164 LAEID^. 



Adult in hreeding-iiilumage. Head and upper neck dark slate- 

 colour, terminated by a narrow deep black collar ; mantle slate- 

 grey, much lighter than the head ; the inner secondaries merely 

 tipped with white, the rest of the secondaries and the five upper 

 primaries almost wholly white; the remaining primaries black on 

 both sides of the shafts, with conspicuous white tips and broad 

 white margins along the greater part of the inner webs ; edge of 

 wing to the carpal joint black ; tail, and the underparts up to the 

 coUar, white : bill black to the angle, chrome-yellow anteriorly ; 

 inside of the mouth vermilion ; iris dark brown ; a narrow vermilion 

 ring round the eye, beneath which is a minute white speck ; tarsi 

 and toes brown to blackish. Total length 13 inches, culmen 1-.35, 

 wing 10'75, tail 4"75, depth of fork 1, tarsus 1'4, middle toe with 

 claw 1"35. The sexes appear to be alike in size and plumage. 



In examples a year younger the white tips to the outer primaries 

 are less conspicuous, and there is a considerable amount of black on 

 the sixth primary from the outside. In specimens from Alaska the 

 tarsi and toes are darker than in birds from Greenland. 



Adidt hi ivintcr (Callao, Peru ; Dec). Similar, but head white, 

 with grey streaks which coalesce on the nape and hind neck, pro- 

 ducing a greyish-black appearance ; quills worn and faded in colour, 

 and their tips abruptly broken off', as if cut ai'tificially : bill duller 

 in colour ; tarsi brown. By the beginning of April the new 

 primaries, with broad white tips, are fuUy developed, and the head 

 is plentifully sprinkled with slate-grey. 



Immature (nearly two years old). Head chiefly slate-grey, mottled 

 with white, especially on the throat, collar ill-defined; rectrices 

 slightly tipped with ash : bill with very little yellow anteriorly. 



Young. Forehead dull white ; head grey, mottled with buff' ; 

 feathers of the upper parts ash-grey, with edges which are buffish 

 at first, and become greyish with increasing age ; rectrices broadly 

 tipped with black ; underparts chiefly white ; on the sides of the 

 neck an ash-brown band, which is seldom complete and exceedingly 

 variable in extent : biU horn-brown ; tarsi and toes flesh-colour to 

 brownish. 



Hab. Entire Circumpolar regions in summer. In winter as far 

 as the Bermudas and South Texas on the Atlantic side ; in the 

 Pacific down to 12° S., on the coast of Peru, in great numbers ; 

 thus considerably overlapping the Galapagos Islands, the head- 

 quarters of the next species, X.furcata. 



a. Juv. St. Mount's Bay, Cornwall, Vingoe Coll. 



autumn. 

 b-d. Ad. st. "Arctic Seas." Purchased, 



e. Ad. sk. Sabine's Is., above Disco, General Sir Edward 



lat. 75° 29' N., long. 60° 9' Sabine [P.]. 



W., July 25th, 1818. (Type.) 



/. Ad. ; ^r. Juv.sk. Disco Bay, Greenland (K H. Saunders Coll. 



Why7n})er). 

 h. Juv. sk. Mouth of the river Clyde, H. Saunders Coll. 



Baffin Land, 70° 20' N., 



68° W., Aug. 20th {J. B. 



Walker,' Erik'). 



