Chapter II: Part 2

Cranial indices (breadth across bullae/length of skull × 100) as established for random samples of the different species of the genus (exclusive of _D. ordii_) ranged from 60.8 to 67.6. In the subspecies of _D. ordii_ the same index varies from 59.7 to 65.2 with an average of 63.4. In other words, the degree of specialization indicated by this one index, in a few subspecies of _D. ordii_, is almost as great as that in _Dipodomys deserti_, which on the basis of total morphology appears to be the most specialized species in the genus. Also, on the basis of this same index, some subspecies of _D. ordii_ are more generalized than is any other species in the genus.

There is a general tendency for the nasals to decrease in length and the rostrum to decrease in width as the southern limits of the range of _D. ordii_ are approached. In ascertaining the decrease in length of the nasals an index was obtained as follows: nasals/interorbital width × 100 (see Table 4). The width of the rostrum, however, does not decrease in the same degree, nor at the same rate, as does the length of the nasals. This decrease in length of the nasals and in width of the rostrum may be correlated with the mean annual relative humidity of the environment. It is known (Howell and Gersh, 1936:8) that desert rodents, more exactly kangaroo rats, have a water retention mechanism in the kidneys and walls of the urinary bladder which enables them more efficiently to conserve metabolic water. The significance of the decrease of the area of the nasal mucosa, which seems to be related to relative aridity, is not yet properly understood.

In no cranial feature other than shortened nasals and narrowed rostrum, does _Dipodomys ordii_ show a gradation such that it might be termed a cline. Other parts of the skull that were measured do not vary greatly.

Perhaps the greatest amount of variation in the skull is in features which are not readily measurable by the usual physical means. The shape and size of the pterygoid fossae vary from almost round to rather ovoid in a given series of animals from one locality; the size and configuration of the zygomatic arches vary from slender to robust and from straight to curved laterally; the size of the lacrimal processes varies much in any given series, as do also the degree of expansion of the distal end of the nasals, the convexity of the braincase and the curvature of the upper incisors. In all instances where these features varied much, one size or shape was more pronounced in the series than any other size or shape. Thus, when comparisons were made, the size and certain shapes were the criteria used in assigning the animals under consideration to a given subspecies.

Subspeciation in _Dipodomys ordii_ seems to have been influenced by water barriers. It is known (Grinnell, 1922:28) that kangaroo rats lack the ability to swim. Large stable rivers such as the Colorado, Snake and Columbia serve as effective barriers to further dispersal of kangaroo rats. Streams that freeze over in the winter months, however, are not efficient barriers. This is indicated by the "blending" of morphological characters of _D. o. nexilis_ and _D. o. sanrafaeli_ along the Green River which freezes over.

Any mountain which has vegetational belts above the Transition Life-zone would serve as a barrier to the dispersal of these animals. The Uinta Mountains, lying in an east-west direction, are interposed between the ranges of _D. o. priscus_ and _D. o. uintensis_. The high Wasatch Mountains and their associated outliers, lying in a north-south direction in Utah, serve as an efficient barrier to the east-west movement of kangaroo rats and as a result, the subspecies east of the mountain mass are remarkably different from those to the west.

TABLE 4

PROPORTIONATE DECREASE OF NASALS

===========================================================
Width Length Least Nasals
of of interorbital ------------
rostrum nasals orbital Interorbital
width × 100
-----------------------------------------------------------
terrosus 4.1 14.75 13.5 91.6
luteolus 4.35 13.9 12.95 93.1
evexus 4.3 14.35 13.75 94.8
montanus 4.1 13.5 12.65 93.8
ordii 3.5 13.3 13.0 97.7
idoneus 3.7 13.2 13.75 103.5
palmeri 3.3 12.8 13.0 101.1
-----------------------------------------------------------

The first three columns represent the actual measurements of the
various elements; the fourth column is the index established.

Six different complexes (groups) of subspecies of _D. ordii_ have probably arisen as a result of geographical separation.

The Great Plains complex consisting of _D. o. richardsoni_, _D. o. oklahomae_, _D. o. evexus_, _D. o. terrosus_, _D. o. luteolus_, _D. o. priscus_ and _D. o. medius_ are, with the exception of _D. o. priscus_, inhabitants of the high plains grassland habitat. _D. o. priscus_ inhabits the red Desert of Wyoming.

The Gulf Coast complex, comprising _D. o. sennetti_ and _D. o. compactus_ are separable from all others by small auditory bullae and short tail. _D. o. compactus_ probably has differentiated from _D. o. sennetti_ since the cutting off, by wave action, from the mainland, of the islands on which _D. o. compactus_ lives.

The Mexican complex consisting of _D. o. obscurus_, _D. o. fuscus_, _D. o. idoneus_ and _D. o. palmeri_ have probably differentiated by natural selection acting on fortuitous variations, but I lack first hand knowledge of the region concerned.

The southwestern complex consists of _D. o. chapmani_, _D. o. extractus_, _D. o. attenuatus_ and _D. o. ordii_. _D. o. attenuatus_ and _D. o. chapmani_ are subspecifically distinct owing to geographic isolation, although both kinds show intergradation where their ranges approach that of _D. o. ordii_.

The western desert complex, composed of _D. o. monoensis_, _utahensis_, _cineraceus_, _columbianus_, _cinderensis_, _fetosus_, _celeripes_, _marshalli_, _inaquosus_, _pallidus_, _panguitchensis_ and _fremonti_ was isolated from the other complexes of _D. ordii_ by the Quaternary uplift of the Wasatch Mountain mass, consisting of the Wasatch, Fish Lake and San Pitch mountains and the Wasatch, Aquarius, Paunsaugunt and Kaiparowits plateaus, and the concurrent reëstablishment of drainage systems. The drainages are those of the Colorado and Columbia rivers and that of the Snake River from Blackfoot, Idaho, to the junction with the Columbia. _D. o. fremonti_ has been isolated on the upper reaches of the Fremont River which arises from the eastern side of the Wasatch Divide. _D. o. panguitchensis_ has been isolated in Panguitch Valley as a result of the canyons formed by the Sevier River in Utah. _D. o. cineraceus_, although its subspecific and insular status are in doubt, appears to have been isolated on Dolphin Island, Great Salt Lake, Utah.

The intermontane complex consisting of _D. o. montanus_, _longipes_, _cupidineus_, _nexilis_, _sanrafaeli_ and _uintensis_, like the western desert complex, has become separated from the remainder of the subspecies of the species _D. ordii_ by Quaternary geologic events. _D. o. cupidineus_ has been cut off by the gorges of the Colorado River to the south and the Virgin River to the north. _D. o. sanrafaeli_ is separated from _D. o. uintensis_ by the Tavaputs Plateau and by the Roan and Book cliffs, and is separated from the range of _D. o. nexilis_ by the Colorado River although there is intergradation between _D. o. nexilis_ and _D. o. sanrafaeli_. _D. o. longipes_ has been separated from the rest of this intermontane complex by the San Juan and Colorado rivers, but to the east it intergrades freely with adjacent subspecies. _D. o. montanus_ has been relatively isolated in the San Luis Valley of Colorado and New Mexico, but in the southern part of its range it does show intergradation with other subspecies.

