344 MICROTINiE 



Fur soft, dense, and moderately long; hairs of back, in a 

 specimen collected in May, about 12 mm. in length. General 

 colour above greyish-brown, below greyish-white, the dorsal 

 and ventral colours merging insensibly on flanks. Hair bases 

 slaty everywhere, irregularly and considerably darkening the 

 under surface. Tail clothed with short stiff hairs, which do 

 not completely conceal the scaly annulations ; provided with a 

 short, stiff and thin pencil, 5-6 mm. in length ; bicoloured, dark 

 brown above, white on sides, below, and (in the single adult 

 specimen examined) at the tip. Feet white. 



Young pelage. — The young male, upon which the species was 

 based, differs from the adult described above in its greyer or 

 bluer general colour. 



Skull (Fig. 96) large, strongly built, long and narrow ; gently 

 convex above from before backwards, the highest point in the 

 mid-parietal region. Occiput vertical. Rostrum rather long 

 and of moderate breadth. Nasals normal, ending flush with 

 incisors in front, and, with the premaxillaries, about opposite 

 the middle of the superior maxillary root of the zygoma behind. 

 Temporal ridges fusing anteriorly in old age to form a weak 

 but linear sagittal crest in the interorbital region; moderately 

 approximated posteriorly and compressing the rather large inter- 

 parietal. Interorbital region considerably constricted. Post- 

 orbital squamosal crests well developed; anterior squamosal 

 encroachment well marked in adult, and the interstephanic 

 portion of the frontals conspicuously narrowed. Upper border 

 of jugal boldly convex. Infraorbital canal and its outer wall 

 normal; no superior preorbital zygomatic notch. Alveolar 

 portion of maxilla shallow, the molar capsules not rising up 

 conspicuously in the floor of the orbit, nor obstructing the sphen- 

 orbital fissure. Anterior palatal foramina moderately large. 

 Palate slightly abnormal behind; the posterior median sloping 

 septum very broad, flat, and ill defined; postero-lateral pita 

 very shallow. Pterygoid fossae of normal depth; ectopterygoid 

 plates moderately developed. Mesopterygoid fossa rather wide 

 and shallow, reaching forwards to middle of m^. Presphenoid 

 and basisphenoid not strikingly compressed. Auditory bullae 

 large, conspicuously inflated, with very thin and papery walls; 

 middle ear without any trace of spongy bone ; mastoid portion 

 slightly inflated; tegmen tympani articulating by squamous 

 contact with alisphenoid. Stapedial artery enclosed in a bony 

 tube as it approaches stapes; but apparently naked during its 

 passage through the stapes. 



Mandible normal, with long, slender corouoid and angular 

 processes ; horizontal ramus rather slender, not so deep as in 

 most voles towards the symphysis. Alveolus of lower incisor 

 terminates at the posterior base of the condylar process immedi- 

 ately below the dental foramen; it passes from the hngual to 

 the labial side of the jaw below m^ without disturbing this 



