216 MICROTIN^ 



subspecies), E. brevicaudus, E. carolinensis, and E. idahoensis 

 appear to represent the Old World glareolus group ; E. caurinus, 

 E. dawsoni, E. orca, E. ungava, E. mazama, E. ohscurus, E. occi- 

 dentahs and E. nivarius are, judging from the descriptions, 

 possibly more or less modified members of the rutilus group ; 

 while E. phceus and E. wrangeli appear to represent the nageri 

 group. E. rufocanus does not seem to have any American 

 equivalent unless indeed E. mazama, and E. californicus can be 

 regarded as dwarfed representatives; possibly too E. jnoteus 

 may belong to the same group. 



A. — glareolus group. 

 tEvotomys, sp. 



1882. Arvicola (Evotomys) glareolus Newton Vert. Forest Bed, p. 82, 



PI. XIV, figs. 1-lc. 

 1900. Microtus (Evotomys) glareolus Hinton and Kennard, Essex 



Nat., 11, p. 348. 

 1910. Evotomys sp. Hinton, Proc. Geol. Assoc, 21, p. 497. 



Remains of a small species of Evotomys occur in the Cromerian 

 Upper Freshwater Bed at West Runtou, Norfolk, in the High 

 Terrace deposits of the Thames at Ingress Vale, near Greenhithe, 

 Kent, and in the early Middle Terrace deposits of the Thames 

 at Grays Thurrock, Essex. 



Apart from one or two fragmentary mandibular rami from 

 West Runton the material available from the deposits mentioned 

 consists merely of a considerable number of isolated cheek- 

 teeth. In enamel pattern and rooting these are exactly like those 

 of E. glarelous; but they are perhaps a trifle smaller and tl^ 

 infolds contain rather less cement than in the recent species. 

 Pending the discovery of more complete remains it is not possible 

 to define this early member of the E. glareolus group with precision. 



1. tEvotomys harrisoni sp. n. 

 1910. Evotomys sp. Hinton, Proc. Geol. Assoc, 21, p. 494 (second or 



smaller species of the Ightham Fissures). 

 1914. Evotomys glareolus Barrett-Hamilton, History of British 



Mammals, 2, p. 421. 



Ttjpe. — An adult skull, lacking the interparietal, jugals and 

 right auditory bulla, but otherwise perfect; collected by Dr. 

 Frank Corner. 



Type locality and horizon.- — -Fissure deposit of Ightham, near 

 Sevenoaks, Kent, England. Late Pleistocene. 



Range in time and space. — Probably widely distributed in the 

 late Pleistocene deposits of Britain ; but remains sufficiently 

 perfect to admit of precise determination have hitherto been 

 found only at Ightham. 



Characters.— &ku.\l somewhat smaller (condylo-basal length, 

 in old age, 22-8 mm.) than in equal-aged E. glareolus britannicus, 



