29141	----	Transcriber's Note. The layout of the column headings in the table at the end of this text has been changed for ease of reading. Otherwise the text remains unchanged. Two New Pocket Gophers from Wyoming and Colorado BY E. RAYMOND HALL and H. GORDON MONTAGUE University of Kansas Publications Museum of Natural History Volume 5, No. 3, pp. 25-32 February 28, 1951 University of Kansas LAWRENCE 1951 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Edward H. Taylor, A. Byron Leonard, Robert W. Wilson Volume 5, No. 3, pp. 25-32 February 28, 1951 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1951 23-6627 Two New Pocket Gophers from Wyoming and Colorado BY E. RAYMOND HALL AND H. GORDON MONTAGUE In the academic year of 1947-48 Montague studied the geographic variation in _Thomomys talpoides_ of Wyoming. His study was based upon materials then in the University of Kansas Museum of Natural History. Publication of the results was purposely delayed until previously reported specimens from certain adjacent areas, especially in Colorado, could be examined. In the autumn of 1950 one of us, Hall, was able to examine the specimens from Colorado; also, the specimens from Wyoming accumulated in the past two seasons of field work in Wyoming were examined by Hall. A result of these studies is the recognition of two heretofore unnamed subspecies of the northern pocket gopher in southeastern Wyoming. Grateful acknowledgment is made of the opportunity to study the Coloradon specimens in the Biological Surveys Collection of the United States National Museum, and of the financial assistance from the Kansas University Endowment Association which permitted the field work in Wyoming. Descriptions and names for the two new subspecies are given below: =Thomomys talpoides rostralis= new subspecies _Type._--Female, adult, skull and skin, no. 17096 Mus. Nat. Hist., Univ. Kansas; from 1 mi. E Laramie, 7164 ft., Albany County, Wyoming; obtained on July 16, 1945, by C. Howard Westman; original no. 320. _Range._--Southern Wyoming and south in the mountains of Colorado to the Arkansas River but not including the Colorado River drainage except in Grand County and part of Routt County. _Diagnosis._--Size medium (see measurements); upper parts ranging from between Cinnamon-Rufous and Hazel (capitalized terms are of Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) in the eastern part of the range to between Argus Brown and Brussels Brown in the western part of the range; sides Cinnamon-Rufous; throat whitish; remainder of under-parts whitish, in many specimens tipped with Ochraceous-Buff; feet and tail whitish; rostrum long; nasals ordinarily truncate posteriorly; temporal ridges nearly parallel; interpterygoid space broadly V-shaped. _Comparisons._--From _Thomomys talpoides clusius_ (topotypes), _T. t. rostralis_ differs in: Body longer; color more reddish (lighter with less brownish and more ochraceous); rostrum both longer and broader, actually and also in relation to length of the skull; skull broader interorbitally; upper molariform tooth-row longer; tympanic bullae less inflated. For comparison with _T. t. attenuatus_ to the east, see the account of that subspecies. From _Thomomys talpoides macrotis_ (topotypes) to the southeast, _T. t. rostralis_ differs in: Body shorter; upper parts slightly more ochraceous and less grayish; skull averaging smaller in all measurements except that interorbital region is broader and rostrum and upper molariform tooth-row are longer; nasals truncate versus emarginate, and consistently shorter; basilar length consistently less in specimens of equal age; mastoidal breadth less in 16 of 17 specimens of _rostralis_; temporal ridges parallel instead of divergent posteriorly; exposed parts of upper incisors shorter; tympanic bullae more angular antero-laterally. From _Thomomys talpoides fossor_ (specimens from Rico, Silverton, Hermit and Pagosa Springs, all in Colorado), the subspecies to the southward, _T. t. rostralis_ differs in: Longer body; lighter color of upper parts; nasals truncate rather than rounded posteriorly; temporal ridges more nearly parallel (less divergent posteriorly); rostrum longer (averaging longer and broader); skull wider across zygomatic arches in 11 of 12 specimens of _rostralis._ _Remarks._--Geographic variation is evident in the material examined. In the initial study, one of us, Montague, separated the material from the Medicine Bow Range in Wyoming as a subspecies different from that at Laramie and the adjoining mountains to the eastward because of the darker color of the western animals and the smaller size of males. Acquisition of more material from still farther west (Sierra Madre) in Wyoming and the examination of material in the United States Biological Surveys Collection from Colorado discloses that there is a cline of increasing intensity of color from the geographic range of _T. t. cheyennensis_ at Pine Bluffs, Wyoming, westward to the eastern side of the Sierra Madre at a locality three miles east and five miles north of Savery, Wyoming. A further deterrent to setting apart the animals of the Medicine Bow Mountains as a separate subspecies is the large size of males from the North Platte River Valley southeast of Saratoga. The males from the valley of the North Platte are intermediate in size between those from the Medicine Bow Mountains and those from the Laramie River Valley. Females from the same places are available in longer series and show less variation. If there is a difference in size in the females, those from the mountains are larger than those from lower elevations on either side. The examination that one of us, Hall, has made of the related materials from Colorado reveals, as we supposed would be the case, that a large area formerly assigned to the geographic range of _Thomomys talpoides fossor_ is to be assigned to the geographic range of the newly named _Thomomys talpoides rostralis._ It should be added that, at this writing, the lack of ideally complete material from southwestern Colorado leaves some doubt as to the range of variation properly to be included within the geographic range of _T. t. fossor._ Consequently, study of a larger number of specimens from more localities in Colorado may show that the boundary between the geographic ranges of _T. t. fossor_ and _T. t. rostralis_ should be shifted from where we have tentatively placed it. _Specimens examined._--Total number, 168. Unless otherwise indicated, those from Colorado are in the United States National Museum, Biological Surveys Collection, and those from Wyoming are in the Museum of Natural History of the University of Kansas. =Colorado.= _Routt Co._: Hahns Peak, 2; Hayden, 1. _Jackson Co._ Pearle, North Park, 9000 ft., 2; Canadian Creek, North Park, 6; 5 mi. E Canadian Creek, 1; Rabbit Ear Mts., Arapaho Pass, 5. _Larimer Co._: Elkhorn, 7000 ft., 1; Estes Park, 7. _Grand Co._: Coulter, 4. _Boulder Co._: Longs Peak, 3; Gold Hill (the skin only; skull does not belong), 1; 3 mi. S Ward, 9000 ft., 10 (K. U.); 5 mi. W Boulder, 7. _Gilpin Co._: Blackhawk (U. S. N. M.), 2. _Jefferson Co._: Golden, 1; Golden foothills, 7300 ft., 1. _Park Co._: Como, South Park, 9800 ft., 1. _El Paso Co._: Cascade, 1 (too young for certain sub-specific identification). =Wyoming.= _Carbon County_: 13 mi. E and 6 mi. S Saratoga, 8500 ft., 1; 14 mi. E and 6 mi. S Saratoga, 8800 ft., 1; 7 mi. S and 11 mi. E Saratoga, 5; 8 mi. S and 6 mi. E Saratoga, 10; 10 mi. N and 14 mi. E Encampment, 8000 ft., 2; 10 mi. N and 16 mi. E Encampment, 8000 ft., 1; 8 mi. N and 16 mi. E Encampment, 8400 ft., 10. _Albany Co._: 2-1/4 mi. ESE Browns Peak, 10300 ft., 7; 3 mi. ESE Browns Peak 10000 ft., 5; 2 mi. S Browns Peak, 10600 ft., 7; 3 mi. S Browns Peak, 1; 2 mi. E and 1/2 mi. S Medicine Bow Peak, 10800 ft., 2; 5 mi. N Laramie, 7200 ft., 1; 1 mi. E Laramie, 7164 ft., 18; Laramie Mts., 10 mi. E Laramie (8500 ft., 2; 9000 ft., 1), 3 (U. S. B. S.); 5-1/2 mi. ESE Laramie, 8500 ft., 4; 8 mi. E and 4 mi. S Laramie, 8600 ft., 5; 8 mi. E and 6 mi. S Laramie, 8500 ft., 1; 15 mi. SE Laramie, Pole Mtn., 8200 ft., 3 (U. S. B. S.); 1 mi. SSE Pole Mtn., (8250 ft., 4; 8350 ft., 6), 10; 1 mi. S Pole Mtn., 8350 ft., 2; 2 mi. SW Pole Mtn., 8300 ft., 6; 2-1/2 mi. S Pole Mtn., 8340 ft., 1; 3 mi. S Pole Mtn., 1; Woods P. O., 2 (U. S. N. M.); Fort Russell, 1 (U. S. N. M.); Sherman, 2 (U. S. N. M.). _Additional records._--Bailey (N. Amer. Fauna, 39:101, 112, November 15, 1915) has recorded the following specimens, which on geographic grounds, would presumably be referable to _Thomomys talpoides rostralis._ COLORADO: Estes Park (referred by Bailey, p. 101, to _T. t. clusius_), 1; Colorado City, 1; Colorado Springs, 2-1/2 mi. N, 6000 ft., 1; Colorado Springs, east of Palmer Park, 1; Montgomery, 3; Nederland, 4; Teller County Divide, 1. These specimens have not been examined by us. =Thomomys talpoides attenuatus= new subspecies _Type._--Male, adult, skull and skin, no. 15095 Mus. Nat. Hist., Univ. Kansas; from 3-1/2 mi. W Horse Creek Post Office, 7000 ft., Laramie County, Wyoming; obtained on July 16, 1945, by Henry W. Setzer; original no. 629. _Range._--Southeastern Wyoming from Niobrara County south into Weld County, Colorado. _Diagnosis._--Size small; color pale (whitish); skull smooth and, relative to its length, slender; rostrum relatively long; nasals truncate posteriorly; middle parts of zygomatic arches straight; temporal ridges low and more widely separated in middle extent than at anterior or posterior ends; tympanic bullae rounded and moderately inflated; interpterygoid space V-shaped. _Comparisons._--From _Thomomys talpoides bullatus_ (topotypes) to the northward, _T. t. attenuatus_ differs in smaller size, lighter (less brownish, more whitish) color, smaller and slenderer skull. In detail, some cranial features diagnostic of _attenuatus,_ when compared with _bullatus,_ are: Anterolateral angle of zygoma less nearly a right angle; temporal ridges bowed outward at middle, instead of straight, and farther apart posteriorly than anteriorly instead of nearly parallel; sides of basioccipital nearly straight instead of concave. From _Thomomys talpoides cheyennensis_ (holotype and Wyoming specimens from: Pine Bluff; 1 mi. W Pine Bluffs, 5000 ft.; 12 mi. N and 1/2 mi. W Pine Bluffs) to the eastward, _T. t. attenuatus_ differs in smaller size throughout and more slender skull. The two subspecies are indistinguishable in color. From _Thomomys talpoides macrotis_ (topotypes) to the southward, _T. t. attenuatus_ differs in smaller size, slightly lighter (less brownish and more whitish) color, smaller and slenderer skull. From _Thomomys talpoides rostralis_ (specimens from the type locality) to the westward, _T. t. attenuatus_ differs in smaller size; lighter (grayer, less brownish) color, smaller and less angular skull. From _Thomomys talpoides clusius_ (topotypes) to the northwestward, _T. t. attenuatus_ differs in shorter body, slightly grayer color, less width across mastoid region of skull, smaller tympanic bullae, and more obtuse anterolateral angle on zygoma. _Remarks._--This subspecies is of smaller size than any of the geographically adjoining subspecies. Intergradation with _T. t. cheyennensis_ is shown by specimens from two miles south and nine and one-half miles east of Cheyenne, Wyoming. Intergradation with _T. t. bullatus_ or _T. t. clusius_ or both is suggested by the larger size of the specimen from five miles southwest of Wheatland, Wyoming. Although large, this skull has the slender proportions of _attenuatus_ to which the specimen is tentatively referred. Although the specimens from Avalo, Colorado, are typical _attenuatus,_ the specimen from Pawnee Buttes, Colorado, is somewhat larger than typical _attenuatus_ and suggests intergradation with the subspecies to the southward, for example, at Flagler, Colorado. _Specimens examined._--Total number, 44, and unless otherwise indicated in the Museum of Natural History of the University of Kansas. =Wyoming.= _Niobrara County_: 10 mi. N Hatcreek Post Office, 5300 ft., 1. _Platte Co._: 5 mi. SW Wheatland, 1 (U. S. B. S.). _Goshen Co._: Little Bear Creek, 20 mi. SE Chugwater, 1 (U. S. B. S.). _Laramie Co._: 5 mi. W and 1 mi. N Horse Creek P. O., 7200 ft., 1; 3-1/2 mi. W Horse Creek P. O., 7000 ft., 6; 2-1/5 mi. W Horse Creek P. O., 6600 ft., 1; 2 mi. W Horse Creek P. O., 6600 ft., 2; Horse Creek 6500 ft., 1; 3 mi. E Horse Creek P. O., 6400 ft., 5; 6 mi. W Islay, 2 (U. S. B. S.); 2 mi. S and 1/2 mi. E Pine Bluffs, 5200 ft., 1; 7 mi. W Cheyenne, 6500 ft., 1; Cheyenne, 7 (U. S. N. M.); 1 mi. S and 4-1/2 mi. E Cheyenne, 5200 ft., 1; 2 mi. S and 9-1/2 mi. E Cheyenne, 5200 ft., 3; Arcola, 5200 ft., 4. =Colorado.= _Weld Co._: Pawnee Buttes, 5300 ft., 1 (U. S. B. S.). _Logan Co._: Chimney Canyon, 10 mi. NE Avalo, 5100 ft., 5 (U. S. B. S.). _Museum of Natural History, University of Kansas, Lawrence. Transmitted January 15, 1951._ TABLE 1. MEASUREMENTS, IN MILLIMETERS, OF TWO SUBSPECIES OF THOMOMYS TALPOIDES. ______________________________________________________________________ Column A Catalogue number or number of averaged individuals Column B Sex Column C Total length Column D Length of tail Column E Basilar length Column F Length of hind foot Column G Zygomatic breadth Column H Least interorbital constriction Column I Mastoidal breadth Column J Length of nasals Column K Breadth of rostrum Column L Length of rostrum Column M Alveolar length if maxilliary tooth-row A | B | C | D | E | F | G | H | I | J | K | L | M _T. t. rostralis,_ from type locality 17092 |Male |220|56 |28 |33.2|23.7|6.4 |19.5|15.5|8.1 |17.5| 8.2 17095 |Male |228|68 |30 |33.3| - |6.5 |18.8|15.0|7.4 |17.3| 7.3 17091 |Male |212|56 |27 |33.0|22.8|6.5 |18.7|14.2|8.5 |16.2| 7.6 Average|Male |220|60 |28.3|33.2|23.2|6.5 |19.0|14.9|8.0 |17.0| 7.7 9 av. |Female|214|56 |27.1|31.6|22.4|6.5 |18.5|14.4|7.8 |16.8| 7.9 min. |Female|198|45 |25 |30.0|20.7|6.2 |17.7|13.2|7.4 |15.4| 7.1 max. |Female|230|72 |28.5|33.5|23.3|7.0 |19.8|14.9|8.1 |17.7| 8.4 _T. t. attenuatus,_ from type locality 15095 |Male |202|61 |26 |30.1|21.2|6.6 |18.2|13.6|7.3 |16.0| 7.0 15094 |Male |189|56 |24 |29.7|20.1|5.7 |17.2|12.4|7.2 |14.8| 6.9 from 2-1/2 mi. W Horse Creek P. O., 6600 ft. 15100 |Male |196|58 |27 |30.2|21.7|6.1 |18.4|14.5|7.5 |16.3| 7.0 3 av. |Male |196|58 |25.7|30.0|21.0|6.1 |17.9|13.5|7.3 |15.7| 7.0 from type locality 15096 |Female|203|59 |26 |30.0| - |6.1 |18.0|14.1|7.3 |16.3| 6.8 15098 |Female|192|69 |26 |28.8|19.8|5.5 |17.2|12.0|6.7 |14.7| 7.3 Horse Creek, 6500 ft. 15103 |Female|181|58 |25 |29.6|19.5|5.9 |16.3|13.0|6.9 |15.2| 7.0 3 mi. E Horse Creek P. O., 6400 ft. 15107 |Female|190|54 |27 |30.5|20.5|6.0 |17.9|13.5|7.3 |16.4| 6.8 15106 |Female|192|55 |26 |30.8|21.5|6.5 |18.2|12.7|7.6 |15.5| 7.0 5 av. |Female|192|59 |26 |29.9|20.3|6.0 |17.5|13.1|7.2 |15.6| 7.0 
