NATURAL SCIENCES OP PHILADELPHIA. 551 



The tail is very long. I do not mean, however, that the lateral tail feathers 

 are greatly produced, as in macroura and paradisea, (though that is not improbably 

 the case in the summer plumage) for the depth of the fork is not greater com- 

 paratively, than in hirundo ; but the whole tail is produced, the central feather? 

 being absolutely as long as in macroura, which is a larger bird. The outer wets 

 of the lateral tail feather is very dark colored. even more so than is that of 

 macroura, and the outer webs of the other feathers are shaded with grayish ; 

 but in the adult it is probable that the colors will be the same with those of the 

 last-named species. A striking feature of Pikei is the pure white of the whole 

 under parts, of the rump, and of the neck behind between the black pileum and 

 the back, there being not the slightest trace of the plumbeous wash, so conspic- 

 uous in macroura, hirundo, etc. The species in this respect agrees with S. para- 

 disea, and, like that species, may perhaps, during the breeding season, acquire 

 a rosy tint on the under parts. 



I regard this species as intermediate between S. macroura and paradisea. 

 though most closely allied to the former. In the foregoing remarks the differ- 

 ences between the two have been pointed out. With the latter S. paradisea it 

 agrees in several particulars : slenderness of bill, color of under parts and of 

 feet, &c. It is at once to be distinguished by its much darker colored upper 

 parts, different markings of primaries, pure white rump, slenderer and smaller 

 bill and feet, greater elongation of central tail feathers, &c. 



The acquisition of perfectspecimens of various stages of this interesting Tern, 

 of whose changes of plumage we can only judge by analogy, and with whose 

 habits we are entirely unacquainted, is a particular desideratum in North Amer- 

 ican Ornithology. 



Sterna paradisea Briinn. 



Slema paradisea, Briinnich, Orn. Bor. 1764, p. 46, and of recent authors. Law- 

 rence, Gen. Rep. 1858, 863. 



Sterna Vougalli, Montagu, Orn. Diet. Suppl. 1813, and of most authors, inclu- 

 ding Audubon and Nuttall. 



Sterna Macdougalli, Macgillivray, Man. Ora. ii. p. 233. 



Thalasssca Dougalli, Kaup. 



Hydrocecropis Dougalli, Boie, Isis, 1844, p. 179. 



Diag. (nupt. temp, ad.) S. rostro tenue, nigro, basin versus rubescente. 

 pedtbus rubro-aurantiis ; cauda longissima, valde forficata, fere albida, remigL- 

 bus omnibus interne albo-marginatis ad apices ipsas ; corpore supra perlaceo, 

 subtus rosaceo-alho. 



Habitat. Atlantic coasts of Europe and America. 



In a number of equally adult examples, I find that the color of the bill varies ; 

 in most the black extends nearly or quite to the base, in others fully the basal 

 third of the bill is reddish. The extreme points of both mandibles are yellow- 

 ish. The color of the mantle is lighter than that of any other species ; the 

 tail, exceedingly long and tapering, is of so light a pearly blue as to be almost 

 white. A most striking feature of coloration of this species consists in the 

 well-defined, broad white inner margins of all the primaries extending quite 

 around the tips of the feathers, on to the outer webs on the first and second 

 primaries. Immature and winter specimens have the bill brownish black ; the 

 front white; the crown and nape dull black, variegated with white. The lateral 

 tail feathers want the great elongation and attenuation they acquire during t he- 

 breeding season, the tail being no more deeply forked than that of Forsteri. or 

 even of hirundo. 



This species is so distinct in characters, that a comparison with any other is 

 needless. 



The American bird has never, I believe, been separated from the European. 

 The specimens I have compared appear identical in every respect. 



1362.] 



