STEENA ALEUTICA, ALEUTIAX TEEN. 697 



from anotlier direction, viz, tlie deep incision of tbe webs, which is as well marked 

 perhaps as in H.fuligiiwsa, bnt which eviiltiitly falls short of the requirements of Hi/- 

 drochelidon in this respect. With all this mimetic resemblance to several s|ieuies of a 

 different group, S. alcutica cannot be severed froiu ibose of Sltiiia proper. ILie species 

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

 the upper parts ; ^. aleutica, like macrura and its allies, is strongly washed on the under 

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

 white, in strong contrast. 



The differences between S. fuliginosa and one of the typical Slenia;, as hinindo for 

 example, are strongly marked, and were only th:s species to be taken into considera- 

 tion, it might seem advisable to separate it generically ; but iuvejtigation of inter- 

 mediate forms shows the propriety of retaining Haliplana to be very questionable. 

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

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

 called Sterna, as infuscata, lunata, and perhaps other exotics with which I inn not well 

 acquainted, these being referable to either genus with equal propriety. Finally, 

 another strong link is afforded by this S. aleutica, which is unquestionably a Sterna, yet 

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



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

 doubtless breeding plumage, having been shot in 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 probab ly be retained ; so will some black upon the occii)ut. The general 

 colors will be paler, the wings more canescent. Touug birds will differ in imperfec- 

 tion of the head m.arkings, much as just suggested ; the bill and feet may be in jnirt 

 light colored ; tbe under parts pure white. \ 



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

 s-ime region as the type, and are exactly like it. Dr. Finsch's determination that the 

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

 fication, after careful examination of Pallas's description. 



St(bge)iiis HALrPLAiN'A, Wagl. 



<^ Sterna, Gm., Syst. Xat. i, 1TS6, 605, et aliq. 



= Onychoprion, Wagl., Isis, 183'2. 277. {Sterna serrnta, Fokst.) 



= Planetis, Wagi.., Isis, ] t*3-2, 1-22-2 (type — ?). 



^Haliplana, Wagl., Isis, lt^:5'2, 1224." {S. fuliginosa, Gm.) 



= Haliplanes, apud Blas., List B. Enr. 16'&2, 22. 



"^Anom, Less., Descr. Maamif. et Ois. lr^47, 255, nen Leach. 



<^ Bydroehelidon, Bp., List, 163,?, 6\, pnrlim ; nee BoxE. 



= Thalasdpora, BoiE (fide Gray ; type given as " infuscata, Licht."). 



= Melanostema, Bl. (fide Gray). 



Gen. CH.tR. 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 brJhd, especially at the base, and bnt slightly convex ; 

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

 slightly convex;, the eminentia symphysis obtuse and little developed ; the tomia of 

 both mandibles inflected. Xasal groove long and deep, but rather irregularly defined, 

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

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

 exceedingly long, pointed, but the first primary scarcely longer than tbe second. Tail 

 very long, very deeply forked, as in Sterna, but the feathers broader and stiffer, and 

 not so regularly tapering. Feet moderately long, the tibiae denuded for a consider- 

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

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

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

 size and slender, graceful form. Bicolor. Characters of mouth as in Sternina: gen- 

 erally. Trachea of sm.iU calibre flattened above, but socm becoming quite cylindrical. 

 Lower larynx very small, its muscles feeble. Bronchial half-rings very delicate, but 

 distinct from the first, which is as usual larger and stronger. Zone of prorentricular 

 glands unusually narrow. Hep.atic and cystic ducts very short. Cceca* minute, 



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

 obtained by my own scalpel. In the specimens examiued the oesophagus was not 

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

 80 as to be membranous and transparent." The organ in question was of pretty uni- 

 form calibre throughout, and as muscular as in any other Tern. There must have 

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

 be the case. I cannot account for the difference in length of coeca as given by him, 

 and as I have found. In iny specimens the cceca, instead of being like those of the 

 Leatridina, are exceedingly short, and strictly stemine iu character. 



