212 MILLER 



Specime7is examined. — Six, all from the type locality. 



Remarks. — Unlike the Tioman rat, JMus siantajiicus retains the 

 external appearance of the mainland form, but differs widely in its 

 cranial characters. In the latter it shows an approach to the much 

 larger Tambelan representative of the group. 



MUS TAMBELANICUS sp. nov. 



Type. — Adult male (skin and skull). No. 101665 United States 

 National Museum. From Big Tambelan Island. Collected August 

 10, 1899. 



Characters. — Much larger than ^Tus siantanicus oxXh^iowa of M. 

 ' alexandrinus ' occurring in Trong, Lower Siam. Fur coarser than in 

 the related species ; color about as in Mus tiomanicics^ or slightly more 

 red, but ventral surface darker and more yellow. Skull with rostrum 

 relatively even more heavily built than in J7}/5 siantaiiiciis^ but with 

 dorsal surface less flattened. 



Color. — Back a fine grizzle of dull cinnamon and blackish brown, 

 the two colors nearly equally mixed. Sides nearly clear cinnamon, 

 brightening to russet on flanks. Ventral surface dull buff, faintly and 

 irregularly marked with brownish, and very obscurely contrasted with 

 color of sides. Feet sepia. Tail uniform dark brown throughout. 



Skull. — The skull most nearly resembles that of Miis siantanlcus 

 but is much larger and the rostrum is relatively broader than in the 

 Anambas species. Region between anterior zygomatic roots convex 

 laterally^ not flat or concave as in the allied species. Dorsal profile of 

 nasals when viewed from in front slightly convex, but much less so 

 than in Mus tiom.anictis and the Trong form of M. ' alcxai/dri/n/s. 

 Lateral margins of rostrum nearly parallel. Teeth larger tlian in the 

 related species, but not disproportionately so. 



Measurements . — External measurements of type : head and body 

 (tail imperfect) 216; hind foot 42 (39); ear from meatus 21; ear 

 from crown 15; width of ear 16.4. Two adults from Pulo Bunoa 

 measure: (No. 101646, 9) total length 425; head and body 203 ; 

 tail vertebnc 222; hind foot 40 (37); and (No. 101642, 9) total 

 length 375; head and body iSi ; tail vertebra? 191 ; hind foot 40 (37). 

 An adult male (No. 101669) ^•"<^'''^ Pulo Wai measures: total length 

 393; head and body 191 ; tail vertebnc 203; hind foot 41 (38). 



Cranial measurements of type: greatest length 47; basal length 

 41; basilar length 38; palatal length 24; least width of palate be- 

 tween anterior molars 4.6; diastema 13; length of incisive foramen S ; 

 combined breadth of incisive foramina 3.8; length of nasals 17; com- 



