From _Dipodomys ordii evexus_, _D. o. montanus_ differs as follows: Size smaller in all measurements taken except width across auditory bullae which is greater; color darker, ventral stripe of tail continuous to end of pencil; least width of supraoccipital less (2.5 mm. in _D. o. montanus_ and 3.5 mm. in _D. o. evexus_); extension of premaxillae posterior to nasals greater; braincase more inflated dorsally; bullae relatively as well as actually larger and more inflated ventrally; pterygoid fossae narrower anteroposteriorly and wider laterally than in _D. o. evexus_; jugal straight or nearly so as contrasted to bowed laterally; lacrimal processes smaller. For comparison with _Dipodomys ordii medius_ see account of that subspecies. [Illustration: FIG. 26. Known occurrences and probable geographic range of the subspecies of _Dipodomys ordii_ in the southwestern fourth of the range of the species. 14. _D. o. ordii_ 17. _D. o. chapmani_ 31. _D. o. longipes_ ] _Remarks._--This subspecies of _Dipodomys ordii_ appears to be restricted to the San Luis Valley of Colorado and New Mexico. Intergradation, between _Dipodomys ordii ordii_ and _D. o. montanus_, is noted in animals from Gran Quivira, Mesa Jumanes, New Mexico. These animals have the frontomaxillary suture and extension of the premaxilla as in _D. o. ordii_ and the nasals and inflation of the auditory bullae as in _D. o. montanus_. In the majority of characters they are, however, referable to the latter. Intergradation is noted also in animals from 4 miles southwest of Cimmaron, New Mexico, in that they resemble _D. o. richardsoni_ in the shape of the nasals and the width and length of the rostrum but in the remainder of the characters studied resemble _D. o. montanus_ to which they are referred. Baird, in the original description, gives "near Fort Massachusetts" as the type locality for this subspecies. Miller (1923) lists the type locality as "Fort Massachusetts (now Fort Garland)." Fort Massachusetts and Fort Garland are two different ex-army posts. Old Fort Massachusetts was situated on what is now the Trinchera Ranch which is north of the town of Fort Garland. Old Fort Garland is approximately one-half mile south of the town of Fort Garland. The two abandoned army posts were no more than twelve miles apart. In 1946, at neither abandoned post could I find any habitat suitable for kangaroo rats. _Specimens examined._--Total, 148, distributed as follows: