600 Description of Meadow Mouse. 
vidual as small as the largest of about thirty specimens of the 
northern animal. The average difference in length, without the 
tail, is nearly 25 mm. (about an inch). In typical austerus, the 
hind foot averages 19 to 20 mm., while in the new form it averages 
but 16 to17 mm. In adult skulls of austerus the average basilar- 
length falls between 24 and 25 mm.; in the northern form it falls 
between 20 and 21 mm. In reference to its diminutive size, I have 
named the northern mouse 
ARVICOLA AUSTERUS MINOR, sub-sp. nov. 
Northern Prairie Meadow Mouse. 
Type 392%, male, Merriam Collection. From Bottineau, Turtle 
Mt., Dakota, August 27, 1887. 
Description of Type.—Similar to Arvicola austerus, but much 
smaller; length from end of nose to tip of tail vertebrae (measured 
in the flesh), 133 mm.; tail vertebre, 36 mm.; hind foot, 16.5 mm.; 
ears rather prominent, slightly overtopping the fur. 
Color.—Upper parts uniform grizzled gray; under parts whit- 
ish, washed with pale cinnamon. Viewed from behind, looking 
away from the light, the entire head, back and sides appear to be 
finely and closely lined with silvery. The fur of the belly is 
plumbeous basally and nearly white apically. There is no sharp 
line of demarkation between the color of the sides and that of the 
belly. Tail bicolor, the light color of the under surface reaching 
well up on the sides. 
Description of other Specimens.—The type, which is from Turtle 
Mt., Dakota, is very closely matched by specimens from several 
places in the Red River Valley (particularly from Travare, Dakota, 
and Ortonville, Minnesota); and by a few of the Elk River speci- 
mens. A male from Elk River (No. 3424), collected June 2, 1886, 
is almost a duplicate of the type, except that the belly is darker— 
it is more sparsely haired, and the plumbeous basal portion of the 
fur shows through. Other specimens from Elk River have the 
upper parts strongly suffused with brown, and the belly strongly 
washed with cinnamon. 
In others there is as much whitish on the belly as in the he 
while in others still the under parts are of the “muddy rust color 
so often seen in true austerus. This is pronounced in No. Hit, 
