702 



the underfur a dull, buffy wood-brown (2 mm.) at tip, the longer 

 hairs black, those of sides and rump with conspicuous buffy tips 

 or sub-terminal areas about 4 mm. in length. In both specimens 

 the long hairs are more conspicuous than in any other European 

 Microtus that I have examined. On sides the buffy wood-brown 

 is nearly clear and distinctly more yellow than the cream-buff of 

 Ridgway, but on back it is coarsely and conspicuously "lined" 

 with black, the general effect of the two colours approaching 

 olive or bister. Underparts yellowish cream-buff irregularly 

 clouded by the slaty bases of hairs. Feet a dull, light, brownish 

 buffy. Tail obscurely bicolor, pale 

 buffy below, dull brownish above. 



Skull. — The skull differs from that 

 of all other known European species 

 of Microtus in its very highly arched 

 brain-case, which gives the dorsal 

 profile a uniform convexity that is ex- 

 ceedingly characteristic. Interorbital 

 region, in the two skulls examined, 

 rather broad, with distinct median 

 longitudinal concavity and low but 

 evident lateral ridges.* Nasals 

 slightly tapering, their width pos- 

 teriorly about three-fourths that 

 anteriorly, their posterior termination 

 square, slightly exceeded by nasal 

 branch of premaxillary. In both of 

 the skulls examined the length of 

 nasal decidedly surpasses that of 

 diastema, a condition not observed 

 in other European species. Palatal foramina large, their width 

 relatively to that of rostrum greater than in 

 M. arvalis. Auditory bullae not peculiar, their 

 size relatively about as in M. arvalis. 



Teeth.— The teeth are strictly of the M. 

 arvalis type. Terminal loop of both m 3 and 

 m 1 shortened as compared with the other 

 European members of the arvalis group, so 

 that in the former the third inner re-entrant 

 angle is very shallow, and the extreme pos- 

 terior portion of the tooth is a nearly straight 

 loop, almost as wide as long, and evenly con- 

 stricted from both sides proximally, while in fio. mi. 

 the latter the outer re-entrant angle is prac- Mierotus cairerx. x 5. 

 tically absent, this peculiarity being carried 

 to a greater extreme than in M. sandayensis sandayensis, the 

 only other European Microtus in which it is known to occur 



* The ridges may eventually unite;, but the form of the interorbital 

 region in the young adult is different from that in any of the other 

 European species at the same stage. 



Fiq. 140. 

 Microtus cabreree. Nat. size. 



