Examination of both skins and skulls of the hoolock gibbon has shown that 2 well-marked geographic races can be distinguished, which are separated by the Chindwin river in Burma. The name H. h. leuconedys is proposed for the eastern ssp., which is distinguished by its white preputial tuft, the separation of the white eyebrow streaks, and other less important features. One locality, Dalu, near the Chindwin headwaters, shows intergrades between the 2 races.