148 Miller Seven New Rats collected in Siam. 



breadth, 14; breadth of braincase above roots of zygomata, 16; depth of 

 braincase at front of basioccipital, 10.8; fronto-palatal depth at posterior 

 extremity of nasals, 8.8; least depth immediately behind incisors, 7; 

 maxillary toothrow (alveoi), 6.8; width of first upper molar, 2; mandi 

 ble, 21.5; mandibular toothrow (alveoli), G.5. 



Specimens examined. One, the type. 



Remarks. While this species is very distinct from Mu9Jerdoni t its re 

 lationship to Mus surifer is questionable. Dr. Abbott writes that he ex 

 amined numerous individuals and that in the flesh they could be invaria 

 bly distinguished from the species with which they were associated. 

 The white spot on the head he regards as a normal character. 



Mus surifer sp. nov. 



Type adult male (skin and skull) No. 86,746 United States National 

 Museum, collected in the mountain of Trong, Lower Siam, at an altitude 

 of about 3,000 feet, January 14, 1899. 



Characters. In general appearance much like Musjerdoni and M. pellax, 

 but larger and more robust than either. Fur thickly spiny. Tail about 

 equal to head and body, though usually somewhat longer, bicolor with 

 exception of terminal third or fourth, which is entirely dull white. 

 Hind leg from knee to heel usually ochraceous on both sides thus separating 

 white of inner side of thigh from that of foot. Skull much larger and 

 more conspicuously ridged than that of Musjerdoni. 



Fur. The -fur is as in Mflbyerdoni and M. cremoriventer. 



Color. Upper parts uniform tawny ochraceous, heavily sprinkled with 

 blackish brown on posterior half of back, less so on shoulders and head. 

 Sides, flanks, cheeks and outer surface of legs clear tawny ochraceous. 

 Underparts white to base of hairs. The white extends down inner sides 

 of front legs to wrists, but on hind legs it normally reaches barely be 

 yond knee, below which the entire leg is ochraceous, though slightly 

 dulled on inner side by the dusky bases of the hairs. Occasionaly, how 

 ever, the white extends in a narrow irregular line to heel. Feet dull 

 white. Ears and dorsal surface of tail to terminal third or fourth dark 

 brown. Underside of tail and whole of terminal third or fourth dull 

 white. 



Tail. The tail is distinctly annulated, though less evenly than in 

 Mus cremoriventer . There are about 12 rings to the centimeter at middle. 

 The rings are indistinctly divided into sections slightly longer than broad, 

 from the free edge of each of which spring 1-3 hairs equal in length to 

 width of about one and one half rings. At tip the rings become nar 

 rower and less regular, the hairs at the same time increasing in abund 

 ance, but not in length, and not forming a pencil. 



Skull. The skull of Mus surifer (PI. V, Fig. 4) is conspicuously larger 

 than that of M. jerdoni (PI. V, Fig. 1), though not very different in form. 

 Supraorbital ridges high and continued backward to interparietal, and 

 in old individuals forming a strong postorbital angle. Incisive foramina 

 relatively much shorter and wider than in Mus jerdoni, distinctly wider 

 posteriorly than anteriorly. 