31025	----	UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Volume 9, No. 11, pp. 357-361 January 21, 1957 A New Species of Pocket Gopher (Genus Pappogeomys) From Jalisco, México BY ROBERT J. RUSSELL UNIVERSITY OF KANSAS LAWRENCE 1957 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Harrison B. Tordoff Volume 9, No. 11, pp. 357-361 Published January 21, 1957 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1957 26-5801 A New Species of Pocket Gopher (Genus Pappogeomys) From Jalisco, México BY ROBERT J. RUSSELL J. R. Alcorn collected a number of pocket gophers of the genus _Pappogeomys_ in the states of Jalisco, Nayarit, and Colima. The bulk of this material was obtained in 1949 and 1950. Full treatment of these interesting pocket gophers will be given by the author in a future publication. Among the _Pappogeomys_ collected by Alcorn were three specimens from the high Sierra del Tigre, an isolated range not previously sampled for pocket gophers. The Sierra del Tigre is situated in southern Jalisco and western Michoacán, and, like most of the mountainous terrain in this region of México, is volcanic in origin. To the south the Sierra del Tigre descends abruptly to lower elevations of the arid coastal plains, uninhabited by gophers of this genus. The small pocket gopher occurring in the Sierra del Tigre seems to be an undescribed species of the genus _Pappogeomys_ which may be known as =Pappogeomys alcorni= new species _Type._--Adult female, skull and skin; No. 39806, University of Kansas, Museum of Natural History; 4 mi. W Mazamitla, 6600 ft., Jalisco, México; October 18, 1950; obtained by J. R. Alcorn, original number 12835. _Distribution._--Known only from the Sierra del Tigre, and probably occurs only at higher elevations within the geographic limits of this isolated range of mountains. _Diagnosis._--Size medium for genus (see measurements); tail naked, short relative to length of head and body; hind foot short; hairs of upper parts and underparts Plumbeous basally and Orange-Cinnamon apically (capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912); large nasal patch Cinnamon-Buff in two specimens, but Pale Pinkish-Buff in holotype; white throat spot small and inconspicuous, throat mostly bright Cinnamon-Buff; auricular patch pure Plumbeous, hairs lacking cinnamon-colored tips; tarsi with Cinnamon-Buff hairs; dentition as in _P. bulleri_ except that enamel plate of posterior wall of M1 reduced to a vestige present only on inner fourth, outer three-fourths of posterior wall of M1 without trace of enamel; zygomata slender, bowed outward; jugal long, widely separating maxillary and squamosal arms of zygoma; skull deep (measured from a point on the frontal to a point on the palate directly below and between the maxillary teeth); rostrum narrow and short; nasals broadly truncate posteriorly, and not decurved anteriorly; narrow across mastoid processes of squamosals; anterior palatine foramina small and rounded in outline, not slitlike. _Comparisons._--Compared with _Pappogeomys bulleri_, the only other named species of the genus, _P. alcorni_ differs, as follows: Nasal patch cinnamon or buffy instead of white; enamel plate of posterior wall of M1 reduced to inner fourth rather than developed completely across posterior wall of tooth; nasals broadly truncate posteriorly instead of narrow and emarginate; anterior palatine foramina short and round instead of long and slitlike. _Measurements._--The type and an adult female topotype (in parentheses) measure, as follows: Total length, 210 (210); length of tail, 61 (63); length of hind foot, 29 (28); condylobasal length, 38.0 (36.9); basilar length, 32.8 (31.9); breadth across zygomata, 24.2 (24.8); palato-frontal depth, 15.0 (14.8); palatal length, 24.7 (24.1); length of nasals, 12.7 (12.8); breadth of braincase, 18.1 (17.5); breadth across mastoid processes of squamosals, 21.5 (21.4); breadth of rostrum, 8.4 (8.1); length of rostrum, 16.9 (16.3); alveolar length of maxillary tooth-row, 9.3 (8.8); breadth across angular processes of rami, 26.1 (26.2). _Specimens examined._--Three, all from Jalisco, as follows: 4 mi. W Mazamitla, 2; 3 mi. WSW Mazamitla, 1. _Remarks._--The features which distinguish _Pappogeomys alcorni_ seem to be beyond the range of variation in _Pappogeomys bulleri_. In view of the absolute quality of the differences between _P. alcorni_ and _P. bulleri_, it seems best to regard the former as a species, rather than as a subspecies of _P. bulleri_. Moreover, it seems unlikely that actual intergradation of the two species can occur, since the broad, low valleys between the higher terrain, where pocket gophers of this genus are found, do not offer suitable habitat for _Pappogeomys_. In every example of _P. bulleri_ that I have seen (more than 100 specimens, representing all of the named subspecies) the anterior palatine foramina are long and slitlike and the nasals are always narrow and emarginate posteriorly, whereas in _P. alcorni_ the anterior palatine foramina are short and round and the nasals broad and squarely truncate posteriorly. The conspicuous nasal patch of _P. alcorni_ is large and bright cinnamon or buffy, and, although the nasal patch may be large in some subspecies of _P. bulleri_, in each specimen possessing the patch the hairs are whitish with little or no trace of pigmentation. One of the most interesting features of _P. alcorni_ is the reduction of enamel on the posterior wall of the first upper molar. In _P. alcorni_ the enamel present is thick, but it occurs only on the inner one-fourth of the posterior wall of the tooth. The enamel is always complete in _P. bulleri_; but in some old individuals it becomes thin with wear, and at a casual glance may appear to be partly or entirely absent. Close examination under magnification reveals, however, in every specimen of _P. bulleri_, a fine line of enamel completely across the posterior wall. It seems that the posterior enamel plate of M1 is disappearing in both _P. bulleri_ and _P. alcorni_. In both species the enamel on the posterior wall of M1 does not extend down the crown so far as the level of the alveolus, whereas the anterior plate of enamel on M1, for example, extends well below the alveolus of the tooth. Even though disappearance of the posterior enamel seems to be a trend in both species, it has proceeded farther in _P. alcorni_ than in _P. bulleri_. Examination of the posterior wall of M1 in _P. alcorni_ disclosed only the vestige of enamel on the inner side of the tooth, and no enamel, not even a thin plate, was present on the remainder of the posterior wall of the tooth. The name _alcorni_ is proposed as a token of appreciation to Joseph Raymond Alcorn, whose collecting has greatly enriched our knowledge of the mammals of México. _Transmitted August 30, 1956._ 26-5801 * * * * * Transcriber's Notes: Bold text is shown within =equal signs=. Italic text is shown within _underscores_. 
31141	----	Four New Pocket Gophers of the Genus Cratogeomys from Jalisco, Mexico BY ROBERT J. RUSSELL University of Kansas Publications Museum of Natural History Volume 5, No. 31, pp. 535-542 October 15, 1953 University of Kansas LAWRENCE 1953 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, A. Byron Leonard, and Robert W. Wilson Volume 5, No. 31, pp. 535-542 October 15, 1953 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1953 24-8662 Four New Pocket Gophers of the Genus Cratogeomys from Jalisco, Mexico By ROBERT J. RUSSELL In the course of my taxonomic study of the genus _Cratogeomys_, a high degree of variation was found between several populations of these gophers in central Jalisco. Two species, _C. gymnurus_ and _C. zinseri_, occur in this part of the state. Previously _C. gymnurus_ was known only from southern Jalisco and _C. zinseri_ only from extreme eastern Jalisco, but through the efforts of J. R. Alcorn specimens were obtained of both species in the central part of the state. These large gophers are difficult to collect, and I am grateful to him for securing this significant material. Costs of the field work were defrayed by the National Science Foundation and the Kansas University Endowment Association. Thanks are due also to those in charge of the United States Biological Surveys Collection for the loan of comparative material. Study of the recently acquired specimens taken in central Jalisco reveals two undescribed subspecies each of _C. gymnurus_ and _C. zinseri_. These may be known and described as =Cratogeomys gymnurus tellus= new subspecies _Type._--Female, adult, skull and skin, No. 33454 Mus. Nat. Hist., Univ. Kansas; from 3 mi. W Tala, 4300 ft., Jalisco, México; obtained on June 2, 1949, by J. R. Alcorn, original No. 9376. _Range._--North-central Jalisco; known from several localities in the vicinity of Tala. _Diagnosis._--Size large (see measurements); tail long, naked; hind foot small; color pale for species, upper parts Kaiser Brown (capitalized terms are of Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912), bases of individual hairs Plumbeous, tips Hazel, underparts creamy-white, bases of hairs Plumbeous; skull large, relatively narrow, rugose; zygomatic breadth narrower posteriorly than anteriorly; rostrum shallow, relatively broad in males, narrower in females; interorbital region broad; braincase narrow and flattened; basioccipital relatively wide, especially anteriorly; mastoid processes of squamosal large, knoblike; paroccipital processes long, extending laterally over more than half the width of mastoid bullae; upper incisors projecting anteriorly; maxillary teeth relatively large. _Comparisons._--From topotypes of _C. g. gymnurus_ from Zapotlan, Jalisco, the most closely related subspecies, _C. g. tellus_ differs in: Body smaller (total length averaging 338 instead of 341 in females and 356 instead of 369 in males); hind foot smaller (averaging 45 instead of 50 in females and 47 instead of 51 in males); color more brownish above, creamy-white rather than buffy below; skull smaller, especially in females (basilar length averaging 55.3 instead of 57.5 in females and 57.7 instead of 60.5 in males), narrower, and more rugose; zygomatic breadth less in females (averaging 42.5 compared with 46.2), greater in males (48.0 compared with 46.7); zygomata more nearly parallel; auditory bullae relatively smaller; mastoid processes of squamosal larger, knoblike; paroccipital processes longer, extending farther laterally; rostrum less massive; upper incisors projecting anteriorly, instead of being strongly recurved; maxillary teeth relatively larger. From near-topotypes of _C. g. inclarus_ from the Sierra Nevada de Colima, Jalisco, _C. g. tellus_ differs in: Hind foot smaller; color paler brownish above in contrast to glossy black, creamy-white below rather than buffy, feet clothed with whitish instead of brownish hairs; skull larger (basilar length averaging 55.3 in females compared with 53.2, no males available for comparisons); zygomatic breadth less; nasals longer, extending posterior to front edge of anterior roots of zygomata rather than ending even with, or slightly behind, them; rostrum more massive; mastoid processes of squamosal larger; paroccipital processes extending farther laterally; upper incisors projecting anteriorly, rather than recurved; maxillary teeth larger (length of maxillary tooth-row averaging 14.6 compared with 13.3). Close