( 599 ) 



This rat is a very peculiar one, and I have considerable doubt whether it 

 ought to be in\t in Mi/s at all, but in the absence of marked differential characters 

 of generic importance I do not think it advisable to form a geuus for it at 

 present. 



3. Mus colletti spec. nov. 



A dark-coloured spinous rat, with 3 — 3 = 12 mammae. 



Size medium. Fur of medium length, ordinary hairs of back about 12 mm. 

 in length, liberally mixed on the rump with longer piles attaining 30 mm., and 

 also, to a very variable extent, with flattened spines, about 12 mm. long and 

 ^ mm. in breadth. General colour above heavily lined grizzled greyish brown, 

 not unlike that of Mus sordidus, Gould, the spinous hairs and the long jjiles 

 broadly tipped with black, the others with creamy buiF, the latter colour becoming 

 rather more dominant on the sides. Undersurface jiale soiled buffy, not sharply 

 defined, the slaty bases of the hairs showing through. Face dark grizzled 

 grey, like back. Ears of medium size, almost naked, brown, their extreme 

 edges lighter. Outer side of arms and legs like back, inner sides like belly ; 

 ujiper surface of hands and feet dull whitish or brownish white. Tail rather 

 shorter than head and body, prominently scaled (12 rings to the .centimetre), 

 well haired, the hairs averaging about 2 scales in length proximally, shorter and 

 less numerous terminally; uniformly black. Mammae, 3 — 3=12. 



Skull not unlike that of 2J. sordidus in general shape, though smaller ; the 

 interorbital region similarly narrow, its edges margined by a well-marked bead 

 running back to the outer corners of the interparietal. Zygomatic plate broad, 

 convex above. Palatal foramina long, narrow, reaching back to the anterior 

 lamina of m'. Bullae fairly large. 



Dimensions of the ti/pe, measured in skin : — 



Head and body, 136 mm. ; tail, lOT ; hindfoot, 29 ; ear, 16. 



Skull, basilar length, 31 mm.; zygomatic breadth, 18-5 ; nasals, length, 12'5; 

 interorbital breadth, 4'7 ; braiucase, breadth, 14'0 ; zygomatic plate, 4-2 ; palate, 

 length, 17-3; diastema, 10; palatal foramina, 7'3x2; length of upper molar 

 series (worn down), 6"3 ; of another specimen, 6'6. 



llab. S. Alligator Kiver, Northern Territory, Australia. 



Tijpe : ikVioXA female. B. M. No. 4. 4. 4. 4. Original number, 1838. Collected 

 August 30th, 1903, by Mr. J. T. Tunuey; presented to the British Museum by the 

 Hon. Walter Rothschild. 



" Dug out of hole in open clay flats." 



Twenty-five sjjecimens examined. 



This rat is perhaps a tropical representative of Mus sordidus, which it 

 resembles in its dark colour and general characters ; but it is smaller than 

 that species, and far more harshly clothed, M. sordidus being quite a soft-furred 

 animal. Correlated with the harshness of the fur the strong lining of the back 

 is unusually conspicuous, almost resembling in this respect the members of the 

 genus Sigmodon. 



I have named this species in honour of my friend Dr. llobert Collctt, of 

 Christiania, the author of the chief paper on the mammals of the region in 

 which it occurs.* 



* P. Z. S. 1897, p. 317. 



