644 LARUS TRIDACTYLUS, KITTIWAKE GULL. 



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

 tarsus ; the tip decurved and attenuated ; the convexity ofcidmen vegidar and gradual 

 from base to tip; goiiys coufave, in coiise<iuence of the great deflexion of the apex of 

 lower mandible ; outline of rami slightly concave ; emiu(nitia symphysis well marked 

 and acute, but not large. Wings very long, pointed, reaching beyond the tail ; tin; 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 uniucised margins. Hallux rudimentary, 

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



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



A small genus, differing from Lams in few particulars : the attenuated, decurved 

 shape of the bill and concave gonys ; the short tarsi ; the pattern of coloration of the 

 long, pointed wings; the full, rounded iuterdigital membranes; and especially the 

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

 Larus. The markings of the in'imary qtiills are different. The changes of pluniage of 

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



In Lams 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 ligamentously. 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, movahly 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 The ungual phalanx is obsolete in most in- 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-fornied claw. 



There are but 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 I'egion. They may 

 be thus tabulated: 



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



Aving, 12.00. 



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

 lanx ... TRIDACTYLrS. 



h. Hallux better formed, bearing a claw var. lotzebiii. 



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



wing, 13.00 BREVIROSTRIS. 



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

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

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



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

 Lams niveus of Pallas as a Eissa, and deducing therefrom a lUssa tiivea to antedate and 

 take the place of JUssa brachyrhyncha or Brandt's i?. hrevirosiris. Then from the fact 

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

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

 nyms of both speciee for eitlier of them, others often giving liie synonyms of Kolzebui 

 for what, according to their description, is the brevirostrls, and vice rersd. Quite re- 

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

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

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

 and the young as L. brachyrhynchns. 



The whole matter may thus be sunnned 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 B. tridactyla, the puoper name of which is (probably) 

 Koizcbui. The other is a very different species, with a short, bright yellow bill, coral- 

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

 brachyrliynchus. 



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

 the heads of the two species. 



LAEUS (EISSA) TEIDACTYLUS, Linu. 



The Common Kittiwakc. 



Larus rissa, BrCnx., Orn. Bor. 1764, 42.— Linx., Svst. Nat. i, 17G6, 224.— Gm.. Syst. Nat. 



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

 Laroides rissa, Breiim, V. D. 18:51, 755, pi. 37, f. 3. 

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



