648 LARUS EBURNEUS, IVORY GULL. 



is to snch a coiiditiou of the hallux as I have described under R. kotzehui that snch 

 expression properly applies. 



Synomjmy.—l luight discourse at great length on this subject, but it would scarcely 

 be i)roiitable ; and I will therefore confine myself to the more definite among the many 

 things that might be said. In the first place, I throw Larus niveus Pallas entirely ont 

 of the present consideration (see elsewhere in this memoir, and also my discussion of 

 the point in Pr. A. N. S. Phila. 1862, p. 307). Nevertheless other w^riters have come to 

 dift'ereut conclusions, and taking up the name, give us Bissanivea for the bird, as shown 

 in the above synonymy. But Bruch's Eissa nivea of 1855 is, I take it, from his descrip- 

 tion, rather B. liot7.chn) than this species. Eissa drevirostris of Brandt (whose original 

 notice I have not seen) is, by both Bruch and Bonaparte, located here ; I presume that 

 there is no reasonable doubt on this score. Bruch's hrerirostris is certainly this species. 

 Lawrence's hrevirontris is mixed; his expression, feet " coral-red," brings it here ; the 

 rest of his brief diagnosis carries it elsewhere ; but I have no doubt he meant this 

 species rather than kotzebni. 



This is Larus hracliijrhynchus Gould, above quoted, just as described and figured by 

 him. It is to be carefully distinguished from Larm braclujrliyncluis Richardson, which 

 is simply the American form of canun. 



Some authors have here located Larus eUrirostris, Schimper (see, however, Blasius, 

 J. f. 0. 186G, 73). 



Subgenus Pagophila, Kaup. 



< Gavia, BoiE, Isis, 1822, 563. 



= PagojjhUa, Kaup, Sk. Ent. Eur. Thierw. 1829, 69. 



= Cetosparacffs, MACGiLLiviiAY, Man. Br. Orn. ii, 1842,251 (by err. Catosparactes, Gray). 



Gen. char. Bill Aery short, much less than the head, about equal to the greatly 

 abbreviated tarsus, very stout, but little compressed. Nasal sinus deep, the nostrils 

 placed far forward. Legs and feet very short and stout, the scales of the tarsus and 

 toes large and rough. Tibia feathered to near the joint; tarsus about equal to the 

 middle toe without the claw ; claw^s all large, stout, and much curved. luterdigital 

 webs narrow and deeply incised. Wings very long, the primaries more or less falcate 

 and attenuated. Size moderate ; general form stout ; color entirely white. 



FagophUa differs from other Lariuo' in its short, stout, obtuse bill ; much abbreviated, 

 very stout and roughened tarsus and toes ; feathered tibia, deeply excised webs, &c. ; 

 and constitutes one of the better-marked subgenera of the subfamily. The habits of 

 the species composing the genus also difi'er notably from those of other Gulls, as 

 attested by all observers. 



Cetosparach'S of Macgillivray (1842), based upon the Lams ehurneus, is antedated by 

 raijophUa of Kaup (1829) with the same type. Gavia, applied by Boie to this group, 

 was first used by Mcehriug in a ditferent connection. 



LAllUS (PAGOPHILA) EBUENBUS, Gm. 



Ivory Gull. 



Larus eburneus, Gm., Syst. Nat. i, 1788, 596.— Lath., lud. Orn. ii, 1790, 816.— Temm., Man. 

 181.5, 498 ; ii,'l820, 769.— Vieill., Nouv. Diet. 1818, 494 ; Fn. Fran^. 1828, 389.— 

 NiLSS., Orn. Suec. ii, 1823, 171.— Steph., Gen. Zool. xiii, 195.— Less., Tr. Orn. 

 1831, 618.— Bp., Syn. 1828, No. 297.— Nutt., Man. ii, 1834, 301.— Jen., Man. 1835. 

 276.— AUD.. Orn. Biog. iii, 1835, .571 ; Syn. 1839, 326; B. Am. vii, 1844, 150, pi. 

 445.— Keys. & Blas., Wirb. 1840, 96.— Naxjm., V. D. x, 1840, 341, pi. 263.— Schl., 

 Rev. Ciit. 1844, 126 ; Mus. P.-B. iv, 1863, Lari, p. 5.— Coues, Key, 1872, 313. 



Gavia ehurnea, Boie, Isis, 1822, 563.— Brehm, V. D. 1831, 765.— Bp., List, 1838, 62. 



Pagophila cbnniea, Kaup, Sk. Eut. Eur. Thierw. 1829. 69.— Gray, Gen. of B. iii, 1849, 

 655 ; List Br. B. 1863. 237.— Lawji., B. N. A. 1858, 836.— Bp., Consii. ii, 1856, 

 230; Compt. Rend. 1856, 771.— Neavt., P. Z. S. 1861, 400 (eggs); Ibis, 1865, 

 507.— COL'ES, I'r. Phila. Acad. 1862, 308.— Malmg., J. f. O. 1865, 200.— Blas., 

 J. f. O. 1865, 384. 



Cefosparacics eburneus, Macgil., Man. ii, 1842, 252 ; Hist. Br. B. v, — , — . 



Larus albus, Scua:vi'., Mus. Orn. 1779, 65, pi. 42. 



Larus auididus, Fabr., Fn. Groenl. 1780.— Flem., Br. An. 142. 



Larus uivcus. Mart., Spitzb. 77, pi. 4, f. A. (uec auct.). 



Gavia nivea, Brehm, V. D. 1831, 766, pi. 38, f. 1. 



I*af/opJiila nivea, Bp., Consi>. Av. ii, 1856, 230 ; Compt. Rend. 1856, 771. 



fMvus bravJijitarsus, Hole., Fn. Groenl. 1846, 52. 



Pagopliila b'rachgtarsus, Br.ucn, J. f. 0. 1855, 287.— Lawk., B. N. A. 1858, 856.— Coues, 

 Pr. Phila. Acad. 1862, 309. 



