MAMMALS OF THE NATUNA ISLANDS I3I 



Teeth'as in the i-elated species. 



AIeasureme7its. — External measurements of type : total length 748 ; 

 head and body 342 ; tail vertebrae 406 ; hind foot 79 (74). 



Cranial measurements of type : greatest length 48. 6 (70) ;^ basal 

 length 57 (59) ; basilar length 52 (53) ; diastema 15.6 (16) ; length 

 of nasals 22 (23.4) ; breadth of nasals anteriorly 12 (13) ; breadth of 

 nasals posteriorly 6 (7) ; interorbital breadth 27 (28) ; lachrymal 

 breadth 28.4 (31) ; breadth between tips of postorbital processes 38 

 (41) ; zygomatic breadth 41 (44) ; mastoid breadth 31 (32.6) ; man- 

 dible 40 (41.6) ; maxillary toothrow (alveoli) 14 (14); mandibular 

 toothrow (alveoli) 14.6 (14.4). 



Speci77iens examined. — One, the type. 



Remarks. — While this squirrel exactly resembles the other black 



backed species with untufted ears, so far as external characters are 



concerned, it seems to be well differentiated in cranial peculiarities. 



No black backed Ratufa has hitherto been recorded from the Na- 



tunas. 



RHINOSCIURUS sp. 



An immature long-nosed squirrel was taken on Sirhassen Island, 

 June 4, 1900. In the absence of material for comparison I am unable 

 to determine the species. The genus is new to the islands. 



ARCTOGALIDIA INORNATA sp. nov. 



Type. — Adult- male (skin and skull) No. 104859 U. S. National 

 Museum. Collected on Bunguran Island, North Natunas, June 23, 

 1900. Original nuinber 502. 



Characters. — Much smaller than Arctogalidia leucotis from the 

 Malay Peninsula or A. stigmatica from Borneo (greatest length of 

 skull about 100 instead of 115) and in color paler than either, the dark 

 dorsal stripes obsolete in adult. 



Color. — General color of back and sides light silvery gray irregu- 

 larly suffused with buff and slightly darkened by blackish hair-tips and 

 by appearance at surface of hair-brown basal portion of fur. The 

 buff suffusion is least noticeable on back, slightly more apparent on 

 sides and flanks, and most evident on sides of neck, where it usually 

 brightens almost to buff-yellow in distinct contrast with surrounding 

 parts. On middle of back there is a trace of the middle dark stripe 

 of the three normally present in members of the genus. Head essen- 

 tially like back though somewhat more gray. Muzzle and ill-defined 



' Measurements in parentheses are those of the type of Ratufa 7nelanopepia. 

 2 Teeth very much worn and many of them absent. 



