ARA'ICOLA 739 



fossorial structure. Tliis is shown by the more pronounced 

 forward projection of the upper incisors, and more particularly 

 by the shortening and widening of the brain-case in general and 

 the slightly greater obliquity of the occipital region. Flattened 



Fig. 153. 

 Arvicola terre.stris. Nat. size. 



area between lateral ridges on brain-case tending to assume a 

 diamond-shaj)ed outline rather than that of an irregular paralello- 

 gram. Antero-posterior diameter of interparietal usually more 

 than half transverse diameter, the outer margins of the bone 

 almost squarely truncate. 



Teeth. — Except for their slightly smaller size the teeth 

 exactly resemble those of Arvieola ampMbius. 



Measurements. — Adult female from Holme, Mandal, Norway : 

 head and body, 167 ; tail, 94) ; hind foot, 29. Adult male from 

 Christiania, Norway : tail, 105 ; hind foot, 29. Adult from 

 Vefsen, Nordland, Norway : hind foot, 31 ; ear, 16. Adult 

 female from Jem tland, Sweden: head and body, 187; tail, 104; 

 hind foot, 30. Two adults from near Stockholm, Sweden : hind 

 foot (dry), 27 "6 and 29*4. For cranial measurements see Table, 

 p. 742. 



Specimens examined. — Thirty-eight, from the following localities : — 

 NoBWAY : — Vefsen, Nordlaud, 1 ; Elverum, Hedemarken, 1 (U.S.N.M.) ; 



Christiania, 1 (U.S.N.M.); Asker, Christiania, 1 (U.S.N.M.); Holme, 



Mandal, 15. 



Sweden :—Jemtland, 7; Upsala, 2 (B.M. and U.S.N.M.); Upland, 2 



3 B 2 



