SCIURUS LINGUNGENSIS sp. nov.
1895. ? Sciurus lowi natunensis Thomas and Hartert, Novitates Zoologicæ, II, p. 491. (Bunguran and Pulo Laut.)
Type.—Adult male (skin and skull) No. 104693 U. S. National Museum. Collected on Pulo Lingung off southern extremity of Bunguran, North Natuna Islands, June 19, 1900. Original number 494.
Characters.—Externally similar to Sciurus natunensis (Thomas), but slightly larger (hind foot with claws 36 instead of 33.6). Skull larger than that of S. natunensis, the audital bullæ much broader anteriorly.
Color.—The color is precisely as in Sciurus natunensis, and therefore requires no detailed description.
Skull.—Skull larger than that of Sciurus natunensis (see measurements) but not different in general form. The audital bullæ are, however, readily distinguishable by the much greater development of the anterior inner lobe. In Sciurus natunensis this lobe is so small as scarcely to form any part of the general contour of the bulla. In S. lingungensis it is nearly equal to the anterior outer lobe, together with which it imparts a distinctly triangular outline to the ventral aspect of the bulla.
Measurements.—External measurements of type: total length 229; head and body 140; tail vertebræ 89; hind foot 36 (33.7); ear from meatus 12; ear from crown 7. A second specimen from the type locality gives precisely the same measurements.
Cranial measurements of type: greatest length 38 (36);[18] basal length 33 (31); basilar length 30 (29); palatal length 17 (16); greatest length of nasals 11 (10); greatest width of both nasals together 5 (5); interorbital breadth 12 (11.4); zygomatic breadth 22.4 (20); mastoid breadth 17 (16.6); depth of braincase at anterior edge of basi-occipital 13.6 (13); mandible 23 (22); maxillary toothrow (alveoli) 6.4 (7); mandibular toothrow (alveoli) 7 (7).
Specimens examined.—Two, both from the type locality.
Remarks.—While Sciurus lingungensis is scarcely distinguishable from S. natunensis by external characters alone, size of the skull and form of the audital bullæ are clearly diagnostic. Both species from the Natunas are separated from the Bornean S. lowi Thomas by their well developed ears, and shorter broader rostral portion of skull.