64 



MICROTIN^ 



genus in the subfamily, comprising a very large number of recent 

 and fossil forms and ranging over most of the Palsearctic and 



Fig. 37. — Microtus orcadensis sandayensis Miller. 



Dorsal, ventral, and lateral views of skull, enlarged ; the small figure 

 shows the skull in dorsal view, natural size. 



Nearctic regions. The oldest known remains are those found 

 in the later Pliocene (Cromerian Beds) of Britain; but these 



