the color is precisely like that of Ratufa anambæ and R. melanopepla it requires no description.

Skull and teeth.—The skull is immediately recognizable by its general narrowness, but particularly in the region of the anterior zygomatic roots. Ratio of lachrymal breadth to greatest length, 39. In the other black backed species it is about 42. Audital bullæ narrower and more elongate than in R. melanopepla, and more elevated above level of basi-occipital (when skull is held upside down). Lateral processes of basi-occipital obsolete.

Teeth as in the related species.

Measurements.—External measurements of type: total length 748; head and body 342; tail vertebræ 406; hind foot 79 (74).

Cranial measurements of type: greatest length 48.6 (70);[21] basal length 57 (59); basilar length 52 (53); diastema 15.6 (16); length of nasals 22 (23.4); breadth of nasals anteriorly 12 (13); breadth of nasals posteriorly 6 (7); interorbital breadth 27 (28); lachrymal breadth 28.4 (31); breadth between tips of postorbital processes 38 (41); zygomatic breadth 41 (44); mastoid breadth 31 (32.6); mandible 40 (41.6); maxillary toothrow (alveoli) 14 (14); mandibular toothrow (alveoli) 14.6 (14.4).

Specimens examined.—One, the type.

Remarks.—While this squirrel exactly resembles the other black backed species with untufted ears, so far as external characters are concerned, it seems to be well differentiated in cranial peculiarities. No black backed Ratufa has hitherto been recorded from the Natunas.

RHINOSCIURUS sp.

An immature long-nosed squirrel was taken on Sirhassen Island, June 4, 1900. In the absence of material for comparison I am unable to determine the species. The genus is new to the islands.

ARCTOGALIDIA INORNATA sp. nov.

Type.—Adult[22] male (skin and skull) No. 104859 U. S. National Museum. Collected on Bunguran Island, North Natunas, June 23, 1900. Original number 502.

Characters.—Much smaller than Arctogalidia leucotis from the Malay Peninsula or A. stigmatica from Borneo (greatest length of skull about 100 instead of 115) and in color paler than either, the dark dorsal stripes obsolete in adult.

Color.—General color of back and sides light silvery gray irregularly suffused with buff and slightly darkened by blackish hair-tips and by appearance at surface of hair-brown basal portion of fur. The buff suffusion is least noticeable on back, slightly more apparent on sides and flanks, and most evident on sides of neck, where it usually brightens almost to buff-yellow in distinct contrast with surrounding parts. On middle of back there is a trace of the middle dark stripe of the three normally present in members of the genus. Head essentially like back though somewhat more gray. Muzzle and ill-defined eye ring blackish. Cheeks and short median stripe on forehead dull whitish gray. Under parts essentially like back, but buff tinge more diffuse. Feet and ears dark brown. Tail like back but darkening to uniform brown beyond middle.

Newly born young are clear bluish gray, with scarcely a tinge of buff. The three black dorsal stripes are clearly defined and normal in extent.

Skull.—In addition to its smaller size the skull differs from that of the Bornean Arctogalidia stigmatica in the relatively larger braincase, and less prominent audital bullæ. The braincase is nearly as broad as in the Bornean species, but the zygomatic width is distinctly less. Audital bullæ less raised above level of basi-occipital when skull is held upside down and viewed from behind. The sagittal crest, though of normal development in very old individuals, is absent at an age when it is well grown in the larger species. In Arctogalidia leucotis and A. stigmatica, even in animals so young that the teeth are unworn and all the sutures of the rostrum plainly visible, the sagittal crest is a knife-like ridge extending from proencephalon to lambdoid suture, and rising to a height of about 4 mm. over middle of braincase. In much older individuals of A. inornata, with worn teeth and nearly obliterated rostral sutures, the crest is represented by a low ridge about 5 mm. wide over middle of braincase and flat or grooved on top. At this stage it rises very inconspicuously above level of the adjacent surface, from which it is distinguished more by the texture of the bone than by actual form.

Teeth.—The teeth are uniformly much smaller than in Arctogalidia leucotis and A. stigmatica, but I can detect no important differences in form.

Measurements.—External measurements of type: total length 1027; head and body 469; tail vertebræ 558; hind foot 78 (73.) External measurements of an adult female: total length 911; head and body 431; tail vertebræ 480; hind foot 77 (72).

Cranial measurements of type: greatest length 102 (115);[23] basal length 96 (106); basilar length 92 (103); median palatal length 53 (60); palatal breadth between anterior molars 13 (15.4); zygomatic breadth 55 (60); breadth between tips of postorbital processes 41 (39); constriction in front of postorbital processes 19 (18); constriction behind postorbital processes 13 (12); breadth of braincase above roots of zygomata 32 (33); mastoid breadth 36 (38); mandible 76 (86); maxillary toothrow (exclusive of incisors) 34[24] (41); mandibular toothrow (exclusive of incisors) 39 (44); crown of first upper molar 5.4 × 5 (5.4 × 5.6); crown of second upper molar 4 × 5 (5.4 × 6.4); crown of second lower molar 7 × 4.2 (8.4 × 5.4).

Specimens examined.—Seven (two young in alcohol and one skull without skin), all from the type locality.

Remarks.—Arctogalidia inornata is so distinct from the previously described species as to require no special comparisons. It is common on Bunguran where it frequents the cocoanut trees, living for the most part in the tops among the leaf stalks.