4 ALLEN'S NATURALIST'S LIBRARY. 



tinguished from those of the Kittiwake by their greater gloss, 

 the small excrescences are not so crowded together, and are 

 a little more flattened than they usually are in the last- 

 mentioned species. Axis, 2-15-2-4 inches; diam., 1-65-1-75. 



THE KITTIWAKE GULLS. GENUS RISSA. 



Rissa, Stephens, in Shaw's Gen. Zool. xiii. part i, p. 189 (1826). 



Type, R. tridactyla (Linn.). 



The chief character which distinguishes the Kittiwakes from 

 the rest of the Gulls is the rudimentary condition or absence of 

 the hind toe. The tarsus is much shorter than the middle toe 

 with its claw, and the tail shews a slight tendency to be forked. 



Mr. Howard Saunders admits two species of Kittiwakes, our 

 own familiar species (R. tridactyla) with dark brown feet and 

 white under wing- coverts, and R. brevirostris^ from the Arctic 

 Pacific Ocean, with vermilion-coloured feet and grey under 

 wing-coverts. A third form, R. pollicaris, with a slightly more 

 developed hind-toe than in normal R. tridactyla, and chiefly 

 but not exclusively from the North Pacific, is recognised by 

 some American naturalists, but is disallowed by Mr. Saunders. 



I. THE KITTIWAKE GULL. RISSA TRIDACTYLA. 



Larus tridactylus, Linn. Syst. Nat. i. p. 224(1766); Seebohm, 



Hist. Brit. B. iii. p. 340 (1885). 

 Rissa tridactyla (Linn.), Macgill. Brit. B. v. p. 515 (1852); 



Dresser, B. Eur. viii. p. 447, pis. 607, 608 (1878) ; 



B. O. U. List Brit. B. p. 187 (1883); Saunders, ed. 



Yarrell's Brit. B. iii. p. 650 (1884); id. Man. Brit. B. 



p. 667 (1889) ; Lilford, Col. Fig. Brit. B. part xxiv. 



(1893); Saunders, Cat. B. Brit. Mus. xxv. p. 305 (1896). 



Adult Male. General colour above light slaty-grey, with 

 narrow white ends to the scapulars ; wing-coverts grey like the 

 back ; bastard-wing, primary-coverts, and quills light slaty-grey, 

 the inner primaries fringed at the ends, and the secondaries 

 narrowly tipped with white ; the outer primaries grey, white 

 along the inner webs ; first primary black along the outer web, 

 and also for two inches at the tips ; the second and third 

 primaries also black at the ends, this black tip decreasing on 



