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.
Characters.—Externally like Ratufa anambæ and R. melanopepla. Skull about equal to that of latter in length, but conspicuously narrower.
Color.—As 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.