732 SYSTEMATIC SYNOPSIS. — LONGIPENNES. 



306. PHAETHON. (Gr. iaWav, Phaethon, son of the sun.) Tropic Birds. Character as above. 

 Tea. P. aethe'reus. (Lat. mthereus, pertaining to the upper air.) Ked-billed Tropic Bird. 

 Bill i;ed ; tarsi and part of toes light colored ; rest of toes black. Plumage pure white, on 

 nearly all the upper parts iinely barred with black ; black markings on sides under wings ; a 

 transoeurar fascia, outer webs and part of inner webs of most of the primaries, most of several 

 inner secondaries, and most of the shafts of the taU-feathers, black, the shafts of the long middle 

 pair, however, white in most of their extent. Length about 36.00 inches, including the long 

 tail-feathers ; without these, about 18.00 ; wing 12.00 ; long middle tail-feathers up to 18.00 ; 

 tarsus 1.00 ; middle toe and claw 1.75 ; bill 2.50 along culmen, nearly 1.00 deep at base. Trop- 

 ical and subtropical America, accidental in N. Am. ; said to have straggled to Newfoundland 

 in one instance (Freke, Pr. Roy. Soc. Dublin, 1879) 

 763. P. flaviros'tris. (Lat. flmmrostris, yellow-billed.) Yellow-billed Tropic Bird. Bill 

 and tarsi yellow ; toes black. Plumage white, tinged with salmon or rosy on the under part? 

 and long tail-feathers; lacking the barring with black of the last, species, but with definite 

 black areas — a transocular fascia, an oblique band on lesser wing-coverts and thence on scap- 

 ulars and inner secondaries, shaft-stripes on outer five or six primaries, stripes on the iianks, 

 and most of the shafts of the tail-feathers, including the middle pair. Smaller than the last; 

 development of middle tail-feathers about the same; wing 11.00; bill notably smaller, only 

 about 3.00 along culmen and 0.75 deep at base. This is the species figui-ed by Audubon (8vo, 

 pi. 427) under the wrong name of P. tethereus, which belongs to the foregoing. Tropical and 

 subtropical America, rare or casual in the U. S., as on the Gulf coast. Has strayed to Western 

 New York in one instance (Cottes, Bull. Nutt. Club, v, 1880, p. 63). 



ZII. Order LONGIFENNES : Long-winged Swimmers. 



Long-wmged Natatores with open nostrils cmd small free or no hind toe. — Wings long, 

 pointed, reaching when closed beyond the base, in many cases beyond the end, of the tail, which 

 is usually lengthened and of less than 20 rectrices (oftenest' 12). Legs more or less perfectly 

 beneath centre of equilibrium when the body is in thfe 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, rudi- 

 mentary, or absent; tibise naked below. Bill of variable form, but never extensively membra- 

 nous nor lamellate, the covering homy throughout, sometimes discontinuous. 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 substantially put together than either of the two preceding, — not that its 

 components are not suflBciently 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 vrith loons, auks, and plover, are quite close, while the digestive system 

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

 bers of the order, the tibia develops an apophysis, as in the loons ; while even in external 

 characters, one genus at least (Halodroma) resembles the Akidce. It is not certain that the 

 order must not be broken up, or rather enlarged and diflferently defined, to include some of the 

 genera now ranged under Pygopodes. 



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

 and concavo-convex, but in the Procellwriidm they become tumid and spongy " {Huxley) ; 

 basypterygoid processes may be wanting, but they are certainly present in many cases. The 

 nasal bones are schizorhinal in La/ridce, holorhinal in Proeellariidte. There is apparently one 

 pair of syringeal muscles throughout the order. The oesophagus is capacious and distensible ; 

 there is no special crop ; the proventiculus is a bulging of the gullet ; the gizzard is small and 



