LAIUD.E — THE GULLS AND TERNS — PAGOPllILA. 



197 



the (lifl'eronce in lorm is not less striking thivn that of size. The genus Sterna offers scarcely less 

 ol' a contrast between the huge, Gull-like S. caspia and the minute ^'. antillurmn. In order to 

 sepiirate the more marked variations of form in either of these genera, however, it woulil he neces- 

 surv to name a larger number of sulxlivisiona than most authors would recognize as distinct genera. 

 Notwithstanding this fact, we are convinced that, while such a procedure undoubtedly sini]dities 

 the nomenclature, it by no means expresses the true relationship of the forms so designated to call 

 all the s(juare-tailed Gulls (excepting Pagophila and liissa) Ltn-us, and all the fork-tailed Terns 

 with fully webbed-feet Sterna. In fact it is only from want of suitable material that we have not 

 atti'iupted a suUlivlsion of the genera Lams and Sterna in their comprehensive sense. Allowing, 

 liitTefore, each the fullest possible scope, we submit the following analysis of the North American 

 ''(Miora of Laridm : — 



Larinm. 



1. Pagophila. Tail even ; hind toe perfectly developed, though small ; tarsus shorter than 



the middle toe and claw, serrate behind. Color entirely white, t'le young sparsely spotted 

 with dusky. Size medium. 



2. Rissa. Tail even, or slightly emarginate ; hind t')e rudimentary, or altogether absent ; 



tarsus much shorter than the middle toe without its claw, not serrate behind. Above, 

 pearl-bliie, beneath white ; young similar, but with a black nuchal patch (and in one 

 species a black shouKler-patch). Size medium. 



3. LaruB. Tail even ; hind toe always well developed ; tarsus always longer than the middle 



toe with its claw, not serrate behind. Size and coloration extremely variable, but young 

 always very different from the adults. 



4. Rhodostethia. Tail graduated, or wedge-shaped. Size small. Adult pearl-blue above, 



rosy white beneath and on head and neck, the latter encircled by a black collar. 

 J. Xema. Tail forked. Size small. Adult pearl-gray above, white beneath, including the 

 ii> ck all round, the head dusky. 



Stemince. 



6. Sterna. Tail decidedly forked ; webs of the toes filling the greater part of the interdigital 



spaces, buL both with a concave or scalloped anterior outline. Size extremely variable. 



7. Hydrochelidon. Tail emarginate ; webs of the toes very deeply scalloped, occupying 



much less than holf the interdigital space. Size small. 



8. AnouB. Tail graduated, or wedge-shaped ; webs of the toes completely filling the inter- 



digital spaces, and scarcely or not at all scalloped in front. 



K 



1 



Genus FAGOFHUiA, Kauf. 



Gavia, Boie, Isis, 1822, 563 (type, Lnriis cburncus, Phiits).* 



Pii(jnj)hiln, Kaup, Nat. Syst. Kur. Tliicrw. 1829, 69 (type, Larus cburnciis, Piiirrs). 



Cctosparadcs, Macoill. Man. Brit. Orn. II. 1842, 251. 



Char. Size medium ; tail even ; hind too well developed, though small, the nail relatively 

 luf;o ; tai'sus .shorter than the middle toe and claw, roughly granular or aLnost serrate behind; 

 color entirely white in the summer adult ; white, sparsely spotted with dusky, in the winter 

 lilmiiagc (and young?). 



The genus ragnphila contains but one well established species, although several nominal ones 

 have been recognized, all of which were probably based upon special stages, or somewhat abnormal 

 inilividuals, of P. eburnea. 



' It is quite probable that a propT adheronco to the rules of nomenclature will require the use of Oaria 

 for lliis f,'cuus instead of Pnpophita ; but at present we are unwilling to make tlio change. (Cf. Ste.ineokr, 

 " I'roc. U. S. Nat. Mus." Vol. C, p. 39.) 



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