1888.] 



MAMMALS OF CHRISTMAS ISLAND. 



533 



closely with one another and with the type, the only point in which 

 they vary being in the degree in which the under surface is white 

 or brown. All the females have the mammary formula 1 — 1 =4. 



4. MUS NATIVITATIS, Sp. n. 



Skull. — Basal length 46'8, greatest breadth 24'8 ; nasals, length 

 20*5; iuterorbitalbreadth 8'7; interparietal, length 7" 1, breadth 12*5; 

 infraorbital foramina — length of outer wall 4"1, breadth from outer 

 corner of one to that of the other, 13'4 ; palate — length 26*7, 

 breadth outside ra.' 9"0, inside m.^ 4'5 ; diastema 15'5; length of 

 anterior palatine foramina 9"3 ; length of upper molar series 7'6, 

 Lower jaw — length (bone only) 30, (to incisor-tips) 34'6, greatest 

 height, obliquely, from coronoid to angle, 15. 



Size large ; form thick and clumsy, the limbs and tail stout and 

 heavy, but the head peculiarly small, slender and delicate. General 

 colour dark umber-brown all over, the belly not, or scarcely, lighter 

 than the back. Ears small, laid forward they barely reach to the 

 posterior canthus of the eye. Fur of back long, thick, and coarse, 

 but without the extremely long piles so characteristic of M. macleari, 

 the longest hairs being about 40 or 45 millim. in length. Hands 

 and feet very thick and heavy ; the claws, especially on the fore feet, 

 enormously broad and strong, not compressed, more than twice the 

 size of those of M. macleari, and evidently modified for burrowing. 

 Palms and soles naked, smooth ; the pads broad, low, and rounded, 

 unusually little prominent ; last hind foot-pad elongate. Tail 

 shorter than the body without the head, very thick, evenly tapering, 

 nearly or quite naked ; its scales triangular, very large, the rings 

 averaging about 7 or 8 to the centimetre'; its colour uniform blackish 

 brown througiiout, above and below, the white skin, however, 

 showing to a certain extent between the scales. 



Skull disproportionally small, light and delicate; compared with that 

 of M. macleari it is slightly shorter and very considerably narrower. 



^ 10 to 12 in M. macleari. 



