204 BULLETIN NO VII. 
although received in too poor condition to be preserved or 
satisfactorily studied, attracted attention on account of its 
obviously reduced size. There seemed to be no reason to sus- 
pect that it was not fully mature, while its measurements ex- 
cluded it from normal A. riparius, which, except in the matter 
of size, it completely resembled. 
Length of trunk, 3.50; tail, 1.30; sole, 0.70; palm, 0.41; nose 
to eye, 0.40. 
In the absence of other specimens or further information as 
to the presence or absence of normal 4. riparius in the North- 
western part of the state this stands as an isolated case of little 
value, except as it may direct attention to this question whether 
we have a permanent boreal variety of Arvicola in Minnesota. 
As there is little or nothing in the form of the bones of 4A. 
borealis to distinguish it from 4A. riparius proper, the follow- 
ing measurements may serve to indicate the proportions of 
both forms: The upper number (units = ;}, inch) in each case 
refers to A. borealis, the lower to A. riparius. Total length of 
skull, Tuo (i. e. in borealis 0.9 in riparius 1 inch); zygomatic 
width 42; length of nasals, 34; length of temporals, 3; medial 
length of parietals, 39; length of molar series, 32; length of 
upper incisors, 4$; lena of scapula, 4°; tent of humerus, 
45; length of radius, #3; longest esa eis 48; pelvis, $8; 
femur, #2; tibia, $4; free portion fibula, 34; longest metatarsal, 
39; (It is worthy of notice that the difference in size, so notic- 
able in all other measurements, disappears in comparing the 
length of bones of the hand and foot, although the size in other 
respects is greater in the larger animal). The seventeen cau- 
dal vertebrae, 14°. The number of caudal vertebrze seems to 
be the same, but a greater diversity in size is exhibited here 
than elsewhere. The last seventeen vertebrze were measured 
in each case. 
Arvicola (Chilotus) pallidus MERRIAM. 
Quite recently Dr. Merriam has described from Dakota: a 
species of the subgenus Chilotus, which may yet be encoun- 
tered in Minnesota.* The species is said to strikingly differ 
from the other known North American species of Arvicola in 
the extreme paleness of coloration and the extreme shortness 
of tail. 
*C. HART MERRIAM. Description of a new species of Field Mouse (Arvicola pallidus) 
from Dakota. 
