XEMA FUECATUM, SWALLOW-TAILED GULL. 661 



DiAG. X. viivoi; cttudd emarginatd, capite cucullaio, collo torquaio, rosiro nigro apice flavo, 

 pedibus nigris. Long. tot. 14.00 j)oll. 



Hah. — Arctic regious of Loth hemispheres. Spitzbergeu. In America, south in win- 

 ter to New York, and Great Salt Lake, Utah. 



Adult, breeding plumage. — Bill black to the angle, abruptly bright chrome from angle 

 to tip. Mouth bright orange ; eyelids orange ; legs and feet' black. Hood uniform clear 

 deep slate, bounded inferiorly by a ring, narrowest on the nape, of deep velvety black. 

 Lower part of neck all round, tail and its coverts, four inner primaries, secondaries, 

 greater part of greater coverts, tips of tertials, except the innermost, and whole under 

 parts, pure white. Mantle slate-blue, extending quite to the tips of the inner tertials. 

 Edge of wing, from the carpal joint with the bastard wing, black. First live prima- 

 ries, with their shafts, black ; their extreme tips, and the outer half of the inner wel)s, 

 to near the end, white. Other primaries white, the sixth with a touch of black on thi^ 

 outer web. Eniargination of tail 1.2.5 inches. 



Z>MHCHSio««.— Length, 13.75 ; wing, 10.75 ; bill, 1 ; along gape, LOO; height at angle, 

 0.30 ; tarsus, 1.25 ; middle toe and claw, same. 



Young-of'the-gtar.—CSo. 50182, Plover Bay, Sept. 1867.) Tail forked, nearly as in the 

 adult. Bill small and weak, ilesh-color and dusky. Legs apparently llesh-colored. 

 No hood nor collar. Most of the head, the back of the neck, and upper parts in gen- 

 eral, slatj--gray, transversely waved with brownish-white ; each feather ))eing tipju.d 

 with this color. Under parts white. Tail white, wiih a broad teiminal bar of black, 

 an inch wide on the central rectrices, growing narrower on the others successivelv ; on 

 the outermost sometimes invading only one web. Tins black bar very narrowly edged 

 with white. Wings surprisingly similar to those of the adult, but the while on ihe 

 inner webs more restricted, and the white tips very small or wanting altogether. 

 Dimensions a little less than those of the adult. 



The pictura of the primaries in the above-described specimen is remarkably like the 

 adult's, considering how young the specimen is; but I presume the condition is con- 

 stant, or at least usual. As the bird advances toward mal urity the primaries gain more 

 decided white tips; the black bar disappears from the tail; the upper parts become 

 first mottled with the clear pearl-blue of the adults, then lose altogether the feathers 

 of the present hue and pattern. Exactly at what time the hood and collar are assumed 

 I cannot say ; I should judge not till the second year. 



The yellow tip of the bill varies greatly in size. Half of the bill may be yellow ; 

 or the yellow may be reduced to nil : but birds with an entirely black bill are not often 

 seen. The adult winter plumage I have not seen, and cannot say whether the hood is 

 lost or not; but I should judge, from analogy, that it is not retained. The species 

 varies less than most Gulls : in i'act I have little to add to the above on this score. The 

 bill varies, as usual, in length and stoutness. Young birds look something like young 

 Cnracocephalns phihuklpliia, but I believe the tail is always at least emargiiiate. 



This species was lirst introduced in 1818 by Capt. J. .Sabine as Larun mbinci, but its 

 peculiarities were almost immediately made the basis for generic separation by lA-ach. 

 Macgillivray referred it to the genus Garia. I have not been able to verity Bonaparte's 

 quotation of " Larun coUaiiit Sabine." The same author incorrectly gives Leach as 

 authority for the specific name. 



XEMA FURCATUM, (ISTeb.) Bruch. 

 Swailow-tuiled Gull. 



Mouctte a queue fourchuc, Nkisoix, Kev. Zool, iii, 1840, 290. 



LaruH furcatuM, I'ltKV. & Dj;.s Ml1{.s, Zool. Voy. Venus, Ois. 1855, 277, pi, 10. 



A'cHia furraluni, BlUCll, J. f, O, 18,')3, 103,— CoLKS, Key, 1.^72, 317 ; Check-list, No. .'59. 



CmigruH Junulus, By., " 1854,"— Bmxii, J, f, O. 185^, 2'.I2.— Br„ Compt. liend. l^.Mi, 



771.— Lawh., B, N. a, Ifcue, 857.— CoLics, I'r. I'liila. Acad. I8t)2, 312.— Blas., 



J. f. O. 1805, 37U. 



;. " L. Hupra cinei-acnis, capite colloqiiefuliginouc nigrtxeenlihuH ; itublus alhut>; strigdpost- 

 ulari et bust J'lontali albis ; palpebrin aurontiii), tunsta pulminque rubiia.'' 



Hub. — Coast of California, (?) Also, Arctic regions. 



Adult. — Bill of moderate robustness, much bent at the tip, black at its ba.sc, white 

 toward its apex, with "a small rounded white Hjiot on either side ot the base of the 

 upper mandible," Tarsi, toes, anil iiitenligital membranes, red; the claws Itlack, 

 Irides red the [edges of tlie] eyelids (irniige. Head, and grejtter part of the neek all 

 round, black [''f/ri^ bruu." Nr.nof.x ; "fuligiuoxr nignxcintlbus." Vity.\<tH\ and l)y.n 

 Mrits], Mantle light gniy ['• blaue grix." .Nkmoi .\ ]. Breast, belly, under surliues of 



the wings, and the tail, pure white. The folded wings reaeh iiiclies bevond tlio 



tail, I'rimarieb bordered both iulernally and ex.ernally with black. Middle win};. 



DiAO 



01 



