660 



EODENTIA 



Prance, northern Italy, the central portion of the Balkan Penin- 

 sula, Asia Minor and northern India. 



Diagnosis. — Principal characters as in the genus ; third upper 

 molar with three re-entrant angles on inner side ; skull with 

 brain-case narrow and high, or broader and more flattened, its 

 surface ridged and angular ; interorbital region narrow, the 

 temporal ridges- well developed ; elements of posterior edge of 

 palate well defined. 



Remarks. — The subgenus Microtus contains most of the 

 members of the genus. Twelve species are now known to occur 

 in western Europe. 



KEY TO EUROPEAN POEMS OF THE SUB-GENUS MICROTUS. 



Second upper molar with two closed triangles on 



inner side M. agrestis, p. 662. 



Condylobasal length of skull in largest individuals 

 27 to 28-4 mm. 

 First upper molar with third inner triangle 

 usually present; underparts heavily washed 



with wood-brown (Hebrides) M. a. exsul, p. 669. 



First upper molar with third inner triangle 

 usually absent ; underparts slightly or not 

 washed, with wood-brown. 

 Brain-case relatively long, the distance from 

 condyle to back of interorbital constric- 

 tion, decidedly greater than zygomatic 

 breadth (Alps and their immediate 

 neighbourhood; marshes near mouth 



of Rhone) M. a,, levernedii, p. 671. 



Brain-case relatively short, the distance from 

 condyle to back of interorbital constric- 

 tion about equal to zygomatic breadth 



(Scandinavia) M. a. agrestis, p. 668. 



Condylobasal length of skull in largest individuals 



24-6 to 26-6 mm. 



Auditory bulla small and flattened, its greatest 



diameter (from paroccipital process to tip 



of anterior spine) contained about 3J times 



in condylobasal length of skull (Portugal 



and north-western Spain) M. a. rozianus, p. 680. 



Auditory bulla large and inflated, its greatest 

 diameter contained about 3 times in condy- 

 lobasal length of skull. 

 Condylobasal length of skull in largest indi- 

 viduals 25 to 26 mm. (England and 



southern Scotland) M. u. hirtns, p. 673. 



Condylobasal length of skull in largest indi- 

 viduals 25 '4 to 26 '6 mm. 

 General colour of upper parts darker, 

 usually with decided tinge of russet 



(Northern and central Scotland) M. a. neglectus, p. 675. 



General colour of upper parts lighter, 



usually with no decided tinge of russet 



(West-central Continental Europe).... M. a. bailloni, p. 672. 



Second upper molar with one closed triangle on 



inner side. 



First lower molar with three re-entrant angles 



on outer side M. ratticejps, p. 708. 



