474 



MURID^— MIMOMYS 



pliocene Forest Bed of Norfolk. Both M. plioccsnicus and 

 intermedius have since been recorded from the Pliocene of 

 Tegelen-sur-Meuse, Belgium (Newton, Bull. Soc. Beige GM., 

 Mdm. Pal., 21, 592-6, 1908; 24, 231, 1910), and of Gorkum, 

 Holland (Rlitten, Diluviale Sdugethiere Niederlande, 1909-10, 

 88) ; but Hinton believes that the specimens from Tegelen 

 referred to M. intermedius, really belong to M. newtoni, or 

 a near ally. 



The genus is of peculiar interest, since it appears to 

 represent the ancestral stock of modern Arvicola. Its members 



Fig. 78. — Cheek-Teeth of Mimomys : (i) left m^ of Mimomys pliocanicus (crown view), from 

 the pliocene Norwich Crag of England ; (2) right m-^ of M. intermedim (crown view), 

 from pliocene Upper Freshwater Bed of Cromer, Norfolk ; (la and 2a), external views of 

 same ; 2a is reversed to facilitate the comparison with la ; 8 times life size. (Drawn by 

 M. A. C. Hinton.) 



are amongst the earliest microtines found in Britain, having 

 been detected in the late pliocene Norwich Crag. 



Judging from the jaws and teeth, some species (J/, newtoni) 

 agreed in size with medium-sized Microtus, others i^M. inter- 

 medius) with lemmings. The general pattern of the cheek-teeth 

 resembles that of Arvicola, but, instead of growing persistently 

 as in the latter, they are provided with roots when adult. In 

 M. plioccsnicus, m^ has in young stages of wear a third outer 

 infold or valley formed in the way normal in cheek- 