comparison with _C. g. imparilis_ from Pátzcuaro, Michoacán, is not needed, _but C. g. tellus_ differs especially in: Color of underparts and hairs of feet whitish rather than brownish; skull smaller; zygomatic breadth greater; interorbital constriction broader; nasals longer; maxillary tooth-row longer. _Measurements._--Averages of three adult females, including type, and the measurements of an adult male (in parentheses) from the type locality are: Total length, 338 (356); length of tail, 92 (87); length of hind foot, 45 (47); occipitonasal length of skull, 64.1 (68.7); basilar length, 55.3 (61.4); zygomatic breadth, 42.7 (48.0); interorbital breadth, 9.6 (11.4); greatest height of cranium, taken from palate perpendicular to line touching two highest points on top of skull, 23.9 (25.3); least depth of rostrum, 10.6 (11.7); breadth of rostrum, 14.7 (16.5); length of nasals, 23.6 (25.2); width across mastoid processes of squamosal, 43.8 (49.7); height of occiput, 18.1 (19.9); length of maxillary tooth-row, 14.6 (15.2). _Remarks._--The distribution of _C. gymnurus_ is spotty; its occurrence seemingly depends on edaphic conditions. The isolation of soils with textures suitable to this animal has resulted in the isolation of gopher populations. The distribution is similar to that of species occurring on islands. In this instance, however, the populations of gophers are separated by soils of heavy texture which render burrowing difficult or impossible for gophers. Such conditions have led to a high degree of subspeciation in a relatively short distance. For example, four subspecies of _C. gymnurus_ occur in Jalisco, and, all are within an area scarcely fifty miles in diameter. _Cratogeomys gymnurus tellus_ is the northernmost subspecies of _C. gymnurus_. It is known from only the vicinity of Tala, west of Guadalajara, and its range probably is not much more extensive than this because of the localized distribution of suitable soils. _Specimens examined._--Total number ten, as follows: 3 mi. W Tala, type locality, 5; 1 mi. NE Tala, 3; 1 mi. S El Refugio, 2. =Cratogeomys gymnurus atratus= new subspecies _Type._--Female, adult, skull and skin, No. 31880 Mus. Nat. Hist., Univ. Kansas; from Top of Cerro Viejo de Cuyutlán, 9700 ft., 19 mi. S and 9 mi. W Guadalajara, Jalisco, México; obtained on February 17, 1949, by J. R. Alcorn, original No. 7902. _Range._--Known only from the type locality on the Cerro Viejo. _Diagnosis._--Size small (see measurements); tail long; hind foot small; color dark, upper parts glossy Blackish Brown, bases of hairs Plumbeous, sides Chestnut Brown, underparts Pale Ochraceous-Buff or Warm Buff mixed with Plumbeous of the hair bases; skull small, lightly constructed, relatively deep; zygomata relatively weak; zygomatic breadth wider posteriorly than anteriorly; rostrum relatively wide, especially in males; nasals relatively long, truncate posteriorly; interorbital constriction narrow; braincase inflated; mastoid processes of squamosal only slightly wider than zygomatic breadth; auditory bullae relatively large; paroccipital processes weakly constructed, but extend laterally over half the width of mastoid bullae; upper incisors projecting anteriorly, rather than being strongly recurved; maxillary teeth small. _Comparisons._--From topotypes of _C. g. gymnurus_ from Zapotlan, Jalisco, _C. g. atratus_ differs in: Body smaller (total length averaging 300 in females compared with 341, a male measured 315 compared with an average of 363); tail shorter, hind foot smaller; color of upper parts darker, glossy Blackish-Brown rather than reddish brown, underparts paler; skull smaller (basilar length averaging 48.6 compared with 57.5, a male measured 50.0 compared with an average of 59.0); zygomata more weakly constructed; zygomatic breadth less, and wider posteriorly than anteriorly; braincase more inflated; nasals shorter; rostrum relatively narrower and shallower; width across mastoid processes of squamosals less; paroccipital processes less strongly constructed, extending farther laterally; upper incisors projecting anteriorly rather than being strongly recurved; maxillary teeth smaller (length of maxillary tooth-row averaging 11.2 compared with 14.9). From _C. g. tellus_, that occurs to the northwest, _C. g. atratus_ differs in: Body smaller; hind foot slightly smaller; upper parts darker; underparts Pale Ochraceous-Buff rather than creamy-white; skull smaller (see measurements); zygomatic breadth less, and wider posteriorly than anteriorly; nasals shorter, truncate posteriorly rather than emarginate; rostrum narrower and shallower; maxillary teeth smaller. From near-topotypes of _C. g. inclarus_ from the Sierra Nevada de Colima, _C. g. atratus_ differs in: Body slightly smaller; hind foot smaller (averaging 42 compared with 49); color of upper parts near the same, underparts paler; skull smaller, narrower, weaker in construction; zygomatic breadth less; nasals relatively longer, but actually shorter (averaging 19.7 compared with 20.3); upper incisors projecting anteriorly rather than being recurved; maxillary teeth smaller. _Measurements._--The type and an adult female (its measurements in parentheses) yield measurements as follows: Total length, 300 (299); length of tail, 78 (83); length of hind foot, 43 (40); occipitonasal length of skull, 56.3 (55.5); basilar length, 49.3 (47.8); zygomatic breadth, 37.9 (36.5); interorbital breadth, 8.7 (8.1); greatest height of cranium, as explained above, 21.6 (20.7); least depth of rostrum, 9.2 (8.8); breadth of rostrum, 12.8 (12.7); length of nasals, 19.4 (20.0); width across mastoid processes of squamosal, 38.2 (37.1); height of occiput, 16.9 (17.3); length of maxillary tooth-row, 11.9 (11.3). _Remarks._--_Cratogeomys gymnurus atratus_ is the smallest subspecies known for the species, and is so distinct from other described subspecies, that it is difficult to select one as the closest relative. In color, _C. g. atratus_ closely resembles _C. g. inclarus_, which occurs at comparable elevations in the Sierra Nevada, but the skulls are unlike. Among named subspecies of _C. gymnurus_, the skull of _tellus_ most closely resembles that of _atratus_, and, although they differ greatly in size, _C. g. tellus_ seems to be the closest relative of _C. g. atratus_. This newly described subspecies is known only from Cerro Viejo and is probably restricted to the higher elevations on this mountain. _Specimens examined._--Seven, Top of Cerro Viejo de Cuyutlán, 19 mi. S and 9 mi. W Guadalajara. =Cratogeomys zinseri zodius= new subspecies _Type._--Male, adult, skull and skin, No. 31879 Mus. Nat. Hist., Univ. Kansas; from 13 mi. S and 15 mi. W Guadalajara, Jalisco, México; obtained on February 6, 1949, by J. R. Alcorn, original No. 7747. _Range._--Known only from the type locality. _Diagnosis._--Size small (see measurements); tail short; hind foot small; upper parts Sayal Brown, underparts Pinkish Buff, hind foot whitish; skull small, narrow; outline of dorsal profile of skull concave; zygomatic breadth narrow; nasals actually short, but relatively long; width across mastoid processes of squamosal short; auditory bullae inflated; interorbital constriction narrow; maxillary teeth relatively large. _Comparisons._--From topotypes of _C. z. zinseri_ from Lagos, Jalisco, _C. z. zodius_ differs in: Body smaller (see measurements); tail shorter, hind foot smaller; upper parts dull brownish instead of reddish-brown, underparts paler, hairs of feet whitish instead of brownish; skull smaller, especially in females, narrower; dorsal profile of skull concave or flat (females) rather than convex; zygomatic breadth less; rostrum narrower and shallower; nasals actually shorter, but relatively longer in relation to length of skull; width across mastoid processes of squamosal shorter; maxillary teeth smaller. _Measurements._--The type and an adult male (his measurements in parentheses) yield measurements as follows: Total length, 318 (324); length of tail, 95 (89); length of hind foot, 41 (41); occipitonasal length of skull, 60.5 (59.1); basilar length, 52.4 (51.8); zygomatic breadth, 40.6 (39.0); interorbital breadth, 8.3 (8.8); greatest height of cranium, as explained above, 22.6 (22.4); least depth of rostrum, 11.2 (10.4); breadth of rostrum, 13.3 (13.9); length of nasals, 21.7 (21.2); width across mastoid processes of squamosal, 37.1 (36.8); height of occiput, 17.7 (17.9); length of maxillary tooth-row, 13.0 (13.3). A nearly adult female measured: Total length, 292; length of tail, 81; length of hind foot, 39; occipitonasal length of skull, 53.3; basilar length, 46.5; zygomatic breadth, 34.1; interorbital breadth, 7.8; greatest height of cranium, 21.0; least depth of rostrum, 9.8; length of nasals, 18.0; width across mastoid processes of squamosal, 32.2; depth of occiput, 15.9; length of maxillary tooth-row, 12.1. _Remarks._--This newly described subspecies is the smallest of known races of _C. zinseri_, and it is seemingly more closely related to _C. z. zinseri_ than to the subspecies newly named below from the north end of Lago Sayula. The skulls of females are especially small and delicate in structure; the males are larger with more massive skulls. _C. z. zodius_ is known to occur in the foot hills north of the Cerro Viejo, the mountain from which _C. g. atratus_ was described above. _Specimens examined._--Seven, 13 mi. S and 15 mi. W Guadalajara. =Cratogeomys zinseri morulus= new subspecies _Type._--Male, adult, skull and skin, No. 36679 Mus. Nat. Hist., Univ. Kansas; from N end Lago Sayula, 4400 ft., 9 mi. N and 2 mi. E Atoyac, Jalisco, México; obtained on March 23, 1950, by J. R. Alcorn, original No. 10889. _Range._--Known only from the type locality in central Jalisco. _Diagnosis._--Size large (see measurements); tail short; hind foot large; upper parts Fuscous-Black, strongly mixed with Walnut Brown, underparts Cinnamon-Buff, bases of all hairs Plumbeous; skull large, broad, rugose; outline of dorsal profile slightly concave, almost flat; zygomata strongly constructed, maxillary arm almost touching squamosal arm over jugal; wide across zygomata; nasals actually and relatively long; rostrum relatively narrow; auditory bullae inflated, relatively large; maxillary teeth relatively large. _Comparisons._--From topotypes of _C. z. zinseri_ from Lagos, Jalisco, _C. z. morulus_ differs in: Tail shorter (averaging 96 in females compared with 101, 94 in males compared with 115); color darker above, Fuscous-Black instead of Cinnamon-Rufous, underparts paler; skull larger (occipitonasal length 63.7 rather than averaging 58.5 in females and 68.6 rather than 63.1 in males); wide across zygomata; nasals actually and relatively longer; rostrum relatively narrower; wider across mastoid processes of squamosal; auditory bullae inflated, relatively larger; maxillary teeth larger. From _C. z. zodius_, that occurs to the northeast, _C. z. morulus_ differs in: Body larger (see measurements); hind foot larger; color of upper parts darker, underparts paler; skull much larger, broader, more rugose; dorsal profile of skull slightly concave rather than convex; wider across zygomata; nasals actually and relatively longer; rostrum broader, more massive; wider across mastoid processes of squamosal; auditory bullae larger; maxillary teeth larger. _Measurements._--The type and an adult female (her measurements in parentheses) from the type locality measure: Total length, 358 (338); length of tail, 94 (97); length of hind foot, 49 (45); occipitonasal length of skull, 68.6 (63.7); basilar length, 58.0 (55.6); zygomatic breadth, 49.3 (45.0); interorbital breadth, 9.6 (8.9); greatest height of cranium, as explained above, 26.1 (24.6); least depth of rostrum, 12.5 (10.8); breadth of rostrum, 14.5 (13.7); length of nasals, 25.9 (22.5); width across mastoid processes of squamosal, 47.7 (42.8); height of occiput, 19.8 (17.8); length of maxillary tooth-row, 13.9 (13.8). _Remarks._--_Cratogeomys zinseri morulus_ is the darkest subspecies known of _C. zinseri_. It differs widely from other subspecies of this species in color and the large size of the skull. _Cratogeomys zinseri_ occurs over the same general area as _C. gymnurus_ in central Jalisco, although these two species seemingly do not share the same local habitat. _C. zinseri_ differs from _C. gymnurus_ as follows: Tail relatively longer; skull wider across zygomatic arches than across mastoid processes of squamosal (reverse true in _C. gymnurus_); zygomata strongly bowed outward anteriorly; maxillary arm of zygomata almost touching squamosal arm (instead of widely separated from each other) above jugal; rostrum relatively narrower, less massive; border of nasals parallel or laterally swollen instead of gradually tapering. _Specimens examined._--Four, N end of Lago Sayula, 9 mi. N and 2 mi. E Atoyac. _Museum of Natural History, University of Kansas, Lawrence. Transmitted June 12, 1953._ 24-8662 * * * * * Transcriber's Notes: Page 538: Changed lead to led (conditions have lead to a high degree). Bold text is shown within =equal signs=. Italicized text is shown within _underscores_. 
