MICROTUS 659 



Characters. — -Bony palate terminating posteriorly in a sloping 

 median ridge and two lateral pits ; lower incisor with root 

 extending to outer side of molar-roots, rising high above level of 

 cutting surface of molars, and forming a noticeable protuberance 

 on outer surface of ascending portion of mandible at base of 

 articular process ; molars permanently rootless, growing con- 

 tinuously from a persistent pulp and not wearing away in old 

 age ; pattern of enamel folding characterized by acuteness of 

 salient angles ; mammae, 8 ; plantar tubercles, 6 ; neither fur, 

 external form, nor skull modified for aquatic or subterranean life. 



SemarJcs. — The genus Microtus as here understood, restricted 

 to the species with normal skull, palate and enamel folding, 

 8 mammae, 6 plantar tubercles, and no special modifications of 

 external form, is the largest and most widely distributed group 

 in the sub-family. About 100 species are now recognized, a 

 number which will be materially increased as the fauna of the 

 interior of Asia becomes better known. Fifteen species are here 

 recognized as occurring in western Europe. Among them are 

 represented two sub-genera. 



Sub-Genus MICROTUS Schrank. 



1798. Microtus Schrank, Fauna Boioa, i, p. 72 (Microtus terrestris Schrank 



= Mus arvalis Pallas). 

 1817. Mynomes Rafinesque, Amer. Monthly Magazine, n, p. 45 (Mynomes 



pratensis Rafinesque = Arvicola permsylvanicus Ord). 

 1836. Semiotomys de Selys-Longchamps, Essai monographique sur les 



Campagnols des environs de Liege, p. 7. Part (arvalis and 



1857. Paludicola Blasius, Saugethiere Deutschlands, p. 333. Part (amphi- 



bius = scherman, nivalis and ratticeps). Not of Wagler, 1830. 

 1857. Agricola Blasius, Saugethiere Deutschlands, p. 334 (agrestis). 

 1867. Praticola Patio, Les Campagnols du Bassin du Leman, p. 34 



(included amphibius = scherman, nivalis, arvalis, ratticeps and 



campestris = agrestis). Not of Swainson, 1837. 

 1867. Sylvicola Patio, Les Campagnols du Bassin du Leman, p. 63 



(agrestis). Not of Harris, 1782. 

 1883. Microtus Lataste, Le Naturaliste, n, p. 348. 

 1890. Gampicola Schulze, Schriften Naturwiss. Viereins d. Harzes in 



Wernigerode, v, p. 24. Part (arvalis, subterraneus and campestris 



= agrestis). 

 1894. Tetramerodon Rhoads, Proc. Acad. Nat. Sci., Philadelphia, p. 282 



(Arvicola tetramerus Rhoads). 

 1896. Microtus Miller, North American Fauna, No. 12, p. 62, July 23, 1896. 

 1899. Euarvicola Acloque, Faune de France, Mammiferes, p. 49 (agrestis). 



Type species. — Microtus terrestris Schrank = Mus arvalis 

 Pallas. 



Geographical distribution. — Northern portions of both hemi- 

 spheres, south in America to southern Mexico, and in the Old 

 World to Portugal, central Spain, the Mediterranean coast of 



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