No evidence of intergradation with any other race was noted. To the south the range of D. o. evexus is separated from that of D. o. montanus by a high, transverse ridge of the Rocky Mountains which is inhospitable to these animals. Much territory inhospitable to Dipodomys intervenes also between the ranges of D. o. evexus and 3883D. o. luteolus, but there are areas connecting the northern part of the range of D. o. evexus and the southwestern part of the known range of D. o. luteolus, in which Dipodomys may occur. If kangaroo rats occur in these areas it is to be expected that they will show intergradation between the two subspecies concerned.
Specimens examined.—Total, 24, all from Colorado, distributed as follows: Chaffee County: Salida, 10 (3 USBS; 7 AMNH). Fremont County: Canyon City, 13 (USBS). Pueblo County: Pueblo, 1 (USBS).
Dipodomys ordii medius new subspecies
Perodipus montanus richardsoni, [Bailey], N. Amer. Fauna, 25:144, October, 1905 (part—the part from Santa Rosa, New Mexico).
Type.—Male, no. 118526, U. S. Nat. Mus. Biol. Surv. Coll.; Santa Rosa, Guadalupe County, New Mexico; obtained on October 5, 1902, by Jas. H. Grant, original no. 565.
Range.—From north-central New Mexico, southeastward to west-central Texas; marginal localities are, in New Mexico: 15 mi. N Ojo Caliente, Gallina Mts., Deer Creek, San Pedro; in Texas: 20 mi. N Monahans, Colorado, 7 mi. E Post, 6 mi. SW Muleshoe.
Diagnosis.—Size medium (see measurements). Color dark; entire dorsal surface (14") between Orange-Cinnamon and Cinnamon, purest on sides and flanks, dorsal surface lightly washed with black; arietiform markings, pinnae of ears, plantar surfaces of hind feet, dorsal and ventral stripes of tail, brownish-black. Skull of medium size; nasals long; medial mastoid portion of auditory bullae well inflated caudad; braincase vaulted; external auditory meatus small; rostrum short and truncate; medial auditory portion of auditory bullae relatively little inflated; pterygoid fossae ovate; zygomatic arches slender and relatively straight; junction of jugal and zygomatic process of maxilla heavy.
Comparisons.—From Dipodomys ordii richardsoni, D. o. medius differs as follows: Tail longer; hind foot shorter; color darker; arietiform markings more distinct; white lateral stripes of tail narrower; ventral stripe of tail in most specimens complete to end of pencil; postauricular spots less pronounced; hip stripe narrower and in some specimens almost obliterated; skull smaller in all measurements taken; angle of dorsal extension of premaxilla with zygomatic process of maxilla more nearly 90°; braincase more vaulted; medial mastoid portion of auditory bullae more inflated, and coming to more of a point; medial auditory portion of auditory bullae more inflated ventrally; rostrum shorter and narrower; external auditory meatus smaller.
From Dipodomys ordii montanus, D. o. medius differs in: Color lighter in all pigmented areas; skull larger in all respects; rostrum shorter and heavier; bullae more inflated; zygomata, while nearly straight, are bowed slightly laterally; pterygoid fossae more ovate; foramen magnum larger; pterygoid foramina smaller.
Compared with Dipodomys ordii ordii and Dipodomys ordii sennetti, D. o. medius is larger and darker. The skull is also larger in all measurements taken.