The complexes mentioned above are represented graphically in Figure 22, in a way that expresses some of my ideas as to their genetic relationships.

The indices used to determine the amount of specialization that each complex of subspecies has undergone are as follows:

The Body index (head and body/length of tail × 100) is the expression of the elongation of the tail as an organ of balance while the length of the head and body remain relatively constant. As the tail elongates the index decreases and as the tail becomes shorter the index increases.

The Pedal index (hind foot/head and body × 100) is the expression of the development of the hind foot as an element essential for the saltatorial habit. As the hind foot elongates the index will increase; elongation of the hind foot is interpreted as a specialization.

The Cranial index (breadth across bullae/length of the skull × 100) reflects the degree of development of the tympanic or mastoid region, or both, and is thought to be an adaptation for more acute hearing and possibly for more delicate balance. Inflation of the tympanic bullae is thought to be a specialization. As the auditory bullae become more inflated, the index increases toward 100.

The Bullar index (width of maxillary arches/breadth across bullae × 100) also expresses the degree of inflation of the auditory bullae. In a generalized mammal, at least in the heteromyids, the index would be 100, but as the auditory bullae become larger the index will decrease from 100.

In attempting to arrange the subspecies of _D. ordii_ according to degree of specialization, the geographic positions of the subspecies have been considered along with the information provided by the above-mentioned indices. These indices were used in the same way as were the indices for the species of the genus. In Tables 5 and 6 and in the accounts and maps the subspecies are arranged from the least specialized to the most specialized.

TABLE 5

INDICES FOR THE SUBSPECIES OF _DIPODOMYS ORDII_

======================================================
Body Pedal Cranial Bullar
------------------------------------------------------
richardsoni 88.85 34.35 60.95 88.25
oklahomae 86.75 35.5 61.7 90.25
compactus 127.7 37.25 59.75 88.35
sennetti 94.25 34.0 62.85 85.95
evexus 80.1 35.7 60.5 92.9

medius 80.4 33.7 63.55 85.9
obscurus 62.95 86.4
terrosus 75.25 35.05 61.6 86.85
fremonti 80.55 34.7 62.9 85.5
uintensis 77.2 35.3 62.3 86.0

monoensis 85.4 36.4 63.4 85.6
ordii 79.05 37.6 62.75 86.9
luteolus 75.0 37.05 62.35 86.3
extractus 83.65 34.35 64.3 84.25
chapmani 75.05 36.35 62.9 85.65

montanus 80.4 36.15 64.25 82.5
cinderensis 85.1 37.2 65.15 84.75
fetosus 81.8 38.85 63.95 83.95
utahensis 80.2 36.95 64.45 84.35
columbianus 78.5 37.55 64.25 84.9

idoneus 72.3 36.6 64.2 85.0
priscus 74.9 39.45 62.3 84.95
celeripes 91.85 38.75 65.0 84.25
cineraceus 75.5 39.1 63.9 84.8
marshalli 81.5 37.3 65.2 83.0

inaquosus 78.05 37.9 64.25 83.05
attenuatus 73.5 37.35 64.0 83.4
fuscus 79.8 39.0 64.3 83.2
longipes 75.7 37.1 64.3 82.75
pallidus 76.9 40.75 64.35 84.65

nexilis 77.1 40.7 64.95 78.45
cupidineus 73.15 39.1 64.1 80.85
palmeri 72.25 37.15 65.1 80.45
------------------------------------------------------

TABLE 6

NUMERALS (derived from Table 5) ARE INDICATIVE OF THE RELATIVE
DEGREE OF SPECIALIZATION OF THE SUBSPECIES OF _DIPODOMYS ORDII_

=========================================================
Body Pedal Cranial Bullar Average
---------------------------------------------------------
richardsoni 4 3 3 4 3.5
oklahomae 5 8 5 2 5.0
compactus 1 19 1 3 6.0
sennetti 2 2 10 10 6.0
evexus 15 8 2 1 6.5

medius 12 1 15 11 9.75
obscurus 12 7 10.0
terrosus 25 6 4 6 10.25
fremonti 11 5 12 14 10.5
uintensis 20 7 7 9 10.75

monoensis 6 12 14 13 11.25
ordii 17 23 9 5 13.5
luteolus 27 15 8 8 14.5
extractus 8 4 25 22 14.75
chapmani 26 11 11 12 15.0

montanus 13 10 23 30 19.0
cinderensis 7 18 32 19 19.0
fetosus 9 26 17 24 19.0
utahensis 14 14 28 21 19.25
columbianus 18 22 21 17 19.5

idoneus 31 13 20 15 19.75
priscus 28 30 6 16 20.0
celeripes 3 25 30 23 20.25
cineraceus 24 28 16 18 21.5
marshalli 10 20 33 28 22.75

inaquosus 19 24 22 27 23.0
attenuatus 29 21 18 25 23.25
fuscus 16 27 24 26 23.25
longipes 23 16 26 29 23.5
pallidus 22 32 27 20 25.25

nexilis 21 31 29 33 26.0
cupidineus 30 29 19 31 27.25
palmeri 32 17 31 32 28.0
---------------------------------------------------------

1. _D. o. richardsoni_
2. _D. o. oklahomae_
3. _D. o. compactus_
4. _D. o. sennetti_
5. _D. o. evexus_
6. _D. o. medius_
7. _D. o. obscurus_
8. _D. o. terrosus_
9. _D. o. panguitchensis_
10. _D. o. uintensis_
11. _D. o. sanrafaeli_
12. _D. o. fremonti_
13. _D. o. monoensis_
14. _D. o. ordii_
15. _D. o. luteolus_
16. _D. o. extractus_
17. _D. o. chapmani_
18. _D. o. montanus_
19. _D. o. cinderensis_
20. _D. o. fetosus_
21. _D. o. utahensis_
22. _D. o. columbianus_
23. _D. o. idoneus_
24. _D. o. priscus_
25. _D. o. celeripes_
26. _D. o. cineraceus_
27. _D. o. marshalli_
28. _D. o. inaquosus_
29. _D. o. attenuatus_
30. _D. o. fuscus_
31. _D. o. longipes_
32. _D. o. pallidus_
33. _D. o. nexilis_
34. _D. o. cupidineus_
35. _D. o. palmeri_ ]

=Dipodomys ordii=

Ord Kangaroo Rat

_Dipodomys ordii_ is a medium sized, relatively short-tailed, five-toed species of a color about average for the genus. As in other members of the genus, the hind legs and feet are disproportionately long as an adaptation to the saltatorial mode of progression. The upperparts are buffy, reddish or blackish, depending on the subspecies, but the entire ventral surface, dorsal surfaces of the hind feet, supraorbital and postauricular spots, forelimbs, hip stripes, lateral stripes of the tail and the tail at the base are pure white. The skull has a relatively short rostrum, moderate to large auditory bullae, relatively wide interparietal, relatively wide maxillary arches and grooved upper incisors.

