LABIDiE— THE 6rrLr-8 AND TBBNS. 237 



Genus XEMA Leach. 



Xema "Lbaoh," Boss's Voy. App. 1819, p. Ml. ■ Type, Larus sahinii Sab. 



Obn. Ceab. Tail emarginate. or slightly forked: otherwise like the smaller species of 

 Lama. 



This genua contains a single species, the Fork-tailed or Sa- 

 bine's Gull (X sahinii). Another species, the Swallow-tailed Gull 

 {Oreagrus furcatiis) , of the Galapagos Archipelago has often been 

 referred to the genus, but the differences of structure between 

 the two are so marked as to require its reference to a different 

 genus. (See Proo. U. ,S. Nat. Mm., Vol. XII., 1889, p. 117.) 



Xema sabinii (Sabine). 



SABttni'S GULL. 



Fopnlar synomym. Fork-tailed Gull. 



Larus sabinii 3. Sab. Trans. Linn. Soc. xii, 1818, 520. pi. 29. 



Xema sa6ini Edw. & Bevebl. App. Boss's Voy. Baff. Bay, 4to ed,1819, Ivii. 



Xema sabinii Lawb. iu Baird's B. N. Am. 1858, 857.— Bated, Cat. N. Am. B. 1859, No. 6R0.— 



Saundees, p. Z. S. 1878, 209.— CouES. 2d Check List, 1882, No. 790.— B. B. & E. Water 



B. N. Am.ii, 1884, 269.- A. O. U. Cheek List, 1886, No. 62.-EiDaw. Man. N. Am. B 



1887, 38. 

 Xema sabinei CoUES, Proc. Acad. Nat. Sol. Phila. 1862, 311; Key, 1872, 317; Check List, 1873. 



No. 558; B. N. W. 1874, 660.— BlDGW. Norn. N. AnS. B. 1881, No. 677. 

 Xema oollaris "Sohreibbbs." Boss, in App. Boss's Voy. Baff. Bay, H, 8vo. ed. 1819, 164 



(nee ScB.R'EiBERB,=lihodostethia rosea! Cf. Saundees, P. Z. S. 1878, p. 209). 



Hab. Clroumpolar Begions ; in winter migrating south, in America, to Massachusetts, 

 New York, the (Jreat Lakes, Kansas, and the Great Salt Lake, Utah. Very abumfant in 

 Alaska. Bermndas, one instance (Saundees). Macabi Island, coast of Peru, lat. 8° S. (one 

 specimen, fide Bauhdebs, P. Z. S. 1878, p. 210). ' 



Sp. Ceab. Adult, in summer: Head and upper part of neck plumbeous, bounded 

 below by a well-defined collar of black, widest behind; lower part of the neck, entire lower 

 parts, tail, upper tail-coverts, and lower part of rump snow-white, (he lower part faintly 

 tinged with delicate rose-pink in some freshly killed specimens. Mantle deep bluish gray 

 (nearly the same shade as in Larus franklinii) the secondaries pure white, becoming grad- 

 ually pale grayish blue toward bases; most pf the exposed portion of the greater coverts 

 also white,' forming, together with the secondaries, a conspicuous longitudinal white stripe 

 on the closed wing. Four ou'er primaiies black, broadly tipped svith white, the inner webs 

 broadly margined with the same; fifth quill with the greater part of the inner web, and 

 about 1.75 inches of the terminal portion of the outer, white, ihe remainder black; remain- 

 ing Quills white; outer border of the wing, from the carpal joint back to the primary 

 coverts, including the latter'and the alula, uniform black. Bill black, tipped with yellow; 

 eyelids reH ; Iris brown; feet dull lead-oolor. claws black" (L. M. Tuknee, M. S.). a dult, in 

 winter: Similar to the summer plumage, but head and neck white, except occiput, nape, 

 and auricular region, which are dull dusky plumbeous. Young, first plumage: Crown, 

 nape, back, scapulars, wlug-coverts, and rump brownish gray, each feather bordered ter- 

 minally with light fulvous or pale grayish buff.this ftilvous border preceded on the tertials, 



