LONGIPENNES, LONG-AVINGED SWIMMERS. — GEN. 278. 307 



small, linear, but remaining patulous. Tail with the two middle feathers in tlie 

 adult filamentous and extraordinarily prolonged, the rest short and broad. 



The tropic birds resemble a large, stout tern in their general figure ; the bill, 

 especiallj', being almost exactly like that of a tern. The principal external 

 peculiarity is the development of the middle tail-feathers ; the feathering of the 

 gular sac and the permanent patulence of the nostrils are other features. They 

 are graceful birds on the wing, capable of protracted flight, venturing far from land. 

 They are gregarious at all times, and nest in communities along coasts and on 

 islands, in rocky places or among low trees and bushes. As implied in their name, 

 they are birds of the torrid zone, though in their extensive wanderings they visit 

 Southern seas, and have even been rej^orted from latitude 40° N. There are but three 

 well determined species : P. flavirostris (below) ; P. wtliereus, and P. rubricauda. 



278. Genus PHAETHON Linnseus. 



i ' 5 " Tropic Bird. White, satiny, rosy-tinted; long tail feathers reddened, 

 black-shafted ; sides of head, wings and flanks varied with black ; bill orange ; 

 tarsi yellow ; toes and webs black; young with more black on upper parts. 

 Wing 11 ; bill l|-2 ; tarsus 1; tail 4-5, its middle feathers up to 15-20. 

 Gulf Coast, rare or casual. P. cethereus Xutt., ii, 503 ; AuD., vii, 64, pi. 

 427; B. Jiavirosir is JiRANDT I Lawr. iu Bd., 885. . . . flavikostris. 



Order LONGIPENNES. Long-winged Swimmers. 



Wings long, pointed, reaching when closed bej'ond the base, in manjr cases 

 beyond the end, of the tail, which is usually lengthened and of less than 20 rec- 

 trices (oftenest 12). Legs more or less perfectly beneath centre of equilibrium 

 when the body is in the horizontal position ; the crura more nearly free from the 

 body than in other Natatores, if not completely external. Anterior toes palmate ; 

 hallux never united with the inner toe, highly elevated, directly posterior, very small, 

 rudimentary or absent ; tibite naked below. Bill of variable form, but never exten- 

 sively membranous nor lamellate, the covering horny throughout, sometimes dis- 

 continuous. Nostrils variable, but never abortive. No gular pouch. Altricial. 



This order, which may be recognized among web-footed birds by the foregoing 

 external characters, is less substantiall3r put together than either of the two preceding 

 — not that its components are not sufficiently related to each other, but because the 

 essential points of structure are shared to a considerable extent by other groups. 

 Thus the osteological resemblances of longipennine birds with loons, auks, and 

 plover, are quite close, as noted by Huxley ; while the digestive system agrees in 

 general characters with that of other fish-eating birds. In some of the lower 

 members of the order, the tibia develops an apophysis, as in the loons ; while 

 even in external characters, one genus at least, Halodroma, resembles the Alcidce. 

 It is not certain, that the order must not be broken up, or rather enlarged and 

 differently defined, to include some of the genera now ranged under Pygopodes. 



The palate has the schizognathous structure ; "the maxillo-palatines are usually 

 lamellar and concavo-convex, but' in the Procellariidoe they become tumid and 

 spongy" {Huxley) ; basipterj'goid processes may be often wanting, but they are 

 certainly present in many more cases than Huxley supposed. There is appar- 

 ently one pair of syringeal muscles throughout the order. The 03Sophagus is capa- 



