ALCIDiE — THE AUKS — SIMOIIIIYNCHUS. 



513 



color of bill dull brownish. Youmj (= Uria dahia, Pallas) : Bill simple and smooth as in the 

 winter iulult, but smaller ; plumage a^ in the adult, but crest and auricular filameuta aljsent or but 



Summer adult. 



slightly developed. Bill dull brownish. Total length, about 9.00 inches ; wing, 5.25 ; culraen, 

 .45 ; tarsu.s, 1.00 ; middle toe, with claw, 1.35. 



Judging from the very extensive series of specimens before us, it appears that the young gradu- 

 ally assume both the frontal crest and the white auricular filaments during the latter part of their 





Winter adult. 



first year, the peculiar character of the bill being gradually assumed at the appi-oach of the breoil- 

 ing-season. Perfectly adult birds apparently retain as permanent ornaments the curled frontal 

 crest and line of white acicular feathers across the ,^uricular region ; but after the close of the 

 breeding-season the basal horny parts of the bill (perhaps also of the entire bill, since the terminal 

 VOL. II. — G5 



