° 1919 J Dwight, Larus fuscus and Lams affinis. 545 



is usually diagnostic. I would also call attention to another 

 neglected character quite as good as any only less obvious, and 

 that is the wing pattern. 



In the adults of fusczis, three or four of the distal primaries are 

 black, the fifth usually being the first to show a pattern which is 

 in the nature of a gray wedge (Plate XXI), while in affinis the 

 gray wedges begin on the first or second primary (Plate XX). 

 As a rule the wedges in fuscus are rather obscure and in color 

 much like the mantle, while in affinis the wedges and the color 

 are both clearly defined; that is to say, the dark bird has a dark 

 pattern, the lighter bird a lighter one. Saunders (Brit. Mus. Cat. 

 XXV, 1896, p. 253) noticed these differences and yet he did not 

 rightly appraise them, and being a binomialist he allowed "affinis" 

 to stand as a full species, although he was fully alert to the facts 

 and saw the close relationship. My material from Russia is 

 limited to one specimen, so I do not feel competent to pass judg- 

 ment on " taimyrensis" of Buturlin, which may perhaps be worth 

 recognizing as a large geographical race. One needs to be very 

 sure Gulls are sexed correctly if they are to be separated on size 

 alone, for while females are regularly smaller in dimensions than 

 males, particularly noticeable in the bills, there is always an over- 

 lapping of large females and small males. Buturlin's position 

 that fuscus is a separate species is not well taken, although it is 

 rather a curious distribution by which the dark mantled form of 

 Scandinavia thrusts itself between the gray mantled form breeding 

 to the west of it and to the east as well. The specimens I have 

 examined measure as follows: 



Larus fuscus fuscus Linnaeus. 



10 adult males, wing 415-438 (423), tail 152-169 (160) 

 tarsus 58-66 (63.6), toe without claw, 45-52 (49.1), culmen, 49- 

 55 (52), depth of bill at base, 15-18 (16), at angle, 16-19 (16.5). 



5 adult females, wing 394-410 (400.8), tail 142-159 (149.8), 

 tarsus 57-60 (58.8), toe without claw, 42-47 (45), culmen, 45-48 

 (46.2), depth of bill at base, 14-16 (14.9), at angle, 15-17 (15.7). 



