AVES LARID^E. 2 1 5 



"This species so closely resembles the Xema ridibtmdum Boie, that 

 Mr. Gould observes, he should have hardly ventured to have character- 

 ized it as distinct ; but as M. Vieillot and Meyen have deemed this neces- 

 sary, he adopts their view. I have compared a suite of specimens, which 

 I procured from the Rio Plata, the coast of Patagonia, and the Straits of 

 Magellan, with several specimens of the Xema ridibundum ; the only dif- 

 ference which appears to me constant, is that the primaries of the X. 

 cirrocephalum, in the adult winter plumage, both of male and female, are 

 tipped with a white spot (a character common to some other species), 

 whereas in the X. ridibundum the points are black. The beak of the 

 latter species, especially the lower mandible, is also a little less strong, 

 or high in proportion to its length. In the immature stage, I could per- 

 ceive no difference whatever in the plumage of these birds. The propor- 

 tional quantity of black and white in the primaries, given by Meyen as 

 the essential character, varies in the different states of plumage. The 

 specimens described by this author were procured from Chile. The soles 

 of the feet of my specimens were coloured, deep ' reddish orange,' and the 

 bill dull 'arterial blood-red' of Werner's nomenclature. 



"In the plains south of Buenos Ayres I saw some of these birds far 

 inland, and I was told that they bred in the marshes. It is well known 

 that the black-headed gull (Xema ridibundum], which we have seen comes 

 so near the X. cirrocephalum, frequents the inland marshes to breed. It 

 appears to me a very interesting circumstance thus to find birds of two 

 closely allied species preserving the same peculiarities of habits in Europe 

 and in the wide plains of S. America. Near Buenos Ayres this gull as 

 well as the L. dominicanus sometimes attends the slaughter-houses to pick 

 up bits of meat." (Voy. "Beagle," Darwin, Birds, pp. 142-143.) 



LARUS DOMINICANUS Lichtenstein. 



Gabiota major, Azara, Apunt. III. p. 338 (1802). 



Larus dominicanus, Licht. Verz. Doubl. p. 82 (1823: ex Azara); Darwin, 

 Voy. "Beagle" Birds, p. 142 (1841 : Buenos Ayres and Bahia Blanca); 

 Eraser, P. Z. S. 1843, P- I! 9 (Chile); Hartl. Ind. Azara, p. 26 

 (1847); Des Murs in Ga y' s Hist. Chil. Zool. I. p. 480 (1847) ; Gould, 

 P. Z. S. 1859, p. 97 (Falkland Islands); Scl. P. Z. S. 1860, p. 390 

 (Falklands); Abbott, Ibis, 1861, p. 165 (Falkland Islands, breeds in 



