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 A. 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 A. 

 borealis to distinguish it from A. riparius proper, the follow- 

 ing measurements may serve to indicate the proportions of 

 both forms : The upper number (units = T ^ inch) in each case 

 refers to A. borealis, the lower to A. riparius. Total length of 

 skull, y 9 ^, (i. e. inborealis 0.9 in riparius 1 inch); zygomatic 

 width |f; length of nasals, ||; length of temporals, ff ; medial 

 length of parietals, |; length of molar series, |f ; length of 

 upper incisors, -^ ; length of scapula, f; length of humerus, 

 ff; length of radius, ff; longest metacarpal, ff; pelvis, f|; 

 femur, |f; tibia, f; free portion fibula, j; longest metatarsal, 

 |f; (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, \%% . The number of caudal vertebrae seems to 

 be the same, but a greater diversity in size is exhibited here 

 than elsewhere. The last seventeen vertebras were measured 

 in each case. 



Arvicola (Chilotus) pal I id us 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. 



