Miller and HolUster — New Mammals Collected in Celebes. 97 



species is almost an exact miniature of Rattus mamosurus of the mountains 

 of northeastern Celebes. 



Rattus hamatus, sp. nov. 



Type from Goenoeng Lehio, Middle Celebes. No. 218,680, U. S. 

 National Museum; skin and skull of adult c?" (teeth moderately worn); 

 collected January 16, 1917, by H. C. Raven; original number 3095. 



Diagnosis. — A medium-sized rat superficially resembling the darker 

 members of the Rattus chrysocomus group, but with skull and teeth wholly 

 unlike those species; apparently not belonging in any of the recognized 

 species-groups of Rattus. Size about as in Rattus marmosurus Thomas ; but 

 tail much shorter and with only the distal half whitish. Pelage soft and 

 full, but shorter than in marmosurus, and without the long overlying hairs 

 of that species. Coloration above, dark gray, finely flecked with buff; sides 

 like back; underparts buffy-gray, the hairs gray at bases and yellowish 

 buff at tips; hands and feet dusky, the digits whitish. Vibrissae long, 

 reaching back to shoulders. 



Skull resembling in general shape that of Rattus dominator, but much 

 smaller; antorbital plate extending well forward, about as in R. norvegicus; 

 rostrum long, much longer than in norvegicus or rattus; supraorbital ridges 

 distinct over frontals, faintly indicated on parietals; auditory bullae small 

 and angular; palatal foramina reaching just back of anterior plane of first 

 molars; palate projecting only slightly beyond plane of posterior edge of 

 last molars. Pattern of molar teeth essentially as in Rattus norvegicus, but 

 m^ more elongated, the anterior column especially projecting far forward, 

 with small supplementary tubercle; and the crown length of m* more than 

 half the length of entire toothrow. Upper toothrows converging anteriorly; 

 spreading posteriorly; incisors narrow, opisthodont (less so than in R. 

 dominator) . 



Measurements. — Type: Head and body, 183; tail, 185; hind foot, 42; ear 

 from notch, dry, 18.6. Skull of type: Greatest length, 46.1; condylobasal 

 length, 41.3; palatal length, 25.0; zygomatic breadth, 22.6; interorbital 

 breadth, 6.5; mastoid breadth, 7.3; nasals, 18.4 x 5.0; antorbital notch to 

 end of premaxilla, 15.8; mandible, 26.6; upper toothrow, alveoli, 8.8; lower 

 toothrow, alveoli, 8.3; m^, crown, 4.6; m^-m', crowns, 4.4. 



Specimens examined. — Two from the type locality. 



Remarks. — This peculiar rat resembles externally some of the darker, 

 white- tailed members of the chrysocomus group. The characters of the 

 skull and teeth, however, show it to be not a member of that group. The 

 skull mostly resembles, in general characteristics, skulls of Rattus dominator, 

 but is much smaller. The pattern of the molar teeth differs considerably 

 from that of either dominator, celebensis, or marmosurus, and agrees well 

 with the pattern normal to Rattus norvegicus and its allies. Except for the 

 strictly norvegicus-like molar pattern and the projecting antorbital plate, 

 the skull resembles in no other character skulls of norvegicus, and it is easy 

 to believe that the relationship is not particularly close with the norvegicus 

 group. The general characters of the skull would seem to throw the species 

 in the composite "xanthurus" group, regardless of the external resemblance 



