LARUS DELAWARENSIS, RING-BILLED GULL. 637 



blue of the adults, the wiDjf coverts being almost entirely dusky, with lighter maro-ins 

 to the feathers. Head, neck, and under parts, mottled with white and dusky. Prima- 

 ries uniformly black; secondaries with a patch of brownish-black near the ends; 

 tertials wholly brownish-black, narrowly tipped with whitish. Tail wi^h a broad, 

 subterminal band of black, narrowly tipped with ^\hi^e. Terminal half of bill black, 

 the extreme tip yellowish. 



Tounri-of-the-yem- hi Juf/ust. — Everywhere mottled thickly with brownish-black, on 

 the upper parts the feathers with yellowish-white edges, the pearl-blue of the adults 

 scarcely apparent, except on the wing-coverts. Terminal two-thirds of bill with the 

 tip black, the rest light flesh-color. Other parts as in the preceding. 



DjjncHs/oHs.— Length, 19.75; extent, 48.50; wing, 14.75; bill above, 1.70; gape, 2.30 ; 

 height at nostril, 0.45 ; at angle, 0.50 ; tarsus, 2.05 ; middle toe, 1.80. 



The (itiaiomical characters of this species do not differ iu any notable degree from 

 those of L. smi'hsonianiis, already fully described. 



Altliough of about the same size as L. cauus, this species may readily be distinguished 

 from it. It is rather larger ; the bill, somewhat longer, is much more robust, the angle 

 much more strongly developed, and are both mandibles crossed by a well-defined bar near 

 the angle, wanting in carius. The upper parts are very decidedly lighter, being a very 

 light pale blue, instead of darker bluish-gray. The characters of the primaries are 

 quite different. In dclaivarerisis the bases of the primaries are very light bluish-white, 

 on the first almost pure white, and extending to within three inches of the tip of the 

 second. In canus the light bases of the feathers are very much more restricted, the 

 difference especially conspicuous on the second primary, the color of the bases bluish- 

 gray, scarcely lighter than the back. The subterminal spots on the first and second 

 primaries in delawarevsis are small, divided by the black shaft, and not longer on the 

 outer than on the inner vane, while in vanus the spots are nearly twice as large ; that 

 on the first longer on the outer than on the inner vane, and not divided by the black 

 shaft. Canus has, moreover, a spot ou the third primaij^ wanting in delawartnsis. 



The relationshij) of this species to the L. hraclujrhijnclius of Richardson will be found 

 discussed under the head of the latter. There is no other North American Gull with 

 which the present requires comparison. 



This species, iu common with others of the genus, varies very considerably in size. 

 The difference in the length of wing and tarsus of the largest and smallest specimen 

 before us amounts to a full inch iu the former, and 0.35 of an inch in the latter. The 

 longest tarsus measures 2.25, the shortest 1.90. The difference in the bills is consider- 

 able. The smallest specimen before me is an adult female from Laramie River ; the 

 largest a yoiing bird of the year from Labrador. Both Bonaparte and Bruch present a 

 species or variety in their monographs, distinguished from zonorhijnchus by its larger 

 size, more robust bill, &c. An adult winter specimen before me, from Nebraska, dif- 

 fers in these and some other respects from the ordinary standard. The bill is every way 

 larger and stouter, the culmeu terminally more convex, the emiuentia symphysis 

 perhaps less strongly developed. The head and neck are streaked rather than spotted 

 with tlusky, and the first primary has a more decidedly white apex. The chord of the 

 culmeu measures 1.75 ; height of bill at nostrils, 0.53 ; at emineutia symphysis, hardlj- 

 greater. The wing is 15.25 inches from the cardial joint. The feet are not larger nor 

 stouter than average of delawareiisis. A second specimen, from the interior of Arctic 

 America, a little surpasses these measurements, being so large that it would be taken 

 at first sight for califomicus, but for the ring around the bill and the different pattern 

 of the primaries. Without feeling assured that these specimens constitute even a de- 

 cided variety, I present the above considerations to show how greatly the species may 

 vary in size, and to indicate exactly iu what consists this species or variety of the 

 authors quoted. 



Althougli the present is a marked and well-characterized species, there has been con- 

 siderable c(»nfusion resj)ecting it, occasioned by its being confounded by some authors 

 with the European canus, and by others, and the greater majt)rity, with the canus of 

 Ricliardson, which is the succeeding species. It may therefore be well to trace its his- 

 tory from the beginning. 



In lhl5 a "Tootii-liillcd Gull" (L. delawarensis) is characterized by Ord, in Guthrie's 

 Geograi)hy. as al)()ve. This, as Mr. Lawrence has shown, can bt^ no other than the 

 present bird. " His account of the nu'asurements and coloration agrees precisely with 

 the adult L. zonorhjiiicluis, the only character to reeoncih' is tiie toothed bill. Tliis I 

 consider as a possible malformation, or i)robabiy an accidental tootliing, caused by its 

 being worn in some particular mode of feeding." — (Lawi{.) In an adult and very old 

 bird before us, the culmeu along its entire length is jagged and irregularly serrate. 

 This same feature along the eommissun^ would iiroduce jirecisi-ly the "Tooth-billed 

 Gull" of Ord. Moreover, this nialfbrniation actually t-xists along the commissure of 

 a Lams ocridcntalix, now before us, thus i)ro\iiig that tlie character is entirely acci- 

 dental an<l not confined to a single species, and fully eontirming the position assumed 

 by Lawicnee. Pt luirannsis being undoubtedly, therelore, the present sp<'cies, is the 

 first distinctive appellution, and must take priority over the more usual nume of zono- 

 rhynclius Richardson. 