32623	----	~University of Kansas Publications~ ~Museum of Natural History~ Volume 7, No. 12, pp. 591-608 March 15, 1955 Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México BY ROBERT J. RUSSELL AND ROLLIN H. BAKER ~University of Kansas~ ~Lawrence~ 1955 ~University of Kansas Publications, Museum of Natural History~ Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Robert W. Wilson Volume 7, No. 12, pp. 591-608 Published March 15, 1955 ~University of Kansas~ ~Lawrence, Kansas~ PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1955 25-5679 Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México By Robert J. Russell and Rollin H. Baker The plateau pocket gopher, _Cratogeomys castanops_, inhabits open lands from southeastern Colorado southward onto the Mexican Plateau as far south as southern San Luis Potosí and southeastern Zacatecas and southeastward to the Coastal Plain of northern Tamaulipas. This species occurs at elevations from as low as 26 feet at Matamoras in Tamaulipas to as high as 8700 feet in valleys of south-eastern Coahuila. In 1934, Nelson and Goldman (Proc. Biol. Soc. Washington, 47:135-154, June 13, 1934) revised the genus _Cratogeomys_ and decided that six subspecies of _C. castanops_ occurred in Coahuila. In the present account, we describe four previously unknown subspecies from Coahuila, exclude from the state two others recorded from there by Nelson and Goldman, and show that three others named previously from adjacent Mexican states do occur in Coahuila. This makes eleven subspecies now known from that state. From Coahuila Nelson and Goldman had 35 study specimens of _C. castanops_ from seven localities and we have had 234 specimens from 63 localities. Consequently we have been able to define with greater certainty, than formerly was possible, the geographic distribution of _C. castanops_ in this Mexican state and similarly analyze more completely the geographic variation. Coahuila is near the center of the geographic range of _C. castanops_. The occurrence of 11 subspecies within the state seems to be the result of partial or perhaps, in some cases, total isolation of populations of _C. castanops_ because of the highly dissected topography and the variability of the soil. _Cratogeomys castanops_ is a sedentary animal preferring open plains mantled by suitable soils, preferably sandy in texture, in which the animals can dig their elaborate underground systems of runways. Thin soils of hard texture and rocky soils do not offer optimum habitat for _C. castanops_, and the animals usually are absent or uncommon in such situations. Desert mountains with their thin rocky soils, elevated passes, perpendicular rocky cliffs, and stands of oaks and conifers at higher elevations present impassable barriers for pocket gophers of this species. The Río Grande, bordering Coahuila to the north, in many places flowing through steep-walled cañons, also seems to be a barrier that this fossorial rodent does not cross; distinct subspecies occur on the two sides of the river directly opposite each other (also see Nelson and Goldman, _op. cit._: 143). Smaller streams, such as the Río Salado, Río Nazas and Río Salinas, seem to be unimportant barriers to the passage of these pocket gophers. The food supply of _C. castanops_ seems adequate in most situations and consequently food is unimportant in governing the distribution of this species. Principal foods of _C. castanops_ are fleshy tuberous roots of well-distributed desert shrubs, but in the valleys of the high mountains of southeastern Coahuila, where desert shrubs are absent, roots and leaves of low-growing forbs are eaten. Three distinct habitats for _C. castanops_ occur in Coahuila. The state is crossed by a series of mostly impassable, mountainous ridges beginning at the northwestern boundary at the Cañon de Boquillas on the Río Grande and extending southeastward to the east-central border. This divides Coahuila into a more humid and less elevated northeastern area which is an inland extension westward of the Coastal Plain and a more arid and higher western and southern area which is a part of the "Mesa del Norte" of the Mexican Plateau. In the extreme southeast the still higher elevated plains and intermontane valleys within the Sierra Madre Oriental afford a third habitat for populations of this species. The subspecies of these pocket gophers found in any one of these three habitats show greater affinity to each other than they do to any subspecies found in the other habitats. Generally speaking, populations of _C. castanops_ from northeastern Coahuila are related, as a group, in color and cranial features. Partial isolation of subspecies in this area results chiefly from discontinuity of suitable soils rather than from topography. These pocket gophers occur most commonly in the deep, sandy soils which are found along streams, especially where farm lands are irrigated. In western and southern Coahuila, mountains extending in both north-south and east-west directions act as partial barriers to the passage of _C. castanops_. Within this large area, pocket gophers occur in desert basins many of which are enclosed on two or more sides by mountains. Even so, with the exception of the smaller _C. c. consitus_ of northwestern Coahuila, all known subspecies occurring at lower elevations in the western and southern part of the state show close relationships in color and cranial features. Those subspecies in the higher parts of southeastern Coahuila by their small size and dark color reflect to a high degree their isolation in an elevated habitat. Males of _C. castanops_ differ greatly from females of equal age; consequently animals of the same sex, as well as of the same age, are used herein for taxonomic comparisons. Since, of any given age-group, females show less individual variation than do males, we have relied more on the characteristics of the females in this taxonomic study. Only specimens taken at approximately the same times of the year have been compared for color of pelage. Capitalized color terms are those of Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912. Specimens made available through the courtesy of the authorities of the Biological Surveys Collection of the United States National Museum are indicated in the accounts of subspecies as BSC; other specimens listed are in the collection of the University of Kansas Museum of Natural History. Assistance with field work is acknowledged from the Kansas University Endowment Association and the National Science Foundation. In any one of the lists of "Specimens examined" beyond, the order of arrangement of the localities is from north to south. Those localities listed in Roman type are represented on the distribution map (Figure 1) by blacked-in circles. Each of several circles covers two or more localities because the localities are close together. In any such instance the northernmost place is listed in Roman type and the names of the other places follow in Italic type. Measurements in millimeters are given in table 1 for females and in table 2 for males. +Cratogeomys castanops convexus+ Nelson and Goldman 1934. _Cratogeomys castanops convexus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:142, June 13, type from 7 mi. E Las Vacas [= Villa Acuña], Río Grande Valley, Coahuila (opposite Del Río, Texas). _Distribution._--Extreme northern Coahuila, east and north of the Serranías del Burro (see fig. 1). _Diagnosis._--Previously known from only one specimen, a subadult female, this subspecies has not been well diagnosed. At hand we have five near topotypes of _convexus_ (including two adult females and one adult male) and specimens assignable to this subspecies from several other localities. This subspecies may be characterized as follows: Size medium (see tables 1 and 2); dorsal profile of skull convex in females and flat, especially posteriorly, in males; zygomata weakly constructed and not widely flaring; mastoid and tympanic bullae inflated; nasals short; rostrum broad and short; maxillary teeth large. [Illustration: ~Fig. 1.~ Geographic ranges of the subspecies of _Cratogeomys castanops_ found in Coahuila, México. Guide to subspecies 4. _C. c. bullatus_ 8. _C. c. subsimus_ 1. _C. c. convexus_ 5. _C. c. ustulatus_ 9. _C. c. goldmani_ 2. _C. c. consitus_ 6. _C. c. jucundus_ 10. _C. c. subnubilus_ 3. _C. c. sordidulus_ 7. _C. c. excelsus_ 11. _C. c. planifrons_] _Comparisons._--From topotypes of _Cratogeomys castanops angusticeps_ Nelson and Goldman, found to the north and east across the Río Grande in Texas, _convexus_ differs in: Body larger; upper parts more reddish, especially on sides; skull with zygomata less heavy, nasals broader, pterygoids smaller, maxillary teeth larger. For comparisons of _convexus_ with the subspecies of _C. castanops_ found to the west, south and southeast, see accounts of the subspecies to follow. _Remarks._--The geographic range of _convexus_ is restricted, being bounded on the west and southwest by mountains, especially the Serranías del Burro, and on the north and east by the Río Grande. The range of the subspecies found to the southeast may not be continuous with that of _convexus_. At least, in the area between Villa Acuña and Piedras Negras, along the Río Grande, no specimens were obtained and no sign was observed. We suspect that in this area the species occurs only locally if at all. A specimen taken near the Río Grande in Coahuila, opposite Samuels, Texas, and assigned to _Cratogeomys castanops clarkii_ by Nelson and Goldman (op. cit.:140), has been examined by us and is referable to _convexus_. This specimen is typical of _convexus_ except for the lesser inflation of the mastoid bullae and tympanic bullae. Conspicuous differences between _convexus_ and _angusticeps_ indicate that the Río Grande is an effective barrier to passage by these rodents. _Specimens examined._--Total, 14, all from Coahuila: Río Grande, 17 mi. S Dryden, Terrell Co., Texas, 6; Río Grande, opposite Samuels, Val Verde Co., Texas, 1 (BSC); Villa Acuña, 5; Cañon del Cochino, 21 mi. E and 16 mi. N Piedra Blanca, 1; 11 mi. W Hda. San Miguel, 1. +Cratogeomys castanops bullatus+ new subspecies _Type._--Female, adult, skin and skull, No. 48498, Univ. Kansas Mus. Nat. Hist., 2 mi. S and 6-1/2 mi. E Nava, 810 ft., Coahuila; 16 June 1952; obtained by Robert J. Russell, original number 276. _Distribution._--Desert lowlands of northeastern Coahuila, from the Río Grande to as far southwestward as the Río Sabinas (see fig. 1). _Diagnosis._--Body medium for the species (see tables 1 and 2); tail long; hind foot small; upper parts Light Ochraceous-Buff (in summer pelage) and Orange-Buff (in winter pelage), bases of hairs Plumbeous; underparts white to pale buffy; skull small, broad and slightly convex in dorsal outline; zygomata widely flaring; palate short; rostrum short; nasals short; mastoid and tympanic bullae inflated; basioccipital with lateral edges parallel; maxillary teeth small. _Comparisons._--From _Cratogeomys castanops convexus_, found to the north, _bullatus_ differs in: Hind foot shorter; skull much broader in relation to length; rostrum narrower but, relative to length of skull, wider; tympanic bullae slightly more inflated; incisors and maxillary teeth smaller. From topotypes of _Cratogeomys castanops angusticeps_, found across the Río Grande and upstream from localities where _bullatus_ is known to occur, _bullatus_ differs in: Body slightly smaller; color paler, especially on sides; skull shorter and broader; rostrum shorter and broader; nasals shorter; mastoid and tympanic bullae more inflated; maxillary teeth smaller. For comparisons of _bullatus_ with the subspecies of _C. castanops_ found to the west and south, see accounts of the subspecies to follow. _Remarks._--_Cratogeomys castanops bullatus_ in small size resembles _C. c. tamaulipensis_ Nelson and Goldman of the lower Río Grande Valley in Tamaulipas, but the two differ markedly in cranial features. _Cratogeomys c. bullatus_ is smaller than _convexus_ but these two subspecies resemble each other in color and cranial characters. Both have an arched skull, inflated mastoid and tympanic bullae, short nasals, and a short rostrum. Comparison of _bullatus_ with _angusticeps_, which occurs across the Río Grande but not directly opposite the range of _bullatus_, indicates that these two subspecies are less closely related than _bullatus_ is to _tamaulipensis_ and _convexus_. _Cratogeomys castanops bullatus_ is especially common in sandy soils in the vicinity of Nava where the mounds were in fallow irrigated fields and other open places between extensive live oak thickets. South and west of the Río Grande the animals were less abundant and lived in heavier soils usually as individuals or in small groups. Specimens were taken at elevations from as low as 800 feet to as high as 2,000 feet. _Specimens examined._--Total, 24, from: 2 mi. S and 6-1/2 mi. E Nava, 810 ft., 2; 2 mi. S and 12 mi. E Nava, 800 ft., 1; _3 mi. S and 12 mi. E Nava, 800 ft._, 4; 29 mi. N and 6 mi. E Sabinas, 5; 10 mi. E Hacienda La Mariposa, 2000 ft., 1; La Gacha [= La Concha], 1600 ft., 8; 8 mi. S and 8 mi. E Hacienda La Mariposa, 1900 ft., 1; 9 mi. S and 11 mi. E Sabinas, 1050 ft., 2. +Cratogeomys castanops ustulatus+ new subspecies _Type._--Female, adult, skin and skull, No. 34589, Univ. Kansas Mus. Nat. Hist., Don Martin, 800 ft., Coahuila; 19 August 1949; obtained by W. Kim Clark, original number 1034. _Distribution._--Extreme northeastern Coahuila from the vicinity of Presa Don Martin southward into northwestern Neuvo León in the valley of the Río Salado and its tributaries at least as far south as the vicinity of Vallecillo (see fig. 1). _Diagnosis._--Body large for species (see tables 1 and 2); hind foot short; upper parts Apricot Buff (in fresh summer pelage) and Salmon-Buff strongly mixed with black (in fresh winter pelage); underparts Light Ochraceous-Buff; skull large, especially in females, and broad; zygomatic arches widely flaring; palate long; rostrum broad; nasals long; mastoid and tympanic bullae not conspicuously inflated; incisors narrow; maxillary teeth large. _Comparisons._--From _Cratogeomys castanops bullatus_ found to the north, _ustulatus_ differs in: Body larger; tail shorter; upper parts darker, more rufous and less buffy; skull larger, especially in palate, nasals, and rostrum; zygomata more widely flaring; tympanic bullae less inflated; incisors slightly larger; maxillary teeth larger. From topotypes of _Cratogeomys castanops tamaulipensis_ found to the southeast, _ustulatus_ differs in: Body larger; upper parts, in winter pelage, darker, more rufous and less buffy; underparts paler; skull larger, especially in palate, rostrum and nasals; zygomata more widely flaring; tympanic bullae more inflated; pterygoids larger; basioccipital narrower, its sides parallel instead of convex; maxillary teeth smaller. From _Cratogeomys castanops subsimus_, found to the southwest, _ustulatus_ differs in: Tail shorter; hind foot smaller; upper parts darker, more rufous and less pinkish-buff; skull