﻿July, J89G.] 



SUBGENUS PEDOMYS. 



55 



BacJ: upper molar. — The last maxillary tootli lias tlie same general 

 form as that of Alticola, but is simpler in structure, thus recalling 

 the corresponding tooth in Lofiurus (tig. 25). There are usually only 

 two lateral triangles and four salient angles. The posterior loop is 

 lengthened in the axis of the jaw as in Altieola. 



Mammcv. — There are four mamma^, all inguinal. 



Feet. — The feet are well haired, hut rather less densely than in Alti- 

 cola. Plantar tubercles five — the faintest possible trace of a sixth 

 sometimes present. Claws on all four feet well developed, those on 

 hind feet longest. 



Fur. — The fur is much shorter and more dense than in Alticola. 



Miscellaneous characters. — The ears, and apparently the eyes, also, 

 are smaller than in Alticola. The whiskers are very short, reaching 

 scarcely to the ears, while in Alticola they are probably longer than in 

 any other subgenus of Microtus. 



Geyieral remarlxs. — Hyperacrius is most closely related to Alticola., from 

 which it differs chiefly in its highly modified skull and reduced number 

 of footpads and mammie. Minor differences are to be found in the rela- 

 tive size of the ears and in the character of the feet. Hyperacrius 

 appears to be modified for a more strictly underground life than Alticola. 

 It requires no close comparison with any other 

 subgenus, though it bears a superficial likeness 

 both in external form and in cranial characters to 

 Fitymys. The structure of the bony palate and 

 the i)attern of enamel folding readily distinguish fig. 28.-Euauiei pattern of 

 it from the latter, however. "'o^^^' t^'^^ti^ ^licrotus (Hy- 



TTn XI Tr- ^ • 1 -XT peracnus)fcrtths.{x5.) 



vVhether Microtus wynnei may be associated 

 with Microtus fertil is in the subgenus Hyperacrius is a matter of doubt. 

 At my request Mr. G. E. H. Barrett-Hamilton has examined the speci- 

 mens of Alticola in the British Museum with special rei^rence to the 

 relationships of M. wynnei. He finds that this species, as already 

 noticed by Blanford, has only five plantar tubercles, but that in other 

 characters it does not agree with the brief diagnosis oi Hyperacrius that 

 I sent him. The fur is long, as in the species of Alticola^ and the skull 

 apparently lacks the peculiar form seen in Hyperacrius. The number of 

 mammaicannot be determined in M. icy unci nor in any of the species 

 of Alticola in the British Museum. For the present it is not safe to 

 attempt to refer Microtus loynnei definitely to one subgenus or the other. 



Subgenus PEDOMYS Baird. 

 1857. Fedomys Baird, Mamm. N. A., p. 517, 1857. Type Arvicola aiisterus LeConte. 



Geographic distribu tion of type species. — Transition and Upper Austral 

 zones in the central United States and adjoining British Provinces. 



Geographic distrihutio7i of subgenus. — The range of this subgenus is 

 the same as that of Microtus austerus, the only known species. 

 Essential characters : 

 Palate normal. 



m 3 without closed triangles. 



