EVOTOMYS 



647 



Diagnosis. — Size medium (hind foot about 18 mm. ; condylo- 

 basal length of skull, 25 mm.) ; tail noticeably less than half as 

 long as head and body, very densely haired, its pencil at least 

 one-quarter as long as vertebrae ; dorsal area clear bright chest- 

 nut, sharply but not conspicuously contrasted with colour of 

 sides. 



Colour. — Dorsal stripe a clear bright reddish brown approach- 

 ing the chestnut of Ridgway, faintly darkened by a slight 

 admixture of black-tipped hairs. Sides and face ochraceous-buff. 

 TJnderparts cream-colour or dull whitish, darkened by the slate- 

 grey bases of the hairs, which show through irregularly at 

 surface. Feet whitish. Ear concolor with dorsal stripe. Tail 

 sharply bicolor, brownish tinged with red above, dirty white below. 



Skull. — In general the skull resembles that of Evotomys 

 glareolus. Brain-case shorter and more squarish in outline when 

 viewed from above, its upper surface, together with that of 

 rather wide interorbital region somewhat flattened. Postorbital 

 processes obsolete. Palate and mesopterygoid space relatively 

 narrower than in E. glareolus ; posterior termination of palate 

 usually not an entire-edged shelf, since the lateral groove on each 

 side habitually opens freely into posterior nares, thus isolating 

 median portion of shelf from the outer extremities adjoining 

 alveoli. 



Teeth. — Molars relatively smaller and weaker than in Evotomys 

 glareolus. Enamel pattern essentially as in E. glareolus but 

 re-entrant angles tending to be deeper, those of the opposite 

 sides more conspicuously alternating, and salient angles more 

 acute, so that inner triangles of maxillary teeth 

 seldom if ever assume a circular outline. An- 

 terior outer re-entrant angle of m s fully as 

 deep as second, the anterior portion of the 

 tooth therefore never assuming the Alticola-like 

 aspect characteristic of that region in E. glareo- 

 lus ; inner side of m 3 always with three deep 

 sub-equal re-entrant angles. Second lower molar 

 nearly or quite divided into four alternating 

 closed triangles and a posterior closed loop ; no. 126. 



m 3 showing a decided tendency to assume a Evotomys rutaus. 

 similar form owing to the depth and distinct Enamel pattern, x 5. 

 alternation of its re-entrant angles. 



Measurements. — External measurements of an adult from 

 Karesuando, Sweden (from well-made skin) : head and body, 98 ; 

 tail, 23; pencil, 12; hind foot, 18. Adult from Lappmark, 

 Sweden (no exact locality) : hind foot, 17. For cranial measure- 

 ments see Table, p. 657. 



Specimens examined. — Seventeen, from the following localities :— 

 Nobway: Sydvaranger, 3 (U.S.N.M.) ; Porsanger, 2 (U.S.N.M.). 

 Sweden : Lapland, no exact locality, 7 (B.M. and U.S.N.M.) ; Tornea, 

 Lappmark, 3 (B.M. and U.S.N.M. ; Karesuando, Norbotten, 2 (U.S.N.M.). 



