﻿62 



NORTH AMERICAN FAUNA. 



[Xo. 12. 



Through Mr. True's kindness I have been able to examine one of the 

 alcoholic specimens on which Baird based this descrix^tion. This si^eci- 

 men (No. 2533, from Tomales Bay, Oal.^) is in good condition and shows 

 most of the peculiarities to which attejition was called. The thicken- 

 ing of the edge of the auricle is, however, due to disease or to the 

 action of the parasites which often attack the rims of the ears in the 

 voles and other small rodents. The anterior base of the ear is not essen- 

 tially different from the same region in Pitymys^ though the valvular 

 fold is slightly more developed. It is i^robable that by means of this 

 fold the meatus in FHymys^ as well as in most if not all of the voles^ 

 can be tightly closed. 



Subgenus MICROTUS Scliraiik. 



1798. Miowtus Schrauk, Fauna Boica, I, Isto Abth., p. 72, 1798. Type by elimination 



Microtus teyrestrls Schrauk = Mus arvalis Pall. 

 1817. Mynomes Rafinesqne, Am. Monthly Magazine, II, p. 45, 1817. Type Mynomes 



pratensis Raf. = Arvicola pennsylvanicus Orel. 

 1836. Herniotomy s DeSelys Lougchamps, Essai Monographique snr les Campagnols 



des environs de Liege, p. 7, 1836, part (included arvalis and terrestris). 

 1857. Hemiotomys Baird, Mamm. N. Am., p. 515, 1857. 



1849. Keodon Hodgson, Ann. and Mag. Nat. Hist., 2d ser., Ill, p. 203, 1849. Type 



JSfeodon silcMmensis Hodgson, 

 1857. Paludtcola Blasius, Fauna der Wirbelthiere Deutschlands, I, jj. 333, 1857, part 



(included terrestris, nivalis, and raiticeps). 

 1857. Agricola Blasius, Fauna der Wirbelthiere Deutschlands, I, p. 334, 1857. Type 



Arvicola agrestis. 



1867. Praticola Fatio, Les Campagnols du Bassin du Leman, p. 36, 1867, part (included 



terrestris, nivalis, arvalis, raiticeps, and campestris) . 

 1867. Sylvicola Fatio, Les Campagnols du Bassin du L6man, p. 63, 1867. Ty^iQ Arvi- 



Gola agrestis. 



1890. Campicola Schulze, Schriften Naturwiss. Vereins d. Harzes in AVernigerode, V, 

 p. 24, 1890, part (included arvalis, snMcrranens, and campestris). 



1894. Tetramerodon Rhoads, Proc. Acad. Nat. Sci. Phila., p. 282, 1894. Type Arvicola 

 tetramerus Rhoads. 



Geographic distrihution of type species. — Central Europe. 

 Geographic distribution of suhgemis. — Boreal region of both hemi- 

 spheres, south to Mexico, northern India, and southern Europe. 

 Essential characters : 



Palate normal. 



m 3 without closed triangles. 



m 1 normally with 5 closed triangles and 9 salient angles. 



m 3 normally with 3 closed triangles and 7 or 8 salient angles. 



Mammae, 8. 



Plantar tubercles, 6. 



Sole moderately hairy. 



Claws of hind feet longest. 



Fur not specially modified. 



Shdl. — In true Microtus (PI. I, fig. 3) the skull lacks the peculiar 

 modifications found in such subgenera as Lagurus, Fitymys, Chilotus, 



1 No. 2529 from Steilacoom, Wash., also mentioned by Baird, is lost. 



