348 PLEISTOCENE GEOLOGY OH THE THAMES VALLEV. 



the upper teeth may also represent M. ratticeps. Yet seeing that 

 M. arvalis is unknown at present from Grays by any indubitable 

 specimen, and that M. ratticeps is very rare at this locality, we 

 feel justified in referring these remains provisionally at all events 

 to M. agrestis. The species has not previously been positively 

 recorded from the Pleistocene of the Thames Valley. It is 

 known, however, from other Pleistocene deposits. 



Microtus ratticeps. We have in our collection from 

 Grays three specimens of the third upper molar of a small vole. 

 They present four well developed external angles such as 

 characterize the corresponding tooth in the figure of the denti- 

 tion of the typical M. ratticeps given by Prof. Blasius (II., 

 p. 366, fig. 201). Although this tooth is variable in M. ratticeps, 

 sometimes agreeing with M. afvalis and M . agrestis in having only 

 three external angles, still we know of no vole whose variations 

 agree in this respect with the typical form M. ratticeps. We, 

 therefore, have little doubt of the correctness of referring these 

 specimens to this form, and it is to be hoped that the still 

 more characteristic anterior lower molar will be found at Grays. 

 The species is known from the Pleistocene of Crayford and 

 Erith and from other strata of a similar age. 



Microtus amphibius. The remains referred to M. 

 amphihius from the Orsett Road Section include a left ramus 

 with the anterior and second molars and numerous detached 

 teetlL They all agree with recent examples in the pattern of 

 the crowns. In size, however, they diflfer ; nearly all the 

 examples that we have obtained from Grays are small, approach- 

 ing M. intermedins in this respect, but as none of the teeth are 

 fanged it is clear that they represent a local and small race of 

 M. amphihius. 



The Water-vole has long been known from the deposits 

 of Grays and other places in the Thames Valley, and has 

 likewise been obtained from many other Pleistocene beds. It is 

 somewhat doubtful whether it occurs in the Norfolk Forest 

 Bed. 



Microtus (Evotomys) glareolus. A first upper cheek 

 tooth of the left side from the Orsett Road Section, in our 

 possession, agrees with the corresponding teeth of recent 

 examples of the Bank- vole in pattern, size, and the possession of 



