Seven adults, all in winter pelage, were taken late in March from a pond near the west side of Slim Buttes (5 mi. S and 14 mi. E Buffalo). Testes of three adult males measured 17, 19, and 22; of three females, none evidenced reproductive activity. ~Mus musculus~ Linnaeus, 1758 House Mouse The house mouse evidently is uncommon in rural environments in northwestern South Dakota. One subadult female was trapped along a "weedy" fencerow, 2 mi. N and 5 mi. W Ludlow. ~Zapus hudsonius campestris~ Preble, 1899 Meadow Jumping Mouse Eleven specimens of this jumping mouse were taken from a relict population restricted to a shrub-grass habitat adjacent to a small spring-fed stream and impoundment in Deer Draw (10 mi. S and 5 mi. W Reva). Similar isolated populations may be present in the few other suitable mesic habitats in Harding County, but we have trapped extensively, yet unsuccessfully, for _Zapus_ in such situations; specimens are known, however, from the Long Pine Hills and from along the Little Missouri River in adjacent Carter County, Montana. It is of interest that a relict population of _Peromyscus leucopus_ also occurs in Deer Draw. The testes of two adult males obtained on June 3 measured 7, whereas those of one taken on May 16 measured 16. Seven embryos (measuring 8 in crown-rump length) were carried by a molting female trapped on June 16. Our specimens of _Zapus_, currently under study by Paul B. Robertson, appear to be intergrades between the subspecies _campestris_ and _intermedius_, but resemble the former more closely than the latter. ~Erethizon dorsatum bruneri~ Swenk, 1916 Porcupine _Specimens examined_ (11).--NW 1/4 sec. 15, R. 5 E, T. 22 N, 1; 2 mi. N, 5 mi. W Ludlow, 3; 4 mi. S, 7 mi. W Ladner, 1; 10 mi. S, 4 mi. W Reva, 1; 10 mi. S, 5 mi. W Reva, 4; 2 mi. S, 5 mi. E Harding, 1. The porcupine is a common resident of the pine-clad buttes of Harding County and individuals were occasionally encountered some distance from pines. We noted porcupines almost nightly in June of 1961 along the road that parallels the Slim Buttes to the east, and found a number that had been struck by automobiles along this and other roadways in, or adjacent to, wooded areas. Visher (1914:90) earlier reported _Erethizon_ from Harding County. Order Carnivora ~Canis latrans latrans~ Say, 1823 Coyote _Specimens examined_ (8).--North Cave Hills, 1; N of Slim Buttes, 1; N end Slim Buttes, 1; 6 mi. N, 4 mi. W Camp Crook, 2; W of East Short Pine Hills, 1; E of Short Pine Hills, 1; Sheep Mountain, 1.