_Comparisons._--From _Dipodomys ordii utahensis_, _D. o. fetosus_ differs as follows: Hind foot longer; color lighter; skull larger; rostrum, relatively as well as actually, shorter and wider; nasals longer and wider; interorbital region narrower; braincase less vaulted; interparietal region narrower; auditory bullae more inflated laterally, posteriorly and ventrally; foramen magnum smaller. From _Dipodomys ordii celeripes_, _D. o. fetosus_ differs as follows: Larger; color darker; arietiform markings present; skull larger; rostrum longer and wider; nasals longer and less inflated distally; interorbital region wider; auditory bullae somewhat more inflated; zygomatic arches more robust. For comparisons with _Dipodomys ordii monoensis_, _D. o. columbianus_, _D. o. pallidus_, _D. o. panguitchensis_ and _D. o. cinderensis_ see accounts of those subspecies. _Remarks._--_Dipodomys ordii fetosus_ has a small geographic range. Hall (1946:416) points out that the interorbital breadth in topotypes is less than in those from any other part of the range. This feature, therefore, is not useful in characterizing this subspecies. Intergradation with _Dipodomys ordii columbianus_ is noted in the greater total length and the somewhat darker color in animals from Coal Valley and Garden Valley, Nevada. In the part of the range which lies in Utah, none of the animals is typical and all are intergrades in color and cranial characters with _Dipodomys ordii celeripes_. _Specimens examined._--Total, 136, distributed as follows: =Nevada=: _Nye County_: White River Valley, 15 mi. WSW Sunnyside, 5500 ft., 26 (MVZ); White River Valley, 16-1/2 mi. WSW Sunnyside, 5500 ft., 6 (MVZ); 14 mi. NNE Sharp, 1 (MVZ); Garden Valley, 15 mi. NE Sharp, 1 (MVZ); Garden Valley, 14-1/2 mi. NE Sharp, 3 (MVZ); 8-1/2 mi. NE Sharp, 17 (MVZ). _Lincoln County_: E side Coal Valley, 14 mi. N Seeman Pass, 4850 ft., 4 (MVZ); 2 mi. SE Pioche, 1 (MVZ); E side Coal Valley, 10 mi. N Seeman Pass, 1 (MVZ); Desert Valley, 20 mi. SW Pioche, 1 (MVZ); 2 mi. N Panaca, 4800 ft., 17 (16 MVZ; 1 CAS); Desert Valley, 21 mi. W Panaca, 10 (MVZ); Crystal Spring, Pahranagat Valley, 4000 ft., 2 (MVZ); 10 mi. E Crystal Springs, 5000 ft., 1 (MVZ); 15 mi. S Groom Baldy, 1 (MVZ). =Utah=: _Millard County_: 5 mi. S Garrison, 5400 ft., 12 (MVZ); Pine Valley, Sec. 33, T. 25 S, R. 17 W, 5000 ft., 16 (UU); Warm Cove, Sec. 34, T. 25 S, R. 18 W, 5500 ft., 2 (UU); Desert Range Experiment Station, 50 mi. W Milford, 5252 ft., 10 (9 UU; 1 BYU). =Dipodomys ordii utahensis= (Merriam) _Perodipus montanus utahensis_ Merriam, Proc. Biol. Soc. Washington, 17:143, July 14, 1904. _Perodipus ordii utahensis_, Goldman, Proc. Biol. Soc. Washington, 30:113, May 23, 1917. _Dipodomys ordii columbianus_, Grinnell, Journ. Mamm., 2:96, May 2, 1921.