466 RODENTIA 



Phenacomys. 1 — 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. 



Arvicola. 2 — 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. 0. Thomas : — 



The common Water- Vole (A. 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 (A. 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). 



2 Lacepede, Mem. dc Flnstitut, vol. iii. p. 495 (1801). Many writers employ 

 the earlier name Microtus for the true Voles. 



