_Comparisons._--From _Dipodomys ordii ordii_, _D. o. sennetti_ differs in: Size smaller, tail shorter; color darker; skull smaller; nasals longer; rostrum wider; auditory bullae less inflated; external auditory meatus smaller; pterygoid fossae more rounded; zygomatic arches heavier. From _Dipodomys ordii medius_, _D. o. sennetti_ differs as follows: Size smaller; color darker, but with less red in pelage; skull markedly smaller in all respects. From _Dipodomys ordii compactus_, _D. o. sennetti_ differs in: Size somewhat less; color darker; skull with total length greater; orbit smaller; least interorbital width greater; braincase more inflated; width across auditory bullae more; interparietal region wider; external auditory meatus larger; medial part of audital portion (see Howell, 1932) of auditory bullae larger. _Remarks._--_Dipodomys sennetti_, along with _Dipodomys compactus_, was regarded by Davis as conspecific with _Dipodomys ordii_. Reasons for placing these two kinds of kangaroo rats as subspecies of _D. ordii_ are given in the account of _Dipodomys ordii compactus_. This subspecies is known only from north of the Rio Grande which may serve as a barrier to the spread of the animal into northern Tamaulipas. _Specimens examined._--Total, 20, all from Texas, distributed as follows: _Atascosa County_: Somerset, 2 (TCWC). _LaSalle County_: 8 mi. NE Los Angeles, 1 (TCWC); 8 mi. E Encinal, 1 (TCWC). _Kleberg County_: 2 mi. S Riviera, 9 (TCWC). _Jim Hogg County_: Hebronville, 8 (LACM). _Brooks County_: Falfurrias, 2 (LACM). _Willacy County_: 28 mi. E Raymondville, 2 (TCWC). =Dipodomys ordii evexus= Goldman _Dipodomys ordii evexus_ Goldman, Journ. Washington Acad. Sci., 23:468, October 15, 1933. _Perodipus montanus richardsoni_ Warren, Mammals of Colorado, p. 76, 1910 (part--the part from Salida, Colorado). _Type._--Male, adult, no. 150990, U. S. Nat. Mus. Biol. Surv. Coll.; Salida, Chaffee County, Colorado (altitude 7000 ft.); obtained on November 10, 1907, by Merritt Cary, original no. 1245. _Range._--Upper Arkansas River Valley of south-central Colorado, from Salida to Pueblo. _Diagnosis._--Size large (see measurements). Color dark, entire dorsal surface between (_16´´_) Pinkish Cinnamon and Cinnamon-Buff, purest on sides and flanks, upper parts strongly suffused with black; arietiform markings, pinnae of ears, plantar surfaces of hind feet and dorsal and ventral stripes of tail, blackish. Skull of medium size; rostrum short and wide; nasals short; auditory bullae but slightly inflated; braincase but slightly vaulted.