790 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XIV. 



Teeth. — The teeth of the type are somewhat worn, but they appear to be in 

 every way similar to those of Mus rattus. 



Measurements. — External measurements of type : Total length, 387 mm. ; 

 head and body, 202 ; tail, 185 ; hind foot, 35 ; ear from meatus, 19 ; ear from 

 crown, 14 ; width of ear, 15. 



Cranial measurements of type : Greatest length, 44 mm. ; basal length, 40 ; 

 basilar length, 38 ; palatal length, 22*6 ; least width of palate between anterior 

 molars, 4*6 ; diastema, 12*6 ; length of incisive foramen, 7'8 ; combined breadth 

 of incisive foramina, 4 ; length of nasals, 16 ; combined breadth of nasals, 4*6 ; 

 zygomatic breadth, 21*8 ; interorbital breadth, 6"4 ; breadth of braincase above 

 roots of zygomata, 16*2 ; mastoid breadth, 16*8 ; occipital depth at front of 

 basioccipital, 13 ; fronto-palatal depth at posterior extremity of nasals, 9*6 ; 

 least depth of rostrum immediately behind incisors, 7"6 ; mandible, 25 ; maxil- 

 lary toothrow (alveoli), 7*8 ; width of front upper molar, 2 ; mandibular 

 toothrow (alveoli), 6'8. 



Specimens examined. — One, the type. 



Remarks. — Mus pulliventer di&evs so conspicuously from its allies of the 31us 

 rattus group that it needs no special comparison with any of them. The flat- 

 tened skull and dark colour of the under parts are sharply diagnostic. 

 Mus ATRATUS, new species. 

 Type.— Adult female (skin and skull), U.S.N.M. No. 111868. Collected on 

 Barren Island, Andamans, 7th January 1901, by Dr. W. L. Abbott. Original 

 number, 818. 



Characters. — Size and proportions as in Mus andamanensis, but fur spineless. 

 Colour of under parts yellowish brown, back strongly suffused with black (often 

 entirely black). Skull shorter, broader, and more robust than that of Mus 

 andamanensis, the audital bullae smaller. Teeth as in Mus andamanensis and 

 3Ius rattus, but much larger. 



2?'«r. — The fur consists of the usual elements. The spines, however, are so 

 reduced in diameter as to appear like ordinary hairs unless examined with a 

 lens. 



Colour. — Upper parts almost exactly as in 3Ius flebilis and Mus andamanensis 

 except that the fur is strongly suffused with a slaty black like that of Mus 

 rattus. In two of the eight specimens the brown remains in excess of the 

 black, but in the other (including the type) the latter. predominates, nearly or 

 quite to the exclusion of the brown. Belly yellowish brown (rather paler and 

 less yellow than the ochraceoua buff of Eidgway) in the brown-backed speci- 

 mens, slaty in the others. Only one skin, however, lacks a distinct brownish 

 wash ever the slaty under parts. Feet sprinkled with whitish or slaty hairs. 

 Ears and tail uniform dark brown. 



Tail.— The tail is distinctly annulated. At middle there are about ten rings 

 to the centimetre. The boundaries of the scales are sharply defined, much 

 more so than in Mus sto/cus and Mus fleUUs. From the base of each scale grow 

 three hairs which in length are equal to the width of two rings. Though 

 better developed than in the larger Andaman rats, these hairs do not conceal 

 the annulation of the^tail. 