shorter; zygomata less widely flaring; palate shorter; rostrum averaging slightly narrower; nasals shorter; incisors narrower; maxillary teeth slightly smaller. For comparison of _ustulatus_ with the subspecies of _C. castanops_ to the southwest, see account of that subspecies to follow. _Remarks._--_Cratogeomys castanops ustulatus_ is a large-sized pocket gopher with a relatively larger, skull. In size o£ skull, _ustulatus_ is exceeded only by _C. c. subsimus_ found beyond the mountains in the southern part of Coahuila. In size, _ustulatus_ differs so markedly from _bullatus_ that the two can be distinguished easily by this feature alone. The skull of _C. c. convexus_ approaches that of _ustulatus_ in size, but is smaller in all respects, save breadth of rostrum. This pocket gopher is found commonly along the Río Salado and its watershed. Fallow cotton fields in the vicinity of Anahuac [= Rodríques], Nuevo León, are preferred living places. This subspecies was found at elevations as high as 1000 feet and as low as 600 feet. _Specimens examined._--Total, 10, from: Don Martin, 800 ft., 5; _base of Don Martin Dam_, 2; _2 mi. SE Don Martin Dam, along Río Salado_, 2; 5 mi. SE Don Martin, 1. _Records from Nuevo León._--Total, 14, from: 9 mi. N and 2 mi. W Anahuac [= Rodríques], 1; 4 mi. N and 1 mi. W Anahuac [= Rodríques], 5; 3 mi. N Lampazos, 4; 1 mi. N Vallecillo, 1000 ft., 1; Vallecillo, 20 mi. S Río Salado, 1000 ft., 3. +Cratogeomys castanops jucundus+ new subspecies _Type._--Female, adult, skin and skull; No. 56603, Univ. Kansas Mus. Nat. Hist.; Hermanas, 1205 ft., Coahuila; 5 December 1953; obtained by Robert W. Dickerman, original number 2051. _Distribution._--Arid plains and broad intermontane valleys of east-central Coahuila (see fig. 1). _Diagnosis._--Body largest for the species (see table 1); tail long; hind foot large; upper parts in winter pelage Ochraceous-Buff, in summer pelage Antimony Yellow; underparts Pale Ochraceous-Buff; skull medium in size, broad; zygomata moderately flaring; palate medium in length; rostrum broad; nasals moderately long; maxillary teeth small. _Comparisons._--From _Cratogeomy castanops ustulatus_, found to the east, jucundus differs in: Body larger; tail longer; hind foot larger; upper parts paler, more ochraceous and less rufous; skull averaging smaller; zygomata slightly less expanded laterally; palate and nasals shorter; squamosal breadth less; mastoid bullae less inflated, especially in females; rostrum slightly narrower; maxillary tooth-row shorter. From topotypes of _Cratogeomys castanops tamaulipensis_, found to the southeast, _jucundus_ differs in: Body larger; tail longer; hind foot smaller; upper parts, in winter pelage, paler, more ochraceous and less rufous; skull larger; zygomata more widely flaring; palate longer; rostrum broader; tympanic bullae more inflated; basioccipital with sides parallel instead of convex; maxillary teeth smaller. From _Cratogeomy castanops excelsus_, found to the southwest, _jucundus_ differs in: Body larger; hind foot averaging larger; upper parts darker, more ochraceous, and less buffy; underparts darker, more buffy and less whitish; skull slightly smaller; zygomata less widely flaring, especially in females; palate shorter; nasals shorter; squamosal breadth less; mastoid bullae more inflated; incisors narrower. From _Cratogeomys castanops subsimus_, found to the south, _jucundus_ differs in: Body larger; tail shorter; hind foot shorter; upper parts paler, more ochraceous and less yellowish; skull smaller; zygomata less widely expanded laterally; palate and nasals shorter; rostrum narrower; squamosal breadth less; maxillary tooth-row shorter. From _Cratogeomys castanops bullatus_, found to the north, _jucundus_ differs in: Body larger; tail averaging longer; hind foot larger; color of upper parts more ochraceous and less rufous; underparts darker, more buffy and less whitish; skull larger, especially in length, in width across zygomata, in lengths of palate, rostrum and nasals; mastoid and tympanic bullae less inflated; squamosal breadth greater. _Remarks._--_Cratogeomys castanops jucundus_ is large, exceeding subsimus in dimensions of the body, but differing from _subsimus_ in relatively smaller skull. Passage to the north and northeast by _jucundus_ is at least partly blocked by inhospitable mountainous country; the resulting semi-isolation may be one reason for the distinctive characteristics of _jucundus_ compared with those of _bullatus_ and _ustulatus_. Two specimens from Monclova, assigned to _tamaulipensis_ by Nelson and Goldman (op. cit.:142), are here referred to _jucundus_ on the basis of cranial characters and size. Specimens were trapped in fallow irrigated fields in the vicinity of Monclova. Others were taken in deep soils in desert flats. _Specimens examined._--Total, 19, from: Hermanas, 1205 ft., 9; _1 mi. S Hermanas_, 2; 1 mi. N and 13 mi. E Cuatro Ciénegas, 2; 5 mi. N and 2 mi. W Monclova, 1; _2 mi. N and 1 mi. E Monclova_, 1; Monclova, 2 (BSC); Hisachalo [= Huisachalo], 2. +Cratogeomys castanops sordidulus+ new subspecies _Type._--Female, adult, skin and skull; No. 56614, Univ. Kansas Mus. Nat. Hist.; 1.5 mi. NW Ocampo, 3300 ft., Coahuila; 16 December 1953; obtained by Robert W. Dickerman, original number 2164. _Distribution._--Desert plains of north-central Coahuila, surrounded for the most part by higher mountainous country (see fig. 1). _Diagnosis._--Body large for species (see tables 1 and 2); tail short; hind foot large; upper parts Ochraceous-Buff (in summer pelage) and Orange-Buff (in fresh winter pelage); underparts Pale Ochraceous-Salmon; skull medium in size and narrow; zygomata narrow; rostrum narrow; palate short; nasals medium in length; basioccipital small and narrow; mastoid bullae not greatly inflated; tympanic bullae inflated; incisors small; maxillary teeth small. _Comparisons._--From _Cratogeomys castanops jucundus_, found beyond the mountains to the southeast, _sordidulus_ differs in: Body smaller; tail shorter; hind foot slightly smaller; upper parts darker, more ochraceous and less yellowish, with plumbeous bases of hairs more conspicuous; underparts darker, more buffy and less whitish; skull slightly shorter, more nearly flat, and narrower; zygomata less widely flaring; rostrum narrower; mastoid bullae less inflated; incisors and maxillary teeth slightly smaller. From _Cratogeomys castanops excelsus_, found to the south and southwest, _sordidulus_ differs in: Body slightly smaller; tail shorter; hind foot slightly larger; upper parts darker, more ochraceous and less pinkish-buff; underparts darker, more buffy and less whitish; skull smaller and narrower; zygomata less widely flaring; sides more nearly parallel and not expanded anteriorly; palate shorter; rostrum narrower and, in relation to greatest length of skull, longer; tympanic bullae slightly more inflated; incisors and maxillary teeth smaller. From _Cratogeomys castanops consitus_, found to the north and west, _sordidulus_ differs in: Body larger; hind foot larger; upper parts paler, more ochraceous and less rufous; skull decidedly larger and wider; zygomata more widely flaring; palate and nasals longer; rostrum broader; mastoid bullae and tympanic bullae larger; maxillary teeth smaller. From topotypes of _Cratogeomys castanops clarkii_ (Baird), found to the northwest, _sordidulus_ differs in: Body larger; tail shorter; upper parts, in winter pelage, paler, more ochraceous and less dark-rufous; skull slightly smaller and narrower; rostrum narrower; nasals slightly shorter; sides of basioccipital more nearly parallel instead of wedge-shaped; mastoid bullae less inflated; incisor and maxillary teeth smaller. From _Cratogeomys castanops convexus_, found to the northeast, _sordidulus_ differs in: Body larger; tail shorter; upper parts slightly darker, more ochraceous and less buffy; skull narrower; zygomata more nearly parallel and less expanded anteriorly; rostrum narrower and longer; nasals longer; squamosal breadth greater; mastoid bullae less inflated; maxillary teeth smaller. From _Cratogeomys castanops bullatus_, found to the east, _sordidulus_ differs in: Body larger; hind foot larger; upper parts darker, more ochraceous and less buffy; skull larger in all respects; zygomata more widely flaring; tympanic bullae less inflated; maxillary teeth larger. _Remarks._--_Cratogeomys castanops sordidulus_ is limited to the Llano de Ocampo, an elevated, desert plain surrounded on three sides, west, south and east, by higher mountainous country which seems to bar the passage of this rodent. On the eastern side this barrier extends north to the very banks of the Río Grande in the Cañon de Boquillas. This subspecies, therefore, is in contact with other populations of _Cratogeomys_ only to the north and northwest. This subspecies is well characterized by size, color and cranial characteristics. _Cratogeomys castanops sordidulus_ is not abundant; groups of mounds constructed by one or a few individuals were found in widely separated places. Mounds were often small, appeared old and, in other ways, were inconspicuous on arid flats. The animals were taken at elevations as low as 3250 feet and as high as 4150 feet. _Specimens examined._--Total, 13, from: 50 mi. N and 20 mi. W Ocampo, 4150 ft., 1; 18 mi. S and 14 mi. E Tanque Alvarez, 4000 ft., 4; 1-1/2 mi. NW Ocampo, 3300 ft., 6; _Ocampo_, 1; 5 mi. N and 19 mi. W Cuatro Ciénegas, 3250 ft., 1. +Cratogeomys castanops consitus+ Nelson and Goldman 1934. _Cratogeomys castanops consitus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:140, June 13, type from Gallego, 5500 ft., Chihuahua. _Distribution._--Arid high plains from central Chihuahua, east and southeast at least into northwestern Coahuila (see fig. 1). _Comparisons._--From _Cratogeomys castanops lacrimalis_ Nelson and Goldman, specimens from Boquillas and Marathon north of the Río Grande in Texas, _consitus_ differs in: Body smaller; tail and hind foot shorter; upper parts paler, more light buffy and less rufous; underparts paler, light buffy instead of dark buffy; skull decidedly smaller; zygomata slightly less widely flaring; palate especially shorter; rostrum narrower; squamosal breadth less; incisors smaller. From topotypes of _Cratogeomys castanops clarkii_, found to the north along the Río Grande, _consitus_ differs in: Body smaller; tail and hind foot shorter; upper parts paler, more buffy and less rufous; skull markedly smaller, especially in palate and nasals; zygomata less widely flaring; tympanic bullae more inflated; mastoid bullae less inflated; basioccipital parallel-sided as opposed to wedge-shaped. From _Cratogeomys castanops convexus_, found to the east, _consitus_ differs in: Body smaller; tail and hind foot shorter; upper parts paler, more buffy and less ochraceous; underparts paler, white or light buffy instead of pale ochraceous; skull smaller; zygomata less widely flaring; palate shorter; rostrum decidedly narrower and, relative to length of skull, longer; squamosal breadth less; incisors smaller. From _Cratogeomys castanops excelsus_, found to the south, _consitus_ differs in: Size smaller; tail and hind foot shorter; upper parts darker, more rufous and less pinkish-buff; skull conspicuously smaller, especially in palate, rostrum, and nasals; zygomata less widely flaring; mastoid bullae and tympanic bullae more inflated; incisors smaller; maxillary teeth relatively larger. For comparison of _consitus_ with _Cratogeomys castanops sordidulus_, see previous account. _Remarks._--_Cratogeomys castanops consitus_ is a small pocket gopher (see tables 1 and 2); the largest adult available to us is much smaller than the smallest adult of any adjacent subspecies. Specimens from Coahuila assigned to _consitus_ compare favorably with topotypes although those from the vicinity of Jaco are smaller, paler and have a narrower rostrum and smaller maxillary teeth. An immature male trapped three miles northeast of Sierra Mojada is tentatively assigned to _consitus_. This subspecies seems to be rare in northwestern Coahuila and small colonies are widely scattered. _Cratogeomys castanops clarkii_ (Baird) may occur along the Río Grande in extreme northwestern Coahuila. No specimens are known from Coahuila, and none was found in the vicinity of Boquillas, Coahuila, in 1952. _Specimens examined._--Total, 8, from: 3 mi. N and 9 mi. E El Pino, 1; 6 mi. E Jaco, Chihuahua, _in_ Coahuila, 6; 3 mi. NE Sierra Mojada, 1. +Cratogeomys castanops excelsus+ Nelson and Goldman 1934. _Cratogeomys castanops excelsus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:143, June 13, type from San Pedro, 10 mi. W Laguna de Mayrán, Coahuila. _Distribution._--Desert plains of southwestern Coahuila and northeastern Durango (see fig. 1). _Comparisons._--_Cratogeomys castanops excelsus_ is characterized by large size and pale color; it is the palest subspecies of _C. castanops_. Of adjacent subspecies, excelsus most closely resembles _C. c. subsimus_ which occurs to the east and resembles least _C. c. consitus_, which occurs to the northwest. From _Cratogeomys castanops subsimus_, found to the east, _excelsus_ differs in: Body averaging slightly larger; tail and hind foot shorter; upper parts paler, more light buffy and less yellowish; skull smaller; palate especially shorter; rostrum narrower; nasals shorter; incisors slightly smaller; maxillary tooth-row shorter. Compared with topotypes of _C. c. goldmani_, found to the south, _excelsus_ differs in: Body larger; hind foot smaller; upper parts in winter pelage paler, more buffy and less rufous; skull larger; zygomata more widely flaring; rostrum broader; nasals shorter; tympanic bullae larger and more inflated; maxillary teeth larger. Specimens of _excelsus_ from the vicinity of Torreón, in southwestern Coahuila, are slightly smaller in cranial dimensions than more typical examples of the subspecies. In small size, at least, these specimens show some resemblance to _goldmani_ to the south. The range of _excelsus_ approaches that of _C. c. consitus_ in west-central Coahuila (see fig. 1), but no evidence of intergradation between these two subspecies could be ascertained. For comparison of _excelsus_ with _consitus_, see account of the latter. _Remarks._--_Cratogeomys castanops excelsus_ lives in the deep soils of the arid interior basin of southwestern Coahuila and adjacent parts of Durango. This animal is common in the cultivated areas in, and in the vicinity of, the formerly extensive Laguna de Mayrán. East of this laguna the land becomes progressively higher, and _C. c. subsimus_ occurs in the higher, more dissected part of this area. _Specimens examined._--Total, 33, from: 8 mi. E and 2 mi. S Americanos, 3500 ft., 3; 4 mi. N Acatita, 3600 ft., 9; 20 mi. S El Hundido, 1; San Pedro, 2 (BSC); _1 mi. SW San Pedro de las Colonias, 3700 ft._, 4; 10 mi. N and 11 mi. W San Lorenzo, 2; 2 mi. E Torreón, 12. +Cratogeomys castanops subsimus+ Nelson and Goldman 1934. _Cratogeomys castanops subsimus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:144, June 13, type from Jaral, Coahuila. _Distribution._--Desert