Porzana cinerea ocularis Hartert, Novit. Zool., 31, 1924, p. 264 (Ruk, Guam).
Poliolimnas cinereus collingwoodi Mathews, Syst. Avium Australasianarum, 1, 1927, p. 95 (Pelew, Marianne, Carolines); Hand-list Japanese Birds, rev., 1932, p. 197 (Guam, Koror, Yap, Truk); Hachisuka, Birds Philippine Islands, 1, 1932, p. 236 (Marianne, Pelew, Caroline); Peters, Check-list Birds World, 2, 1934, p. 198 (Marianne, Caroline, Pelew); Bryan, Guam Rev., vol. 13, no. 2, 1936, p. 15 (Guam); Mayr, Birds Southwest Pacific, 1945, p. 288 (Guam, Palau, Yap, Truk, Bikini); Delacour and Mayr, Birds Philippines, 1946, p. 64 (Micronesia); Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 48 (Ulithi?, Truk).
Porzana cinerea collingwoodi Rensch, Mitt. Zool., 1931, p. 468 (Marianne, Karolinen, Palau).
Poliolimnas cinereus micronesiae Yamashina, Tori, 10, 1940, p. 679 (Bikini); Hand-list Japanese Birds, 3d ed., 1942, p. 221 (Guam, Babelthuap, Koror, Yap, Truk, Bikini).
Geographic range.—Micronesia: Mariana Islands—Guam; Palau Islands—Koror, Babelthuap; Caroline Islands—Yap, Ulithi?, Truk; Marshall Islands—Bikini.
Characters.—Adult: A slightly built, long-legged rail with forehead and anterior crown light gray with darker, slate-colored feather shafts; color more olive-brown on occiput and nape; eyestripe dark slate extending to occiput; superciliary from bill to eye, and stripe below eye, white; chin and throat ashy-white; sides of head, neck and breast ashy-gray, lighter on breast and whitish on abdomen; sides of abdomen ashy-brown becoming more buffy on tibia and under tail-coverts; mantle olive-colored becoming lighter and more brownish on back, rump, and scapulars; wing-coverts similar in color but feathers with broad dark brown shaft-marks; wings brown, first primary with whitish outer web; under wing gray with some lighter streaks; tail dark brown, lighter on edges; bill horn colored, tan below; feet brown; iris vermillion.
Immature: Resembles adult, but head more rufous, upper parts marked with buffy rufous; eye stripe light rufous-brown; underparts tinged with rufous.
P. c. micronesiae differs from P. c. collingwoodi Mathews of the Philippines by having more pale gray and less olivaceous-brown on the nape and shoulder; darker on the under tail-coverts; and having a shorter culmen. P. c. brevipes (Ingram) of the Volcano Islands differs from P. c. micronesiae by being paler on upper parts, particularly back and wing-coverts and more washed with buff below; by having a shorter, thicker culmen; and by having a shorter tarsus.
Measurements.—Measurements are shown in [table 17].