 1881, Third Series, Vol. V, p. 59. In the first-cited article 

 the trachea of the Surf Scoter is figured, drawn to the same scale 

 as that of the Velvet Scoter (ill. fusca) in Yarrel's British Birds, 

 Vol. IV, p. 480. The trachea of the Black Scoter {0. nigra) is 

 figured on p. 475 of the' latter work. 



All the Scoters agree in having the s\Tinx itself normal, while 

 according to Beddard, in all other ducks, so far as known, with the 

 exception of the xery different Biziura (and probably Erismatura 

 also) this organ is modified into a remarkable, usually as^,^nmetrical, 

 bony or partly membranous box. In Somateria (S. moUissima) 

 the presence of a very slight symmetrical enlargement of the syrinx 

 indicates the relationship of the Somaterise with the Oidemije 

 (Beddard, The Structure and Classification of Birds, pp. 463-4). 



The diagnostic characters of the two genera of Scoters as above 

 limited may be summed up as follows: 



Oidemia. — Bill smaller, commissure shorter than inner toe with 

 elaw; basal portion of maxilla bulbous-enlarged above but scarcely 

 laterally, the swelling bare; outline of facial feathering nearly 

 straight, not angled. 



Tenth (outer) primary, in adult male, greatly attenuated, shorter 

 than the eighth. Tail relatively long, decidedly more than twice 



