short grasses, with relatively little ground cover.

Three of our four specimens are immature--two males collected on May 31
(testes 10, 12) and a female taken on June 25. An adult male trapped on
June 18 was in winter pelage, but molt was underway on the crown,
between the ears, and over the upper back and shoulders.

~Neotoma cinerea rupicola~ J. A. Allen, 1894

Bushy-tailed Wood Rat

_Specimens examined_ (8).--2 mi. N, 5 mi. W Ludlow, 5; 12 mi. N Buffalo,
1 (USNM); 7 mi. N, 2-1/2 mi. W Camp Crook, 3300 ft., 1; 2 mi. S, 5 mi. E
Harding, 1.

This woodrat is relatively uncommon, yet widely distributed, in
northwestern South Dakota. The species probably occurs throughout the
rocky areas in the hills and buttes of Harding County, and also
frequents abandoned or little-used buildings and feed stations for
livestock. All of our specimens were trapped in rocky habitats, but in
many such places we trapped unsuccessfully for _Neotoma cinerea_, even
though some sign of its presence frequently was evident. Five of our
seven specimens (all taken late in June or early in July) are young of
the year in grayish pelage. An adult male trapped on July 14 had testes
that measured 14.

Over and Churchill (1945:40) mentioned a specimen, which they referred
to the subspecies _N. c. cinerea_, that "probably came from the Slim
Butte area of Harding County." Visher (1914:89) recorded the species as
"plentiful and general" in the county.

~Microtus ochrogaster haydenii~ (Baird, 1858)

Prairie Vole

_Specimens examined_ (40).--NE 1/4 sec. 22, R. 1 E, T. 23 N, 1; NW 1/4
sec. 15, R. 5 E, T. 22 N, 1; 2 mi. N, 5 mi. W Ludlow, 4; 4 mi. S, 7 mi.
W Ladner, 19; 1/2 mi. W Reva, 2; SW 1/4 sec. 30, R. 7 E, T. 18 N, 3; 10
mi. S, 5 mi. W Reva, 10.

The prairie vole is the most abundant of the three microtines that are
known from Harding County. Our specimens came primarily from areas of
relatively dense grasses, such as those found in stream bottoms and
along fencerows. At two places, along a fencerow 1/2 mi. W Reva and in
Deer Draw, 10 mi. S and 5 mi. W Reva, _Microtus ochrogaster_ and the
meadow vole, _M. pennsylvanicus_, were trapped together.

Nine females taken late in May and in June carried an average of 4.4
(3-6) embryos that averaged 14.8 (4-25) in crown-rump length. Each of
two lactating females taken in late May had six placental scars. Testes
of seven adult males taken in May and June averaged 13.1 (12-16) in
length.

~Mi