The only other five-toed kangaroo rats with which _Dipodomys ordii_, at places, shares its geographic range, are _Dipodomys panamintinus_ and _Dipodomys microps_. _Dipodomys ordii_ can be distinguished from _Dipodomys panamintinus_ by smaller size (for instance the hind foot is shorter instead of longer than, 44 mm.) and narrower expanse of maxillary arches in relation to breadth across the auditory bullae, and from _Dipodomys microps_ by the awl-shaped, instead of chisel-shaped, lower incisors.

The species _D. ordii_ is divisible into 35 subspecies, accounts of which follow:

=Dipodomys ordii richardsoni= (Allen)

_Dipodops richardsoni_ Allen, Bull. Amer. Mus. Nat. Hist., 3:277,
June 30, 1891.

_Dipodomys phillippi_, Knox, Trans. Kansas Acad. Sci., 4:22, 1875,
(part--the part from Osborne, Kansas).

_Dipodomys phillipsi ordi_, Coues and Allen, Monogr. North
American Rodentia, p. 542, 1877 (part--the part from Ft. Cobb,
Oklahoma).

_Perodipus richardsoni_, Allen, Bull. Amer. Mus. Nat. Hist.,
7:260, August 21, 1895 (part--the part from Pendennis, Kansas).

_Cricetodipus richardsoni_, Trouessart, Catalogus Mammalium,
1:581, 1897.

_Perodipus montanus richardsoni_, Bailey, N. Amer. Fauna, 25:144,
October 1905 (part--the part from Canadian, Texas).

_Perodipus ordii richardsoni_, Goldman, Proc. Biol. Soc.
Washington, 30:113, May 23, 1917.

_Dipodomys ordii richardsoni_, Grinnell, Journ. Mamm., 2:96, May
2, 1921.

_Type._--Male, no. 3025/2345, Amer. Mus. Nat. Hist.; on one of the
sources of the Beaver River, Beaver County, Oklahoma; obtained on
October 26, 1887, by Jenness Richardson and John Rowley, Jr. (After
Allen, original description, type not seen.)

_Range._--Southwestern Nebraska, eastern Colorado, northeastern New
Mexico, Panhandle of Texas, and western parts of Oklahoma and
Kansas; marginal localities are: in Nebraska: Bladen, Haigler; in
Colorado: Olney; in New Mexico: Clayton; in Texas: 6 mi. S and 1
mi. W Quitaque, Vernon; in Oklahoma: 3 mi. S Cleo Springs; in
Kansas: Medora.

_Diagnosis._--Size large (see measurements). Color dark; entire
dorsal surface Cinnamon-Buff, purest on sides and flanks, upper
parts suffused with black; arietiform markings, pinnae of ears,
plantar surfaces of hind feet, dorsal and ventral stripes of tail,
blackish; in some specimens the ventral stripe of tail does not
extend to tip of pencil. Skull large; rostrum short and wide;
nasals long; zygomata relatively heavy; auditory bullae well
inflated and wide; thus with short rostrum giving appearance of
nearly equilateral triangle; upper incisors long and robust.

_Comparisons._--From _Dipodomys ordii luteolus_, _D. o.
richardsoni_ differs as follows: Size smaller in external
measurements except length of body which is longer; color darker,
except on plantar surfaces of hind feet and dorsal and ventral
stripes of the tail which are lighter; ventral stripe of tail, in
most specimens, continuous to end of pencil, whereas in _D. o.
luteolus_ ventral stripe is present on only proximal two-thirds;
skull larger in all measurements taken; zygomatic arch heavier;
auditory bullae relatively as well as actually more inflated;
external auditory meatus egg-shaped as contrasted to nearly round
in _D. o. luteolus_; pterygoid fossae rounded as compared to ovate
in _D. o. luteolus_.

From _Dipodomys ordii oklahomae_, _D. o. richardsoni_ differs as
follows: Size larger in all measurements taken; color darker in
all pigmented areas; skull larger in all respects; auditory bullae
larger and more inflated ventrally; jugal straight or nearly so
instead of bowed laterad; pterygoid fossae smaller; nasals
straight instead of inflated as a "bulb" distally.

For comparisons with _D. o. montanus_ and _D. o. evexus_, see
accounts of those subspecies.

Remarks.--This race of _Dipodomys ordii_ is readily distinguished from _Dipodomys ordii evexus_, from the valley of the upper Arkansas River, by larger size, larger skull and lighter color. Intergradation with _Dipodomys ordii luteolus_ occurs rather freely in northeastern Colorado, as indicated by specimens from 3 miles northeast of Fitzsimmons, 6 miles east and 1 mile north of Denver and Barr Lake. These specimens resemble _D. o. richardsoni_ in light color, greater inflation of the auditory bullae and the shape of the pterygoid fossae but resemble _D. o. luteolus_, to which they are here referred, in the length of the nasals, the least interorbital width and in the external measurements. In the southern part of the range of _D. o. richardsoni_ intergradation occurs with _Dipodomys ordii medius_, as at 6 miles southwest of Muleshoe, Texas. Specimens from there have the long, wide rostrum and narrow skull of _D. o. richardsoni_ but in the sum total of their characters more closely resemble _D. o. medius_. At Texline, Texas, the animals show intergradation in the length and shape of the nasals and degree of convexity of the cranium but are referable to _D. o. richardsoni_.

In fine, intergradation occurs at all points where the range of _D. o. richardsoni_ touches that of any other geographic race. No one series of it is as uniform as are most series of specimens of other known races. _Dipodomys ordii richardsoni_ shows a mixture of characters. Nevertheless, each of the populations studied has characters in most of the animals that make this form recognizable as a taxonomic unit--a unit that seems, as yet, not to have become stabilized even in the central parts of its range.

Coues and Allen (1877:542) list specimens from Fort Cobb, Arkansas. It is known that the Post Office Department, for administrative purposes, attached certain towns and military installations in Indian Territory (now Oklahoma) to the State of Arkansas. Thus it is apparent that Fort Cobb, Arkansas, as recorded by Coues and Allen (_loc. cit._) is Fort Cobb, Oklahoma. Specimens from Fort Cobb would be expected to be _D. o. richardsoni_.

_Specimens examined._--Total, 351, distributed as follows:

=Nebraska=: _Adams County_: Bladen, 10 (AMNH). _Dundy County_:
Haigler, 1 (USBS).

