PLECTROPHENAX. 403 



6 s . Larger, with much larger and longer bill. Male: "Wing 4.25-4.70 (4.45), 

 tail 2.85-3.20 (2.99), culmen .47-.52 (.50), gonys .26-.29 (.28). Female : 

 Wing 4.10-4.25 (4.20), tail 2.75-2.80 (2.77), culmen .48-.50 (.49), gonys 

 .24-.27 (.26). Eggs .93 X -69. Sab. Prybilof Islands, Alaska, and Com- 

 mander Islands, Kamtschatka. 



— . P. nivalis townsendi Bidgw. Prybilof Snowflake. 1 

 Male with black on only two middle tail-feathers, and on these restricted to a 

 subterminal spot (sometimes almost obsolete) ; female with only four mid- 

 dle tail-feathers chiefly blackish. Adult male in summer : Pure white, in- 

 cluding entire back ; a blackish spot on inner web of first tertial (sometimes 

 second also) ; terminal portion (less than exposed half) of longer quills black, 

 this reduced on fifth quill (and, if present, on sixth also) to a small spot near 

 tip of inner web, the outer webs of all edged and margined terminally with 

 white; two middle tail-feathers marked near end of inner webs with a small 

 black spot ; bill entirely black. In winter, similar, but top and sides of head 

 washed with deep rusty, the hind-neck, back, rump, and band, across chest 

 more faintly tinged with same; bill yellow, tipped with dusky. Adult female 

 in summer: Pure white, the back and scapulars narrowly streaked with 

 blackish (streaks broader and more wedge-shaped on scapulars), tertials with 

 most of concealed portion blackish, the outer webs partly buffy brown, outer 

 webs of second to fourth, fifth, or sixth quill dusky quite to the base, but 

 broadly edged with white, all of them broadly margined at tips with the 

 same; alulse dusky bordered with white, and primary coverts sometimes 

 dusky medially, but often entirely white ; four middle tail-feathers blackish 

 or dusky, broadly margined (both webs) with white, this involving nearly 

 whole of outer web of next to middle pair; bill dusky. In winter similar, 

 but upper parts, especially top of head and ear-coverts, washed with rusty, 

 and bill yellow, tipped with dusky. Young : Top of head, hind-neck, back, 

 scapulars, rump, and lower tail-coverts brownish gray (rather paler than 

 in P. nivalis), the scapulars and interscapulars dusky centrally, forming broad 

 but indistinct streaks ; tertials with tips of both webs and broad edging to 

 outer web umber-brown, the rest black; wings otherwise chiefly white, but 

 marked with dusky, as in adults ; lower parts dull white, purer posteriorly, 

 tinged with pale smoky gray anteriorly ; bill lemon-yellow. Male : Length 

 about 7.00-7.50, wing 4.60-4.65 (4.62), tail 3.10-3.15 (3.12), culmen .44, gonys 

 .24-.25. Female : Length about 6.50-7.00, wing 4.20-4.30 (4.25), tail 2.70- 

 2.90 (2.83), culmen .42-.43, gonys .23. Sab. Breeding on Hall Island (prob- 

 ably also St. Matthew's Island), Bering's Sea, and in winter visiting western 

 coast of Alaska (St. Michael's to Nushagak). 



535. P. hyperboreus Bidgw. McKay's Snowflake. 



1 New subspecies. Type, No. 106,695, Otter Island, Bering's Sea, June 8, 1885; C. H. Townsend. 



