72 Proceedings of the Biological Society of Washington. 



orbital breadth, 6.7; mastoid breadth, 16.8; mandible, 24.0; maxillary 

 tooth row (alveoli), 7.7; mandibular tooth row (alveoli), 7.2. 



Specimens examined. — Twenty-three from the type locality and 2 from 

 Toware, Bada. 



Remarks. — These specimens have been compared with about 150 skins 

 and skulls of RaUH.s chrysocomiis (including for the present Mus fratroruin 

 Thomas) from numerous localities in North Celebes. The specimens of 

 chrysocomus vary considerably in size but average larger than examples of 

 the new form from Middle Celebes, with much more distinctly yellowish 

 flecking. The northern species always has the terminal portion and the 

 whole underside of the tail whitish. The color of the upperparts in some 

 specimens of adspersus approaches very closely to that of the type specimen 

 of Rattus andrewsi (Allen) from Pulo Boeton, off the coast of southeastern 

 Celebes, which proves to be a member of the chrysocomus group. 



Rattus nigellus, sp. nov. 



Type from Bumbaroedjaba (near Toboli), northern Middle Celebes. 

 No. 218,140, U. S. National Museum; skin and skull of adult cf (teeth 

 moderately worn); collected November 8, 1916, by H. C. Raven; original 

 number 2936. 



Diagnosis. — A small, dark member of the chrysocomus group with long, 

 soft pelage. Flanks as dark as back, median area of underparts cinnamon 

 drab. Flecking of upperparts brown, not yellowish ; wrist and heel blackish ; 

 toes whitish. Tail short, almost entirely blackish, with only a slight 

 indication in a few specimens of light color on underside. Skull smaller 

 than that of Rattus adspersus. 



Measurements. — Type: Head and body, 160; tail, 131; hind foot, 34. 

 Skull of type: Condylobasal length, 35.8; zygomatic breadth, 17.5; inter- 

 orbital breadth, 6.3; mastoid breadth, 15.5; mandible, 21.6; maxillary 

 tooth row (alveoli), 6.5; mandibular tooth row (alveoli), 6.6. 



Specimens examined. — Twelve, all from northern Middle Celebes, on 

 east side of neck of land connecting Middle Celebes with North Celebes: 

 Bumbaroedjaba, 11; Laboea Sore, 1. 



Remarks. — This small species is related to R. adspersus rather than to 

 R. chrysocomus of North Celebes. It is easily distinguished from adspersus 

 by its lesser external measurements; longer, softer pelage; and small skull. 



Rattus penitus, sp. nov. 



Type from Goenoeng Lehio (southwest from Lake Lindoe), Middle 

 Celebes; above 6,000 feet altitude. No. 218,686, U. S. National Museum; 

 skin and skull of adult cf (teeth moderately worn); collected January 21, 

 1917, by H. C. Raven; original number 3109. 



Diagnosis. — A mountain member of the chrysocomus group with long, 

 soft, cinnamon-flecked fur; sides dark like upperparts; belly grayish buff'; 

 feet scantily haired with grayish or whitish, toes whiter. Entire underside 

 and terminal third of tail above, whitish. Skull with extraordinarily 

 enlarged rostrum, which is thickened throughout, and only very slightly 