=Colorado=: _Crowley County_: Olney, 1 (USBS). _Kiowa County_:
Chivington, 3 (USBS). _Otero County_: 18 mi. S La Junta, 4 (AMNH);
Higbee, 1 (USBS). _Bent County_: 4 mi. SE Las Animas, 4100 ft., 3
(MVZ). _Prowers County_: Lamar, 9 (LACM); 1 mi. S Lamar, 4000 ft.,
11 (KU). _Baca County_: Gaumes Ranch, 4600 ft., NW Corner, 1
(USBS).

=Kansas=: _Cheyenne County_: 23 mi. NW St. Francis, 5 (KU).
_Rawlins County_: 2 mi. NE Ludell, 2 (KU); 1-1/2 mi. W Ludell, 1
(KU). _Wallace County_: Lacey Ranch, 4-1/2 mi. E and 9 mi. S
Wallace, 1 (KU); unspecified, 2 (KU). _Logan County_: 5 mi. W
Elkader, 2 (KU); unspecified, 1 (UM). _Gove County_: unspecified,
1 (KU). _Trego County_: Banner, 8 (USNM); Parrington Ranch, 12 mi.
S Collyer, 2 (KU); unspecified, 8 (USNM). _Ellis County_: Ellis, 1
(USBS). _Lane County_: Pendennis, 10 (USBS). _Hamilton County_:
Coolidge, 2 (CNHM); 1 mi. E Coolidge, 5 (KU). _Pawnee County_: 1
mi. S Larned, 4 (KU); 2 mi. S and 1/4 mi. W Larned, 2 (KU); 3 mi.
S and 1-1/2 mi. W Larned, 10 (KU). _Edwards County_: Kinsley, 3
(USBS); 3-1/2 mi. E Kinsley, 5 (KU); S side Arkansas River, 2 mi.
S Kinsley, 1 (KU); 1 mi. W and 3-1/2 mi. S Kinsley, 9 (KU).
_Stafford County_: Little Salt Marsh, 15 mi. N and 3 mi. E
Stafford, 2 (KU). _Reno County_: Medora, 1 (UM); 2 mi. W and 1/2
mi. S Medora, 4 (KU). _Kiowa County_: 5 mi. N Belvidere, 1(KU).
_Pratt County_: Cairo, 2 (USBS). _Sedgwick County_: Wichita, 6
(AMNH). _Morton County_: 10 mi. N and 3 mi. E Elkhart, 34-1/2
(KU). _Seward County_: 1 mi. E Arkalon, 7 (KU); Liberal, 1 (KU);
unspecified, 1 (KU). _Meade County_: Meade, 1 (USNM); 13 mi. SW
Meade, 13 (6 AMNH; 7 KU); 17 mi. SW Meade, 2 (KU). _Clark County_:
12 mi. S Ashland, 1 (UM); unspecified, 3 (KU). _Barber County_:
Medicine Lodge, 4 (USBS); 1 mi. W Aetna, 3 (KU); 1/2 mi. W Aetna,
2 (KU); Aetna, 3 (KU); 1 mi. SW Aetna, 1 (KU); 1-1/2 mi. SW Aetna,
1 (KU); 1 mi. S Aetna, 5 (KU); unspecified, 2 (KU). _Harper
County_: 4-1/2 mi. NE Danville, 12 (KU); 2 mi. NE Runnymede, 3
(KU).

=New Mexico=: _Union County_: Clayton, Apache Canyon, 1 (USBS).
_Quay County_: Glenrio, 10 (LACM).

=Oklahoma=: _Cimmaron County_: Kenton, 1 (CM). _Beaver County_:
1-1/2 mi. N Beaver, 7 (KU); Beaver River, 8 (7 AMNH; 1 CNHM).
_Harper County_: 3 mi. S of Englewood, Kansas, 2 (MVZ); 4-1/2 mi.
N Laverne, 1 (UM). _Woods County_: 2 mi. W Edith, 1 (USBS); Alva,
12 (UM); Waynoka, 18 (UM); 3 mi. SW Waynoka, 1 (USBS). _Alfalfa
County_: 4 mi. SE Cherokee, 1 (USBS). _Ellis County_: Shattuck, 1
(USBS). _Woodward County_: Woodward, 9 (USBS). _Major County_: 3
mi. S Cleo Springs, 1 (USBS).

=Texas=: _Dallam County_: Texline, 8 (USBS). _Lipscomb County_:
Lipscomb, 8 (USBS). _Hemphill County_: 17 mi. NE Canadian, 1 (MVZ);
1 mi. W Canadian, along Red Deer River, 12 (MVZ); 1/2 mi. W
Canadian, along Red Deer River, 7 (MVZ); Canadian, 5 (USBS).
_Oldham County_: Tascosa, 6 (USBS). _Wheeler County_: 1 mi. W
Mobeetie, 2 (MVZ); Mobeetie, 8 (USBS); Wallace Ranch, SW Wheeler
County, 1 (TCWC). _Hall County_: Newlin, 1 (USBS). _Wilbarger
County_: Vernon, 5 (USBS). _Floyd County_: 6 mi. S and 1 mi. W
Quitaque, 1 (UM).

=Dipodomys ordii oklahomae= Trowbridge and Whitaker

_Dipodomys oklahomae_ Trowbridge and Whitaker, Journ. Mamm.,
21:343, August 14, 1940.

_Dipodomys ordii oklahomae_, Davis, Journ. Mamm., 23:332, August
14, 1942.

_Type._--Female, young adult, no. 265454, U. S. Nat. Mus., Biol.
Surv. Coll. (formerly Univ. of Oklahoma, Mus. Zool., no. 14517);
north bank of South Canadian River, 2-1/4 mi. S Norman, Cleveland
County, Oklahoma; obtained on March 16, 1934, by H. L. Whitaker,
original no., X-catalog no. 29312 of U. S. Nat. Mus.

_Range._--Known only from the South Canadian River Valley west of
Minco, Canadian County; and east to Lexington, Cleveland County,
Oklahoma.

_Diagnosis._--Size medium (see measurements). Color light, entire
dorsal surface near (_c_) Vinaceous-Buff, paler on sides with
great suffusion of white; arietiform markings, pinnae of ears,
plantar surfaces of hind feet, proximal ventral portion of tail
and dorsal stripe on tail, brownish. Skull of medium size; rostrum
wide; nasals short, projecting but slightly anteriorly to
incisors; zygomatic processes of maxillae heavy; bullae not
greatly inflated.

_Comparisons._--_Dipodomys ordii oklahomae_ differs from _D. o.
richardsoni_ as follows: Size smaller; color lighter in all
pigmented areas; ventral stripe of tail extending only one-fourth
the length rather than three fourths or to end of tail; skull
smaller in all measurements taken; rostrum heavier; auditory
bullae less inflated; pterygoid fossae larger; braincase slightly
more inflated; nasals more expanded distally; interparietal region
wider.

