Aphanolimnas monasa Sharpe, Bull. British Ornith. Club, 1892, p. 20 (Kuschai); Finsch, Deut. Ver. zum Schulze der Vogelwelt, 18, 1893, p. 457, pl. 4 (Ualan); Wiglesworth, Ibis, 1893, p. 214 (Kushai); Sharpe, Cat. Birds British Museum, 23, 1894, p. 115 (Kushai); Matschie, Journ. f. Ornith., 1901, pp. 110, 113 (Ualan); Mathews, Syst. Avium Australasianarum, 1, 1927, p. 93 (Caroline Islands); Hand-list Japanese Birds, rev., 1932, p. 197 (Kusaie); Peters, Check-list Birds World, 2, 1934, p. 189 (Kusaie); Hand-list Japanese Birds, 3d ed., 1942, p. 221 (Kusaie); Mayr, Birds Southwest Pacific, 1945, p. 288 (Kusaie); idem, Audubon Mag., 47, 1945, p. 280 (Kusaie).
Porzana tabuensis Sharpe, Cat. Birds British Mus., 23, 1894, p. 111 (Kushai).
Pennula monasa Dubois, Syn. Avium, 2, 1904, p. 969 (Kuschai).
Porzana tabuensis tabuensis Kuroda, in Momiyama, Birds Micronesia, 1922, p. 42 (Kusaie).
Geographic range.—Micronesia: Caroline Islands—Kusaie (probably extinct).
Characters.—Sharpe (1894:115) gives the following description: "Adult. Black with a bluish-grey reflexion; quills and tail somewhat browner; inner wing-coverts brownish with white spotting, outer edge of first primary dull brownish, chin and middle of the throat somewhat paler; bill blackish (Hartlaub.)."
Remarks.—Two specimens of this rail are known. The two were taken by Kittlitz on his visit to Kusaie in December and January of 1827-'28. Coultas made a search for the bird in 1931 and failed to obtain it; he suggested that the high population of introduced rodents may have been a factor contributing to its extinction. The bird is considered to be extinct by the authors of the Hand-list of Japanese Birds (Hachisuka et al., 1942:221).
The two known specimens are in Leningrad, and Mayr sent examples of Porzana tabuensis there for comparison. The following is a translation of the letter received by Mayr from Boris Stegmann dated at Leningrad, December 7, 1937.
"I have compared the two specimens of Porzana tabuensis with our specimens of Aphanolimnas monasa. The difference is in my opinion of generic value. Aphanolimnas is distinctly larger and more robust. The bill is not only absolutely but also relatively longer. Its length (measured from the forehead) reaches to the end of the second phalanx of the middle toe while it not nearly reaches it in tabuensis. The proportions of feet and toes are the same in both, but the feet are distinctly heavier in Aphanolimnas. The wings are relatively shorter in Aphanolimnas and the wing feathers are very soft. The wing is also much more rounded, the first primary is about 21 mm. shorter than the wing tip. The tail consists of very soft loose feathers which resemble only distantly true tail feathers. It is therefore questionable whether this bird was at all able to fly.