LARIDjE THE GULLS AND TERNS. 237 



GENUS XEMA LEACH. 



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



GEN. CHAR. 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 Proc. U. S. Nat. Mus., Vol. XII., 1889, p. 117.) 



Xema sabinii (Sabine). 



SABINE'S GULL. 



Popular synomym. Fork-tailed Gull. 



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



Xema sabini EDW. & BEVERL. App. Ross's Voy. Baff. Bay. 4to ed. 1819, Ivii. 



Xema sabinii LAWR. in Baird's B. N. Am. 1858. 857. BAIRD, Cat. N. Am. B. 185ft, No. 680. 



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



B. N. A.m. ii, 1884, 2i>9. A. 0. U. Check List, 1886, No. 62.-RiDGW. Man. N. Am. B < 



1887. 38. 

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



No. 558; B. N. W. 1874, 660. RIDGW*. Norn. N. Am. B. 1831. No. 677. 

 Xema co'laris "SCHREIBEUS," Ross, in App. Ross's Voy. Baff. Bay, ii, 8vo. ed. 1819, 164 



(nee 8cHREiBERS, = W/iodoste/'7i(a rofea! Cf. SAUNDERS. P. Z. S. 1878, p. 209). 



HAB. Circumpolar Regions; 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 (SAUNDERS). Macabi Island, coast of Peru.lat. 8 S. (one 

 specimen, fide SAUNDERS, P. Z. S. 1878. p. 210). 



SP. CHAR. 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 \\hite, becominggrad- 

 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 whi'e stripe 

 on the closed wing. Four ou'er prima' ies black, broadly tipped \vith white, the inner webs 

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

 about 1.75 inches or 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 alulas. uniform black. Bill black, tipped with yellow; 

 eyelids re i ; iris brown; feet dull lead-color, claws black" (L. M. TURNER, M. S.). A dull, in 

 winter: Similar to the summer plumage, but head and n 'ck 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 tjertials, 



