in forty-four specimens out of fifty examined, while only six specimens have the _A. platyrhynchos_ type of plumage. Yamashina cites also as evidence favoring his conclusion that hybridization has taken place the results obtained from the crossing of captive _A. platyrhynchos_ and _A. poecilorhyncha_. It is his assumption that there has been a resident form of _A. poecilorhyncha_ in the Marianas, apparently resembling closely that which occurs in the Palaus and at Truk (_A. p. pelewensis_), and that stragglers of _A. platyrhynchos_ from the north occasionally reach the Marianas where hybridization between the two species occurs. Yamashina remarks (1948:123): "The opportunity for hybridization should occur more rarely in the south, and thus more frequent back-crossing of the hybrid with the indigenous _Anas poecilorhyncha_ on Tinian and Guam explains the superabundance there of the _poecilorhyncha_ type. As the hybridization should have taken place more frequently to the north in Saipan, the ratio of the occurrence of the _platyrhynchos_ type is logically higher there." The Common Mallard (_A. p. platyrhynchos_) has not been recorded in Micronesia, but according to Yamashina (1948:123) "winters frequently just north of the Marianas in the Bonin and Volcano Islands." This remarkable explanation for the development of the Marianas Mallard is not questioned by this author, who feels that hybridization may be found to be the cause for other unusual forms of life in island habitats whose ancestry has not been explained. As Yamashina comments, the special environments of islands together with small and restricted populations of animals are factors which could favor such development. =Anas poecilorhyncha pelewensis= Hartlaub and Finsch Australian Gray Duck _Anas superciliosa_ var. _pelewensis_ Hartlaub and Finsch, Proc. Zool. Soc. London, 1872, p. 108. (Type locality, Pelew Islands.) _Anas superciliosa_ Hartlaub and Finsch, Proc. Zool. London, 1868, pp. 8, 118 (Pelew); Sclater, Proc. Zool. Soc. London, 1869, p. 659 (Pelew); Gray, Hand-list Birds, 3, 1871, p. 82 (Pelew); Salvadori, Ornith. Papuasia, 3, 1882, p. 395 (Pelew); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p. 70 (Pelew); Salvadori, Cat. Birds British Mus., 27, 1895, p. 206 (Pelew); Oustalet, Nouv. Arch. Mus. Hist. Nat. Paris, (3), 8, 1896, p. 50 (Palaos).