ARVICOLA AGRESTIS. 205 



and maxillary characters of which, the fossils of both Kirk- 

 dale and Kent's Hole closely agree. The upper incisors 

 have a slightly convex and entire anterior enamelled sur- 

 face, which in the fossils has lost the deep yellow colour that 

 characterises the enamel in the recent Water-vole. The first 

 molar consists of five triangular prisms, one anterior, two 

 on the outer, and two on the inner side, alternately dis- 

 posed ; the second molar has four triangular prisms, as has 

 also the third molar; and these teeth, (fig. 76 #,) pro- 

 gressively decrease in size from the first to the last, as in 

 the recent species. The molars of the lower jaw, (fig. 

 76 &,) present the same close correspondence with those in 

 the recent Water-vole. 



Remains of the Arvicola amphibia have been found in 

 newer pliocene deposits, associated with those of the usual 

 extinct Mammalia, as at Erith and Stutton, at Crayford, 

 Kent, and at Grays in Essex. They are very abundant in 

 the lacustrine deposits, and the fluvio-marine crag along the 

 Suffolk and Norfolk coasts. It is only from some of the 

 older tertiary deposits in these parts, that I have noticed 

 any well-marked indications of a species of Arvicola dis- 

 tinct from any now known to inhabit Britain. The re- 

 mains to which I refer were portions of upper and lower 

 jaws, discovered in the older pliocene crag near Norwich, 

 from which molars of Mastodon angustidens have been ob- 

 tained ; they indicated a species of Arvicola intermediate 

 in size between the Water-vole (Arvicola amphibia,) and 

 the Field-vole (Arvicola arvalis). 



