644 LARUS TEIDACTYLXJS, KITTIWAKE GULL. 



base, shorter than the head, equal to middle toe without the claw, longer than the 

 tarsus ; the tip decurved and«attennated ; the convexity of culmen regular and gradual 

 from base to tip; gonys concave, in consequence of the great deflexion of the apex of 

 lower mandible; outline of rami slightly concave ; cmiuentia symphysis well marked 

 and acute, but not large. Wings very long, pointed, reaching beyond the tail ; the pri- 

 maries pointed, first longest. Tail moderately long, even ; slightly emarginate in the 

 young. Legs stout and short. Tarsus shorter than middle toe alone ; anterior toes all 

 long, and united by broad, full webs with unincised margins. Hallux rudimentary, 

 or not well formed, the ungual phalanx being generally obsolete. 



Anatomical characters. — Generally as in Larus, except those of the hallux. 



A small genua, differing from Larus in few particulars : the attenuated, decurved 

 sliape of the bill and concave gonys ; the short tarsi ; the piittern of coloration of the 

 long, pointed wings ; the full, rounded interdigital membranes ; and esx>ecially the 

 rudimentary character of the hallux of the typical species, readily distinguish it from 

 Larus. The markings of the primary quills are different. The changes of plumage of 

 the young, and the winter vesture, are also characteiistic. 



In Larns tridactylus the two bones composing the hallux are very small, both together 

 forming merely a knob on the metatarsus. The accessory metatarsal is a small, flat 

 bone, scarcely longer than wide, with a rounded, thin, proximal extremity, lying in 

 apposition, but loosely connected with the side of the metatarsus, and freely movable, 

 being held only ligameutously. Its distal extremity is somewhat enlarged, and has a 

 convex facet for articulation with the phalangeal segment. The latter is a short, ir- 

 regularly-cylindrical ossicle, niovably articulated by a circular, concave facet, with the 

 accessory metatarsal. It tapers somewhat to a rather acute, free, distal extremity, over 

 which the metatarsal skin.is stretched. The ungual phalanx is obsolete in most in- 

 stances, yet we occasionally find it bearing a well-formed olavr. 



There are bnt two species of this group satisfactorily determined. One is the common 

 bird of the North Atlantic, which has a varietal representative in the North Pacific ; 

 the other is a very distinct species, confined to the last-mentioned region. They may 

 be th us tabulated : 



1. Feet dark; bill clouded with olivaceous. Bill, about 1.50 long; 



wing, 12.00. 



a. Hallux rudimentary, without a claw-bearing terminal pha- 



lanx TRIDACTYHTS. 



b. Hallux better formed, bearing a claw var. kotzehui. 



2. Feet coral red (drying yellow) ; bill clear yellow. Bill, about 1.20 ; 



wing, 1.3.00 liREVIROSTRIS. 



It may be proper here to remark upon the bibliography of the species collectively, a 

 point much needing of critical consideration. The sy n-onymy of B. tridactyla is definite 

 enough ; we have only to do with the two northwest JBissce. 



A great mistake of authors, I hope I have been able to prove, is in considering the 

 Larus niveus of Pallas as a Eissa, and deducing therefrom a liissa mrea to antedate and 

 take the place of llUsa irachyrliynclia or Brandt's M. irevirostris. Then from the fact 

 of the characters and relationships of these two very distincf northwestern species not 

 being clearly understood, different authors have indiserimi ^ately adduced the syno- 

 nyms of both species for either of them, others often giving tlie synonyms of Kotzeind 

 for what, according to their description, is the hrevirostris, and vice versa. Quite re- 

 cently the subject has been further complicated by the introduction of a Eissa septen- 

 trionalis, which is no Eissa, but a true Larus, and nothing more nor less than the lesser 

 American Mew-Gull, the adult of which was described by Richardson in 1831 as L. canus, 

 and the young as L. brachyrhynchus. 



The whole matter may thus be summed up : There are on the northwest coast of 

 North America two forms of Rissa (neither of which is L, niveus Pallas). The first of 

 these is the representative of E. tridactyla, the proper name of which is (probably) 

 Kotzcbui. The other is a v<!ry difl'erent species, with a short, bright yellow bill, coral- 

 red or orange-yellow feet ; described by Brandt as L. brevirostris, and by Gould as Larus 

 brachyrhynchus. 



This is the gist of my views on the subject. The matter is more fully discussed under 

 the heads of the two species. 



LAKUS (RISSA) TEIDAOTYLUS, Linn. 



The Common Kittiivake. 



Larus rissa, Bnttxx., Orn. Bor. 1764, 43.— Linn., Syst. Nat. i, 1766, 224.— Gm.. Syst. Nat. 



i, 1788, 594.— Leach, Cat. 1816, 40.— Flbm., Br. An. 1828, 141. 

 Laroides rissa, Brehm, V. D. 1831, 755, pi. 37, f. 3. 

 Larus riga, Gm., Syst. Nat. i, 1788, 594.— Less., Tr. Orn. 1831, 619. 



