146 Miller. Seven New Hats collected in Siam. 



sienna present in about equal quantities. Bister soon disappearing on 

 sides and cheeks. Muzzle hair brown, grayish at sides. A dark shade 

 about eye. Underparts dull buff, sharply denned, much darker and 

 browner than in M. cremoriventer, fading to buffy gray on chin and inner 

 side of legs, down which it extends to join dull white of feet. A small 

 tawny spot on middle of chest. Fur of underparts everywhere conspicuously 

 dusky at base. 



Tail. Except for its shortness the tail is essentially like that of M. 

 cremoriventer. The annulation, however, is a little less distinct, and the- 

 rings are more noticeably divided by cross furrows. In none of the 

 specimens is the tail perfect to extreme tip, but there is no apparent ten 

 dency to form a pencil. 



Skull The skull of Mus.asper (PI. V, Fig. 3) while of about the same 

 length as that of Mus jerdoni (PI. V, Fig. 1) differs conspicuously in the 

 deeper rostrum, strongly cuneate nasals, larger antorbital foramen, 

 heavier, more abruptly flaring and more depressed zygomata, and larger, 

 strongly angled supraorbital ridges. Incisive foramina short and broad, 

 their outer margins convergent anteriorly. Interpterygoid space shorter 

 and wider than in Mus jerdoni. Plate forming outer wall of antorbital 

 foramen essentially as in Mus cremoriventer, and distinctly less convex 

 above than in Mus jerdoni. 



Teeth. The teeth appear to be precisely like those of Mus jerdoni. 



Measurements. External measurements of type: total length, 254; 

 head and body, 133; tail vertebra, 121; hind foot, 27 (25.5); ear from 

 meatus, 18; ear from crown, 13; width of ear, 14. An adult male from 

 the type locality: total length, 235; head and body, 121; tail vertebrae, 

 114; hind foot, 28 (26. 5). The hind foot in two specimens in alcohol 

 measures respectively, 28.6 (27.4) and 26 (25). 



Cranial measurements of type; greatest length, 34; basal length, 28; 

 basilar length, 26; palatal length, 13.4; least width of palate between 

 anterior molars, 3.6; diastema, 8.4; length of incisive foramen, 4.6; com 

 bined breadth of incisive foramina, 2.8; length of nasals, 11; combined 

 breadth of nasals, 3.8; zygomatic breadth, 15.4; interorbital breadth, 

 5.8; mastoid breadth, 11.8; breadth of braincase above roots of zygo 

 mata, 13.6; depth of braincase at front of basioccipital, 9.8: frontopala- 

 tal depth at posterior extremity of nasals, 8; least depth immediately 

 behind incisors, 6; maxillary toothrow (alveoli), 6; width of first upper 

 molar, 1.4; mandible, 17.2; mandibular toothrow (alveoli), 5.4. 



Specimens examined. Six (two in alcohol), all from the type locality. 



Remarks. While Mus axper differs widely from the known mainland 

 representatives of the genus it is probably rather closely related to the 

 Bornean Mus whiteheadi Thomas, a species which I know by description 

 only. Mus asper agrees with the Bornean animal in size, character of 

 fur, color scheme, and general aspect of skull, but differs from it in its 

 shorter tail, lighter color with stronger, contrast between sides and belly, 

 less developed maxillary plate forming outer wall of antorbital foramen; 

 relatively wider incisive foramina, and apparently longer molar row, 



