264: Descriptions of two New Species of Gulls. 



feathers being over an inch longer than the middle ones, where- 

 as in Schreibersi the difference is but half an inch. The latter 

 bird differs also in having the central tail feathers green. 



The above described IIumming-Birds form part of the collec- 

 tion (now in my possession) made by Mr. Wm. E. Moore, on 

 his recent travels in South America. The subjoined extract 

 from one of his letters will give the locality where they were 

 obtained : — 



" The Humming-Birds I gave you were all collected between 

 the head waters of the Napo and Quito ; this journey was per- 

 formed on foot, three hundred miles through a dense forest, at 

 the base of the Bolivian range of the Andes." 



XXXII. — Descriptions of two New Species of Gulls in the 

 Museum of the Smithsonian Institution at Washington. 



By George N. Lawrence. 

 Read June 29th, 185*7. 



I, arns suckleyi. 



Suckley's Gull. 



Adult. Head, neck, under plumage and tail pure white ; 

 back and wings clear pearl blue ; ends of the primaries black, 

 on the first occupying about half its length, and decreasing to 

 the seventh, where it consists only of a subterminal spot ; the 

 first primary is crossed near the end with white for a space 

 of one and a half inches, the second primary is similarly 

 marked, but the white is much less in extent, the tips of both 

 these quills are black, the other primaries all have white tips ; 

 the secondaries and tertiaries terminate largely with white ; 

 bill dusky yellowish-green, except on the ridge of the upper 