From _Dipodomys ordii ordii_, _D. o. oklahomae differs_ in: Size
larger in all measurements taken; color lighter in all pigmented
areas; ventral stripe of tail extending one fourth length of tail
rather than to end; skull larger in all respects; rostrum heavier;
zygomatic arches heavier; bullae more inflated ventrally; cutting
edge of upper incisors wider; pterygoid fossae larger; braincase
more vaulted; nasals more expanded distally; orbital region
larger; interparietal region wider.

_Remarks._--Trowbridge and Whitaker named this kangaroo rat as a full species. The diagnostic characters were the length and breadth of the rostrum and the relatively great inflation of the auditory bullae. Also, _Dipodomys oklahomae_ was not known to intergrade with any other named kinds. Davis (1942:332) treated _D. oklahomae_ as a subspecies of the earlier named species _Dipodomys ordii_. Certain characters in specimens from the type series of both _D. o. richardsoni_ and _D. oklahomae_, such as the shape and configuration of the nasals, the over-all proportion of the skull, tooth pattern and body proportions through individual variation overlap and indicate that these two groups of animals belong to the same species, even though animals from intermediate geographic areas are not available to show actual intergradation. My findings corroborate Davis' conclusion that _D. oklahomae_ should stand as _Dipodomys ordii oklahomae_. In spite of the great similarities shown by the two groups of animals there are still sufficient diagnostic characters between the two groups to enable them to be segregated easily as valid subspecies.

_Dipodomys ordii oklahomae_ is, for some unknown reason, restricted to a limited geographic range. Specimens examined from the upper reaches of the South Canadian River, farther westward, are all referable to _D. o. richardsoni_ rather than, as would be expected, to _D. o. oklahomae_ since the habitat for these animals is continuous from the type locality of _D. o. oklahomae_ to the upper reaches of the South Canadian River. In length and shape of the nasals, degree of inflation of the auditory bullae and width of the interorbital region these specimens from the upper reaches of the South Canadian River are intergrades between _D. o. richardsoni_ and _D. o. medius_. The range of _D. o. medius_ lies to the south of that of _D. o. richardsoni_ and to the southwest of that of _D. o. oklahomae_.

The present range of _D. o. oklahomae_, as now understood, is the most eastern part of the range of the species _Dipodomys ordii_ and of the genus _Dipodomys_. The existence of _D. o. oklahomae_ in this area is a precarious one since its habitat is limited in extent and is periodically flooded.

Although no specimens are known from the area where intergradation between _D. o. oklahomae_ and _D. o. richardsoni_ would be expected to occur, it would seem that when animals from this region become available, intergradation will be shown to occur.

_Specimens examined._--Total, 8, all from Oklahoma, distributed as
follows: _Grady County_: 4 mi. N Minco, 1 (USBS). _Cleveland
County_: 2-1/4 mi. S Norman, 7 (6 OU; 1 USBS).

=Dipodomys ordii compactus= True

_Dipodomys compactus_ True, Proc. U. S. Nat. Mus., 11:160, January
5, 1889.

_Cricetodipus compactus_, Trouessart, Catalogus Mammalium, 1:581,
1897.

_Perodipus compactus_, Elliot, Field Columbian Museum, Zool. Ser.,
2:240, 1901.

_Dipodomys ordii compactus_, Davis, Journ. Mamm., 23:332, August
14, 1942.

_Type._--None designated but Poole and Schantz (1942:406) assumed
it to be a female, no. 19665/35227, only the skin found, from Padre
Island, Cameron County, Texas. April 3, 1888. Purchased from C. K.
Worthen.

_Range._--Padre and Mustang islands, Cameron County, Texas.

_Diagnosis._--Size medium (see measurements); tail short. Color
light; entire dorsal surface Light Ochraceous-Buff, purest on
sides and flanks, upper parts but lightly suffused with black. A
lighter color phase has entire dorsal surface Cartridge Buff,
purest on sides and flanks, upper parts but lightly washed with
black. In both phases, cheeks white; pinnae of ears, plantar
surfaces of hind feet, dorsal stripe of tail, ventral stripe of
tail (in most specimens) present on proximal third of tail only,
brownish. Skull small; rostrum narrow and long; nasals long;
auditory bullae inflated, but greatest breadth across bullae only
slightly more than breadth across zygomatic processes of maxillae;
interparietal region wide.

_Comparisons._--From _Dipodomys ordii sennetti_, _D. o. compactus
differs_ in: Size slightly less; color lighter in all pigmented
areas; skull smaller; auditory bullae slightly less inflated;
interorbital width less; interparietal region wider; nasals
longer.

From _Dipodomys ordii attenuatus_, _D. o. compactus_ differs in:
Body larger; tail shorter; normal color phase darker, and lighter
color phase lighter; skull larger; rostrum wider and longer;
nasals longer; interorbital region wider; auditory bullae
relatively as well as actually less inflated; interparietal region
wider; pterygoid fossae large and round as opposed to small and
ovoid.

Compared with _Dipodomys ordii medius_ and _Dipodomys ordii
ordii_, _D. o. compactus_ is smaller, lighter in color, and has
less inflated auditory bullae and a smaller skull.

_Remarks._--This subspecies of _Dipodomys ordii_ was originally described as _Dipodomys compactus_ by True in 1889 and stood as a full species until Davis (1942:332) relegated it to subspecific status under _Dipodomys ordii_. Davis (_op. cit._) observed close resemblances in external proportions, size of mastoid bullae, width of supraoccipital, and size and shape of the interparietal, between _Dipodomys ordii_ and _Dipodomys sennetti_ and therefore concluded that they were only subspecies of one species. He observed that the difference between _Dipodomys compactus_ and _Dipodomys sennetti_ was of approximately the same degree as that between _Dipodomys sennetti_ and _Dipodomys ordii_. From this he concluded that all three were subspecies of the one species _Dipodomys ordii_.

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.

_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.

_Comparisons._--From _Dipodomys ordii richardsoni_, _D. o. evexus_
differs as follows: Size smaller in all measurements taken; color
darker; ears darker, dorsal and ventral stripes on tail darker,
arietiform markings darker and more distinct, plantar surfaces of
hind feet darker; skull smaller in all measurements; length, as
expressed in percentage of width of skull, greater in _D. o.
evexus_ (66 per cent in _D. o. evexus_, 62 per cent in _D. o.
richardsoni_ which gives the appearance of a long, narrow skull as
contrasted with a rather short, wide skull); auditory bullae less
expanded laterally, posteriorly and ventrally; interparietal
region relatively wider in proportion to greatest width across
auditory bullae; cutting edge of upper incisors narrower;
pterygoid fossae smaller and more nearly circular.

Compared with _Dipodomys ordii luteolus_, _D. o. evexus_ differs
as follows: Size somewhat smaller in external measurements; color
darker in all pigmented areas; skull smaller in two of the seven
measurements taken but in the other five measurements somewhat
larger; auditory bullae less inflated; cutting edge of upper
incisors narrower; zygomatic arch heavier; pterygoid fossae
smaller and more nearly circular; external auditory meatus ovoid
as contrasted to nearly circular; paroccipital processes smaller.

