﻿July, 1896.] 



SUBGENUS ALTICOLA. 



53 



caused by the approximately equal size of the triangles on the opposite 

 sides of the teeth, and (d) by the form of the posterior upi)er molar. 



While the figures published by Blanford ^ in his paper on the voles of 

 the Himalayas, Tibet, and Afghanistan are in many ways inaccLirate.y 

 they give an excellent idea of the general appearance of the teeth in 

 the voles of this grouj). 



Front lotver molar. — The first mandibular molar has normally four 

 closed triangles and seven or eight salient angles. Earely a fifth closed 

 triangle is isolated at the inner basal angle of the anterior loop. The 

 form, relative position, and degree of isolation of the triangles and 

 transverse loops A^ary greatly with the different species. Any one of 

 the reentrant enamel folds may fail to reach the enamel of the opposite 

 side, and consequently any of the triangles may be open at one or both 

 ends. 



Bade upper molar. — The posterior maxillary tooth varies in form in the 

 different species. It is, however, always recognizable by the backward 

 prolongation of the posterior loop in the line of the jaw, a character 

 which is found elsewliere in Ilypcracrius, Chilotus, and Lagiirus only, 

 and in all but the first of these developed to a much less degree. This 

 attenuate posterior loop is followed by three or fonr more or less incom- 

 pletely isolated lateral triangles, these by an anterior loop of the usual 

 form. The tooth is most complex in M. roylel and ill. hlanfordl, in each 

 of which it has six salient angles and two or three closed triangles. 



Other teeth. — Except for the stronger tendenc}^ to bilateral symmetry 

 combined with slight irregularity of outline the other molars do not 

 differ from those of ordinary tetramerodont Microtus. 



Mammce. — The number of mammtiB in the species of Alt i cola has 

 apparently not been recorded. Blanford does not mention it in his 

 descrii^tions of any of the species, and Mr. G. E. H. Barrett-Hamilton, 

 who has made at my request a special examination of the material in 

 the British Museum, is able to add nothing on the subject. In an 

 adult nursing female of a species of Alt i cola closely allied to Microtus 

 albicauda (No. 621G2, U. S. Nat. Mus. Ladak side of Kara Korum 

 Pass, Kashmir) there are eight well-developed mamma?. Hence there 

 is little doubt that eight is the normal number in the subgenus. 



Feet. — The feet are very hairy, the long hairs on the dorsal surface 

 often nearly concealing the claws. Plantar tnbercles six. The claws 

 on all the feet are long and slender, those on the hind feet longer than 

 those in front. 



Fur. — As in most high boreal microtines the fur is long and full. 

 Otherwise it is not peculiar. 



General remarls. — The subgenus Alticola is one of the best character- 

 ized groups in the genus Microtus. The pattern of enamel folding is 

 unlike that of any of the other subgenera, except Ryperacrius, while 

 the palate structure is approached by that of Hyperacrius and the 



1 Joiirii. Asiatic Soc. Bengal, L, Pt. II, PI. I, figs. B, C, B, and E. 



