In any sizeable sample of _Dipodomys sennetti_ there are crania closely resembling those of _Dipodomys ordii ordii_ and others closely resembling those of _Dipodomys compactus_. The external proportions of both _D. sennetti_ and _D. compactus_ are duplicated in _D. ordii_ from El Paso and conversely, specimens with the proportions of typical _D. o. ordii_ occur in populations of _D. sennetti_ and _D. compactus_. Thus, it appears that Davis' usage of the name _Dipodomys ordii compactus_ should stand although there may be a hiatus in geographic occurrence between _D. ordii_ and _D. sennetti_, as of course there is between _D. sennetti_ and _D. compactus_. In _D. o. compactus_ there is a complete enamel ring around the occlusal surface of each molariform tooth; in _D. o. ordii_ this ring is incomplete lingually on each of the molariform teeth and labially on the first three, and in some individuals of _D. o. sennetti_ the enamel ring is complete and in others it is incomplete labially and lingually as in _D. o. ordii_. _Specimens examined._--Total, 44, all from Texas, distributed as follows: _Nueces County_: 19 mi. S Port Aransas, Mustang Island, 27 (17 TCWC; 10 MVZ); Mustang Island, 17 (LACM). =Dipodomys ordii sennetti= (Allen) _Dipodops sennetti_ Allen, Bull. Amer. Mus. Nat. Hist., 3:226, April 29, 1891. _Cricetodipus sennetti_, Trouessart, Catalogus Mammalium, 1:581, 1897. _Perodipus sennetti,_ Elliott, Field Columbian Museum, Zool. Ser., 2:239, 1901. _Dipodomys ordii sennetti_, Davis, Journ. Mamm., 23:332, August 14, 1942. _Type._--Male, no. 3478/2733. Amer. Mus. Nat. Hist.; near Brownsville, Cameron County, Texas; obtained on March 9, 1888, by J. M. Priour. (After Allen, original description, type not seen.) Type locality recorded by Bailey (1905:145) as "Santa Rosa, 85 mi. SW Corpus Christi." _Range._--Southern Texas, south of Corpus Christi; marginal localities, all in Texas are: Somerset, 8 mi. NE Los Angeles, 8 mi. E Encinal, Santa Rosa, 28 mi. E Raymondville, 2 mi. S Riviera. _Diagnosis._--Size small (see measurements). Color dark, entire dorsal surface (_c_) between Pinkish Buff and Cinnamon-Buff, purest on sides and flanks, upper parts mixed with black; arietiform markings, pinnae of ears, dorsal and ventral stripes of tail, plantar surfaces of hindfeet, brownish-black. Skull small; auditory bullae but slightly inflated in relation to size of skull; nasals slightly flaring distally; premaxillae extending but slightly posterior to nasals; interorbital width relatively great; external auditory meatus small; rostrum relatively long and wide; zygomatic arches relatively heavy.