length, the skull of Sciurus procerus is essentially a miniature of that of S. tenuis, as the braincase shows none of the tendency to increased depth characteristic of the Bornean animal. Ratio of rostral depth to distance between middle of interparietal and lower rim of audital bulla, 50. This ratio is 49 in S. tenuis.

Measurements.—External measurements of type: total length 235; head and body 140; tail vertebræ 95; hind foot 35 (33). Average and extremes of four specimens from the type locality: total length 239.5 (235-247); head and body 140; tail vertebræ 99.5 (95-107); hind foot 35.2 (34-36.5); hind foot without claws 32.9 (31.8-34).

Cranial measurements of type: greatest length 34 (38);[17] basal length 28.6 (32); basilar length 26 (29); palatal length 14.6 (16); diastema, 7.6 (8.8); length of nasals 10.4 (11.4); greatest breadth of nasals 4.8 (5.6); interorbital breadth 12 (12.6); zygomatic breadth 20.8 (21); greatest breadth of braincase 17 (17.6); cranial depth from middle of interparietal to lower rim of audital bulla 14 (15); least depth of rostrum 7 (7.2); mandible, 20 (21); maxillary toothrow (alveoli) 6 (7); mandibular toothrow (alveoli), 6 (7).

Specimens examined.—Six, all from the type locality.

Remarks.—This species is immediately distinguishable from its allies by its small skull, scarcely larger than that of Funambulus macclellandi.

SCIURUS NATUNENSIS (Thomas).

1894. Sciurus lowi Thomas and Hartert, Novitates Zoologicæ, I, p. 659. September, 1894 (Sirhassen).

1895. Sciurus lowi natunensis Thomas, Novitates Zoologicæ, II, p. 26. February, 1895 (Revised determination of Sirhassen specimen).

1895. ? Sciurus lowi natunensis Thomas and Hartert, Novitates Zoologicæ, II, p. 491. (Bunguran and Pulo Laut.)

Four specimens from Sirhassen. The average and extreme measurements are as follows: total length 222 (215-229); head and body 135 (133-140); tail vertebræ 86 (82-89); hind foot 33.6 (33-35); hind foot without claw 31.5 (30.5-32).

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.

SCIURUS LUTESCENS sp. nov.

1894. Sciurus notatus Thomas and Hartert, Novitates Zoologicæ, I, p. 659. September, 1894 (part, specimens from Sirhassen).

Type.—Adult male (skin and skull) No. 104668 U. S. National Museum. Collected on Sirhassen Island, South Natunas, June 3, 1900. Original number 429.

Characters.—Allied to Sciurus notatus, but considerably smaller than the Bornean representative of the species. Colors very pale, the under parts buff or cream-buff (Ridgway, pl. v, nos. 13 and 11) irregularly tinged with gray.

Color.—Entire dorsal surface of body and tail a fine grizzle of black and cream-buff, the individual hairs black with two or three cream buff rings. On tail the grizzle is less fine than on back, and it shows a faint tendency to resolve itself into obscure cross bands. On sides of body and on head the cream-buff brightens to buff. Cheeks and muzzle buff, scarcely grizzled. Feet slightly yellower than sides, under parts and inner surface of legs pale buff, palest anteriorly and laterally (where it about matches the cream-buff of Ridgway) brightest along median line. Under side of tail dull ochraceous-buff slightly grizzled with black. Pencil not different from rest of tail. Between the colors of sides and belly are the usual longitudinal stripes. The outer of these is about 5 mm. in width, and cream-buff in color. The inner is about twice as wide, and black, but much obscured by a thick sprinkling of bluish gray hairs. Outer surface of ears concolor with neck, inner surface like cheeks. The sprinkling of bluish gray hairs on sides of belly extends irregularly forward to axilla and inner side of front leg, occasionally to throat and chin.

Skull.—As compared with the Bornean form of Sciurus notatus, the skull of S. lutescens is much smaller (greatest length about 45 instead of 50) the rostrum is relatively shorter and broader, and the audital bullæ are less elongate antero-posteriorly. Teeth as in Sciurus notatus except that they are uniformly smaller.

Measurements.—External measurements of type: total length 355; head and body 177; tail vertebræ, 177; hind foot 45 (41). Average and extremes of six specimens from the type locality: total length 356 (329-375); head and body 186 (177-196); tail vertebræ 170 (152-178); hind foot 43.8 (41-45); hind foot without claws