476 MURIDAZ—ARVICOLA 
teeth of this form resemble those of JZ. zxtermedzus in pattern, 
but their roots are developed only in senile stages of growth. 
Remains of still other species of M/zmomys are known from the 
late Pliocene deposits, but these have not yet been satisfactorily 
defined. | 
GENUS ARVICOLA. 
1799. ARVICOLA, Lacépéde, Tad. des Mammiferes, 10, based on amphibius ; Lataste, 
Le Naturaliste, October 1883, 349 (sub-genus) ; Miller, VW. Amer. Fauna, No. 12, 
66, 23rd July 1896 (sub-genus) ; Miller, daz. and Mag. Nat. Hist., February 1908, 
195 (genus). 
1836. HEMIOTOMYS (sub-genus), E. de Sélys-Longchamps, Hssaz Monographique sur 
les Campagnols des environs de Liége, 7 (part), based on Arvicola (=Microtus) 
fulvus = M. arvalis and A. terrestris = amphibius. 
1857. PALUDICOLA (sub-genus), J. H. Blasius, Saugethiere Deutschlands, i., 333 
(part); based on amphibius = scherman, nivalis, and ratticeps; preoccupied by 
Paludicola of Wagler, 1830, a genus of amphibians. 
1867. OCHETOMYS, L. J. Fitzinger, Sztzungsb. k. Akad. Wiss. (Wien), lvi., June, 
103; based on the Water Rats of Europe. 
1867. PRATICOLA, Victor Fatio, Les Campagnols du Bassin du Leman, 36 (part) ; 
based on amphibius = scherman, nivalis, arvalis, ratticepbs, and campestris 
(=arvalis) ; preoccupied by Praticola of Swainsson, 1837, a genus of birds, 
Synonymy :—The full synonymy is given in Miller’s Catalogue. 
The name Avvico/a was for a time used to designate a large 
genus, including the bulk of the A/zcrotz. It is antedated in 
that sense by zcrotus, but proves to be available for the 
Water Rats. 
Although it is convenient to treat the Water Rats as a 
genus, they are not very sharply differentiated from the Grass 
Mice (J/zcrotus), from which they differ mainly in their larger 
size; relatively longer tails ; in possessing lateral musk-glands ; 
normally five, instead of six, plantar pads; and m* with 3+3 
salient angles and 2+ 2 infolds, as in Chzonomys. Many of the 
species are aquatic; but others are more or less subterranean. 
The fur is long and suitable for commercial purposes, but, doubt- 
less owing to the small size of the animals, is not widely used. 
Distribution:—The Water Rats have a wide range in the 
Palearctic Region, north of the Himalayas, from Norway (to 
the outermost Skerries) and Wales, at least to the river Amoor 
(Schrenck), and from the Norwegian shores of the Arctic 
Ocean with corresponding zones in Siberia to the Mediterranean 
coasts of Spain and France, Central Italy, Bosnia, Rumania, 
