﻿July, 1S96.] 



HISTORY OF CLASSIFICATIONS. 



21 



The groups Semiotomys, Microtus, and Arvicola of De Selys Long- 

 chaiiips are exactly equivalent respectively to tbe subgenera Arvicola^ 

 Pitymys^ aud Microtus of the i:>resent paper, while Myodes is the same 

 as the genus Evotomys. The group Mynomes based ou Eafinesque's 

 description of Mynomes ^pratensis {= Microtus pennsylvaniciis) should be 

 united with Arvicola {Microtus^ as now understood), a course which the 

 author no doubt would have followed had he been acquainted with the 

 type si)ecies. 



Blasius published in 1857, in his 'Fauna der Wirbelthiere Deutsche 

 lands,' a classification of the voles based primarily on the pattern of 

 enamel folding in the first and second molars of the lower jaw and the 

 second molar of the upper jaw. This system differs in many ways from 

 that of De Selys Longchamps, and is as follows: 



Genus Arvicola: 



Subgenus Hiiimda'us (fjlareoliis). 



Subgenus Paludicola {(inn)hiMus l—terrestrisi, nivaJi-s, raiticejys) 

 Subgenus Agricola {agrestls). , 

 Subgenus Arvicola : 



A. Arvicola (campestris, arvalis). 



B. ARcrotus De Selys part (suhterranens, savii). 



The subgenus Arvicola Blasius subdivides into two sections, A. 

 Arvicola and B. Microtus De Selys (part). The former includes tbe 

 species campestris and arvalis, the latter suhterranens and savii. The 

 subgenus Hyjpudwus and the section ALicrotus are equivalent, respec- 

 tively, to the genus Evotomys and the subgenus Fitymys of the present 

 paper. Of the other groups, the restricted Arvicola contains the typical 

 species of the subgenus Microtus^ Agricola, a slightly aberrant form of 

 the same, and Faludicola, the subgenus Arvicola and two aberrant 

 members of the subgenus Microtus. Blasius's subgenera Paludicola and 

 Arvicola are excellent illustrations of the unnatural results of a system 

 of classification based on one set of characters. While there is a general 

 similarity between the enamel pattern of the three species associated in 

 the former, Microtus terrestris differs from J/, ratticeps and M. nivalis 

 in the form of the skull, the number of plantar tubercles, the quality of 

 the fur, and in the presence ot large musk glands on the sides. In the 

 subgenus Arvicola Blasius associates two of the most distinct subgenera 

 of the genus Microtus {Microtus and Pitymys), and treats the differences 

 in the number of mamnii^ and footpads, form of skull, and size of eyes 

 as matters of trifling importance in comparison with the general simi- 

 larity of the enamel pattern. On the other hand, the author recognizes 

 Agricola as a full subgenus, when the chief character on which the group 

 is based is the presence of a minute sux^plemental postero-internal prism 

 on the middle upper molar. 



The classification adopted by Baird (Mamm. Am., 1857) is based 

 on a combination of characters, and is thus much more satisfactory 

 than the artificial arrangement published almost simultaneously by 



