94 W. T. Blanford— On the Voles (Arvicola) of tie [No. 2, 



guished by having on the upper molar two well-marked external and two 

 equally strong internal angles on the front part of the tooth, and a third 

 rounded external angle on the posterior lobe ; whilst in A. roylei and 

 A. blanfordi there is a nearer approach to the structure of A. stoliczkanus, 

 but there are three internal angles on the last upper molar. 



A. sikimensis and A. melanogaster differ from the other Himalayan 

 forms, firstly by having a longer first lower molar with, normally, 9 spaces, 

 though there are fewer in A. melanogaster, owing to some of the angles 

 on opposite sides corresponding ; secondly, in both the first and second 

 upper molars having an additional internal angle posteriorly. In the 

 characters of the first lower and second upper molars, A. sikimensis agrees 

 with the European A. agrestis, the type of the subgenus Agricola of 

 Blasius, and the second upper molar is similar to that in the American 

 subgenus Myonomes of Coues (type A. riparius), of which the first lower 

 molar has but 7 prismatic spaces ; but the first upper molar in A. siki- 

 mensis is different from that in any known European or American form, 

 though, as will presently be noticed, there is a Western-Asiatic species 

 with somewhat similar dentition There can be but little doubt that the 

 distinction was observed by Hodgson ; it was noticed by Jerdon, and 

 appears to have been the principal character upon which Hodgson's genus 

 Neodon was founded. Another peculiarity of A. sikimensis, also mention- 

 ed by the same naturalists, is that the posterior lower molars are scarcely 

 narrower than the preceding tooth. In most species of Arvicola there is 

 a much greater diminution in the breadth of the lower molars posteriorly. 



Although I fully admit the value of the distinction, I fail to see that 

 the presence of this additional angle in the first upper molar of A. siki- 

 mensis proves that that species is generically distinct from A. agrestis 

 (Agricola). The difference appears to me of the same value* as that 

 between A. agrestis, for instance, and A. arvalis ; that is to say, the dis- 

 tinction is merely sectional or subgeneric. I consequently consider Neodon 

 a section or subgenus of Arvicola. 



The species from Moupin, in Eastern Tibet, called A. melanogaster by 

 A. Milne-Edwards, has a somewhat peculiar dentition owing to so many 



* In the 'Scientific Kesults of the Second Yarkand Mission,' Mammalia, p. 41, 

 footnote, I remarked that the additional prism on the last upper molar of A. saxatilis 

 and A. brandti appeared to he quite as important as the presence of one ridge more, 

 than in other species, on the first upper molar of A. sikimensis. After a more exten- 

 sive study of the genus than I had the opportunity of making in Calcutta, I prefer to 

 modify this view The last upper molar in Arvicola appears to be more variable than 

 the first, and differences in the latter tooth appear therefore more important for pur- 

 poses of classification than similar characters in the former. At the same time, I see 

 no reason to alter the view I then expressed that such differences are not of generic 

 valuo. 



