YZ CICONIIFORMES : PHAETHONTIDAE CHAP. 
mentioned,except in some members of Phalacrocorax. The V-shaped 
furcula ancyloses with the sternum in some of the Sub-Order, but 
Fregata differs from all other ornithic forms in the fact that the 
furcula also coalesces with the coracoids at its extremities, while 
the coracoids again unite firmly with the scapula, producing an 
almost rigid framework, considered by Professor Newton to be con- 
nected with the power which the bird possesses of sustaining itself 
nearly motionless in the air.’ The peculiar angular articulation 
of the long eighth cervical vertebra in Plotus, which causes the 
Z-shaped “kink” in the neck, must also be noticed here.2 The 
tongue is rudimentary ; the nostrils are pervious in Phaéthon, un- 
pervious elsewhere, being practically obliterated in adults; the 
syrinx is tracheo-bronchial, except in Sula and Pelecanus, where the 
usual muscles are entirely absent. The subcutaneous air-cells of 
Sula are most remarkable. The newly-hatched young are blind and 
helpless, being naked and covered with blackish skin in Sula, Phal- 
acrocorax, Plotus, and Pelecanus, though they soon acquire a white 
downy coat; in Phaéthon and Fregata they are similarly clothed 
on breaking the shell. The down of the adults is uniformly dis- 
tributed, the aftershaft is diminutive or wanting. The gular sacs, 
horny excrescences on the beak, crests, and so forth, are noted below. 
Fai. I. Phaethontidae.— Phacthon acthereus,P. flavirostris, and 
P. rubricauda are chiefly found in the tropical regions of the south ; 
but the first two species breed about as far north as the tropic 
of Cancer, while they frequent the West Indies, and occasionally 
stray to the Eastern United States, or even Newfoundland.’ The 
third inhabits the southern seas and the Indian Ocean. All these 
Tropic- or Boatswain-birds, as they are denominated, have satin-like 
white plumage—often with a tinge of pink—varied by blackish 
bars or patches above, and black marks near the eye; the bill is 
red, or in P. flavirostris yellow, the metatarsi yellowish and the 
toes chiefly black. In P. rubricauda the long stiff median rectrices 
are dull red with black shafts and very narrow webs, in P. flaviros- 
tris they are pinkish with similar shafts, and in P. aethereus entirely 
white. The sexes are alike, the young being more irregularly 
marked and having no long tail-feathers. 
The members of this Family are true denizens of the ocean, 
1 A. Newton, Dict. Birds, 1893, pp. 293, 294. 
2 W. A. Forbes, P.Z.S. 1882, pp. 208-212. 
* The East American form of P. flavirostris is separated as P. americanus by 
Mr. Ogilvie Grant, Bull. Ornith. Club, vii. 1897, p. xxiv. 
