_Hypotaenidia owstoni_ Hartert, Novit. Zool., 5, 1898, p. 62 (Guam); Safford, Osprey, 1902, pp. 41, 67 (Guam); _idem_, The Plant World, 7, 1904, p. 265 (Guam); Dubois, Syn. Avium, 2, 1904, p. 961 (Mariannes); Safford, Contr. U. S. Nat. Herb., 9, 1905, p. 79 (Guam); Cox, Island of Guam, 1917, p. 21 (Guam); Kuroda, in Momiyama, Birds Micronesia, 1922, p. 42 (Guam); Hartert, Novit. Zool., 34, 1927, p. 22 (Guam); Mathews, Syst. Avium Australasianarum, 1, 1927, p. 84 (Guam); Hand-list Japanese Birds, rev., 1932, p. 196 (Guam). _Hypotaenidia marchei_ Oustalet, Nouv. Arch. Mus. Hist. Nat., Paris, (3), 8, 1896, p. 32 (Type locality, Guam). _Hypotaenidia oustini_ Seale, Occ. Papers Bernice P. Bishop Mus., 1, 1901, p. 30 (Guam). _Rallus owstoni_ Peters, Check-list Birds World, 2, 1934, p. 166 (Guam); Bryan, Guam Rec., vol. 13, no. 2, 1936, p. 15 (Guam); Hand-list Japanese Birds, 3d ed., 1942, p. 220 (Guam); Mayr, Birds Southwest Pacific, 1945, p. 287 (Guam); _idem_, Audubon Mag., 47, 1945, p. 279 (Guam); Watson, Raven, 17, 1946, p. 41 (Guam); Strophlet, Auk, 1946, p. 536 (Guam); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 48 (Guam). _Geographic range._--Micronesia: Mariana Islands--Guam. _Characters._--Adult: A large rail with head, neck, and eye stripe near "mummy brown" with feathers on sides of neck tipped with "russet"; superciliary stripe to back of neck, throat and upper breast near "mouse gray"; mantle, back, scapulars, and some upper wing-coverts dark olive-brown becoming browner on rump and upper tail-coverts; wings dark with brownish spots and barred with white; lower breast, abdomen, under tail-coverts, and tail blackish with white barrings; bill lead colored; feet dark brown; tibia brown; iris red. _Measurements._--Four adult males measure: wing, 120-123 (121); tail, 46-54 (50); full culmen, 37-43 (41); tarsus, 47-51 (50); six adult females measure: wing, 108-118 (112); tail, 38-46 (42); full culmen, 36-39 (37); tarsus, 43-47 (45). _Weights._--The NAMRU2 party obtained specimens with the following weights: two adult males 256, 257; four females 147, 153, 210, 252 grams. _Specimens examined._--Total number, 13 (5 males, 6 females, 2 unsexed), from Mariana Islands, USNM--Guam (Jan. 29, May 8, June 19, 20, 23, 28, 30, July 14, 19, 23, Sept. 8).