XEMA, 37 
Genus RHODOSTETHIA Macemuivray. (Page 23, pl. VIL, fig. 3.) 
Species. 
Summer adult : Mantle and under surface of wing uniform pale pearl-gray, the 
secondaries and innermost quills very broadly tipped with pinkish white, and 
outer web of first quill chiefly black ; rest of plumage white, usually more or less 
(sometimes very strongly) tinged with delicate peach-blossom pink, the middle of 
the neck encircled by a narrow black collar. Winter adult: Similar, but black col- 
lar absent, a blackish spot immediately in front of eye, and top of head tinged with 
pearl-gray. Young, second summer? Similar to summer adult (including collar), but 
smaller wing-coverts, inner secondaries, primary-coverts, alule, and adjacent small 
feathers, together with three outer quills, blackish, the inner web of the latter, how- 
ever, with marginal half pearl-gray ; remaining quills pearl-gray, becoming white 
on innermost quills, and all of them tipped with black; third, fourth, and fifth tail- 
feathers broadly tipped with black. Young: Back and scapulars heavily spotted 
or clouded with dusky or sooty blackish, this color prevailing on lower back, where 
the feathers have buffy tips; top of head and hind-neck also clouded with dusky ; 
middle tail-feathers with the end sooty black for about .85, the succeeding feathers 
on each side tipped with black in decreasing extent to the third, which has but a 
slight mottling of dusky at extreme tip; wing-coverts dusky, or sooty, tipped with 
pale buffy ; two innermost quills pure white, the rest parti-colored; head, neck, 
and lower parts chiefly white, marked anteriorly (except on chin and throat) with 
narrow bars of dusky. Length 11.50-14.00, wing 9.50-10.50, tail 4.00-5.50 (gradu- 
ated for .75-1.25), culmen .65-.75, tarsus 1.20-1.25, middle toe 1.00-1.05. gg 
(single specimen) 1.90 < 1.30, in color like that of Xema sabinii (fide Srrzonm, P. 
Z. §. 1886, 82). Hab. Arctic Ocean, south, in autumn or winter, to northern Alaska, 
Kamtschatka, Disco Bay, Faroes, Heligoland, and (accidentally) England. 
61, R. rosea (Macaiz.). Ross’s Gull. 
Genus XEMA Leaca. (Page 23, pl. IX., figs. 1, 2.) 
Species. 
a, Culmen much shorter than tarsus; tail forked for not more than the length of 
the tarsus; wing not more than 11.25; legs and feet black. (Subgenus 
Xema.) Summer adult: Head and upper neck uniform plumbeous, bordered 
below by a black collar; mantle deep bluish gray; quills black, the five in- 
nermost ones varied with white and plumbeous; rest of plumage white; bill 
black, tipped with yellowish. Winter adult: Similar, but head and neck 
white, except ear-coverts and back of head and neck, which are dull dusky 
plumbeous. Young: Mantle brownish gray, each feather darker subtermi- 
“nally, and margined at tip with pale fulvous or buffy ; tail white, with a broad 
black band near end, this again narrowly tipped with white; upper tail- 
coverts and entire lower parts white. Downy young (fide MippEnDorRFF) : 
