MAMMALS OF MINNESOTA. 



195 



The close relationship between this variety and H. rutilus 

 was first shown by Coues in the Proceedings of the Academy of 

 Natural Sciences of Philadelphia in 1874. The differences con- 

 sist in a somewhat greater size and a considerably greater 

 development of the extremities in accordance with the general 

 law that the extremities are shorter in northern individuals of 

 a species extensively distributed than in southern examples of 

 the same species. If the size be really less than in H. rutilus 

 it forms an exception to the remainder of the law that the 

 absolute size is usually greater. The colors are darker, 

 especially the sides which are a grayish brown instead of hav- 

 ing the milk tinge of H. rutilus. 



In general form there is nothing to distinguish this interest- 

 ing animal from the common field mouse. It can be at once 

 distinguished, however, by the color and the greater develop- 

 ment of the ears. These organs appear quite prominently 

 above the fur and are hirsute, while near the base of the anti- 

 tragus is a tuft of stiff hairs longer than the ear itself. 



The middle of the back from the crown to the root of the tail 

 is of a strong, rusty red color, given a grayish cast by numerous 

 black hairs sprinkled through the pelage. On the sides the 

 red is largely replaced by brown, so that the resulting color 

 is much as in Arvicola riparius. The bases of the hairs every- 

 where are plumbeous. About the face the color becomes a 

 grizzly gray, in old specimens at least. Below greenish white 

 of various degrees of purity is the prevailing color, the fur 

 being much lighter color than in A. riparius. The feet partake 

 in the same coloration. The tail is distinctly bicolored, the upper 

 surface being, as usual, darker than the prevailing color of the 

 back. The vibrissse are rather longer than in A. riparius. Con- 

 siderable variations in the coloration occur, the breadth of the 

 red stripe especially being far from constant, either in width or 

 intensity. 



The following measurements may be taken as a very fair 

 showing of the size of adults, the first being taken in autumn, 

 the second in spring, and in adjacent localities: 



Coues' averages, published in his monographs of North 

 American Rodentia, are placed in the third line for conven- 

 ience of comparison. 



