306 PROCEEDINGS OF THE ACADEMY OF 



tip of lower mandible *48 ; from nostrils to tip of upper mandible , V2 ; depth 

 at base *55, at angle *42 ; width at base - 33. Wing just 12 inches ; tarsus 1-35 ; 

 toe and claw l - 90. Of No. 15,695, the same parts measure respectively, l - 68, 

 56, -90, -54, '40, "40 ; wing, tarsus and toe about the same. 



Habitat. Northwest coast of America. 



This species differs from the R. tridactyla chiefly in the shape of the bill and 

 in the greater developement of the hind toe. Its habitat is also quite different, 

 and I have not the slightest doubt of the propriety of separating that species. 

 From the R. brachyrhyncha, Gould, of which I have before me typical speci- 

 mens, fully mature and in excellent preservation, it is totally distinct, the 

 characters differing in almost every respect. The size, shape and color ol 

 the bill, the color of the mantle, the color of the feet and the markings of the 

 primaries are widely diverse in the two birds. It is unnecessary here to 

 specify these differences, as they may be seen by comparing the description? 

 given. 



While the characters of the species are thus so very distinct and well 

 marked, its synonymy is in a state of confusion only equalled, perhaps, by 

 that of the succeeding species ; and the proper name to be applied to it is a 

 matter of great uncertainty. The history of its synonyms is so intimately 

 blended with that of Rissa brachyrhyncha , that the two may be most conve- 

 niently discussed together. The reasons for the adoption of the name which 

 I chose for this species may, however, be given here. The essential charac- 

 ter of Bonaparte's R. Kotzebui is " simillima praacedenti;" R. tridactyla, "sed 

 halluce magis ex plicato. " The character of the hind toe is precisely the dis- 

 tinctive feature of the specimen now under consideration. Still there are some 

 discrepancies in Bonaparte's description. The wings of the young birds before 

 me are not " black internally ;" the bill is not " very black," nor is the back 

 " remarkably variegated with black and white." Still, in a more immature 

 state of plumage than that exhibited by the specimens before me, these cha- 

 racters may exist ; and therefore, in spite of these discrepancies, I think it 

 advisable to adopt the name, especially as the imposition of a new one, other- 

 wise unavoidable, is thereby obviated. It is well known that at certain ages 

 the R. tridactyla assumes exactly the state of plumage described by Bonaparte: 

 and reasoning by analogy, in view of the close relationship of the two, it might 

 be expected that the same should occur in the present species. 



15. Rissa brachyrhyncha (Gould.) 



Larus brachyrhynchus, Gould, P. Z. S. 1843. Rissa nivca, Gr. secundum 

 Bp. ; (nee L. niveus, Pall. Ris*a brevirosiris, Brandt, secundum Bp. 

 Rissa nivea, ' Bruch," Lawrence, (1858,) Gen. Rep. 855 ; sed nee Bra- 

 chii, qua? species pra?cedens. Descriptio Gouldii ipsius transcripta est. 

 Sp. char. Adult : Bill a uniform clear light straw yellow, without any oliva- 

 ceous tinge ; very short, stout, wide at the base, upper mandible much curved, 

 though not acute nor attenuated ; the convexity of the culmen very great, 

 especially towards the tip, it being, from the nostrils to the tip, almost the 

 arc of a circle, whose centre is the apex of the angle at tbe symphysis ; gonys 

 but very slightly doubly concave, its angle but little developed. Tarsus not 

 much more than two-thirds the middle toe and claw. Wings exceedingly 

 long, reaching much beyond the tail. Head and neck all round, under parts 

 and tail pure white. Mantle deep leaden gray, much darker than in the pre- 

 ceding ; and this color extending to within half an inch of the tips of the 

 secondaries and tertials, which are white. Primaries : First primary with its 

 shaft and outer vane black, its inner vane with a space of dull gray (not 

 white), which, at the base, takes in nearly all the vane, but gradually nar- 

 rows, and, at about two and a half inches from the tip, ends by a well-defined 

 rounded termination about half as broad as the vane itself; second, the outer 

 vane is of the same leaden gray lo within four inches of the tip ; the inner 



