192 BULLETIN NO. VII. 
The eastern Michigan mouse aJthough much less bright than 
H. leucopus has on the sides a decided brownish cast, or even 
fawn color, while the typical western variety has scarcely a 
trace of any other tint than black and white except on the up- 
per surface of the tail. About the head there is the same hoari- 
ness exhibited by other prairie mice, as though faded by the 
sun. As arule there is a less sharply defined line of demarka- 
tion between back and belly than in more eastern specimens 
examined. 
In all the Michigan mice examined the ear is white-rimmed 
in spite of Dr. Coues’ assertion to the contrary. Although the 
dorsal dark area may not reach the hand there is invariably a 
dark blotch on the wrist which may or may not embrace the 
whole upper surface of the hand. 
The following table of measurements, of which all but the 
last two refer to specimens captured near the western line of 
Minnesota, may show the variations in size and can be taken 
as fully trustworthy, having been made with great care from 
fresh specimens: 









Nose . Nos Nos Hind 
No. see Tail. |46 Sead ka aoe foot. | ©: Sex. Date. 
108 | 3.00 | 1.90 | 0.90 | 0.45 | 0.73 | 0.60 | male | July 5, 1885 
ce sa a el ges Ba iestnn ag «os rg gee male | July 5, 1885. 
113 | 3.12 | 1.90 | 0.90 | 0.50 | 0.70 | 0.55 | male | July 7, 1885. 
DUT QO WED OO Ue ian a llemeloeillic cites = |e cei male | July 7, 1885 
118 | 3.20 | 2.00 | 0.85 | 0.50 | 0.70 | 0.50 | male | July 7, 1885. 
TLO GS 245 al Ve2O) Meese Ns eae O: TON. Eaves male | July 9, 1885. 
21 | 8.20 | 2.87 | 0.87 } 0.40") 0568 15.524. female} Nov., 1883. 
SS | BeG0 | DOO tec wets O60") 0.10 for. o male | ? (Alcohol). 


Supramity ARVICOLIN 4%. 
The field mice, which are included in this section of the 
immense rat family, may be readily recognized, as a rule, by 
their rather clumsy and squatty form, blunt muzzle and small 
ears. Tail and limbs are generally short, while the eyes are 
small. The fur is often thick and fluffy, while the colors are 
predominatingly rusty brown. The north temperate regions 
of both hemispheres form the habitat of the majority of the 
species. None occur in South America. As in other northern 
mammals, there is rather a close conformity between the faunz 
of Europe and America. 
The anatomical characters are no less conspicuous. The 
incisors are broad and short. The molars are perfectly pris- 
matic, and their growth is continuous, so that after the crowns 
