LARID.E — THE GULLS AND TERNS — XEMA. 



269 



Genus XEMA, Leach. 



Xema, "Leach," Ross's Yoy. App. 1819, p. Ivii (type, Larm Snhinci, Sab.). 

 11 CreiKjrus, Bonap. Nauni. 1854, 213 (type, Larus fiwcatus, Neboux). 



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

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

 beneath. 



It is very doubtful whether the Larus furcatns, Neboux, should be referred to the genus Xema. 

 Mr. Salvin, who has had the ojjportunity of examining a specimen, i-emarks as follows on this 

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





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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. 506). 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 lij^ a well-defined black collar ; bill black, tipped with yellow ; feet black. Hab. 



Circumpolar Regions. 

 2 X. furcata. Wing, 16.00 inches or more ; tail deeply forked ; hood sooty black, with 



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



Peru ; coast of California ( ?) . 



Xema Sabini. 



THE FORK-TAILED GULL. 



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



Larus Sahinii, ElCH. App. Parry's 2a Voy. 1825, 360. — 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, ])!. 441. 

 Xema Sabini, Edw. & Beverley, App. Boss's Voy. Baf. Bay, 4to ed. 1819, Ivii. 

 Larus (Xema) Sabini, Bruch, J. f. 0. 1853, 103. 



