_Distribution._--Upper Rio Grande and San Luis valleys of the Southern Rocky Mountains, in northern New Mexico and southern Colorado (see fig. 1).
_Distinctive characters._--Yellowish Red (5YR 4/6); size large (see measurements); posterior tongues of premaxillae long, thin, and ac.u.minate; nasals long, thin, posterior margins usually forming a wide V (see fig. 4); bullae rounded ventrally; interpterygoid s.p.a.ce V-shaped, lacking median spicule.
_Comparisons._--From _T. b. aureus_, _T. b. pervagus_ differs as follows: reddish, never yellowish or blackish; posterior tongues of premaxillae thin and not deeply serrated; posterior margins of nasals forming a shallow V; interpterygoid s.p.a.ce V-shaped, lacking a median spicule; basioccipital narrow. For comparisons with _T. b.
internatus_, _T. b. cultellus_, and _T. b. rubidus_, see accounts of those subspecies.
_Remarks._--_T. b. pervagus_ is a well-defined subspecies. There is little variation between the topotypes and specimens from Colorado.
_Specimens examined._--Total 20. _Colorado_: Conejos Co.: _Antonito_, 5 (USNM); _7 mi. E Antonito_, 2 (USNM); 12 mi. E Antonito, 1 (USNM); Conejos River, 6 mi. W Antonito, 8300 ft., 2 (USNM). _New Mexico_: Rio Arriba Co.: Espanola, 10 (USNM).
=Th.o.m.omys bottae internatus= Goldman
_Th.o.m.omys bottae internatus_ Goldman, Jour. Washington Acad.
Sci., 26:115, March 15, 1936; Warren, Mammals of Colorado, p.
160, 1942; Kelson, Univ. Kansas Publ., Mus. Nat. Hist., 5:63, October 1, 1951.
_Th.o.m.omys aureus pervagus_, Warren, Mammals of Colorado, p. 80, 1910, part; Cary, N. Amer. Fauna, 33:137, August 17, 1911, part.
_Th.o.m.omys fulvus pervagus_, Bailey, N. Amer. Fauna, 39:82, November 15, 1915, part.
_Holotype._--Adult male, skin and skull, number 150997, United States National Museum, obtained at Salida, 7000 feet, Chaffee County, Colorado, by Merritt Cary, November 10, 1907.
_Distribution._--Southern Rocky Mountain Province; southwestern part of the Colorado Piedmont, and Raton Section of the Great Plains, to the east of the Sangre De Cristo Range (see fig. 1).
_Distinctive characters._--Yellowish Red (5YR 5/6.5); size medium (see measurements); posterior tongues of premaxillae short; posterior margins of nasals forming a V (see fig. 6); bullae pointed ventrally; interpterygoid s.p.a.ce V-shaped, lacking a median spicule; basioccipital narrow.
_Comparisons._--From _T. b. pervagus_, topotypes of _T. b.
internatus_ differ as follows: uniformly paler, not so reddish; smaller; skull smaller; posterior tongues of premaxillae shorter; bullae smaller, less inflated, and more pointed ventrally; zygomata less angular.
For comparisons with _T. b. cultellus_ and _T. b. rubidus_, see accounts of those subspecies.
_Remarks._--The dividing line between _T. b. internatus_ and _T. b.
cultellus_ is drawn arbitrarily since only one specimen has been collected between La Veta Pa.s.s and the border of New Mexico.
When Goldman (1936:115) named _T. b. internatus_ he included specimens from Union and Colfax counties, New Mexico, and specimens from Gardner, Colorado (not Garfield as stated by Kelson, 1951:66). The specimens from New Mexico and a specimen from Fishers Peak, Colorado, were subsequently a.s.signed to _T. b. cultellus_ by Kelson (_loc. cit._).
The specimen from Fishers Peak shows some characters that might be interpreted as intermediate between _internatus_ and _cultellus_, but shows also some unique characters that can be understood only by further collecting in the regions north and northeast of the type locality of _T. b. cultellus_.
Variation is slight in the large series of topotypes of _T. b.
internatus_. Specimens from other localities in the western part of the range differ little from the topotypes. Specimens from one mile west of Coaldale have slightly more inflated bullae that are more flattened ventrally. Specimens from five miles south of Cotopaxi also have the bullae more flattened ventrally.
Specimens from localities bordering the plains differ from the topotypes and near topotypes, and in general show greater variation from locality to locality. Specimens from 12 miles north of Canon City are dark, resembling _T. b. rubidus_, but cranially agree with specimens from near Colorado Springs in being indistinguishable from specimens from Salida.
Specimens from St. Charles Mesa and Bear Creek near Walsenburg differ from the topotypes in having wider rostra. The specimens from St.
Charles Mesa have more inflated bullae.
