82 ANATID^. 



I-*- CHEN. T^p^ 



Chen, Boie, Ms, 1822, p. 563 C. hyperboreus. 



Chionocheu, Rclmb. Ac. Syst. Nat. p. ix (1852) .... C. hyperboreus. 

 Exanthemops, Elliot, B. N. Am. ii. pi. xliv. (pt. ix., 



1868) C. rossi. 



Range. Arctic Eegions of Northern Hemisphere. 



Key to the Sjjecies. 



a. Bill very rubiiit, the commissure widely 

 gaping and er.closicg a broad blackish 

 space, extending from the corner of the 

 mouth nearly to the tip of the bill ; 

 feathering at tl e base of the upper man- 

 dible, along each side, having a very 

 convex outline; culmen 1-95 inches, or 

 more {Chen). 

 a'. Plumage chiefly greyish brown; the 

 rump (usually) and wing-coverts bluish 



(rrey carulescens, p. 82. 



b'. Plumage of adult entirely white, except 



primaries and their coverts, which are 



grey ; young greyish white, the upper 



parts tipped with dusky greyish. 



a". Length about 23-28 inches, wing 



14-50-50, culmen 1-95-2-30, tarsus 



2-80-3-50 hyperboreus, p. 84. 



b" . Length about 30-38 inches, wing 17'35- 

 17-50, culmen 2-65-2-70, tarsus 3-15- 



3-50 nivalis, p. 86. 



b. Bill comparatively weak ; the commissure not 

 gaping and not enclosing a distinct blackish 

 space ; feathering at base of upper man- 

 dible, along each side, forming a nearly 

 straight oblique line ; culmen 1-70 inch 

 or less ; basal portion of upper mandible 

 often wrinkled and warty (Kranihemops) . . rossi, p. 88. 



1. Chen cserulescens. 



Blue-winged Goose, Ediv. Birds, pi. 152 (Hudson Bay) (1748) ; 



Lath. Syn. iii. 2, p. 469, n. 28 (1785). 

 Anser sylvestris freti hudsonis, Briss. Orn. vi. p. 275 (1760). 

 Anas caerulescens, Linn. S. N. i. p. 198, n. 12 (1766) ; Forst. Phil. 



Turns. Ixii. p. 414, 2 (1772) ; Gm. S. N. i. 2, p. 513, n. 12 (1788) ; 



Lath. Lid. Orn. ii. p. 836, n. 13 (1790) ; Vieill. N. D. xxiii. 



p. 336 (1818) ; Dum. Diet. Sc. Nat. xxxv. p. 468 (1825); ? Bp. 



Comi^t. Bend, xliii. p. 1024 (1856). 

 Oie des Esquimaux, Buff. Hist. Nat. Ois. ix. p. 80 (1783). 

 Anser casrulescens, Bonn. Enc. Meth. i. p. 115, n. 17 (1790) ; Cass. 



Pr. Philad. Ac. 1856, p. 42 ; Baird, Cat. N. Am. B. n. 564 (1859) ; 



Barnston, Ibis, 1800, p. 253 ; Ross, Canrd. Natural, vii. p. 151 



(1862); id. Nat. Hist. Eev. (2) ii. p. 286 (Mackenzie Kiver) 



(1862); Blakist. This, 1863, p. 140; Bree, B. Bur. iv. p. 132 



