NATURAL SCIENCES OF PHILADELPHIA. 303 



it, somewhat so before it. Commissure about straight to near the tip. Tarsus 

 about equal to middle toe and claw. Adult : Bill bluish green, its terminal 

 third bright yellow. Legs and feet dusky bluish green, the webs yellowish. 

 Mantle light grayish blue, or dark pearl blue ; a shade lighter than in canus, 

 much darker than in Delaioarensis. Primaries : The bluish gray bases rather 

 lighter than in canus, much darker than in Delawarensis, but fading into nearly 

 pure white on all but the first, at its juncture with the black portion. These 

 bluish gray bases extend towards the end much further than in canus, as far 

 as in Delawarensis ; and, as in that species, extend on the second, third and 

 fourth feather further along the centre of the feather than on the edges, so 

 that they are bordered for some distance with the black of the terminal por- 

 tions. The black takes in the outer web of the first primary, and nearly the 

 whole of the inner, but rapidly becomes narrower, till on the sixth it is merely 

 a subterminal transverse bar ; the seventh has frequently a spot of black on 

 one or both webs ; first, with a large white spot near the end, two inches long, 

 longer ou the outer than on the inner web, not divided by the black shaft ; 

 the tip of the feather black ; second, with a similar spot, but smaller, not 

 longer on the outer than on the inner web, and divided by the black shaft ; 

 the extreme tip white, as are the apices of all the others except the first. 

 Dimensions: Length 17'50; extent 40 - 00 ; wing 13*75. Bill above 1-40; 

 along gape 2*00 ; height at nostril and at angle *35 ; tarsus and middle toe 

 and claw 1-80. 



Habitat. Interior of Arctic America. North Pacific Coast. 

 I have before me the type specimen of Richardson's Larus brachyrhynchus, the 

 original of this description in the Fauna Boreali-Americana, " a female, killed 

 on the 23d of May, 1826, at Great Bear Lake." "Some brown markings on 

 the tertiaries, primary coverts, and bastard wing, with an imperfect subter- 

 minal baron the tail, point it out as a young bird, most probably just com- 

 mencing its second spring. The rest of its plumage corresponds with that of 

 L. zonorhynchus, except that it wants the extreme white tips of the quill 

 feathers." The specimen is labelled " $, May 23, 1826, Great Bear Lake," 

 and corresponds minutely with the above description. Richardson, however, 

 in drawing up the description from the young bird, fell into the error of 

 giving ' remigibus apice concoloribus, ,, whereas, in the adults, the primaries 

 are as broadly tipped with white as in Delawarensis or canus. In the type the 

 bill is very short, perhaps less than in the average of even young birds ; but 

 there are specimens before me in which it is quite as short. 



A very careful comparison of the types of Larus Sucldeyi and Rissa septen- 

 trionalis with the above specimen, and with the very extensive series of all 

 ages in the collection, shows them to be absolutely identical, and proves that 

 the three names refer to one and the same species. 



The rather intricate discussion of the relationships of Larus niveus, Pallas, is 

 presented elsewhere. The amount of the other synonyms may be stated in 

 a word. There are in North America two species of "Mew-Gulls." One is 

 the Delawarensis, Ord., zonorkynchus, Richd. The other is a bird, the adult of 

 which Richardson mistook for the European canus, Linn, and so named it. 

 the young of which he characterized as L. brachyrhynchus. The error of 

 authors is in not recognizing two species, but considering canus, Rich., and 

 brachyrhynchus, Rich., as intermediate ages, or varieties of zonorhynchus, Rich. 

 As the name of canus is pre-occupied, brachyrhynchus, though based upon the 

 young bird, must stand for the North American species. 



Comparison of L. canus, Linn., of Europe, and L. brachyrhynchus, Rich., of 

 America. Common characters : Small weak bills, without strongly developed 

 angle, or black band ; color of back nearly the same, subterminal and apical 

 spots of primaries identical. Distinctive characters : brachyrhynchus has 

 the bill shorter and smaller, culmen more convex at the end, the 

 angle perhaps comparatively more developed. Size is less, gull blue, a little 



1862.] 



