306 
PROCEEDINGS OF THE ACADEMY OF 
tip of lower mandible *48 ; from nostrils to tip of upper mandible *72 ; depth, 
at base *55, at angle *42 ; width at base *33. Wing just 12 inches ; tarsus 1*35 ; 
toe and claw 1*90. Of No. 15,695, the same parts measure respectively, 1*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 of 
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 descriptions 
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 prsecedenti;” 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 nivea, Gr. secundum 
Bp. ; (nec L. niveus, Pall. Rissa brevirostris, Brandt, secundum Bp. 
Rissa nivea, “ Bruch,” Lawrence, (1858,) Gen. Rep. 855 ; sed nec Bru- 
ehii, quse species prsecedens. 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 the 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 to within four inches of the tip ; the inner 
[June, 
