110 BIRDS OF ILLINOIS. 



Subfamily ANSERIN-ffi.— The Gekse. 

 Genus CHEN Boie. 



Chen Boie, Isis. 1822, 563. Type, Anser hyperboreus F&IjLAS. 

 Exanthemops Elmot. Proc. Phila. Acad. 1868. Type, Anser ror^Kii Baibd. 



Of the three North American species of this genus, two, C. 

 hyperhoi-ea, the type, and C. ccerulescens, are precisely alike in 

 the details of form, the only difference being the coloration, 

 which is vei'y distinct in the two; the third species, C. rossii, 

 while agreeing strictly with C. hyperhorea in plumage, both in 

 the adult and young stages, differs decidedly in the form of the 

 bill, which is quite peculiar. It seems unnecessary, however, to 

 adopt the generic terra E.mntht'mops, proposed for it by Mr. D. 

 G. Elliot, since the difference in the character of the bill from 

 that of the typical species of the genus is hardly of generic 

 value. The species may be distinguished as follows : 



Synopms of Species. 



Common Characters. Adult with whole head and at least part of the neek white (in 

 two of the three speciei? the plumage entirely white, except quiUs, which are blackish): 

 the bill dull purplish red (in life) with whitish nail, and feet purplish red. Young with 

 head and neek grayish, the rest of the plumage either chiefly grayish brown or else 

 striped with grayish on a whitish ground; bill and feet dusky. 



A. Plumage never chiefly white; the adult mainly grayish brown, with bluish-gray rump 

 and wing-covorts, the head and part of the neck white. Young almost wholly 

 grayish brown, including head and neek, 



1, C, oaerulesoens. Bill very robust, the posterior lateral outhne of the maxilla de- 



cidedly concave; commissure widely Raping, and lower outline of the mandible 

 decidedly convex. (Page 110.) 



B, Plumage of the adult pure white, the primaries black. more grayish toward the base; 



young grayish white, the centres of the feathers dai-ker gray. 



2. C. hyperborea. Bill robust, and shaped like that of (7. ca-rulescens. 



13. C, rossii. Bill small, the posterior lateral outline of the maxilla almost perfectly 

 straight, the tomia closely approximated, and the lower outline of the mandible 

 scarcely convex; in older specimens the base of the maxilla corrugated or warty. 

 Wing, 13,75-15.50 inches; culmen, 1.50-1.70; depth maxilla at base, .8i-.95; tarsus. 

 2.30-3.00; middle toe. 1.80-2.05. Hnb. Northwestern North America.] 



Chen ceerulescens (Linn.) 



BLUE-WINGED OOOSE. 



Popular synonyms. Blue Brant; Blue Goose; White-head; Whit«-hoad6d Brant, or 



Goose; Bald Brant;;Blue Wavey (Hudson Bay). 

 Ajiaa oieruleacens Linn. S. N. ed. 10, i, 1758, 124; ed. 12, i, 1766. 198.— Gmkl. S. N. 1, 1788, 



613.-LATH. Ind. Orn. il, 1790. 836. , 



