618 SUBFAMILY LAEIN^, GULLS. 



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

 ican forma we may distinguish three genera, one of them with several sections, as 

 follows : 



Analytical table of the North American genera and aeeiions of Larince. 



I. Tail square Larus. 



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 Blasipus. 



3. Adult entirely white Pagophila. 



h. Hallux usually defective Rissa. 



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



medium and small ; l>ill slender Chroecoceplialus. 



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



III. Tail forked ; small; hooded aiul collared Xema. 



large ; hooded, not collared Creagrus. 



Suhgemis Larus, Linn. 



<^ Lams, Linn., Syst. Nat. 173.5-1766 ; et auct. 

 < Gavia, Mokhr., Gen. Av. 1752. 



> Lenciis, Kaup, Sk. Ent. Eur. Thierw. 1829, 86. (i. marinm.) 



> Laroidcs, Brehm, 1830. — Bp., Cousp. ii, 1850, 217. {L. argeniatus.) 

 "^ Plautus, Reich., 1853. (L. argcntatus.) 



5> Glancns, BiiUCH, J. f. O. 1853, 101. {L. glaucus.) 



'y- Dominicanus, Bruch, J. f. O. 1853, 100. (i. marinus.) 



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



> Garina, Bp., Consp. Av. 1856, 222. {L. audouini.) 

 ^ L'eucus, Bp., Consp. Av. ii, 1856, 215. (L. glaucus.) 



5> Clupeilarus, Bp., Consp. Av. ii, 1856, 220. {L. fuscus.) 

 ;> Gabianus, Bp., Consp. Av. ii, 1856, 212. (i. pacificus.) 



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

 usually very stout, deep at the base, higher than broad, 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 increasing 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 uasal 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 ; tibiae 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 l)ut slightly in proportions among the different species; anteri- 

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

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

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



Of very large or medium size, never very small. Robust 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 Linuiean L. canus, and con- 

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

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

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



* The character of defective hallux, supposed to distinguish Rissa, does not always 

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

 hind toe is jierfectly formed. Pagoplula has stout, roughisli tarsi. The species of 

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

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

 tern-iiko form of the bill, seen in C. miuutus and jyhiladelpkia, the transition is gradual 

 and unbroken to species with a very stout hooked bill. 



