of active hair replacement, most often over
the shoulders; a pregnant female obtained on July 4 had only partially
completed the molt to summer pelage. An adult female in summer pelage
that was taken on August 4 was inexplicably molting on the sides and
over the shoulders.

A May-taken female was parasitized by fleas, _Cediopsylla inaequalis_
(Baker).

~Sylvilagus floridanus similis~ Nelson, 1907

Eastern Cottontail

_Specimens examined_ (2).--4 mi. S, 7 mi. W Ladner, 1; 10 mi. S, 5 mi. W
Reva, 1.

This rabbit is uncommon in northwestern South Dakota and evidently is
strictly associated with riparian habitats. Our only specimens were
taken along the Little Missouri River, where thickets and small
cottonwood trees were prevalent, and at the edge of a thicket in
spring-fed Deer Draw of the Slim Buttes.

A female obtained on June 26 carried eight embryos that measured 26, and
was in process of seasonal molt. Testes of a male shot on May 20
measured 35.

Order Rodentia

~Eutamias minimus pallidus~ (J. A. Allen, 1874)

Least Chipmunk

_Specimens examined_ (31).--2 mi. N, 5 mi. W Ludlow, 15; NW 1/4 sec. 15,
R. 5 E, T. 22 N, 2; 2 mi. S, 3-1/4 mi. W Ludlow, 2; NW 1/4 sec. 32, R. 1
E, T. 20 N, 1; 9 mi. S, 7 mi. W Reva, 1; 10 mi. S, 5 mi. W Reva, 9; NE
1/4 sec. 8, R. 8 E, T. 16 N, 1.

The least chipmunk is common in the buttes and associated badlands
where it most frequently inhabits rocky areas. Visher (1914:88) reported
_E. minimus_ from Harding County ("abundant in badlands"), but his paper
has been overlooked by most subsequent workers. Visher's mention of a
chipmunk from the mouth of the Moreau River in north-central South
Dakota, incidentally, would seem to be in error, as would the report by
Over and Churchill (1945:28) of _Eutamias_ inhabiting "... thickets
along the Little Missouri River of Harding County."

Females evidently bear but one litter annually (in late May) in
northwestern South Dakota and young are weaned by the latter part of
June. Females taken on May 15 and 19 carried embryos (five measuring 30
and three measuring 28, respectively). A lactating female with five
placental scars was obtained on May 24, but eight adult females taken
after June 23 previously had weaned young. Juveniles were collected on
June 24 and 25. Testes of two adult males collected in mid-May measured
11 and 18, but males taken in summer had much smaller testes.

In late spring, most adult least chipmunks molt fro