plains and lower foothills of mountains in south-central Coahuila (see fig. 1). _Comparisons._--From _Cratogeomys castanops goldmani_, found to the southwest, _subsimus_ differs in: Body larger; hind foot larger; upper parts paler, more yellowish and less rufous; skull larger and rougher, having more prominent ridges and crests and deeper fossae for attachment of muscles; zygomata more widely flaring; palate longer; rostrum broader; nasals longer; squamosal breadth greater; maxillary teeth larger. From _C. c. subnubilus_, found to the south, _subsimus_ differs in: Body larger; tail and hind foot shorter; upper parts paler, more yellowish-buff and less blackish; skull decidedly larger in all respects. From _C. c. planifrons_, found at higher elevations to the southeast, _subsimus_ differs in the same respects as _subsimus_ differs from _subnubilus_. For comparisons between _subsimus_ and subspecies to the west, north and northeast, see accounts above. TABLE 1. ~Measurements of Adult Female Cratogeomys from Coahuila, México~ Table legend: Column A: No. av. or cat. no. Column B: Total length Column C: Length of tail Column D: Length of hind foot Column E: Condylobasal breadth Column F: Zygomatic breadth Column G: Length of palate Column H: Breadth of rostrum Column I: Length of nasals Column J: Squamosal breadth Column K: Alveolar length of maxillary tooth-row ======================================================================== A B C D E F G H I J K ------------------------------------------------------------------------ _C. c. convexus_, Villa Acuña 52259 260 86 37 50.6 31.7 33.8 11.7 16.7 29.1 9.3 52261 265 83 38 49.3 31.6 32.9 11.8 15.8 28.9 10.6 _C. c. bullatus_, vicinity of Nava 5 Av. 256 80 36 47.4 30.6 32.6 10.7 17.1 27.9 9.5 Min. 242 72 35 47.0 30.6 32.3 10.0 16.5 27.5 9.2 Max. 263 85 37 47.7 31.1 32.9 11.6 17.8 28.2 9.8 _C. c. ustulatus_, vicinity of Don Martin 8 Av. 273 74 36 51.4 33.5 35.4 11.8 18.8 30.1 10.0 Min. 261 64 35 50.7 32.6 34.8 11.0 17.8 29.1 9.3 Max. 280 83 38 52.1 34.1 36.5 12.5 19.2 30.8 10.6 _C. c. jucundus_, Hermanas 4 Av. 296 85 39 50.9 33.0 34.6 11.5 18.0 29.6 9.4 Min. 294 83 38 49.8 32.1 33.8 11.0 17.0 29.0 9.1 Max. 298 86 39 51.8 33.8 35.0 11.6 18.6 30.1 9.6 _C. c. sordidulus_, 1.5 mi. NW Ocampo 3 Av. 276 79 37 50.4 31.7 34.6 10.9 18.2 30.0 9.1 Min. 270 75 36 49.5 30.6 33.8 10.3 17.7 29.8 8.9 Max. 288 85 39 51.4 32.4 35.2 11.4 18.5 30.1 9.2 _C. c. consitus_, 6 mi. E Jaco, Chihuahua, in Coahuila 4 Av. 229 74 32 43.8 28.1 29.6 9.7 16.0 26.2 8.9 Min. 226 68 31 42.6 27.3 29.4 9.4 15.5 25.7 8.1 Max. 232 78 32 45.8 28.8 29.9 9.9 16.2 26.9 9.2 _C. c. excelsus_, 4 mi. N Acatita 4 Av. 284 82 37 51.4 34.1 35.4 11.6 18.9 31.2 9.5 Min. 274 77 35 51.1 33.6 34.7 10.4 18.4 30.5 9.2 Max. 291 86 38 51.6 34.9 36.1 12.1 20.1 31.7 9.9 _C. c. subsimus_, 12 mi. N and 10 mi. E Parras 34937 287 87 39 53.1 34.9 36.9 11.5 19.4 31.7 10.5 Jaral (BSC) 51049 295 104 40 53.2 34.1 36.9 12.6 18.7 29.7 10.0 _C. c. goldmani_, 1 mi. S Jimulco 55611 250 85 35 46.0 32.6 31.4 10.7 16.3 27.8 9.8 _C. c. subnubilus_, 1 mi. S Carneros 33128 220 65 29 40.8 27.9 27.2 8.7 12.7 24.7 8.1 2 mi. W San Miguel 33132 222 65 30 40.4 26.3 26.6 8.1 13.2 24.5 8.4 1 mi. N Agua Nueva 33127 220 74 29 41.8 24.6 28.4 8.3 14.2 23.9 8.4 8 mi. N La Ventura 34934 235 76 30 42.2 27.9 28.5 9.0 14.3 26.3 7.8 _C. c. planifrons_, 12 mi. W San Antonio de las Alazanas 5 Av. 244 66 32 43.7 28.0 29.1 9.4 14.5 26.2 8.6 Min. 239 62 31 43.3 27.5 28.7 8.9 13.6 25.3 8.3 Max. 247 69 33 44.3 28.5 9.4 9.7 15.3 26.8 8.9 ------------------------------------------------------------------------- TABLE 2. ~Measurements of Adult Male Cratogeomys from Coahuila, México~ Table legend: Column A: No. av. or cat. no. Column B: Total length Column C: Length of tail Column D: Length of hind foot Column E: Condylobasal breadth Column F: Zygomatic breadth Column G: Length of palate Column H: Breadth of rostrum Column I: Length of nasals Column J: Squamosal breadth Column K: Alveolar length of maxillary tooth-row ======================================================================== A B C D E F G H I J K ------------------------------------------------------------------------ _C. c. convexus_, Villa Acuña 52260 275 89 39 55.0 34.4 37.0 12.6 20.0 30.9 10.4 _C. c. bullatus_, 3 mi. S and 12 mi. E Nava 48500 261 80 36 49.7 35.3 34.4 12.4 17.1 29.2 9.5 La Gacha 57028 250 76 34 49.9 34.0 34.4 11.5 16.6 28.4 9.3 _C. c. ustulatus_, Don Martin 34587 280 75 37 54.6 37.3 38.2 13.7 20.6 31.8 10.3 _C. c. jucundus_, Hermanas 56605 311 80 42 56.9 38.7 40.1 13.3 21.0 32.3 9.9 _C. c. sordidulus_, 1.5 mi. NW Ocampo 56733 307 88 37 57.5 49.6 40.3 13.6 22.1 33.1 10.3 _C. c. consistus_, 3 mi. N and 9 mi. E El Pino 54547 289 94 36 53.8 32.6 37.1 12.7 18.8 29.5 9.6 _C. c. excelsus_, 2 mi. E Torreón 40224 315 97 41 54.7 37.8 37.6 12.1 19.5 31.4 9.8 _C. c. subsimus_, Hda. El Tulillo, 5 km. S Hipolito 35772 315 105 40 56.4 35.3 39.5 12.5 20.8 33.8 10.6 2 mi. N Santa Cruz 48517 316 89 40 58.2 37.9 40.3 14.1 21.7 34.8 10.3 _C. c. goldmani_, W foot Pico de Jimulco 55610 255 82 36 48.9 33.4 33.4 11.7 17.7 29.6 9.3 _C. c. subnubilus_, Carneros (BSC) 79484 247 86 34 45.3 30.9 30.8 9.6 15.7 28.4 8.5 8 mi. N La Ventura 34932 250 79 34 46.3 31.8 31.0 9.6 16.4 28.7 8.4 _C. c. planifrons_, 4 mi. S and 6 mi. E Saltillo 35779 254 76 34 48.0 32.2 32.6 9.8 16.6 28.0 8.6 35780 272 85 35 48.8 33.2 34.1 10.5 17.5 29.9 9.5 12 mi. S and 2 mi. E Arteaga 33122 255 72 35 47.0 32.3 31.2 10.5 15.5 28.7 9.0 ------------------------------------------------------------------------ _Remarks._--_Cratogeomys castanops subsimus_ is the largest known subspecies of the species in cranial dimensions, but is exceeded in size of body by _C. c. jucundus_ to the north. Of adjacent subspecies, _subsimus_ is the most closely related to _excelsus_ and shows little or no relationship to the smaller and darker _C. c. subnubilus_ and _C. c. planifrons_, which are found at higher elevations to the south and southeast, respectively. Movements by _subsimus_ to the north, east, and south are barred by inhospitable mountains. Specimens of _subsimus_ from the northeastern part of its range are larger and darker than other specimens assigned to this subspecies. An adult female, assigned to _subsimus_, from the vicinity of Santa Rosa is noticeably smaller and paler than typical specimens of this subspecies. _Cratogeomys castanops subsimus_ occurs in scattered colonies in sandy soils principally in the upper drainage of the Río Salinas. Specimens have also been taken from the foothills of the Sierra Madre Oriental and westward on the elevated desert plains. _Specimens examined._--Total, 22, from: 3 mi. S and 3 mi. E Muralla, 3800 ft., 3; 2 mi. N Santa Cruz, 2; 21 mi. S and 11 mi. E Australia, 4400 ft., 6; Jaral, 3860 ft., 4 (BSC); _Hacienda El Tulillo, 5 km. S Hipolito_, 2; 17 mi. N and 8 mi. W Saltillo, 5200 ft., 1; 3 mi. N and 5 mi. W La Rosa, 3600 ft., 1; 12 mi. N and 10 mi. E Parras, 5000 ft., 1; N foot Sierra Guadalupe, 9 mi. S and 5 mi. W General Cepeda, 6200 ft., 1; _N foot Sierra Guadalupe, 10 mi. S and 5 mi. W General Cepeda, 6500 ft._, 1. +Cratogeomys castanops goldmani+ Merriam 1895. _Cratogeomys castanops goldmani_ Merriam, N. Amer. Fauna 8:160, January 31, type from Cañitas, Zacatecas. _Distribution._--Plains of northeastern Zacatecas, northward into extreme southwestern Coahuila (see fig. 1). _Comparisons._--Compared with _Cratogeomys castanops subnubilus_, found to the east, _goldmani_ differs in: Body larger, tail and hind foot longer; color paler, more rufous and less blackish; skull larger; zygomata more widely flaring; palate larger; rostrum broader; nasals longer; maxillary teeth larger. Compared with _Cratogeomys castanops rubellus_ Nelson and Goldman, found to the southeast, _goldmani_ differs in: Body and skull smaller; zygomata less widely flaring; palate shorter; rostrum narrower; maxillary teeth smaller. _Remarks._--Records of _goldmani_ given here extend the known range of this subspecies northward into southwestern Coahuila. Specimens assigned to this subspecies from Coahuila compare favorably with topotypes of _goldmani_ (see tables 1 and 2) but are slightly paler, and in this respect show some relationship to _excelsus_. The ranges of these two subspecies however, are partly isolated by mountainous country in southern Coahuila. _Specimens examined._--Total, 6, from: W foot Pico de Jimulco, 4600 ft., 1; _Valley Río Aguanaval, 1 mi. S Jimulco_, 4; 1-1/2 mi. N Parras, 1. +Cratogeomys castanops subnubilus+ Nelson and Goldman 1934. _Cratogeomys castanops subnubilus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:145, June 13, type from Carneros, 6800 ft., Coahuila. _Distribution._--Intermontane valleys and plains of southeastern Coahuila and probably adjacent parts of Zacatecas, San Luis Potosí and Nuevo León (see fig. 1). _Comparisons._--_Cratogeomys castanops subnubilus_ needs close comparison only with _Cratogeomys castanops planifrons_, found to the east and from which _subnubilus_ differs in: Body, hind foot and skull smaller; upper parts, in summer pelage, paler, more rufous-buff and less dark russet; underparts paler, more whitish and less blackish; hairs of hind foot reddish rather than blackish; zygomata more widely flaring; palate shorter, especially in females; rostrum broader, especially in females; nasals slightly smaller; squamosal breadth greater; incisors narrower, especially in males; maxillary teeth smaller. From _Cratogeomys castanops rubellus_ Nelson and Goldman, found to the south in San Luis Potosí, _subnubilus_ differs in: Body, hind foot and all parts of skull smaller; upper parts and underparts darker, more blackish and less rufous. _Remarks._--_Cratogeomys castanops subnubilus_ is the smallest subspecies of _C. castanops_ (see tables 1 and 2). This subspecies is dark and lives at high elevations (5500 ft. to 6800 ft.) in deep valley soils in relatively isolated intermontane valleys and elevated plains. It is differentiated to a much higher degree from adjacent subspecies of _C. castanops_ than is usual in this species, and no intergrades between _subnubilus_ and other subspecies have been taken. In the Sierra Guadalupe, _subnubilus_ was trapped at 6700 feet within twomiles of a place where _subsimus_ was taken at 6500 feet. _Specimens examined._--Total, 31, from: 1 mi. N Agua Nueva, 5500 ft., 1; Domingo Cañon, Sierra Guadalupe, 6700 ft., 11 mi. S and 4 mi. W General Cepeda, 1; Carneros, 6800 ft., 6 (BSC); _1 mi. S Carneros, 6000 ft._, 4; 2 mi. W San Miguel, 5500 ft., 3; 8 mi. N La Ventura, 6000 ft., 10; La Ventura, 5600 ft, 6 (BSC). +Cratogeomys castanops planifrons+ Nelson and Goldman 1934. _Cratogeomys castanops planifrons_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:146, June 13, type from Miquihuana, 5000 ft., Tamaulipas (listed, by mistake, as southern Nuevo León). _Distribution._--Elevated montane valleys of Sierra Madre Oriental of extreme southeastern Coahuila, south and east into southwestern Nuevo León and Western Tamaulipas (see fig. 1). _Remarks._--Specimens from Coahuila assigned to _planifrons_ compare favorably with topotypes of this subspecies although they are slightly larger in cranial dimensions (see tables 1 and 2). This small subspecies is darker and slightly larger than _subnubilus_ but in other ways is most closely related to _subnubilus_. _Cratogeomys c. planifrons_ shows little relation to other adjacent subspecies, including _tamaulipensis_, _subsimus_ and _rubellus_, all of which are considerably larger and paler. _Cratogeomys castanops planifrons_ is found in both deep and shallow soils of the high, open valleys of the Sierra Madre Oriental; in Coahuila it was taken at elevations as low as 7200 feet and as high as 8700 feet. _Specimens examined._--Total, 50, from: 4 mi. S and 6 mi. E Saltillo, 7500 ft, 7; 7 mi. S and 4 mi. E Bella Union, 7200 ft., 14; _12 mi. W San Antonio de las Alazanas_, 16; _12 mi. S and 2 mi. E Arteaga, 7500 ft._, 11; 2 mi. E and 2 mi. N San Antonio de las Alazanas, 8700 ft, 2. _Transmitted August 23, 1954._ 25-5679 * * * * * Transcriber's Notes: Emphasis Notation: _text_ - italicized +text+ - bold ~text~ - small caps Possible Typos Corrected Aquanaval => Aguanaval 
33653	----	A New Pocket Gopher (Genus Thomomys) From Wyoming and Colorado BY E. RAYMOND HALL University of Kansas Publications Museum of Natural History Volume 5, No. 13, pp. 219-222 December 15, 1951 University of Kansas LAWRENCE 1951 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor, Robert W. Wilson Volume 5, No. 13, pp. 219-222 December 15, 1951 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1951 24-1359 A New Pocket Gopher (Genus Thomomys) from Wyoming and Colorado By E. RAYMOND HALL Among small mammals accumulated, from Wyoming, in the Museum of Natural History of the University of Kansas, specimens of the wide-spread species _Thomomys talpoides_ are abundantly represented. Subspecific names are available for most of these, but specimens from the Sierra Madre Mountain Range of Wyoming and Colorado prove upon comparison to pertain to an heretofore unnamed subspecies which may be described and named as follows: #Thomomys talpoides meritus# new subspecies _Type._--Male, adult, skull and skin, no. 25628 Mus. Nat. Hist. Univ. Kansas; from 8 mi. N and 19-1/2 mi. E Savery, 8800 ft., Carbon County, Wyoming; obtained on July 19, 1948, by George M. Newton; original no. 4. _Range._--Sierra Madre Mountain Range of southern Wyoming and northern Colorado. _Diagnosis._--Size small (see measurements); color dark, upperparts in worn pelage of July darker than (near, _n_) Raw Umber (capitalized terms are of Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) and in fresh pelage of August between (near, 16') Prout's Brown and Mummy Brown; skull small; relative to basilar length, skull narrow across rostrum, zygomata and mastoids; nasals short and posteriorly truncate; premaxillae extending behind nasals; temporal lines faint and divergent posteriorly. _Comparisons._--From _Thomomys talpoides rostralis_ (North Platte River Valley, SW of Saratoga, Wyoming), the subspecies to the east and south, _T. t. meritus_ differs in: Lesser size, darker color, smaller and slenderer skull. The slenderness is especially noticeable in the breadth across the zygomata, mastoids, and rostrum. From _Thomomys talpoides clusius_ (topotypes), the subspecies to the north and west, _T. t. meritus_ differs in: Color much darker; rostrum longer; skull narrower across mastoids and zygomata; tympanic, and also mastoid, bullae smaller. Resemblance to _T. t. clusius_ is shown in the narrowness of the skull interorbitally and in the shortness of the tooth-row. _Remarks._--The specimens of _Thomomys_ from Wyoming on which the name _T. t. meritus_ is based were obtained by Mr. E. Lendell Cockrum and his associates with the thought that intergradation might be shown between _T. t. rostralis_ to the east and _T. t. clusius_ to the west. The animals showed instead, that there was a subspecies differing from each of the two mentioned subspecies in small size, dark color and slenderness of skull. Acknowledgment of assistance with field work is made to the Kansas University Endowment Association. _Measurements._--Average and extreme measurements of seven adult males and five adult females, from the type locality, are as follows: Total length, [Male] 204 (193-226), [Female] 207 (193-210); length of tail, 56 (46-68), 56 (50-63); length of hind foot, 27.6 (26-30), 27.4 (27-28); basilar length, 30.7 (29.0-33.0), 30.1 (29.5-30.7); zygomatic breadth, 20.4 (18.9-21.6), 19.5 (18.8-20.0); least interorbital breadth, 6.2 (5.8-6.6), 6.1 (5.9-6.3); mastoidal breadth, 17.9 (16.9-18.5), 17.2 (16.7-17.6); length of nasals, 13.7 (12.4-14.7), 13.2 (12.8-13.9); breadth of rostrum, 7.0 (6.5-7.5), 6.9 (6.7-7.3); length of rostrum, 16.3 (15.3-17.5), 15.8 (15.3-16.1); alveolar length of maxillary tooth-row, 7.1 (6.9-7.3), 7.1 (6.8-7.5). _Specimens examined._--Total number 26 and unless otherwise indicated in the Museum of Natural History of the University of Kansas. #Wyoming.#--_Carbon County_: Savery (8 mi. N and 19-1/2 mi. E, 8800 ft., 12; 7 mi. N and 17 mi. E, 8300 ft., 1; 6 mi. N and 12-1/2 mi. E, 8400 ft., 1; 6 mi. N and 13-1/2 mi. E, 8400 ft., 2; 6 mi. N and 14-1/2 mi. E, 8350 ft., 1; 5 mi. N and 3 mi. E, 6800 ft., 1; 4 mi. N and 8 mi. E, 7800 ft., 7300 ft., 3; 4 mi. N and 10 mi. E, 7800 ft., 3) 24. #Colorado#--_Routt Co._ ?: Elkhead Mts., 20 mi. SE Slater, 2 (U. S. B. S.). _Museum of Natural History, University of Kansas, Lawrence. Transmitted October 20, 1951._ 24-1359 
