_Remarks._--While the two specimens agree in all essential characters they differ in numerous minor details. The skin from Pulo Lingung is somewhat darker than the type, but the difference is due to the shade of the brown wash, not to any extension of the black. The skull of this specimen is more rounded posteriorly than that of the type, and the rostrum is shorter. Both specimens show conclusively that their relationships are with the _Sus cristatus_ of the Malay Peninsula and not with the _S. longirostris_ of Borneo, a case which finds an exact parallel in the giant squirrels. MUS INTEGER sp. nov. _Type._--Adult male (skin and skull) No. 104837 U. S. National Museum. Collected on Sirhassen Island, South Natunas, June 7, 1900. Original number 455. _Characters._--A large robust species with coarse but not spinous fur. Relationships with _Mus validus_ Miller, from Trong, Lower Siam, and _Mus mülleri_ Jentink from Sumatra. Differs from the former in smaller size and in the absence of the anterior outer tubercle of the last upper molar, and from the latter in larger size, and yellowish brown (not white) underparts. _Color._--Back and sides a fine grizzle of black and dull ochraceous (the exact shade intermediate between the ochraceous and ochraceous-buff of Ridgway), the two colors nearly equally mixed on back, but the ochraceous in excess on sides. Underparts and inner surface of legs buff. An ill defined drab-gray median line from throat to pubic region. Head darker and more glossy than back, the cheeks distinctly washed with gray. Lips and chin drab-gray. Feet an indefinite brown, darker on metapodials. Ears essentially naked, dark brown. Tail dark brown throughout. Underfur gray (Ridgway, pl. II, No. 8), becoming paler on under parts where it fades irregularly into the general buff. _Fur._--The fur is exactly as in _Mus validus_, that is the grooved bristles are so slender that their true nature is not apparent without use of lens. On middle of back the mass of the fur is about 17 mm. in length, the long terete hairs scattered through it reaching about 30 mm. On rump the fur is longer but not conspicuously so, and there is no noticeable increase in length or abundance of the terete black hairs. _Tail, feet and mammæ._--Tail slightly more coarsely scaled than in _Mus validus_; 9 rings to the centimeter at middle. Hairs scarcely noticeable except toward tip, where they somewhat exceed the breadth of the rings. Feet heavy and robust. Thumb short, with a flat blunt nail. Soles and palms naked, the former with six well developed tubercles, the latter with five. Mammæ, p. 2--2, i. 2--2 = 8.