STERNA ALEUTICA, ALEUTIAN TERN. 697 



from another direction, viz, the deep incision of the webs, which is as well marked 

 ])erhaps as iu H. fttliginosa, but which evidently I'alls short of the requiiemeuts of Hy- 

 (hochelidon iu this respect. With all this mimetic resemblance to several species of a 

 ditferent group, »S'. ahufica cannot be severed from tLose of Sterna proper. The species 

 of Haliplana are white below, and have the tail more or less similarly colored with 

 the upper parts ; iS'. ahittica, like macrura and its allies, is strongly washed on the under 

 parts with a diluted tint of the sinie color as the upper parts, the tail remaining pure 

 white, in strong contrast. 



The ditferences between H. fnUgitiosa and one of the typical Sferna', as hirundo for 

 example, are strongly marked, and were only this species to be taken into considera- 

 tion, it might seem advisable to separate it geuerically ; but investigation of inter- 

 mediate forms shows the propriety of retaining Haliphiiia to be very (luestiouabie. 

 From the extreme of form and pattern of coloration that fidUjinona shows, there are 

 easy gradations toward Sterna proper through panayeiisis, and certain species, usually 

 called Sterna, as infuseala, liinata, and perhaps other exotics with which I am not well 

 ac(][Uainted, these being referable to either genus with e([ual propriety. Finally, 

 another strong link is afforded by this »S'. aleuticu, which is unquestionably a Sterna, yet 

 leans in the direction oi HalipJana in certain points both of form and coloration. 



At present only the original specimen of this species is known. It is in mature, 

 doubtless breeding plumage, having been shot iu June. In winter the species may be 

 expected to differ in wanting the pure black of the crown, which may then be largely 

 replaced by white, obscuring the outlines of the frontal lunula. The stripe through 

 the eye will probably be retained ; so will some black upon the occiput. The general 

 colors will be paler, the wings more canesceut. Young birds will differ iu imperfec- 

 tion of the head markings, much as just suggested ; the bill and feet may be iu part 

 light colored ; the under parts pure white. 



Since the foregoing was penned, three more specimens have come to hand, from the 

 same region as the type, and are exactly like it. Dr. Fiusch's determination that the 

 species is camtschatica of Pallas, is open to grave doubt ; I cannot make such an ideuti- 

 ficatiou, after careful examination of Pallas's description. 



Subgenus Haliplana, Wagl. 



< Sterna, Gm., Syst. Nat. i, 1788, 605, et aVup 



= Otnjehoprioii, Wagl., Isis, 18:52, xJ77. {Sterna serrata, Forst.) 



= rianetis, Wagl., Isis, 1^2, 1222 (type — f). 



=^ HaUpluna, Wagl., Isis, \ri\V2, 12-24. {S. fuliginosa, Gm.) 



= Haltplunes, apud Blas., List 13. Eur. 1802, 22. 



^ A nous, Lkss., Descr. Mammif. et Ois. 1847, 2.55, nee Leach. 



<^ Hi)dri)eheUdon, Bp., List, 1838, (il, partlm ; nee Boxe. 



= Titahofsipora, BoiE {fide Gkay ; type given as " hifuscata, LiCHT."). 



= Melanosterna, Bl. (Jide Guay). 



Gen. char. Bill as long as the head, scarcely exceeded by the tarsus and middle too 

 together, staight, stout at the base, where it is nearly as broad as high, but tapering; 

 the tip rather acute. Culmen broad, especially at the base, and but slightly convex ; 

 gonys straight, ascending, making the commissure scarcely at all decurved ; the rami 

 slightly convex ; the eminentia symphysis obtuse and little developi'd ; the tomia of 

 both mandibles intlected. Nasal groove long and deep, but rather irregularly deliiied, 

 terminating beyond the middle of the bill; the nostrils more anterior than iu Sterna, 

 though not so much so as in Anous. Outline of feathers on bill as in Sterna. Wings 

 exceedingly long, iiointed, but the first primary ,sc;acely longer than the second. Tail 

 very long, very deeply forked, as iu Sterna, but the feathers broader and stiller, and 

 uot so regularly tapering. Feet moderately long, the tibia' denuded for a consider- 

 able distance; toes all short, the inner extremely so; the middli;, with its claw, 

 scarcely longer than the tarsus, which is of moderate length, slender. The webs mod- 

 erately broad, the outer very lightly, the inner more deeply incised. Of moderate 

 size and slender, graceful form. Bicolor. Characters of mouth as iu Stcriiina' gen- 

 erally. Trachea of small calibre tlatt(Mied above, but soon becoming (piite cylindrical. 

 Lower larynx very small, its miiscics h'ebli',. Bronchial half-rings very delicate, but 

 distinct from the fust, which is as usual larger and stronger. Zone of pioventricular 

 glands unusually narrow. llep;iti(^ and cystic ducts very short, (.'(cca * minute, 



• I cannot reconcile Audubon's description of the organs of digestion with the results 

 obtained by my own sealjiel. In the s]ie(imeiis examined the o'sophagns was not 

 " within the thorax dilated into an enormous .sac," nor were its walls "extiemely thin, 

 BO as to be memiiranons and transparent." The organ in (inestion was of pretty uni- 

 form calibre throughout, and as muscular as in any other T<>rn. There must have 

 existed in Audubon's specimen a temporary and accidental dilation, as might readily 

 be th(^ case. I cannot account for the dllVereiice in length of co-ca as given by him, 

 and as 1 hav(> foniul. In my specimens the i(eca, instead of being like those of tho 

 Lealridbw, are exceedingly short, aud strictly sternine in character. 



