618 SUBFAMILY LAEIN^, GULLS. 



antly separated, as the species are all variously interrelated.* Among the North Amer- 

 ican forms we may distingnish three genera, one of them with several eeotious, as 

 follows : 



Aruilytical table of the North American genera and eeciions of Larinm. 



1. Tail square Lakus. 



A. Head never hooded ; under parts never rosy-tinted; Size me- 



dium and large ; bill stout. 

 a. Hallux well developed, with perfect claw. 



1. Adult white, with a colored mantle Larus. 



2. Adult dark, with white head Blaaipm. 



3. Adult entirely white Pagophila. 



h. Hallux usually defective Eima. 



B. Head in summer hooded, and under parts rosy-tinted ; size 



medium and small; bill slender Chrcecocephalug. 



II. Tail wedge-shaped ; neck collared ; small Ehodostbthia. 



III. Tail forked; small; hooded and collared Xkma. 



large; hooded, not collared Creagrus. 



Subgenus Laeus, Linn. 



<C Larus, Linn., Syst. Nat. 1735-1766; el ami. 

 <^ Gavia, Mokiir., Gen. Av. 17.52. 



> Lencus, Kaup, Sk. Ent. Eur. Thierw. 1829, 86. (i. marinus.) 



> Laroides, Brbhm, 1830. — Bp., Cousp. ii, 1850, 217. (i. a/rgentatm.) 

 yPlautus, Eeich., 18.53. {L. argeniatus.) 



S Glaucm, Bruch, J. f. 0. 1H53, 101. (i. glaums.) 

 '^Dominifinnus, Bruch, J. f. O. IS'>-', 100. (L. marinua.) 



'Laroides, Bruch, J. f. O. 1855, 281. (i. glaucus.) 



. Garina, Bp., Consp. Av. 185*;, 222. (L. audomni.) 



■ Leucus, Bp., Consp. Av. ii, 1856, 215. (i. glaucus,) 



' Clupeilarus, Bp., Consp. Av. ii, 1856, 220. (i. fuscus.) 



• Gabianus, Bp., Consp. Av. ii, 1856, 212. (i. paeificus.) 



Gen. char. Bill shorter than the head or tarsus, large, strong, more or less robust, 

 usually very stout, deep at the base, higher than btoad, compressed throughout, the 

 apex not very acute and never much attenuated or decurved. Culmen about straight 

 to beyond the nostrils, then convex, the amount of curvature increating toward the 

 end, varying in different species. Commissure slightly sinuate at its extreme base, 

 then about straight to near the end, where it is more or less arcuato-declinate. Emi- 

 nentia symphysis always large, prominent, and well defined, rather obtuse, seldom 

 acute. Nostrils placed rather far forward in a well-defined nasal fossa, lateral, longi- 

 tudinal, pervious, rather broader anteriorly than posteriorly. Feathers of forehead 

 extending considerably farther on the sides of the upper mandible than on its culmen, 

 but falling considerably short of the nostrils. Wings when folded reaching beyond the 

 tail, the remiges strong, not very acute, first longest, second but little shorter, rest rap- 

 idly graduated. Tail of moderate length, always even, never forked nor rounded. 

 Legs rather slender, of moderate length; tibise bare for a considerable distance above 

 the joint, the naked part smooth. Tarsi about equal to or a little longer than the mid- 

 dle toe and claw, varying but slightly in proportions among the different species ; anteri- 

 orly scutellate, posteriorly and laterally reticulate. Hallux fully developed and always 

 present. Anterior claws stout, strong, little curved, rather obtuse, the inner edge of 

 the middle one dilated. Webs full and broad, scarcely incised. 



Of very large or medium size, never very small. Eobust and powerful. Comprising 

 the largest species of the subfamily and those typical of it. White, with a darker 

 mantle, without a hood ; the head and neck in winter streaked with dusky. 



The preceding paragraphs express the essential characters of the subgenus Larus, as it 

 is here accepted. I take as my type of the section the old Linnsean L. canus, and con- 

 sider as congeneric with that species all the true Gulls which are white, with yellow- 

 ish bills, with a darker mantle, without hoods, and with the head and neck streaked 

 with dusky in winter, and whieh have squarely truncated tails and perfectly developed 



* The character of defective hallux, supposed to distingnish /'issa, does not always 

 hold ; for in a North Pacific form, not specifically distinguishable from B. tridactyla, the 

 hind toe is perfectly formed. Pagrtphlla has stout, roughi.sh tarsi. The species of 

 "Hooded Gulls" (Chrcecocephalus, &c.) are generally small and delicate slender-billed 

 species ; but one, at least, is among the largest of the Gulls, while from the slender, 

 tem-iike form of the bill, seen in 6'. minutus and Philadelphia, the transition is gradual 

 and unbroken to species with a very stout hooked bilL 



