276 Prof. R. Collett on the Occurrence 



(cliiefly immature, although bearing, or having borne, their 

 summer-plumage) follow the shores of the Arctic Ocean 

 down to the North Sea. The specimens in the Norwegian 

 Museums have, as previously mentioned, been obtained both 

 on the southern and northernmost coasts of Norway. 



On examining the specimens of C. adamsi in the Nor- 

 wegian Museums, which are at present at my disposal, and on 

 comparing them ^^ith examples of C. glacialis, I find the 

 following characters to be principally of value : — 



(1) Size. Total length about 850 to 900 mm. (and up- 



wards). 



(2) Shape of the bill. Culmeu straight, shorter than the 



tarsus ^, commissure straight. 



(3) Colour of the bill. Whitish yellow. 



(4) Loiver part of the back. Unspotted. 



(5) Shafts of lite iving-feathcrs (down to nearly the tips) . 



Light horn-colour. 



(6) Lower neck-bar. With 8 to 10 white stripes ; its greatest 



width is in the middle, and would be contained at 

 least twice in the width of the lower black collar. 



(7) The largest white dots on the back. These are con- 



tained about one and a half times in the width of 

 the neck-bar. 



(8) Throat and collars. Blue- black, M'itli a violet gloss. 

 Of these characters the last three are applicable only to 



individuals in their nuptial plumage; the others to those in 

 all plumages, including the fully-grown young birds. No. 5 

 applies also to the not fully-grown young ones. 



When the characters are compared with the corresponding 

 features in C. glacialis, the two species will be seen to differ 

 in the following points : — ■ 



(1) The Size. 



The average length of C. adamsi is about 870 mm.; large 



males attain a length of 900 mm. and upwards ; one specimen 



in the Christiania Museum, from the Porsanger fjord, has a 



total length of 920 mm. The size of C. glacialis is somewhat 



* The bill barelv attains its full lenetli diiriiio the first winter. 



