Dipodomys ordii

Distribution of subspecies of Dipodomys ordii.

Fig. 23.Distribution of subspecies ofDipodomys ordii.1.D. o. richardsoni13.D. o. monoensis25.D. o. celeripes2.D. o. oklahomae14.D. o. ordii26.D. o. cineraceus3.D. o. compactus15.D. o. luteolus27.D. o. marshalli4.D. o. sennetti16.D. o. extractus28.D. o. inaquosus5.D. o. evexus17.D. o. chapmani29.D. o. attenuatus6.D. o. medius18.D. o. montanus30.D. o. fuscus7.D. o. obscurus19.D. o. cinderensis31.D. o. longipes8.D. o. terrosus20.D. o. fetosus32.D. o. pallidus9.D. o. panguitchensis21.D. o. utahensis33.D. o. nexilis10.D. o. uintensis22.D. o. columbianus34.D. o. cupidineus11.D. o. sanrafaeli23.D. o. idoneus35.D. o. palmeri12.D. o. fremonti24.D. o. priscus

Ord Kangaroo Rat

Dipodomys ordiiis 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 whichDipodomys ordii, at places, shares its geographic range, areDipodomys panamintinusandDipodomys microps.Dipodomys ordiican be distinguished fromDipodomys panamintinusby 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 fromDipodomys micropsby the awl-shaped, instead of chisel-shaped, lower incisors.

The speciesD. ordiiis divisible into 35 subspecies, accounts of which follow:

Dipodops richardsoniAllen, 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.—FromDipodomys ordii luteolus,D. o. richardsonidiffers 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 inD. o. luteolusventral 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 inD. o. luteolus; pterygoid fossae rounded as compared to ovate inD. o. luteolus.

FromDipodomys ordii oklahomae,D. o. richardsonidiffers 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 withD. o. montanusandD. o. evexus, see accounts of those subspecies.

Remarks.—This race ofDipodomys ordiiis readily distinguished fromDipodomys ordii evexus, from the valley of the upper Arkansas River, by larger size, larger skull and lighter color. Intergradation withDipodomys ordii luteolusoccurs 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 resembleD. o. richardsoniin light color, greater inflation of the auditory bullae and the shape of the pterygoid fossae but resembleD. 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 ofD. o. richardsoniintergradation occurs withDipodomys ordii medius, as at 6 miles southwest of Muleshoe, Texas. Specimens from there have the long, wide rostrum and narrow skull ofD. o. richardsonibut in the sum total of their characters more closely resembleD. o. medius. AtTexline, Texas, the animals show intergradation in the length and shape of the nasals and degree of convexity of the cranium but are referable toD. o. richardsoni.

In fine, intergradation occurs at all points where the range ofD. o. richardsonitouches 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 richardsonishows 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 byCoues and Allen(loc. cit.) is Fort Cobb, Oklahoma. Specimens from Fort Cobb would be expected to beD. 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 oklahomaeTrowbridge 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 oklahomaediffers fromD. o. richardsonias 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.

FromDipodomys ordii ordii,D. o. oklahomae differsin: 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 oklahomaewas not known to intergrade with any other named kinds.Davis(1942:332) treatedD. oklahomaeas a subspecies of the earlier named speciesDipodomys ordii. Certain characters in specimens from the type series of bothD. o. richardsoniandD. 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 andindicate 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 corroborateDavis'conclusion thatD. oklahomaeshould stand asDipodomys 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 oklahomaeis, 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 toD. o. richardsonirather than, as would be expected, toD. o. oklahomaesince the habitat for these animals is continuous from the type locality ofD. o. oklahomaeto 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 betweenD. o. richardsoniandD. o. medius. The range ofD. o. mediuslies to the south of that ofD. o. richardsoniand to the southwest of that ofD. o. oklahomae.

The present range ofD. o. oklahomae, as now understood, is the most eastern part of the range of the speciesDipodomys ordiiand of the genusDipodomys. The existence ofD. o. oklahomaein 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 betweenD. o. oklahomaeandD. o. richardsoniwould 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 compactusTrue, 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.—FromDipodomys ordii sennetti,D. o. compactus differsin: Size slightly less; color lighter in all pigmented areas; skull smaller; auditory bullae slightly less inflated; interorbital width less; interparietal region wider; nasals longer.

FromDipodomys ordii attenuatus,D. o. compactusdiffers 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 withDipodomys ordii mediusandDipodomys ordii ordii,D. o. compactusis smaller, lighter in color, and has less inflated auditory bullae and a smaller skull.

Remarks.—This subspecies ofDipodomys ordiiwas originally described asDipodomys compactusby True in 1889 and stood as a full species untilDavis(1942:332) relegated it to subspecific status underDipodomys ordii.Davis(op. cit.) observed close resemblances in external proportions, size of mastoid bullae, width of supraoccipital, and size and shape of the interparietal, betweenDipodomys ordiiandDipodomys sennettiand therefore concluded that they were only subspecies of one species. He observed that the difference betweenDipodomys compactusandDipodomys sennettiwas of approximately the same degree as that betweenDipodomys sennettiandDipodomys ordii. From this he concluded that all three were subspecies of the one speciesDipodomys ordii.