_Specimens examined._--Total 93. Chaffee Co.: 2 mi. NNW Salida, 7100 ft., 3; _Salida_, 28 (20 ERW, 8 USNM). Fremont Co.: 12 mi. N Canon City, 5; 1 mi. W Coaldale, 8; _Cotopaxi_, 1 (CSU); _5 mi. S Cotopaxi_, 12. El Paso Co.: 1-1/4 mi. S Colorado Springs, 2; _9 mi.
SSW Colorado Springs_, 2; _17 mi. S Colorado Springs_, 1. Custer Co.: 2-1/2 mi. S Wetmore, 3; Santa Fe Drive and 20th Lane, Blende, 1; St. Charles Mesa, 5600 ft., 2 (CSU); Fork of Huerfano and Cucharas rivers, 2 (CMNH). Huerfano Co.: 11 mi. WNW Gardner, 7000 ft., 3; Gardner, 7000 ft., 2 (USNM); 1-1/2 mi. S Redwing, 3; Bear Creek, near Walsenburg, 2 (CSU); 1 mi. E La Veta, 8; 5 mi. SE La Veta, 2.
=Th.o.m.omys bottae cultellus= Kelson
_Th.o.m.omys bottae cultellus_ Kelson, Univ. Kansas Publ., Mus.
Nat. Hist., 5:64, October 1, 1951.
_Th.o.m.omys fulvus_, Cary, Proc. Biol. Soc. Washington, 20:26, March 27, 1907; Warren, Colorado College Publ., 33:76, January, 1908; Warren, Mammals of Colorado, p. 80, 1910.
_Th.o.m.omys fulvus fulvus_, Bailey, N. Amer. Fauna, 39:80, November 15, 1915.
_Holotype._--Adult male, skin and skull, number 70919, United States National Museum, Halls Peak, Mora County, New Mexico; January 13, 1895, obtained by C. Barber.
_Distribution._--Raton Section of the Great Plains in northern New Mexico and extreme southern Colorado (see fig. 1).
_Distinctive characters._--Dark (topotypes); size medium (see measurements); posterior tongues of premaxillae short; posterior margins of nasals forming a V (see fig. 5).
_Comparisons._--From _T. b. pervagus_, topotypes of _T. b.
cultellus_ differ as follows: darker, not so reddish; smaller; skull smaller; zygomatic arches relatively longer; bullae proportionately smaller and less inflated; basioccipital proportionately wider; posterior tongues of premaxillae shorter.
Topotypes of _T. b. cultellus_ most closely resemble those of _T. b.
internatus_ but differ as follows: darker; zygomatic arches more widely spreading, not so nearly parallel; nasals not so wide; bullae slightly more inflated.
For a comparison with _T. b. rubidus_ see the account of that subspecies.
_Remarks._--Kelson (1951:64) named _T. b. cultellus_ on the basis of six dark specimens (Dark Reddish Brown 5YR 3/4 and 2/2). Nowhere else within the range of this subspecies, as defined by Kelson, do any specimens resemble the topotypes in color.
After comparing topotypes of _T. b. cultellus_ with topotypes of _T. b.
internatus_ of approximately equal age, I disagree with Kelson (_loc.
cit._) on some of the characters which he used to separate _cultellus_ from _internatus_. My findings indicate that _T. b. cultellus_ is not smaller, that its skull is not smaller and not less angular, and that the tympanic bullae are not less pointed ventrally. Further collecting is needed better to limit and diagnose this subspecies.
_Specimens examined._--Total 13. _Colorado_: Las Animas Co.: Fishers Peak, about 8000 ft., 1 (USNM). _New Mexico_: Union Co.: Near Folsom, 4 (CMNH); Colfax Co.: Philmont Ranch, Cimarroncito, 8100 ft., 2. Mora Co.: Halls Peak, 6 (USNM).
[Ill.u.s.tration: Figs. 2-7. Dorsal views of skulls of _Th.o.m.omys bottae_.
1.
Fig. 2. _Th.o.m.omys b. aureus_, 3 mi. W Durango, La Plata Co., Colorado.
No. 72967, Female.
Fig. 3. _Th.o.m.omys b. howelli_, holotype, Grand Junction, 4600 ft., Mesa Co., Colorado. No. 75684 USNM, Female.
Fig. 4. _Th.o.m.omys b. pervagus_, Espanola, 5000 ft., Rio Arriba Co., New Mexico. No. 133614 USNM, Female.
Fig. 5. _Th.o.m.omys b. cultellus_, Fishers Peak, 8000 ft., Las Animas Co., Colorado. No. 129285 USNM, Female.
Fig. 6. _Th.o.m.omys b. internatus_, Salida, 7050 ft., Chaffee Co., Colorado. No. 2757 ERW, Female.
Fig. 7. _Th.o.m.omys b. rubidus_, holotype, 2-9/10 mi. E Canon City, Fremont Co., Colorado. No. 72954, Female.]