114 The Habits of some Arvicolne. [ February, 
that less than fifty specimens of this little mammal have ever 
been taken, of which number more than half have been secured 
by the writers from this same locality. 
This mouse is found on hillsides in high, dry, blue grass pas- 
tures, where flat stones are irregularly scattered over the surface ; 
it especially prefers what are known as “ woods pastures,” con- 
taining little or no undergrowth. 
The locality whence Dr. Haymond obtained his specimen is a 
hillside pasture field, with no trees, sloping towards the east. 
The greater part of the other specimens have been taken from a 
steep rocky hill sparsely covered with timber, known as “ Brown’s 
hill.” 
Cooper’s field mouse has been found breeding from February 
to December. It has never been known, by the authors, to bring 
forth more than four young atatime. In all suckling females 
which have been brought to our attention the mammez have appa- 
rently been but four, one pair pectoral and one pair inguinal. Dr. 
Coues says (Monographs of N. A. Rodentia): “ In No. 9963 (Dr. 
Haymond’s specimen) apparently a nursing female, we find two 
pairs of pectoral mammz and one pair of inguinal mamme, 
without being able to make out any intervening ventral ones. It 
is probable, however, that the species possesses a ventral pair, 
making eight teats in all.” 
In this matter, from the light we now have upon the subject, 
we are not able to coincide with Dr. Coues in his views. 
In young specimens the hair appears finer, shorter and more 
glossy than in more aged examples. As a rule the specimens 
just reaching maturity are darkest, but one old female shows a 
very dark reddish-brown back, and is dark ash below. If there 
is any difference in sexual coloration, the females are slightly the 
darker. 
The nest of this species is always under cover, generally in a 
hollow log or stump, and is composed of fine grass. It is not so 
securely built as the nests of some of the other species of this 
family. 
Cooper’s mice live in winter chiefly upon the stems of blue 
grass and the more tender portions of the white clover. Stores 
of these foods may be found near their winter quarters, In No- 
vember, 1883, a large quantity of the tuberous roots of the plant 
commonly called “wild artichoke” (Helianthus doronicoides Lam.) 
