PLEISTOCENE GEOLOGY OF THE THAMES VALLEY. 347 



Ursus arctos, Linn. 



,, ferox, Richd. 

 Bison bonasus var. priscus, Boj. 

 Bos taurus var. primigenius, Boj 

 Cervus elaphus, Linn. 



,, giganteus, Blum. 

 Capreolus caprea, Gray. 

 Elephas antiquus, Falc. 



,, primigenius, Blum. 

 Rhinoceros antiquitatis, Blum. 

 ,, leptorhinus, Owen. 



,, megarhinus, Christol. 



Sus scrofa, Linn. 

 Equus caballus, Linn. 

 Hippopotamus amphibius, Linn. 

 Mus sylvaticus, Linn. 

 Microtus agrestis, Linn. 



,, ratticeps, Bias. 



,, amphibius, Linn. 



,, (Evotomys) glareolus, Schreb. 

 Castor fiber, Linn. 

 Sorex vulgaris, Linn. 



(b.) Notes on the Species. 



Microtus agrestis. Among the Rodentian remains 

 obtained from the Orsett Road Section are three second upper 

 molars, several mandibular rami, including one in Mr. J. P. 

 Johnson's collection, and numerous detached teeth which are 

 referred to M. agrestis. The only constant dental character 

 which distinguishes the British Field-vole from the Continental 

 M. arvalis is the development of three inner angles in the second 

 upper cheek tooth of the former instead of two in the latter. 

 This accessory angle of M. agrestis is very small. In dealing 

 with detached teeth its possession also serves to distinguish 

 M. agrestis from M. ratticeps. The three teeth from Grays agree 

 with the British Field-vole in this respect and also in size. We, 

 therefore, have no hesitation in placing them with this species. 



With regard to the mandibular rami and the detached teeth 

 other than the second upper molar, the evidence is not so 

 positive. The former plainly belong, from the pattern of the 

 anterior molars, to either M. agrestis or M. arvalis, while some of 



