LARIDJE THE GULLS AND TERNS. 237 



GENUS XEMA LEACH. 



Xema "LEACH," Boss's Voy. App. 1819, p. Ivii. Type, Larus sabinii SAB. 



GEN. CHAB. Tail emarginate. or slightly forked: otherwise like the smaller species of 

 Larus. 



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

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

 (Creagrus furcatus), 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. Mus., Vol. XII., 1889, p. 117.) 



Xema sabinii (Sabine). 



SABINE'S GITLL. 



Popular synomym. Pork-tailed Gull. 



Larus sabinii J. SAB. Trans. Linn. Soc. xii, 1818, 520. pi. 29. 



Xema sabini EDW. & BEVEBL. App. Boss's Voy. Baff. Bay, 4to ed. 1819, Ml. 

 Xema sabinii LAWB. in Baird's B. N. Am. 1858, 857. BAIBD, Cat. N. Am. B. 1859, No. 680. 

 SAUNDEBS, P. Z. S. 1878. 209. COUES, 2d Check List, 1882, No. 790. B. B. & B. Water 

 B. N. Am. ii, 1884, 269. A. O. U. Check List, 1886, No. 62. BIDGW. Man. N. Am. B. 

 1887, 38. 

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



No. 558; B. N. W. 1874, 6GO.-BiDGW. Norn. N. Am. B. 1881. No. 677. 



Xema collaris "SCHBEIBEBS," Boss, in App. Boss's Voy. Baff. Bay, 11, 8vo. ed. 1819, 164 

 (nee ScHBEiBEBS, = .R/todos<e<7ua rosea! Cf. SAUNDEES, P. Z. S. 1878, p. 209). 



HAS. Circumpolar Begions ; in winter migrating south, in America, to Massachusetts, 

 New York, the Great Lakes, Kansas, and the Great Salt Lake. Utah. Very abundant In 

 Alaska. Bermudas, one instance (SAUNDEBS). Macabi Island, coast of Peru, lat. 8 S. (one 

 specimen, ftde SAUNDEBS, P. Z. S. 1878, p. 210). 



SP. CHAB. 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, the 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 of 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 primaries black, broadly tipped with white, the inner webs 

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

 about 1.75 inches of the terminal portion of the outer, white, the 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 alulae, uniform black. Bill black, tipped with yellow; 

 eyelids red ; Iris brown; feet dull lead-color, claws black" (L. M. TUBNEB, M. SJ. Adult, 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, wing-coverts, and rump brownish gray, each feather bordered ter- 

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