From _Dipodomys ordii nexilis_, _D. o. evexus_ differs in: Color
darker; rostrum wider and shorter; interorbital region wider;
breadth across maxillary arches greater; auditory bullae less
inflated; interparietal region larger; zygomatic arches heavy and
bowed laterad; molariform teeth smaller; cutting edge of upper
incisors narrower.

For comparison with _Dipodomys ordii montanus_ see account of that
subspecies.

_Remarks._--This race of kangaroo rat, described from the upper Arkansas River Valley, closely resembles _Dipodomys ordii luteolus_ but differs in darker color, slightly smaller body and larger skull.

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 _D. 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.

Compared with _Dipodomys ordii longipes_, _D. o. medius_ is darker
and smaller.

_Remarks._--This hitherto undescribed race of _Dipodomys ordii_ can readily be distinguished from any of its near neighbors by the characters set forth under diagnosis and comparisons.

Intergradation is noted with _D. o. ordii_, _D. o. longipes_, _D. o. montanus_ and _D. o. richardsoni_. Among named races _D. o. medius_ shows closest affinities with _D. o. richardsoni_ but the two are easily separable. The northwestern extremity of the range of _D. o. medius_ is an area of intergradation in which no specimens are clearly of one subspecies or the other. In specimens from 5 miles east of Abiquiu, New Mexico, three-way intergradation occurs. These animals are like _D. o. medius_ in size, _D. o. longipes_ in color and their cranial proportions are as in _D. o. montanus_. At Deer Creek, New Mexico, and at Monahans, Texas, the animals show intergradation in size of body and agree with _D. o. ordii_ in cranial proportions. In specimens from 6 miles southwest of Muleshoe, Texas, intergradation with _D. o. richardsoni_ in the shape of the skull and width of the rostrum is noted. In the sum total of characters studied, however, these specimens are referable to _D. o. medius_.

_Specimens examined._--Total, 129, distributed as follows:

=New Mexico=: _Rio Arriba County_: 2 mi. SE El Rito, 2 (KU); Rio
Alamosa, 15 mi. N Ojo Caliente, 1 (USBS); 6 mi. E Abiquiu, 4
(USBS); Rinconada, 5 (USBS); Espanola, 6 (USBS). _Sandoval
County_: 12 mi. NW Alameda, 5500 ft., 3 (MVZ). _Santa Fe County_:
Seton's Ranch, near Santa Fe, 1 (USBS); 8 mi. SW Santa Fe, 8 (KU);
San Pedro, 3 (USBS). _San Miguel County_: Pecos, 2 (USBS); 3 mi. S
Pecos, 2 (USBS); Rowe, 6 (LACM). _Bernallilo County_: Bear Canyon,
Sandia Mountains, 7 (USBS); Pajarito, 3 (MVZ). _Guadalupe County_:
Santa Rosa, 10 (USBS). _Lincoln County_: 44 mi. NW Roswell, 5
(MVZ). _De Baca County_: 8 mi. N Fort Sumner, 9 (USBS). _Roosevelt
County_: Kenna, 4 (LACM). _Curry County_: 4 mi. W and 2-3/4 mi. N
Clovis, 1 (MVZ). _Chaves County_: 40 mi. N Roswell, 2 (USBS); 35
mi. N Roswell, 2 (USBS); 15 mi. NE Roswell, 8 (LACM); Stinking
Springs Lake, 3 (USBS).

=Texas=: _Bailey County_: 6 mi. SW Muleshoe, 5 (UM); 9 mi. SW
Muleshoe, 2 (UM). _Garza County_: 7 mi. E Post, 5 (UM). _Martin
County_: Stanton, 4 (USBS). _Howard County_: 6 mi. NE Coahoma, 7
(UM); 1 mi. S Coahoma, 1 (UM); 5 mi. W Big Springs, 2400 ft., 1
(MVZ). _Mitchell County_: Colorado, 5 (USBS). _Winkler County_: 20
mi. N Monahans, 1 (USBS). _Ward County_: Monahans, 1 (USBS).

=Dipodomys ordii obscurus= (Allen)

_Perodipus obscurus_ Allen, Bull. Amer. Mus. Nat. Hist., 19:603,
November 12, 1903.

_Dipodomys ordii obscurus_, Grinnell, Journ. Mamm., 2:96, May 2,
1921.

_Type._--Male, adult, no. 20957, Amer. Mus. Nat. Hist.; Rio Sestin,
northwestern Durango, Mexico; obtained on April 13, 1903, by J. H.
Batty. (Type not seen.)

_Range._--Northwestern and northern Durango, Mexico; marginal
localities are: Rosario, Rio Sestin, Mt. San Gabriel, Rio del
Bocas, Villa Ocampo.

_Diagnosis._--Size small (see measurements). Color dark, entire
dorsal surface (_16''_) between Pinkish Cinnamon and
Cinnamon-Buff, purest on sides, flanks and cheeks, upper parts
strongly suffused with black; arietiform markings, plantar
surfaces of hind feet, pinnae of ears, dorsal and ventral stripes
of tail, brownish. Skull of medium size, nasals long and flared
distally; rostrum long and narrow; interorbital region relatively
narrow; auditory bullae less inflated than in _Dipodomys ordii
palmeri_; interparietal region narrow; zygomatic arches heavy and
bowed laterad; pterygoid fossae ovoid; braincase but slightly
vaulted.

_Comparisons._--From _Dipodomys ordii palmeri_, _D. o. obscurus_
differs in: Size larger; color lighter; nasals shorter and more
flared distally; interorbital width less; lacrimal processes
larger; auditory bullae less inflated; pterygoid fossae ovoid as
opposed to subcircular; zygomatic arches heavier; rostrum shorter
and wider.

From _Dipodomys ordii ordii_, _D. o. obscurus_ differs as follows:
Size smaller; color darker; skull smaller; nasals longer; rostrum
narrower and shorter; interorbital width greater; interparietal
region narrower; narrower across auditory bullae; zygomatic arches
heavier and more bowed laterally; pterygoid fossae more ovoid;
breadth across maxillary arches greater; external auditory meatus
smaller.

With _Dipodomys ordii attenuatus_ and _Dipodomys ordii sennetti_,
_D. o. obscurus_ needs no comparison since it is larger and darker
than either of those subspecies and can readily be told from the
latter by the greater expansion of the auditory bullae.

For comparison with _Dipodomys ordii fuscus_ see account of that
subspecies.

