LARIJS DELAWAEENSIS, RING-BILLED GULL. 637 



blue of the adults, tbe wing coverts being almost entirely dusky, with lighter margins 

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

 ries uniformly black ; secoudaries with a patch of browuisb-black near the ends ; 

 tertials wholly browuisb-black, narrowly tipped with whitish. Tail winh a broad, 

 subterminal band of black, narrowly tipped with white. Terminal half of bill black, 

 the extreme tip yellowish. 



Young-of-the-year in Jugwst. — 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 rgst light flesh-color. Other parts as in the preceding. 



Xiime»«io«s.— 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 anatomical charaotei'S of this species do not differ in any notable degree from 

 those of L. smi'hsonianus, already fnlly described. i 



Although of about the same size as L. vanns, 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 canns. 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 delawarensis 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 tbe second primary, the color of the bases bluish- 

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

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

 outer than on the inner vane, while in canus 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 on the third primary, wanting in delawarensis. 



The relationship of this species to the L. brachjrhynclms 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, in 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 in 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 young bird of the year from Labrador. Both Bonaparte and Bruch present a 

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

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

 fers in these and some other re.spect3 from the ordinary standard. The bill is every way 

 larger and stouter, the culmen terminally more convex, the eminentia symphysis 

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

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

 culmen measures 1.75 ; height of bill at nostrils, 0.53 ; at eminentia symphysis, hardly 

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

 stouter than average of delawarensis. 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 californicus, but for the ring around the bill and the different ijattera 

 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 in what consists this species or variety of the 

 authors quoted. 



Although the present is a marked and w(.'ll-characterized species, there has been con- 

 si<lerable confusion respecting it, occasioned by its beiug confounded by some authors 

 with the European canus, and by othcru, and the greater majority, with the canms of 

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

 tory from the beginning. 



In 1815 a "Tooth-billed Gull" (L. delawarensis) is characterized by Ord, in Guthrie's 

 Geography, as above. This, as Mr. Lawrence has shown, can be no other than the 

 present bird. " His account of the measurements and coloration agrees precisely with 

 the adult L. zonorhynclms, the only character to reconcile is the toothed bill. This I 

 consider as a possible malformation, or probably an accidental toothing, caused by its 

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

 bird before us, the culmen along its entire length ia jagged and irregularly serrate. 

 This same feature along the commissure would produce precisely the "Tooth-billed 

 Gull" of Ord. Moreover, this malformation actually exists along the commissure of 

 a Lams occidentalis, now before us, thus proving that the character is entirely acci- 

 dental and not confined to a single.species, and fully confirming the position assumed 

 by Lawrence. Delawarensis being undoubtedly, therefore, the present si)ecie8, is the 

 first distinctive appellation, and must take priority over the more usual name of zono- 

 rlmjnclius Richardson. 



