144 MiHi-i'. >sv/v// \< n- Rota collected 



Mus cremoriventer sp. nov. 



Type adult male (skin and skull) No. 86,770 United States National 

 Museum, collected in the mountains of Trong, Lower Siam, at about 

 3000 ft. altitude, January 16, 1899. 



Characters. A slender animal about the size of Mus jerdoni Blyth, from 

 Mount Mooleyit, Burmah. Tail much longer than head and body, dark 

 brown throughout, thinly but distinctly penicillate. Fur very thickly spinous. 

 General color dull ochraceous above, whitish cream buff beneath. Skull 

 shorter and relatively broader than that of M. jerdoni. 



Far. As in Mus jerdoni the fur of the back and sides is composed of 

 three kinds of hair, (a) soft fine underfur about 10 mm. in length, light 

 gray at base and ochraceous at tip, (b) broad, grooved bristles slightly 

 longer than the underfur, light horn color at base, those on back blackish 

 at tip, those on sides uniform throughout, and (c) slender terete hairs 20 

 mm. in length, blackish throughout, but darker at tip than at base. The 

 long hairs are rather abundant on back, most numerous posteriorly. On 

 sides they soon disappear. On belly the bristles and underfur alone are 

 present, both much reduced in length, and without dark bases. Legs 

 nearly free from bristles except on outer side. 



Color. General color above dull ochraceous fading to ochraceous buff 

 or dull buff yellow on sides, the sides nearly clear, but back, shoulders, 

 neck and head uniformly sprinkled with black-tipped hairs and bristles 

 which are nowhere in excess of the ochraceous. Cheeks clear ochrace 

 ous buff. Muzzle hair brown, paler at the sides. A narrow dark shade 

 encircles each eye but without forming a distinct eyering. Underparts 

 and inner surface of legs clear light cream buff to base of hairs, sharply 

 defined and extending to wrists and ankles. Feet mixed whitish and 

 sepia. Tail and naked ears uniform dark brown throughout. 



Tail. The slender tail is conspicuously and regularly annulated. At 

 middle there are 11 or 12 rings to the centimeter. The rings are sharply 

 marked off from each other, and so slightly divided by cross furrows 

 that to the unaided eye they appear entire. With a lens they are seen to 

 be made up of rectangular scales slightly longer than broad. The free 

 edges of the rings are slightly crenulate and from beneath them spring 

 stiff black hairs whose length slightly exceeds width of rings. There 

 are usually three hairs to each division of the ring. Toward tip the 

 rings become much narrower and the hairs longer, forming a thin but 

 evident pencil. 



Skull. The skull of Mus cremoriventer (PI. V, Fig. 2) is shorter and broad 

 er than that of M. jerdoni (PI. V, Fig. 1). Its reduction in length is due 

 more to shortening of the rostrum than of the braincase, so that the 

 form of the skull is sensibly altered. Incisive foramina shorter and re 

 latively broader than in Mus jerdoni, their posterior extremity on level 

 with front of first molar. Antorbital foramen smaller than in Mus jer 

 doni but less contracted below. The maxillary plate forming its outer 

 wall is narrow, the greatest width only 2.8 mm. Its anterior border is 

 faintly concave below and faintly convex above, the general slope uni- 