In any sizeable sample ofDipodomys sennettithere are crania closely resembling those ofDipodomys ordii ordiiand others closely resembling those ofDipodomys compactus. The external proportions of bothD. sennettiandD. compactusare duplicated inD. ordiifrom El Paso and conversely, specimens with the proportions of typicalD. o. ordiioccur in populations ofD. sennettiandD. compactus. Thus, it appears thatDavis'usage of the nameDipodomys ordii compactusshould stand although there may be a hiatus in geographic occurrence betweenD. ordiiandD. sennetti, as of course there is betweenD. sennettiandD. compactus.

InD. o. compactusthere is a complete enamel ring around the occlusal surface of each molariform tooth; inD. o. ordiithis ring is incomplete lingually on each of the molariform teeth and labially on the first three, and in some individuals ofD. o. sennettithe enamel ring is complete and in others it is incomplete labially and lingually as inD. 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).

Dipodops sennettiAllen, 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 byBailey(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.—FromDipodomys ordii ordii,D. o. sennettidiffers 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.

FromDipodomys ordii medius,D. o. sennettidiffers as follows: Size smaller; color darker, but with less red in pelage; skull markedly smaller in all respects.

FromDipodomys ordii compactus,D. o. sennettidiffers 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 (seeHowell, 1932) of auditory bullae larger.

Remarks.—Dipodomys sennetti, along withDipodomys compactus, was regarded byDavisas conspecific withDipodomys ordii. Reasons for placing these two kinds of kangaroo rats as subspecies ofD. ordiiare given in the account ofDipodomys 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 evexusGoldman, Journ. Washington Acad. Sci., 23:468, October 15, 1933.

Perodipus montanus richardsoniWarren, 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.—FromDipodomys ordii richardsoni,D. o. evexusdiffers 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 inD. o. evexus(66 per cent inD. o. evexus, 62 per cent inD. o. richardsoniwhich 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 withDipodomys ordii luteolus,D. o. evexusdiffers 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.

FromDipodomys ordii nexilis,D. o. evexusdiffers 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 withDipodomys ordii montanussee account of that subspecies.

Remarks.—This race of kangaroo rat, described from the upper Arkansas River Valley, closely resemblesDipodomys ordii luteolusbut 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 ofD. o. evexusis separated from that ofD. o. montanusby a high, transverse ridge of the Rocky Mountains which is inhospitable to these animals. Much territory inhospitable toDipodomysintervenes also between the ranges ofD. o. evexusand 3883D. o. luteolus, but there are areas connecting the northern part of the range ofD. o. evexusand the southwestern part of the known range ofD. o. luteolus, in whichDipodomysmay 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).

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.—FromDipodomys ordii richardsoni,D. o. mediusdiffers 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; medialmastoid 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.

FromDipodomys ordii montanus,D. o. mediusdiffers 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 withDipodomys ordii ordiiandDipodomys ordii sennetti,D. o. mediusis larger and darker. The skull is also larger in all measurements taken.

Compared withDipodomys ordii longipes,D. o. mediusis darker and smaller.

Remarks.—This hitherto undescribed race ofDipodomys ordiican readily be distinguished from any of its near neighbors by the characters set forth under diagnosis and comparisons.

Intergradation is noted withD. o. ordii,D. o. longipes,D. o. montanusandD. o. richardsoni. Among named racesD. o. mediusshows closest affinities withD. o. richardsonibut the two are easily separable. The northwestern extremity of the range ofD. o. mediusis 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 likeD. o. mediusin size,D. o. longipesin color and their cranial proportions are as inD. o. montanus. At Deer Creek, New Mexico, and at Monahans, Texas, the animals show intergradation in size of body and agree withD. o. ordiiin cranial proportions. In specimens from 6 miles southwest of Muleshoe, Texas, intergradation withD. o. richardsoniin the shape of the skull and width of the rostrum is noted. In the sum total of characters studied, however, these specimens are referable toD. 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).

Perodipus obscurusAllen, 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 inDipodomys ordii palmeri; interparietal region narrow; zygomatic arches heavy and bowed laterad; pterygoid fossae ovoid; braincase but slightly vaulted.

Comparisons.—FromDipodomys ordii palmeri,D. o. obscurusdiffers 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.

FromDipodomys ordii ordii,D. o. obscurusdiffers 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.

WithDipodomys ordii attenuatusandDipodomys ordii sennetti,D. o. obscurusneeds 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 withDipodomys ordii fuscussee account of that subspecies.

Remarks.—D. o. obscurusseemingly 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 betweenD. o. obscurusand an unnamed subspecies ranging to the northeastward. The other specimens in the series from Rio del Bocas are typical ofD. 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).

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