_Remarks._--_D. o. obscurus_ seemingly is not a far-ranging subspecies. The only examples referable to it come from a relatively restricted area of Durango, Mexico. One specimen from Rio del Bocas, Durango, is not typical and shows the characters described for the animals from Chihuahua City and from Casas Grandes. I have considered the possibility that this specimen is an intergrade between _D. o. obscurus_ and an unnamed subspecies ranging to the northeastward. The other specimens in the series from Rio del Bocas are typical of _D. o. obscurus_.

_Specimens examined._--Total, 69, all from Durango, distributed as
follows: Rosario, 20 (AMNH); Villa Ocampo, 5 (AMNH); Rio Sestin, 30
(28 AMNH; 2 CNHM); Mt. San Gabriel, 2 (AMNH); Rio del Bocas, 11
(AMNH); Rancho Santuario, 1 (AMNH).

1. _D. o. richardsoni_ 2. _D. o. oklahomae_ 3. _D. o. compactus_ 4.
_D. o. sennetti_ 6. _D. o. medius_ 7. _D. o. obscurus_ 14. _D. o.
ordii_ 16. _D. o. extractus_ 23. _D. o. idoneus_ 29. _D. o.
attenuatus_ 30. _D. o. fuscus_ 31. _D. o. longipes_ 35. _D. o.
palmeri_ ]

=Dipodomys ordii terrosus= Hoffmeister

_Dipodomys ordii terrosus_ Hoffmeister, Proc. Biol. Soc.
Washington, 55:165, December 31, 1942.

_Dipodomys phillipsi ordi_, Coues and Allen, Monogr. North
American Rodentia, p. 541, August, 1877 (part--the part from
Yellowstone River, Montana).

_Perodipus montanus richardsoni_, Cary, N. Amer. Fauna, 49:124,
December, 1926 (part--the part from Glendive, Montana).

_Type._--Male, no. 93477, Mus. Vert. Zool., Univ. California;
Yellowstone River, 5 mi. W Forsyth, 2,750 ft., Rosebud County,
Montana; obtained on June 2, 1940, by J. R. Alcorn, original no.
1528.

_Range._--Extreme southwestern Saskatchewan and southeastern
Alberta, eastern half of Montana, northern Wyoming and probably
extreme western North Dakota; marginal localities are: 50 mi. W
Swift Current, Saskatchewan; "near Medicine Hat," Alberta; in
Wyoming, Sheep Creek, and 23 mi. SW Newcastle; in Montana,
Medicine Rocks (14 mi. NE Ekalaka), and Glendive.

_Diagnosis._--Size large (see measurements). Color dark, entire
dorsal surface near (_c_) Ochraceous-Buff, purest on sides and
flanks; upper parts mixed with black; arietiform markings, pinnae
of ears, dorsal and ventral stripes of tail and plantar surfaces
of hind feet brownish-black. Skull large; rostrum short, wide and
deep; braincase slightly vaulted; auditory bullae markedly
inflated ventrally; zygomatic arches heavy and bowed laterad;
upper incisors long and robust.

_Comparisons._--From _Dipodomys ordii priscus_, _D. o. terrosus_
differs as follows: Size larger in all measurements taken, except
for length of hind feet, which is less; color darker in all
pigmented areas; skull larger in all parts measured except width
of interparietal, which is less; auditory bullae more inflated
ventrally; zygomatic processes of maxillae wider; rostrum deeper
and shorter.

From _Dipodomys ordii richardsoni_, _D. o. terrosus_ differs as
follows: Size larger; color darker in all pigmented areas; ventral
stripe of tail extending farther distally; skull larger except in
width across auditory bullae, which is the same.

For comparison with _Dipodomys ordii luteolus_ see account of that
subspecies.

_Remarks._--As noted in the comparisons, _D. o. terrosus_ is larger and darker than _D. o. priscus_, _D. o. luteolus_ or _D. o. richardsoni_, its closest geographic neighbors, and does not resemble any of them, but rather resembles _D. o. longipes_ and _D. o. evexus_ in size and appearance, both of which are distantly removed geographically.

Like other subspecies of the species _D. ordii_, _D. o. terrosus_ prefers sandy soils to those of any other type. Two miles east and 1 mile south of Forsyth, Montana, animals were trapped on lenses of sandy soil. These lenses alternated with areas of black loam of similar size. It was noteworthy that burrows were found only in the areas of sandy soil, although paths used by the rats when foraging did extend onto and several crossed the lenses of black loam. We were not permitted to excavate any of these burrows, but conversation with farmers of the immediate vicinity indicated that the burrows were not deep. An eight-inch disc would frequently plow out nests and food caches. It was said that each of several caches contained as much as a peck of wheat.

Intergradation was noted in animals from 23 miles southwest of Newcastle and Arvada, Wyoming. In animals from both localities the pterygoid fossae are more as in _D. o. luteolus_ but referable to _D. o. terrosus_. The specimens from Arvada, although immature, possessed cranial characters which were intermediate between those of _D. o. terrosus_ and _D. o. luteolus_ but the specimens are referable to the former.

_Specimens examined._--Total, 74, distributed as follows:

=Montana=: _Petroleum County_: 24 mi. N Roundup, 8 mi. SW
Flatwillow, 2 (UM). _Garfield County_: Jordan, 10 (1 UM; 2 MVZ; 7
AMNH). _Dawson County_: Glendive, 9 (USNM). _Musselshell County_:
Harvey Ranch, Melstone, 3 (MVZ). _Rosebud County_: Yellowstone
River, 5 mi. W Forsyth, 2750 ft., 7 (MVZ); 2 mi. E and 1 mi. S
Forsyth, 2600 ft., 8 (KU). _Custer County_: Miles City, 1 (USBS).
_Yellowstone County_: Billings, 2 (1 USBS; 1 MVZ). _Big Horn
County_: Fort Custer, 1 (USBS); Crow Agency, 1 (USBS). _Powder
River County_: Powderville, 4 (USBS). _Carter County_: Medicine
Rocks, 15 mi. N Ekalaka, 2 (USBS); Medicine Rocks, 14 mi. N
Ekalaka, 2 (USBS); Clark's Fork, 1 (USBS).

=Wyoming=: _Big Horn County_: Dry Creek, 10 mi. W Germania, 1
(USBS); 3 mi. E Germania, 1 (USBS); Greybull, 2 (USBS); Bighorn
Basin, 1 (USBS). _Sheridan County_: Arvada, 8 (USBS). _Campbell
County_: Little Powder River, 1 (USBS). _Weston County_:
Newcastle, 2 (USBS); 23 mi. SW Newcastle, 4 (USBS). _Fremont
County_: Wilson's Ranch, Sheep Creek, S base Owl Creek Mountains,
1 (USBS).

_Additional records._--=Canada= (Anderson, 1946:131): _Alberta_:
near Medicine Hat, 1; _Saskatchewan_: near Shackleton, 45-50 mi.
NW Swift Current, 1; near Tompkins, 50 mi. W Swift Current, 1.

