466 RODENTIA 
Phenacomys—A North American genus distinguished by its 
rooted molars, and thus connecting the typical forms with 
Cricetines like Neotoma. Several species have been described by 
Dr. C. H. Merriam. 
Arvicola2—The type genus Arvicola has rootless molars, and 
naked soles to the feet. It includes over forty species inhabiting 
Europe, North America, and Asia, a few species entering into the 
northern limits of the Oriental region in India. Three species of 
the genus are found in the British Isles, of which the following 
account is given by Mr. O. Thomas :— 
The common Water-Vole (4. amphibius) is as large as the Brown 
Rat. Its fur is long, soft, and thick, of a uniform grizzled brown 
all over, except when, as is not uncommon, it is wholly black. The 
tail is about half the length of its head and body, and the hind feet 
are unusually long and powerful, although not webbed, and have 
five rounded pads on their lower surfaces. Its molar teeth (see 
Fig. 207) present the following number of prismatic spaces :—in 
the upper jaw the first, or anterior, has 5, the second 4, and the 
third 4, of which the last is very irregular in shape, and is 
sometimes itself divided into two, making 5 in all; in the lower 
jaw the first has 7 spaces, of which the 3 anterior are generally not 
fully separated from one another, the second has 5, and the third 
3. These numbers for the different teeth are taken as the 
characters of the subgenus Paludicola of Dr. Blasius, by whom this 
method of subdividing the genus was first introduced. The Water- 
Vole is one of the commonest English mammals, and is perhaps the 
most often actually seen of all, owing to its diurnal habits. It 
frequents rivers and streams, burrowing deeply into their banks, 
and in this way often causing considerable damage. Its food 
consists almost wholly of water-weeds, rushes, and other vegetable 
substances, but, like so many other Rodents, it will also occasionally 
eat animal food, in the shape of insects, mice, or young birds. 
The female during the warm season of the year has three or four 
litters, each of from two to seven young. The range of the 
Water-Vole extends over the whole of Europe and North Asia, 
from England to China, but it is not found in Ireland. The common 
Field-Vole, or short-tailed Field-Mouse (4. agrestis), representing 
the subgenus Agricola, is about the size of a House-Mouse, but 
with a short stumpy body, and a tail only about one third the 
length of the head and body combined. Its hind feet have six 
pads on their inferior surfaces. The colour is dull grizzled brown 
above, and grayish-white below. Its molar teeth have respectively 
5, 5, and 6 prismatic spaces above, and 9, 5, and 3 below. The 
1 Merriam, Fauna of North America, No. 2, p. 28 (1889). 
* Lacépéde, Mém. de ’Institut, vol. ili. p. 495 (1801). Many writers employ 
the earlier name Jicrotus for the true Voles. 
