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 Wateér-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 a,) pro- 
gressively decrease in size from the first to the last, as in 
the recent species. The molars of the lower jaw, (fig. 
76 6,) 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). 
