DESCRIPTIONS OF NEW SPECIES OF MAMMaLS. 785 



Colour. — Back a coarse grizzle of black and dull ochraceous buflE (distinctly 

 darker than Ridgway's PL v, fig. 10), the latter element in excess. The effect 

 is similar to the general color of Mua validus, but considerably more yellow. 

 The longer hairs are strongly lustrous, so that in certain lights the fur has a 

 noticeable steely gloss. This sheen is very conspicuous at sides of shoulders 

 when the skin is viewed from in front. Sides like back but with buflE even 

 more predominant. Under parts and inner surface of limbs nearly uniform 

 mouse gray (paler than that of Ridgway), This colour is due to the combined 

 eflEecfc of the drab under fur and whitish hair tips. It extends entirely around 

 upper lip and spreads over cheeks, where, however, it becomes mixed with 

 ochraceous buff. Eye surrounded by a very faintly indicated dark ring. 

 Whiskers black. Ears and tail uniform dull dark brown throughout. Feet 

 sprinkled with fine whitish hairs, these nowhere abundant enough to conceal 

 the light brown skin. 



Tail.— Ths tail is rather inconspicuously annulated — ^that is, the bounda- 

 ries of the scales are less sharply defined than in most rats of the same size. 

 At middle there are about ten rings to the centimetre. At first sight the tail 

 appears to be naked, but on close inspection it is seen to be beset with fine 

 appressed hairs 1 to 2 mm, in length, two or three of which spring from the 

 base of each scale. 



MamriuB. — In the single adult female collected one pectoral and three 

 inguinal mamm^ are plainly visible on each side. The skin is in bad condi- 

 tion in the region which the anterior pair of pectoral mammas would occupy 

 if present. Ou the label Dr. Abbott has written " mammse apparently ten," 



Feet. — The feet show no peculiarities of form or structure. Soles naked, 

 with six well-developed tubercles. 



Ears. — The ears are moderately large, their height from crown exactly equal 

 to distance between eye and tip of muzzle. In form they are not peculiar. 

 Both surfaces are naked, except for a fine, close pubescence. 



Skull. — The skull of Mus sioicus differs conspicuously from that of 3Iua 

 validus, Mus vociferans, or Mus howersi in its much lighter structure and more 

 slender form. Viewed from above it does not differ widely from the skull of 

 3Ius vociferans, except that it is more narrow throughout, a difference more 

 noticeable in rostrum and braincase than in the zygomatic region. Supraorbital 

 ridges about as in Mus vociferans. The plate of the maxillary forming outer 

 wall of antorbital foramen is as broad as in Mus validus, but the foramen is 

 widely open below, as in 3Jus vociferans. These characters are very apparent 

 in this view of the skull. Viewed from the side the skull closely resembles 

 that of Mus vociferans, except for the peculiarities already mentioned Zygo- 

 mata much more slender than in the allied species. Viewed from beneath 

 the skull shows its most striking characters. The floor of the braincase is 

 essentially like that of 3Ius vociferans, though the audital buUas are distinctly 

 larger than in the mainland animal. In form the bullae do not differ very 

 materially from those of Mus vociferans, though they are somewhat more 



