LARID.E — THE GULLS AND TERNS — XEMA. 



269 



Genus XEMA, Leach. 



Xema, "Leach," Ross's Voy. App. 1819, p. lvii (type, Larus Sabinei, Sab). 

 ?? Creagrus, Bonap. Naum. 1854, 213 (type, Larus furcatus, Nebocx). 



Char. Size small or medium ; tail forked ; tarsus equal to or rather shorter than the middle 

 toe, with claw ; adult with a dark hood, the plumage otherwise pearl-gray above and white 

 beneath. 



It is very doubtful whether the Larus furcatus, Xeisoux, should be referred to the genus .V. ma. 

 Mr. Salvin, who has had the opportunity of examining a specimen, remarks as follows on this 

 question : "Creagrus, as a genus, differs but slightly from Xema, both having a deeply forked tail. 



X. Sabini, summer adult. 



The former, however, is a more robust form, and has the nostril situated rather nearer the point of 

 the bill. In coloration, Creagrus wants the black ring which encircles the hood of Xema. I 

 doubt whether in a well-considered classification of the Laridce the two genera could be maintained 

 as distinct" (Trans. Zool. Soc. Lond. IX. 1876, p. 50fi). It might also have been added, that the 

 tail of Creagrus is much more deeply forked, and that the coloration of the bill and feet is radically 

 different. 



Assuming, however, that they may be referred to the same genus, their differential characters 

 may be stated as follows : — 



1. X. Sabini. Wing, 11.00 inches or less ; tail slightly forked ; hood plumbeous, bounded 



below by a well-defined black collar ; bill black, tipped with yellow ; feet black. Hah. 



Circunipolar Regions. 

 2 X. furcata. Wing, 1(5.00 inches or more ; tail deeply forked ; hood sooty black, with 



a white frontal liar, but no dark collar; bill and feet red. Hah. Galapagos ; coast of 



Peru ; coast of California (?). 



Xema Sabini. 



THE FORK-TAILED GTJLL. 



Larus Sabini, .1. Sabine, Tr. Linn. Soc. XII. 1818, 520, pi. 29. 



Larus Sabinii, Rich. App. Parry's 2d Voy. 1825, 3fi0. — Sw. & Rich. F. B. A. II. 1831, 428 — 



Nutt. Man. II. 1834, 295. — Aud. Orn. Biog. III. 1835, 561, pi. 285 ; Synop. 1839, 323 ; B. 



Am. VII. 1844, 127, pi. 441. 

 Xema Sabini, Euw. & Beverley, App. Ross's Voy. Baf. Bay, 4to ed. 1813. lvii. 

 Larus {Xnna) Sabini, Bruch, J. f. 0. 1853, 103. 



