WHITE-TAILED TROPIC BIRD. 79 
Genus LEPTOPHAETHON. 
Leptophaéthon Mathews, Austral Av. Rec., Vol. II., pts. 2 and 3, p. 56, Oct. 23rd, 1913. 
Type (by original designation): Phaéthon lepturus dorothee Mathews. 
Lepturus Reichenbach, Nat. Syst. Vogel, p. vit., 1852 (? 1853). Type (by original designa- 
tion): L. edwardsii Reichenbach = Phaéthon lepturus Daudin. 
Not Brisson, Ornith., Vol. VI., p. 479, 1760, nor Swainson 1838. 
Small Phaéthons with strong bills, long wings, long tail, small legs and feet. 
In general features the species of this genus agree with Scwophaéthon, but they 
differ appreciably in size. Proportionately the wing and tail are much longer, the 
tail being differently formed. 
In Sceophaéthon the culmen is more than half the length of the tail without the 
central pair of tail-feathers, which is less than one-third the length of the wing. In 
Leptophaéthon the culmen is less than half the length of the tail as above, which is 
more than one-third the length of the wing. The central tail-feathers in Lepto- 
phaéthon are very long with the webs normal and fairly wide, and the pair next to 
the central pair are long and are twice the length of the oustide pair, the tail being 
thus strongly wedge shaped. In Scewophaéthon the central pair are very long, but 
the webs are degenerate and are scarcely broader than the shaft, while the tail 
otherwise is wedge shaped but without much gradation. The metatarsus is less 
than a quarter of the length of the tail in Leptophaéthon, while in Sceeophaéthon it is 
more than one-third. The middle toe is never pectinate in this family. 
57. Leptophaethon lepturus.—WHITE-TAILED TROPIC BIRD. 
[Phaéton lepturus Daudin, in Hist. Nat. Buffon, ed. Didot, Quadr., Vol. XIV., p. 319 (1799 =] 
Oct. 1802: Ile de France = Mauritius. Extra-limital.] 
Mathews, Vol. IV., pt. 3, pl. 232, June 23rd, 1915. 
Phaéthon lepturus dorothee Mathews, Austral Av. Rec., Vol. II., pt. 1, p. 7, Aug. 2nd, 1913: 
Queensland. 
DisTRIBUTION.—Queensland, breeding on Fiji Islands (?) 
Adult male-—General colour above and below pearl-white ; a circular black line 
in front and over the eye which broadens out behind the latter ; the feathers of the 
hinder crown and nape have dark bases ; median upper wing-coverts black ; primary- 
quills black on the outer web and, including the shafts, white at the tips, the black 
decreasing on the inner ones which have only a black shaft ; outer secondaries white, 
inner ones black and white ; scapulars white, subterminally black with white edges ; 
rump and upper tail-coverts white with black bases and black shafts ; tail-feathers 
white with black shafts ; feathers on the sides of the rump black with white margins. 
Bill red ; eyes white ; feet black; tibia yellowish. Total] length 400 mm. ; culmen 
44, wing 281, tail 115, middle feathers 380, tarsus 24. 
Adult female —Similar to the adult male. 
Immature and Nestling—Not described. 
Nest.—A hole or hollow of a rock or tree stump. 
Eggs.—Clutch, one ; ground-colour buff ; freckled all over with purplish-brown ; 
axis 57 mm., diameter 44. 
Distribution and forms ——Throughout the oceans within the tropics, breeding 
on isolated islets. Three forms were recognised by Mathews in 1913, and no amend- 
ment of consequence has since been provided, thus: L. 1. lepturus (Daudin) from the 
Indian Ocean breeding at Mauritius and Rodriguez ; L. 1. dorothee (Mathews) from 
the East Australian Seas and the Pacific Ocean, in its smaller size throughout ; 
average : culmen 45, wing 258, tail 105 mm. ; average of typical birds: culmen 50, 
