_Phaethon aethereus [?mesonauta]_ Hand-list Japanese Birds, rev., 1932, p. 187 (Kusaie, Marshalls); Hand-list Japanese Birds, 3d ed., 1942, p. 208 (Kusaie, Marshall Islands). _Geographic range._--Tropical parts of Atlantic and eastern Pacific from Cape Verde Islands west to Panama and Galapagos Islands. In Micronesia: Caroline Islands--Kusaie; Marshall Islands--Ratak Chain. _Characters._--Adult: A large, white sea bird with a long white tail; dorsal surface marked with blackish, transverse vermiculations; bill red; tarsus and foot flesh-colored with a yellowish hue, with plantar surface grayish. Immature: Resembles adults but dark transverse bars are broader; crown blacker; bill yellow. _Remarks._--No specimens have been examined. The Red-billed Tropic-bird is placed in the list of birds known from Micronesia on the basis of two observations by the German ornithologist, Otto Finsch. It has not been reported since his time, and may be considered as an unusual record for the area. I am following the Hand-list of Japanese Birds (Hachisuka _et al._, 1942:208) in assigning the bird to the subspecies, _P. a. mesonauta_. =Phaëthon rubricauda rothschildi= (Mathews) Red-tailed Tropic Bird _Scaeophaethon rubricauda rothschildi_ Mathews, Birds Australia, 4, 1915, p. 303. (Type locality, Laysan and Niihau.) _Phaeton rubricaudus_ Finsch, Journ. f. Ornith., 1880, p. 296 (Carolines); _idem_, Ibis, 1881, p. 115 (Ponapé). _Phaeton rubricauda_ Finsch, Proc. Zool. Soc. London, 1880, p. 577 (Ruk); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 73 (Ruk, Ponapé, Marshalls). _Phaeton rubricauda_ Ogilvie-Grant, Cat. Birds British Mus., 26, 1898, p. 451 (Caroline Islands); Hartert, Novit. Zool., 7, 1900, p. 11 (Ruk); Hand-list Japanese Birds, rev., 1932, p. 187 (Pagan, Truk, Ponapé, Marshalls). _Scaeophaethon rubricauda_ Kuroda, in Momiyama, Birds Micronesia, 1922, p. 34 (Mariannes, Ruk, Ponapé, Marshalls). _Phaethon rubricauda rothschildi_ Yamashina, Tori, 7, 1932, p. 406 (Pagan); _idem_, Tori, 10, 1940, p. 676 (Maug). _Phaethon rubricaudus rothschildi_ Hand-list Japanese Birds, 3d ed., 1942, p. 209 (Maug, Pagan, Truk, Ponapé, Marshalls). _Geographic range._--Bonin and Hawaiian islands south to Micronesia. In Micronesia: Mariana Islands--Maug, Pagan; Caroline Islands--Truk, Ponapé; Marshall Islands--exact locality unknown.