474 MURIDAX—MIMOMYS 
pliocene Forest Bed of Norfolk. Both JZ. plzocenicus and 
zntermedtus have since been recorded from the Pliocene of 
Tegelen-sur-Meuse, Belgium (Newton, Bud? Soc. Belge Géol., 
Mém. Pat., 21, 592-6, 1908; 24, 231, 1910), and of Gorkum, 
Holland (Riitten, Dz/wzale Stugethiere Nrederlande, 1909-10, 
88); but Hinton believes that the specimens from Tegelen 
referred to J/. zntermedius, really belong to MZ. newtont, or 
a near ally. 
The genus is of peculiar interest, since it appears to 
represent the ancestral stock of modern Avvicola. Its members 

(1a) (22) 
Fic. 78.—CHEEK-TEETH OF Mimomys: (1) left 7, of Mimomys pliocenicus (crown view), from 
the pliocene Norwich Crag of England; (2) right 7, of d/. intermedius (crown view), 
from pliocene Upper Freshwater Bed of Cromer, Norfolk ; (t@ and 2a), external views of 
same; 2a is reversed to facilitate the comparison with 1a; 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 (JZ. xewtonz) 
agreed in size with medium-sized Accrotus, others (JZ. inter- 
medius) with lemmings. The general pattern of the cheek-teeth 
resembles that of Avwvco/a, but, instead of growing persistently 
as in the latter, they are provided with roots when adult. In 
M. plrocenicus, m, has in young stages of wear a third outer 
infold or valley formed in the way normal in cheek- 
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