176 BIRDS OF ILLINOIS. 



the frontal feathers and those of the cheeks, form a distinct basal angle or lobe; maxillary 

 tomium regular and nearly straight, the lamellae completely concealed. Head with some 

 portions bristly feathered (in males); tertials falcate ; tail small, short, and pointed, com- 

 posed of fourteen pointed feathers. A du.lt males with the plumage pied black and white 

 (the lower parts chiefly black, the upper surface mostly white), the breast more buff or 

 cream colored, the head varied with light green, black, etc. Females and young with the 

 plumage barred with dusky and pale fulvous or rusty, the head and neck streaked with the 

 same. Length about 20.00-26.00 inches. 



The four species which compose this genus differ more or less 

 from one another in form, but they all possess the characters 

 defined above. Like the more or less nearly related genera 

 Arctonetta, Eniconetta, Histrionicus, and Camptolaimus, they are 

 birds of high northern latitudes, barely entering the warm tem- 

 perate zone in winter. 



This genus includes two subgenera, the characters of which are 

 as follows: 



Frontal feathers reaching about hah* way from the base of the maxilliary 

 angle or lobe to the nostril; feathering of lores extending forward to beneath the middle of 

 the nostril; adult males with scapulars and tertials white and top of head black. 



Erionet a. Frontal feathers reaching forward as far as the nostrils ; feathering of the 

 lores extending only about half way to the nostrils ; adult males with scapulars and tertials 

 black, and top of head light grayish blue. 



SUBGENUS SOMATERIA LEACH. 



Somateria LEACH, in Boss's Voy. Disc. 1819, App. p. xlviii. Type, Anas mollissima LINN. 



SUBGEN. CHAB. Anterior point of feathering on forehead reaching only about half way 

 from the point of the naked angle on side of forehead to nostril; feathering of lores extend- 

 ing forward to at least beneath the posterior end of the nostril; adult males with scapulars 

 and tertials white, the top of head chiefly black. 



Three species of this subgenus occur in North America, one of 

 them being only subspecifically distinct from the European 

 Eider (S. mollissima}. One of them visits northern Illinois dur- 

 ing winter, while another may reasonably be expected to occur 

 there, since farther eastward it is found not uncommonly in 

 Massachusetts. 



The differential characters of these two species are as follows : 



S. mollissima boreal is. A dult male with lobe or angle of bill narrow and pointed, its 

 length, from anterior extremity of loral feathering, lJfo-1.52; width across middle, not more 

 than .30; black of head bordered below by pure white, except at posterior extremity; 

 female with angle of bill 1.20-1.40. depth of upper mandib;e at base 0.78-0.95. HAB. Green- 

 land, shores of Cumberland Gulf, and northern Labrador, south in winter to Massachu- 

 setts. 



