As compared with that of _Ratufa ephippium sandakanensis_ Bonhote, the skull in addition to its small size (greatest length 57 instead of 65) differs in general narrowness, in the relatively greater breadth of the nasal branches of the premaxillaries, and in the form of the audital bullæ. When the skull is held upside down and viewed from behind the bullæ are seen to be narrower than in the Bornean animal and to rise to a much greater height above the surface of the basi-occipital. RATUFA BUNGURANENSIS (Thomas and Hartert). 1894. _Sciurus bicolor bunguranensis_ THOMAS and HARTERT, Novitates Zoologicæ, I, p. 658. September, 1894 (Bunguran). 1895. _Sciurus bicolor bunguranensis_ THOMAS and HARTERT, Novitates Zoologicæ, II, p. 491. December, 1895 (Bunguran). 1900. _Ratufa ephippium bunguranensis_ BONHOTE, Ann. and Mag. Nat. Hist., 7th ser., V, p. 497. June, 1900. Thirteen specimens from Bunguran, all in various stages of the change from the bleached winter coat to the summer pelage. In the latter there is some color variation, mostly due to the greater or less distinctness of the drab wash overlying the Prouts-brown or 'chocolate' of the upper parts. Not only does the drab vary in amount in different individuals, but on every specimen it is more noticeable when the animal is viewed from in front. The drab wash is of the same character as that in _Ratufa affinis_, though less conspicuous. As Mr. Thomas has pointed out to me, after examining a specimen of the latter, _Ratufa bunguranensis_ is closely allied to _R. pyrsonota_. Indeed its relationship to the Siamese species is much closer than to the _R. ephippium_ of Borneo. Together with _R. pyrsonota_ the Bunguran giant squirrel differs conspicuously from that of Borneo in its narrow skull, lengthened audital bullæ, dark feet, dark median line on under surface of tail, and entirely brown back. From _R. pyrsonota_, however, it is readily separable by its darker, less ochraceous color both above and below, drab washed back, and by the much less distinct annulation of the hairs of the dorsal surface. RATUFA NANOGIGAS (Thomas and Hartert). 1895. _Sciurus bicolor nanogigas_ THOMAS and HARTERT, Novitates Zoologicæ, II, p. 491. December, 1895 (Pulo Laut). 1900. _Ratufa ephippium nanogigas_ BONHOTE, Ann. and Mag. Nat. Hist., 7th ser., V, p. 498. June, 1900 (Pulo Laut). Four specimens, all from Pulo Laut, the type locality. This strongly characterized dwarf species is allied to _Ratufa pyrsonota_ and _R. bunguranensis_ with which it agrees in color scheme. It is in no way closely related to the large Bornean _R. ephippium_. RATUFA ANGUSTICEPS sp. nov. _Type._--Adult male (skin and skull) No. 104646 U. S. National Museum. Collected on Pulo Lingung, off south coast of Bunguran, June 17, 1900. Original number 481.