=Dipodomys ordii fremonti= Durrant and Setzer

_Dipodomys ordii fremonti_ Durrant and Setzer, Bull. Univ. Utah, 35
(no. 26):21, June 30, 1945.

_Type._--Female, no. 15661, Carnegie Museum, Pittsburgh,
Pennsylvania; Torrey, 7000 ft., Wayne County, Utah; obtained on
July 19, 1938, by W. F. and F. H. Wood, original no. 1562.

_Range._--Known only from the type locality.

_Diagnosis._--Size small (see measurements). Color dark, entire
dorsal surface Cinnamon-Buff, purest on sides, flanks and cheeks;
upper parts strongly suffused with black; arietiform markings,
pinnae of ears, plantar surfaces of hind feet, dorsal and ventral
stripes of tail, brownish. Skull small; upper incisors long;
rostrum deep; jugal bowed laterally; diastema long; upper
molariform tooth-row long.

_Comparisons._--From _Dipodomys ordii panguitchensis_, _D. o.
fremonti_ differs in: Color lighter in all pigmented areas,
particularly ears which are light brown in _D. o. fremonti_ and
black in _D. o. panguitchensis_; skull larger in all measurements
taken; upper incisors longer; rostrum deeper; auditory bullae
deeper; jugal bowed laterally rather than straight; diastema
longer.

From _Dipodomys ordii cupidineus_, _longipes_, _nexilis_,
_uintensis_ and _sanrafaeli_, _D. o. fremonti_ can readily be
distinguished by its smaller size and generally darker color.

_Remarks._--This subspecies of _Dipodomys ordii_ inhabits the upper reaches of the Fremont River in west-central Wayne County, Utah. _D. o. fremonti_ appears to be isolated and is known only from the type locality. _D. o. fremonti_ is so remarkably different from any other subspecies of _Dipodomys ordii_ that a long period of isolation from the ancestral stock (which probably gave rise also to _Dipodomys ordii utahensis_ and _Dipodomys ordii panguitchensis_) is indicated. Although intergradation is not known to occur with other kinds, differentiation has not progressed far enough for these animals to be recognized as a distinct species.

The subspecies closest, geographically, to _D. o. fremonti_ is _D. o. cupidineus_ from which _D. o. fremonti_ differs more than from any of the other named forms.

_Specimens examined._--Total, 9, from Utah, as follows: _Wayne
County_: Torrey, 7000 ft., 9 (CM).

=Dipodomys ordii uintensis= Durrant and Setzer

_Dipodomys ordii uintensis_ Durrant and Setzer, Bull. Univ. Utah,
35 (no. 26):27, June 30, 1945.

_Perodipus longipes_, Allen, Bull. Amer. Mus. Nat. Hist., 8:246,
November 1896 (part--the part from Uncompahgre Indian Reservation,
Utah).

_Dipodomys ordii luteolus_, Moore, Journ. Mamm., 11:88, February,
1930 (part--the part from Vernal, Utah).

_Type._--Male, adult, no. 11634, Carnegie Museum, Pittsburgh,
Pennsylvania; Red Creek, 6,700 ft., 2 mi. N Fruitland, Duchesne
County, Utah; obtained on August 15, 1936, by J. K. and M. T.
Doutt, original no. 3433.

_Range._--Uinta basin of the White, Green and Duchesne river
drainage in northeastern Utah; marginal occurrences are: 2 mi. N
Fruitland, 10 mi. S Ouray, Vernal.

_Diagnosis._--Size large (see measurements); hind foot short.
Color dark; entire dorsal surface, near (_c_) Cinnamon-Buff,
purest on sides and flanks, with moderate suffusion of black on
upper parts; cheeks white; arietiform markings, pinnae of ears,
plantar surfaces of hind feet, dorsal and ventral stripes of tail,
brownish. Skull large; frontomaxillary suture convex mediad;
lacrimal process large; styloid process projects, on ventral
surface of tympanic bulla, beyond middle of external auditory
meatus; nasals flared distally.

_Comparisons._--From _Dipodomys ordii priscus_, _D. o. uintensis_
differs in: Hind foot shorter; color darker; styloid process
projects on ventral part of tympanic bulla well anterior to middle
of external auditory meatus as opposed to projecting to middle;
depth of foramen magnum, expressed in percentage of width across
posterior margin of occipital condyles, greater (86 per cent in
_D. o. uintensis_ and 81 per cent in _D. o. priscus_);
frontomaxillary suture convex mediad as opposed to nearly
straight; lacrimal processes larger; nasals more flared distally.

From _Dipodomys ordii nexilis_, _D. o. uintensis_ differs as
follows: Size smaller; color lighter; interorbital breadth greater;
frontomaxillary suture convex mediad as opposed to concave;
lacrimal processes larger; nasals more flared distally; narrower
across auditory bullae; basal length greater; zygomatic arches
bowed laterad as opposed to relatively straight.

From _Dipodomys ordii longipes_, _D. o. uintensis_ differs as
follows: Size smaller; color darker; auditory bullae wider, longer
and deeper; frontomaxillary suture convex mediad as opposed to
nearly straight; greatest breadth across auditory bullae less.

For comparison with _Dipodomys ordii sanrafaeli_ see account of
that subspecies.

_Remarks._--This large, rather dark race inhabits the desert valleys of the White, Green and Duchesne rivers in northeastern Utah. The race nearest geographically, as well as morphologically, is _Dipodomys ordii priscus_. Intergradation occurs with the latter subspecies at Vernal, Uintah County, in cranial measurements and in color. On the basis of color alone _D. o. uintensis_ can be distinguished from _D. o. sanrafaeli_, the geographic race to the south. Specimens from Jensen are intermediate in color and cranial measurements between _Dipodomys ordii nexilis_ and _D. o. uintensis_ but are referable to the latter.

_Specimens examined._--Total, 40, all from Utah, distributed as
follows: _Duchesne County_: Red Creek, 6700 ft., 2 mi. N Fruitland,
4 (CM); 10 mi. S Myton, 1 (UU); 20 mi. S Myton, 1 (RH). _Uintah
County_: Vernal, 1 (BYU); 20 mi. E Ouray, 5 (CM); Junction Green
and White rivers, 4800 ft., 2 mi. S Ouray, 5 (CM); Pariette Bench,
5000 ft., 8 mi. S Ouray, 8 (CM); Desert Springs, 10 mi. S Ouray, 4
(CM); Pariette Bench, 12 mi. S Ouray, 2 (CM); Jensen, 5 (BYU); E
side Green River, 3 mi. S Jensen, 4 (CM).

=Dipodomys ordii sanrafaeli= Durrant and Setzer

_Dipodomys ordii sanrafaeli_ Durrant and Setzer, Bull. Univ. Utah,
35 (no. 26):26, June 30, 1945.

_Dipodomys ordii longipes_, Stanford, Journ. Mamm., 12:360,
November, 1931 (part--the part from King's Ranch, Utah).