MAMMALS COLLECTED BY DR. W. L. ABBOTT 211 



as in the form of Mus '■ alexandrinus' occurring in Trong, Lower 

 Siam, but skull with noticeably broader, less arched rostrum. 



Color. — Dorsal surface a fine grizzle of dull ochraceous-buff and 

 brownish black, the hairs with a distinct gloss in certain lights. On 

 shoulders and middle of back the brown predominates, and at the 

 same time the ochraceous-buff is duller and paler than elsewhere. On 

 sides, flanks and across lumbar region the dark hairs are less numer- 

 ous and the ochraceous-buff is distinctly tinged with russet. Ventral 

 surface of body and inner side of legs yellowish white, darker, and 

 somewhat brownish tinged across chest. Fur of back pale slate-gray 

 at base, that of ventral surface mostly unicolor to base, but irregularly 

 tinged with gray beneath the surface. Feet light brown. Tail uni- 

 form dark brown throughout. 



Skull and teeth. — The skull of Mus siantanicus is essentially like 

 that of M. tiomanictis and j\I. ' alexandrinus ' except in the form of 

 the rostrum. This differs conspicuously from that of the related spe- 

 cies in its breadth, and in the flatness of the dorsal surface. The 

 characters are most noticeable when the skull is viewed from directly 

 in front. It is then seen that the nasal bones are very slightly de- 

 pressed at the sides only, while in AIus tiomanictis and M. alexan- 

 drinus they are uniformly arched from suture to periphery, the out- 

 line of the two together forming nearly one-half of a circle. Viewed 

 from the side, the dorsal profile of the rostrum appears nearly straight. 

 Viewed from beneath, the sides are seen to be more nearly parallel 

 than in the two related species. Teeth in no way peculiar. 



Measurements. — External measurements of type : total length 356 ; 

 head and body 191 ; tail vertebrce 165 ; hind foot 35 (33) ; ear from 

 meatus i7-^; e^r from crown 14. 8; width of ear 15. Average of five 

 adults from the type locality; total length 365 (349-382) ; head and 

 body 186 (17S-191); tail vertebras 179 (165-191); hind foot 35.6 

 (35-36) ; hind foot without claws 36.9 (33-35). 



Cranial measurements of type : greatest length 42 ; basal length 

 37; basilar length 35 ; palatal length 21 ; least width of palate be- 

 tween anterior molars 4; diastema 12; length of incisive foramen 8; 

 combined breadth of incisive foramina 3; length of nasals 15.4; com- 

 bined breath of nasals 4.6; zygomatic breadth 18; interorbital breadth 

 6.4; mastoid breadth 15.6; breadth of braincase over roots of zygo- 

 mata 16,4; depth of braincase at front of basioccipital 12; fronto- 

 palatal depth at posterior extremity of nasals 9.4; least depth of 

 rostrum immediately behind incisors 7 ; maxillary toothi'ow (alveoli) 

 7; width of first upper molar 2; mandible 23.6; mandibular tooth- 

 row (alveoli) 7. 



