64 THE MAMMALS, REPTILES, AND FISHES OF ESSEX.
cautious, and most difficult to trap. His country cousin
quickly takes warning after a few have been caught, and most
adroitly avoids all snares and gins in the future.
Dr. Bree has recorded (Field, Oct. 5th, 1872, p. 328) the
capture of two hairless Rats at Thorpe-le-Soken. They were
entirely without hair, except for their whiskers. He for-
warded the specimens to the Museum of the Royal College
of Surgeons.
Family ARVICOLIDAE.
Genus Arvicola, Lacep.
Arvicola amphibius, Desmar. Water Rat or Water Vole.
This little animal is common in all parts of Essex,
wherever there are sluggish streams, or where stagnant water
exists in sufficient quantity to hide it.
Bell, quoting G. R. Waterhouse, says : " The animals
comprising this family (Arvicolidae) have all the essential
characteristics of the Muridae, but differ in having rootless
molars and in the form of the lower jaw." There are other
characters given, but the rootless molars seem to be the great
and easily-distinguishing feature separating Muridae and
Arvicolidae.
It will be well to bear in mind that the common Water
Rat is sometimes quite black in colour, and has been
described by Macgillivray (Hist. of Brit. Quad., being
vol. xiii. of the Naturalists' Lib.) under the name of Arvicola
ater. This is, however, merely a variety. This form
has been occasionally mistaken for the old English Black
Rat (Mus rattus), and many of the supposed appearances
of the latter animal can thus be explained.
Its size and numbers considered, the Water Rat does less
damage than any other British member of the family. Its