MAMMALS COLLECTED BY DR. \V. L. ABBOTT 213 



bineJ breadth of nasals 5.4; zygomatic breadth 22.4; interorbital 

 breadth 7; mastoid breadth iS; breadth of braincase over roots of 

 zygomata 17.6; depth of braincase at front of basioccipital 12.S; 

 frontopalatal depth at posterior extremity of nasals 11.4; least depth 

 of rostrum immediately behind incisors 8.8; maxillary toothrow 

 (alveoli) 8; width of first upper molar 2.4; mandible 26.4; mandi- 

 bular toothrow (alveoli) 7.4. 



Specimens examined. — Five, one adult from Big Tambelan Island, 

 two from Pulo Bunoa, an adult from Pulo Wai, and an immature in- 

 dividual from Pulo Gilla. 



Remarks. — ^Iiis tambelatziciis marks, so far as the species repre- 

 sented by the j^resent collection are concerned, the culmination of a series 

 beginning with the light colored, slender skulled animal of Trong. The 

 first step away from this type is represented by AIus tiotnanicus^ in 

 which the color is distinctly darkened, but in which the cranial charac- 

 ters remain practically unchanged. In the representative of the group 

 occurring on the Anambas the rostrum is noticeably altered in form, 

 though the color is less affected than in the Tioman animal. Finally, 

 in the Tambelan Islands a race has been developed carrying the cranial 

 peculiarities even further than in that inhabiting the Anambas ; the 

 changes in form of skull accompanied by marked increase in the gen- 

 eral size of the animal, in the quality of the fur and in the color. 

 The characters of each of these closely related species are remarkably 

 constant in view of the reputation for variation enjoyed by ]\Ius ' alex- 

 andrius.' The adult specimen of M. tambelamcus from Pulo Wai 

 differs from the skins from Big Tambelan in less yellow ventral sur- 

 face, but otherwise it is not peculiar. 



The specimen from Pulo Gilla is too immature to be comparable 

 with the others. 



MUS OBSCURUS sp. nov. 



Type. — Adult male (skin and skull). No. 101764 United States 

 National Museum. From Tioman Island. Collected October i, 

 1899. 



Characters. — Similar to Mtts coficolor Blyth, but larger, and with 

 more coarsely spinous fur. Skull larger than that of ]\Ius coficolor., 

 the dorsal profile less convex, the audital bullae larger and teeth rela- 

 tively smaller. 



Color. — General appearance that of a much overgrown house- 

 mouse. Dorsal surface a fine grizzle of seal brown and dull ochra- 

 ccous-buff, the former predominating on crown of head and in himbar 



