_Characters._--A large petrel with blackish-brown plumage except for belly and under tail-coverts white and throat, upper breast and flanks pale brown; bill black; legs yellowish; feet black. This oceanic bird differs from other petrels and shearwaters of Micronesia by the presence of a white abdomen in contrast with dark plumage on upper parts, throat, and breast. _Remarks._--A petrel which is referred to this subspecies has been taken once in Micronesia, by Hombron and Jacquinot in the Caroline Islands. It may be pointed out that the subspecies _P. r. becki_ Murphy is known from the sea east of the Bismarck Archipelago and might range into Micronesian waters. =Pterodroma hypoleuca hypoleuca= Salvin Stout-billed Gadfly Petrel _Oestrelata hypoleuca_ Salvin, Ibis, 1888, p. 359. (Type locality, Krusenstern Island = Ailuk, Marshall Islands, _fide_ Fisher, Auk., 63, 1946, pp. 587-588). _Oestrelata hypoleuca_ Salvin, Cat. Birds British Mus., 25, 1896, p. 409 (Krusenstern); Godman, Monogr. Petrels, pt. 3, 1908, p. 212 (Krusenstern). _Cookilaria hypoleuca hypoleuca_ Mathews, Syst. Avium Australasianarum, 1, 1927, p. 122, (Marshall Group). _Pterodroma leucoptera hypoleuca_ Hand-list Japanese Birds, rev., 1932, p. 188 (Marshalls); Hand-list Japanese Birds, 3d ed., 1942, p. 210 (Krusenstern); Fisher, Auk, 63, 1946, pp. 387-388 (Ailuk). _Pterodroma hypoleuca hypoleuca_ Mayr, Birds Southwest Pacific, 1945, p. 11 (Micronesia). _Geographic range._--Ranges from the Bonins east to the Hawaiians and south to Micronesia. In Micronesia: Marshall Islands--Ailuk. _Characters._--Upper parts grayish except for forehead whitish, crown and nape sooty-black; underparts whitish except for sides of breast sooty-black; legs and feet flesh color except for tips of toes and webs which are black. _Remarks._--In Micronesia, this petrel is known only from the type locality, Krusenstern or Ailuk, Marshall Islands. Fisher (1946: 587-588) has corrected the confusion regarding the exact position of this type locality. =Phaëthon aethereus mesonauta= Peters Red-billed Tropic-bird _Phaëthon aethereus mesonauta_ Peters, Occ. Papers Boston Soc. Nat. Hist., 5, 1930, p. 261. (Type locality, Swan Key, Almirante Bay, Panama.) _Phaeton aethereus_ Finsch, Ibis, 1880, pp. 329, 333, (Ratak Chain, Marshalls); _idem_, Journ. f. Ornith., 1880, p. 310 (Kuschai); _idem_, Ibis, 1881, p. 109 (Kuschai); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 73 (Kushai, Marshalls); Ogilvie-Grant, Cat. Birds British Mus. 26, 1898, p. 457 (Kushai, Marshalls); Schnee, Zool. Jahrbücher, 20, 1904, p. 390 (Marschall Inseln); Kuroda, in Momiyama, Birds Micronesia, 1922, p. 34 (Kusaie, Marshall Islands).