34314	----	A New Pocket Gopher (Thomomys) and A New Spiny Pocket Mouse (Liomys) from Michoacán, Mexico BY E. RAYMOND HALL AND BERNARDO VILLA R. University of Kansas Publications Museum of Natural History Volume 1, No. 14, pp. 249-256, 6 figs. in text July 26, 1948 University of Kansas LAWRENCE 1948 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman; A. Byron Leonard, Edward H. Taylor Volume 1, No. 14, pp. 249-256, 6 figs. in text July 26, 1948 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1948 22-3338 A New Pocket Gopher (Thomomys) and a New Spiny Pocket Mouse (Liomys) from Michoacán, Mexico By E. RAYMOND HALL and BERNARDO VILLA R. A series of 17 pocket gophers of the species _Thomomys umbrinus_ obtained in 1943 from points 3, 4 and 5 miles south of Pátzcuaro proves upon comparison to be an hitherto unrecognized subspecies which is described and named as follows: #Thomomys umbrinus pullus#, new subspecies _Type._--Male, adult, skin and skull; No. 100151, Univ. California Mus. Vert. Zool.; 5 mi. S Pátzcuaro, 7800 ft., Michoacán, Mexico; March 10, 1943; obtained by Hubert H. Hall, original No. 117. _Range._--Known only from 3 to 5 miles south of Pátzcuaro, Michoacán. _Diagnosis._--Size small (see measurements); color black or between Cinnamon-Brown and Snuff Brown; distal half of tail whitish and all of tail whitish in one specimen; lambdoidal crests perpendicular to sagittal plane of skull; posteroventral face of tympanic bulla rugose; jugal vertical (flat surface not oblique); interpterygoid space truncate at apex with sides curved outward (see figure). _Comparison._--From topotypes of _Thomomys umbrinus supernus_ Nelson and Goldman, _pullus_ differs as follows: More individuals wholly black (except distal half of tail); underparts lacking white; rostrum broader; braincase anteriorly slightly more expanded dorsally; lambdoidal crests perpendicular to sagittal plane rather than inclined posteromediad; interparietal broader, [Male] 5.7 (5.0-7.0) versus 4.5, and in [Female] 6.5 (5.6-7.1) rather than 4.8 (4.4-5.1); flattened middle part of jugal vertical rather than oblique; in side view, mastoid and paroccipital processes farther apart thus exposing larger surface of mastoidal bulla; incisors, in both upper and lower jaws, slightly narrower; molariform teeth smaller, interpterygoid space truncate, at apex, with sides convex mediad, rather than V-shaped; ventral face of tympanic bullae rugose in posterior half rather than smooth. [Illustration: FIGS. 1-3. Three views of the skull of the type specimen of _Thomomys umbrinus pullus_. × 1.] _Remarks._--Among named subspecies of _Thomomys umbrinus_, _T. u. pullus_ most closely resembles _T. u. supernus_, the subspecies next adjacent to the northward. Therefore, the results of comparisons with only that subspecies are here reported upon. _T. u. tolucae_ to the eastward is for one thing a much larger animal and has slightly less procumbent upper incisors. So far as we know, _Thomomys umbrinus_ has not heretofore been reported from Michoacán. Of our seventeen skins, eight are brown, six are black and two are intermediate in color. Most of these pocket gophers lived where there was a good growth of pine trees in the same areas where large pocket gophers of the species _Cratogeomys gymnurus_ occurred. The field notes of the collector of the type of _T. u. pullus_ record that when he was making a shallow excavation to reveal the gopher burrow in which he trapped the holotype, he found the burrow approximately five inches below the surface of the ground and that in digging deeper than was necessary he accidentally broke into the burrow of a _Cratogeomys_. Another member of our field party (E. R. Hall) when removing from its burrow a trapped _Thomomys_ that was caught only by the hind leg, dug around the animal whose burrow was approximately six inches underground and in doing so he also broke through the roof of a burrow of _Cratogeomys_. The burrow of _Cratogeomys_ was approximately sixteen inches below the ground. Nowhere else, except 3 to 5 miles south of Pátzcuaro, have the authors found two kinds of pocket gophers living together. The two-story arrangement south of Pátzcuaro was possible because of the different levels at which the two kinds of animals made their burrows and the two-story arrangement was accidental and exceptional rather than the rule. _Measurements._--Average and extreme measurements of five adults of each sex, are as follows: Total length, male 184 (178-198), female 185 (174-194); length of tail, 54 (48-60), 53 (47-57); length of hind foot, 26.8 (25-29), 27.6 (26-29); weight, 86.1 (78.7-96.9), 74.3 (70.2-84.8) grams; basilar length, 30.2 (28.8-31.3), 28.6 (27.8-29.1); zygomatic breadth, 23.2 (22.3-24.6), 21.3 (20.8-21.8); least interorbital breadth, 5.9 (5.8-6.1), 6.4 (6.0-6.8); mastoid breadth, 17.8 (17.1-18.7), 17.2 (16.6-17.5); length of nasals, 12.4 (11.8-13.0), 11.5 (11.0-12.5); breadth of rostrum, 7.5 (6.9-8.2), 7.1 (6.9-7.3); length of rostrum, 14.1 (13.4-14.5), 13.3 (12.7-13.5); alveolar length of maxillary tooth-row, 7.0 (6.7-7.5), 6.9 (6.8-7.0); palato-frontal depth, 13.2 (13.0-13.4), 12.9 (12.3-13.5). _Specimens examined._--Total, 17, all from 7800 ft., Michoacán, as follows: 3 mi. S Pátzcuaro, 1; 4 mi. S Pátzcuaro, 10; 5 mi. S Pátzcuaro, 6. * * * * * In 1943 a series of fifteen spiny pocket mice, _Liomys irroratus_, was obtained within a radius of five miles of Pátzcuaro and, mostly on geographic considerations, the animals were assigned to _Liomys irroratus alleni_ (Coues). In fact, in his "Revision of the Spiny Pocket Mice," Goldman (N. Amer. Fauna, 34:57, 1911) had thus identified the one specimen available to him from Pátzcuaro. Critical examination of the series, however, revealed cranial features not described in the named kinds from adjoining geographic areas, and comparisons showed that the animal from Pátzcuaro differs subspecifically from any named kind. The new subspecies may be known as: #Liomys irroratus acutus#, new subspecies _Type._--Female, adult, skin and skull; No. 100171, Univ. California Mus. Vert. Zool.; 2 mi. W. Pátzcuaro, 7700 ft., Michoacán, Mexico; March 10, 1943; obtained by E. R. Hall and J. R. Alcorn, original No. 3837 of Alcorn. _Range._--Known only from the vicinity of Pátzcuaro, Michoacán. _Diagnosis._--Size large (see measurements); upper parts dark brown; posterior border of nasals V-shaped with apex directed anteriorly; frontomaxillary suture medially concave or rarely straight; interparietal subcircular; basisphenoid wide; tympanic bullae large. _Comparisons._--From _Liomys irroratus alleni_, _acutus_ differs as follows: Color slightly darker brown on upper parts; size slightly less; posterior border of nasals V-shaped rather than truncate; frontomaxillary suture medially concave or straight instead of convex; interparietal subcircular (anterior border) rather than triangular; basisphenoid broader; tympanic bullae larger and more inflated. From _Liomys irroratus jaliscensis_ (topotypes), _acutus_ differs as follows: Color slightly darker brown on upper parts; size larger, without overlap, in external measurements and in basilar length, length of nasals and mastoid breadth; posterior border of nasals V-shaped rather than almost truncate; frontomaxillary suture medially concave or straight rather than convex; interparietal subcircular rather than quadrilateral; basisphenoid wider; tympanic bullae larger. From _Liomys irroratus pullus_, _acutus_ differs in longer body, shorter tail, slightly longer hind foot; all of upper parts, and especially upper side of tail, more brownish and less blackish; posterior border of nasals and frontomaxillary suture differing in same way as from _alleni_; interorbital region narrower in relation to length of skull; over-all length of skull greater; interparietal anteroposteriorly longer; tympanic bullae more inflated. [Illustration: FIGS. 4-6. Three views of the skull of the type specimen of _Liomys irroratus acutus_. × 1.] _Remarks._--This relatively large, dark-colored, spiny pocket mouse of east-central Michoacán differs from its geographic neighbors in V-shape of posterior border of nasals, semicircular shape of interparietal, medially concave maxillofrontal suture, wide basisphenoid and larger tympanic bullae. The latter character is not constant. Intergradation with _L. i. alleni_ is shown by specimens from Querendaro in which the shape of the interparietal is exactly intermediate between those of topotypes of the two subspecies and also in that the basisphenoid is wider than in _acutus_ but narrower than in _alleni_. Intergradation with _L. i. jaliscensis_ is shown, by specimen No. 120275 (U. S. N. M.) from Zamora, in shape of posterior end of nasals, direction of maxillofrontal suture, and shape of interparietal. In each of these features the specimen from Zamora is almost exactly intermediate between _acutus_ and _jaliscensis_. In large size of tympanic bullae and wider basisphenoid the specimen agrees with _acutus_, but otherwise is nearly as small as _jaliscensis_ to which it is here referred. Actually the specimen could, with almost equal propriety, be referred to either subspecies. _Measurements._--The measurements of two males, Nos. 100184, 100182, and average and extreme measurements of five females, are, respectively, as follows: Total length, 257, 267, 244 (230-251); length of tail, 130, 128, 122 (105-129); length of hind foot, 32, 31, 31 (30-33); length of ear from notch, 16, 17, 15.3 (13.0-19); weight in grams, 71.5, 65.1, 50.8 (44.8-61.8); greatest length of skull, 35.2, 34.9, 33.6 (32.7-34.2); zygomatic breadth, 17.7, 17.5, 16.5 (16.1-17.1); interorbital breadth, 8.4, 8.1, 7.8 (7.5-8.0); length of nasals, 15.1, 14.9, 14.0 (13.3-14.5); width of braincase, 15.9, 15.1, 15.0 (14.7-15.1); alveolar length of upper molariform tooth-row, 6.0, 6.0, 5.6 (5.5-5.9). The measurements were taken according to the method of Goldman (N. Amer. Fauna, 34:10, 1911). Each of the specimens of which measurements are given above is adult; the transverse enamel fold has been obliterated in M1, is represented by only an isolated lake in M2 (except in one female where all trace of the fold has worn away) and is present in M3. _Specimens examined._--Total, 16, all from Michoacán, Mexico, and unless otherwise indicated in the University of California Museum of Vertebrate Zoölogy, as follows: 3 mi. NW Pátzcuaro, 6700 ft., 1; 2 mi. W Pátzcuaro, 7700 ft., 5; 2 mi. W Pátzcuaro, 6700 ft., 2; Pátzcuaro, 1 (U. S. Nat. Mus.); 5 mi. S Pátzcuaro, 7800 ft., 7. * * * * * For the loan of comparative materials we are grateful to Dr. Harold E. Anthony of the American Museum of Natural History, Mr. Stanley P. Young and Dr. Hartley H. T. Jackson of the Biological Surveys Collection in the United States National Museum, Dr. Charles P. Lyman of the Museum of Comparative Zoölogy, and for assistance with the field work to the John Simon Guggenheim Memorial Foundation and to Miss Annie M. Alexander. _Transmitted April 1, 1948._ 22-3338 
34836	----	A New Pocket Gopher (Genus Thomomys) from Eastern Colorado BY E. RAYMOND HALL University of Kansas Publications Museum of Natural History Volume 5, No. 8, pp. 81-85 October 1, 1951 University of Kansas LAWRENCE 1951 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor, Robert W. Wilson Volume 5, No. 8, pp. 81-85 October 1, 1951 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1951 23-7439 A New Pocket Gopher (Genus Thomomys) from Eastern Colorado By E. RAYMOND HALL The pocket gophers of the species _Thomomys talpoides_ in east-central Colorado have long been referred to the subspecies _Thomomys talpoides clusius_ Coues with type locality at Bridger Pass, Wyoming. Recently, two subspecies, _T. t. attenuatus_ and _T. t. rostralis_ (see Hall and Montague, Univ. Kansas Publ., Mus. Nat. Hist., 5(3):25-32, February 28, 1951) were named from along the Wyoming-Colorado boundary with the result that the populations of _Thomomys talpoides_ in east-central Colorado are separated from _T. t. clusius_ of Wyoming by the geographic ranges now ascribed to the recently named _T. t. attenuatus_ and _T. t. rostralis_. The subspecific identity of the animals from east-central Colorado thus is left in doubt. Examination of pertinent materials was made in the expectation that the names _Thomomys talpoides macrotis_ F. W. Miller (Proc. Colorado Mus. Nat. Hist., 9:41, December 14, 1930) and _Thomomys talpoides cheyennensis_ Swenk (Missouri Valley Fauna, 4:5, March 1, 1941) would apply to the specimens, the identity of which is in doubt. This examination discloses instead, as set forth in more detail below, that neither of the two names mentioned immediately above does apply; the Coloradan specimens in question are referable to an heretofore unrecognized subspecies which may be named and described as follows: #Thomomys talpoides retrorsus# new subspecies _Thomomys clusius_, Warren, The Mammals of Colorado, G. P. Putnam's Sons, New York, p. 80, 1910; Cary, N. Amer. Fauna, 33:132, August 17, 1911. _Thomomys talpoides clusius_, Bailey, N. Amer. Fauna, 39:100, November 15, 1915; F. W. Miller, Proc. Colorado Mus. Nat. Hist., 9:41, December 14, 1930; Warren, The Mammals of Colorado, Univ. Oklahoma Press, Norman, p. 162, 1942. _Type._--Male, subadult, skull and skin, No. 69840 Biological Surveys Collection, U. S. Nat. Hist.; from Flagler, Kit Carson County, Colorado; obtained on November 26, 1894, by Clark P. Streator; original No. 4460. _Range._--Western end of the Arkansas Divide in Colorado from eight miles south of Seibert westward to Colorado Springs _Diagnosis._--Size medium (see measurements); upper parts grayish brown; underparts lighter; skull small; tympanic bullae moderately inflated and angular anterolaterally; interpterygoid space narrowly U-shaped; pterygoid hamuli without transverse enlargement; nasals truncate posteriorly; premaxillary tongues projecting posteriorly behind nasals for distance of eight-tenths (0.5-1.1) of a millimeter. _Comparisons._--In comparison with _T. t. fossor_ and _T. t. rostralis_, which occur farther west, selected differences of _T. t. retrorsus_ are: lighter color; larger skull; more inflated tympanic bullae; greater relative (to length of skull) breadth across upper incisors, rostrum, and zygomata. The difference in color is greater in comparison with _fossor_ than with _rostralis_. In comparison with _T. t. macrotis_ (specimens from the type locality), _T. t. retrorsus_ is indistinguishable in color, length of tail, and length of tooth-row, but averages smaller in all other measurements. There is no overlap in length of body, basilar length, zygomatic breadth, mastoidal breadth or length of nasals. The temporal ridges, which mark the limits of the temporal muscles, are straight as opposed to curved and are lower. The tympanic bullae are more angular anterolaterally in _T. t. retrorsus_. From _T. t. attenuatus_ to the north, _T. t. retrorsus_ differs in darker (more brown) color, consistently longer body, relatively (to length of skull) shorter rostrum and nasals. Linear measurements of the two latter structures and length of tail are approximately the same in the two subspecies but all other measurements average more in _T. t. retrorsus_. Also in the latter the temporal lines are approximately parallel instead of being bowed outward in their middle extent and instead of being more widely separated posteriorly than anteriorly. From _T. t. cheyennensis_ to the northeast, _T. t. retrorsus_ differs in slightly darker (more brownish) color, consistently shorter body and rostrum, usually a more narrowly V-shaped interpterygoid space, and smaller average dimensions of the skull, notably in mastoidal breadth and length of the rostrum. _Remarks._--Miller's (Proc. Colorado Mus. Nat. Hist., 9:42, December 14, 1930) mention of a specimen taken on November 9, 1930, "near the head of Beaver Creek in extreme northeastern Elbert County" refers to the specimen, No. 2426 Colo. Mus. Nat. Hist., which is labeled as "8 mi. N. E. Agate, Elbert Co., Colo." Specimens from Colorado Springs, in the collection of the late E. R. Warren, have not been examined but the fact that Cary, Warren 1942, and Bailey (see under synonymy above) each referred the specimens to _clusius_ instead of to the darker _fossor_ gives basis for tentatively referring the specimens to _T. t. retrorsus_. Grateful acknowledgment is made to those persons in charge of the mammal collections of the Denver Museum of Natural History and the Biological Surveys collection of mammals in the United States National Museum for permission to examine and report upon the material listed below (see specimens examined). The study here reported upon was aided also by a contract between the Office of Naval Research, Department of the Navy, and the University of Kansas (NR 161-791). Essential comparative materials were obtained with assistance from the Kansas University Endowment Association. _Measurements._--Measurements of the type, a male, are followed by the measurements of three adult females (69835, 69839 and 69838) from the type locality. Total length, 216, 207, 210, 200; length of tail, 59, 58, 64, 56; length of hind foot, 28, 28, 28, 26; basilar length of skull, 32.8, 32.2, 32.3, 30.8; zygomatic breadth, 23.1, 22.5, ----, 20.5; least interorbital breadth, 6.0, 6.7, 6.2, 6.1; mastoidal breadth, 18.2, 18.8, 17.7, 17.7; length of nasals, 13.0, 13.7, 13.9, 14.0; breadth of rostrum, 7.6, 7.9, 7.4, 7.2; length of rostrum, 14.8, 15.6, 15.7, 16.0; alveolar length of maxillary tooth-row, 7.6, 7.2, 7.7, 7.6. _Specimens examined._--Total number, 13, all from Colorado, as follows: _Elbert County_ (Colorado Mus. Nat. Hist. [= Denver Mus. Nat. Hist.]): Bijou Creek, "near El Paso Co. line", 3; 8 mi. NE Elbert, 1. _Lincoln Co._ (U. S. Biol. Surv. Coll.): Limon, 1. _Kit Carson Co._ (U. S. Biol. Surv. Coll.): Flagler, 7; 8 mi. S Seibert, 1. _Transmitted, February 28, 1951._ 23-7439 
36653	----	SUBSPECIATION IN POCKET GOPHERS OF KANSAS By BERNARDO VILLA-R. and E. RAYMOND HALL University of Kansas Publications Museum of Natural History Volume 1, No. 11, pp. 217-236 November 29, 1947 UNIVERSITY OF KANSAS LAWRENCE 1947 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, H. H. Lane, and Edward H. Taylor Volume 1, No. 11, pp. 217-236 Published November 29, 1947 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FRED VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1947 21-8188 Subspeciation in Pocket Gophers of Kansas By BERNARDO VILLA-R. AND E. RAYMOND HALL Several full species of the genus _Geomys_ have been recorded from Kansas. The purpose of the study now reported upon was to determine the present taxonomic status of these animals and the distribution of each within the boundaries of Kansas. No pocket gopher of any kind has been reported from the southeastern part of the state; in all other parts _Geomys_ is locally common. HISTORY The first published reference that we have found to pocket gophers of Kansas is Prof. Spencer F. Baird's (1857:377, 380) mention of two specimens from Fort Riley. One he identified as _Geomys bursarius_ (p. 377) and the other (p. 380) he doubtfully referred to _Geomys breviceps_. Both specimens were obtained by Dr. W. A. Hammond. J. A. Allen (1874:49) reported pocket gophers from Kansas under the generic name "Geomys?". Professor M. V. B. Knox (1875:21) published a list of Kansas mammals in which he used the names _Geomys bursarius_ Shaw and _Geomys breviceps_ Baird, the last one for the specimen taken by Dr. Hammond, at Fort Riley. Baker (1889:57) employed the name _Geomys bursarius_ Rich. for the gopher "found along the hundredth meridian, between N latitude 38° 30' and 39° 30'." He reported this animal as common in western Kansas. Merriam (1895:129) recorded _G. bursarius_ and _G. lutescens_ from Kansas. Allen (1895:265) recorded five specimens of _Geomys lutescens_ collected between September 16 and October 13 at Long Island, Phillips County, Kansas, by W. W. Granger. Since that time several papers, some of them dealing mostly with habits of pocket gophers, have been published in which reference is made to _Geomys_ in Kansas. Hibbard (1933:240) recognized three species: _G. bursarius_, _G. lutescens_, and _G. breviceps llanensis_. In 1944 (74-75) he recorded _Cratogeomys_ from Meade County, on the basis of two skulls dug out of the ground, and he recognized the same three full species of the genus _Geomys_ that he did in 1933, along with two additional subspecies. Specimens to the total number of 335 from Kansas have been available for the present study of the five subspecies recognized. The reason for arranging all of the named kinds as subspecies of a single species is that intergradation has been found to occur between every pair of kinds having contiguous geographic ranges. The characters previously thought by some writers constantly to differentiate, say, _Geomys lutescens_ of western Kansas from _Geomys bursarius_ of eastern Kansas, prove not to do so; instead, in areas geographically intermediate between the geographic ranges of the two kinds, the pocket gophers are intermediate in morphological characters and therefore are regarded as intergrades. Intergradation of this kind here is accepted as the criterion of subspecies, and lack of such intergradation as the criterion of species. Search for structural characters, distinctive of the different kinds, additional to those characters noted by other writers, has resulted in the finding of a few such characters but they too are subject to intergradation. Therefore the several kinds are arranged as subspecies of a single species which takes the name _Geomys bursarius_ because it is the oldest available name. Detailed comment on specimens showing intergradation are to be found in the accounts of _G. b. bursarius_ and _G. b. major_. METHODS AND ACKNOWLEDGEMENTS The series with the largest number of individuals from one restricted locality was selected for initial study. These individuals were segregated by sex, and specimens of each sex were arranged from oldest to youngest. Each series was divided into age-groups, and within a given age-group of one sex from one locality of what was considered as one species, estimation was made of the amount of individual variation. Thus, it was possible when comparing different kinds of pocket gophers to use only one age class of one season of one sex. Age was estimated to some extent by size of animal and nature of its pelage. The immature pelage is grayer and the hair is more crinkled than in adults. A more certain guide to age, however, is furnished by the skull. With increasing age some sutures disappear, the rostrum increases in length and the ridges marking the limits of the temporal muscles come to fuse and eventually, in males, form a high sagittal crest. Cranial measurements were taken as follows: Basilar length.--From the anteriormost inferior border of the foramen magnum to a line connecting the posteriormost margins of the alveoli of the first upper incisors. Length of the nasals.--The greatest length of the nasals. Zygomatic breadth.--The greatest distance across the zygomatic arches. Mastoid breadth.--The greatest distance across the mastoids. Breadth of rostrum.--Width, perpendicular to long axis of the skull. Interorbital constriction.--The least distance between the orbits. Maxillary tooth row.--The greatest length of the upper molariform tooth row at the alveolar border. Extension of premaxillae posterior to nasals.--From the posteriormost border of the nasals to the posterior end of the extension of a premaxilla. Depth of skull.--From the median suture of the frontals, on the dorsal surface of the skull to the median suture of the palatines at the level of the first molar (not premolar). Length of rostrum.--From the anterior border of the nasal to the maxilla at the lateral end of the hamulus of the lacrimal. In the list of specimens examined, localities are arranged by counties from west to east, beginning at the northwestern corner of the state; specimens in each county are arranged from north to south. If several localities are in the same latitude, the westernmost is listed first. Capitalized color terms are after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912. [Illustration: FIG. 1. Map showing the geographic distribution of the five subspecies of the Mississippi Valley pocket gopher, _Geomys bursarius_, in Kansas, with insert showing range of the species.] In connection with this study each of the authors acknowledges assistance from the John Simon Guggenheim Memorial Foundation and one of us (Villa) is grateful for assistance also to Drs. Isaac Ochoterena and Roberto Llamas of the Biological Institute of Mexico. For the loan of specimens we are grateful to Dr. William B. Davis, of the Agricultural and Mechanical College of Texas; Dr. G. C. Rinker, of Hamilton, Kansas; and Mr. A. J. Kirn, of Somerset, Texas. Unless otherwise indicated, specimens are in the University of Kansas Museum of Natural History. ACCOUNTS OF SUBSPECIES =Geomys bursarius lutescens=, Merriam _Geomys bursarius lutescens_ Merriam, North Amer. Fauna, 4:51, October 8, 1890; Scheffer, Technical Bull., U. S. Dept. Agric., 224:6, January, 1931. _Geomys lutescens_ Merriam, North Amer. Fauna, 8:127-29, January 31, 1895; Lantz, Trans. Kansas Acad. Sci., 19:175, 1905; Lantz, Kansas State Agric. College Bull., 129:335, April, 1905; Hibbard, Trans. Kansas Acad. Sci., 36:240, 1933; Black, 30th Bienn. Rept. Kansas State Board Agric., 35:182, 1937; Swenk, Missouri Valley Fauna, 2:1, February 1, 1940; Allen, Kansas State Teachers College, Emporia, Bull. Inf. in Educ., 20 (no. 5):15, May, 1940; Hooper, Occas. Papers Mus. Zoöl., Univ. Michigan, 420:3, June 28, 1940. _Geomys lutescens lutescens_, Hibbard, Trans. Kansas Acad. Sci., 47:74, 1944. _Type locality._--Sandhills on Birdwood Creek, Lincoln County, western Nebraska. _Distribution in Kansas._--Northwestern Kansas, eastward certainly to Ellis County, southward certainly to Scott County. _Description._--Animals with total length averaging no more than 272 mm.; length of vertebrae of tail averaging no more than 92; hind foot averaging no more than 35. Color: In autumn pelage, upper parts Light Ochraceous-Buff becoming Buckthorn Brown in middorsal region and there forming a faint longitudinal band; sides Pale Yellow Orange. In summer, Buckthorn Brown on upper parts with a dorsal band, especially distinct on specimens from Ellis and Trego counties; specimens from farther west lack the distinct dorsal band. Underparts Gray Drab and sometimes whitish, usually whitish in young specimens; basal color of pelage Deep Neutral Gray; fore and hind feet whitish. Skull: Zygomatic arch broadly and squarely spreading anteriorly; temporal impressions uniting to form a low sagittal crest in adult males, but in adult females and in young males the impressions usually remain apart; shape of interparietal varying from subquadrate in young specimens to subtriangular or triangular in adults; in some young specimens the interparietal is reduced to a minute, ovoid bone. _Comparisons._--See comparisons in the accounts of other subspecies occurring in Kansas. _Remarks._--In his monographic revision of the pocket gophers, Merriam (1895:129) recorded 3 "typical or nearly typical" specimens from Trego County, and 18 "non typical" specimens as follows: Garden Plain, Sedgwick County, 4; Belle Plain, Sumner County, 5; Cairo, Pratt County, 6; Kiowa, Barber County, 2; and Ellis, Ellis County, 1. A detailed discussion of Merriam's account of the distribution of _Geomys lutescens_ in Kansas is given by Swenk (1940:11-12). Judging by specimens in the University of Kansas Museum of Natural History, _G. bursarius lutescens_ in Kansas is restricted to the northwestern part of the state, reaching southward certainly to Scott County and eastward certainly to Ellis County; precise limits of distribution of this subspecies are unknown. Additional collecting is necessary to determine where the range of _lutescens_ meets the ranges of the other subspecies. The specimens studied are remarkably uniform. One specimen obtained in October, in Trego County, is slightly lighter colored than any other from Kansas. In other characteristics it agrees with specimens from northwestern Kansas and from the type locality. _Specimens examined._--Total number 32, as follows: _Cheyenne County_: 23 mi. (by road) NW St. Francis, 3. _Rawlins County_: 2 mi. NE Ludell, 10. _Logan County_: 5 mi. W Elkader, 3; no locality more precise than county, 1. _Trego County_: Wakeeney, 4; 12 mi. S Collyer, Perrington Ranch, 3; no locality more precise than county, 5. _Scott County_: 4 mi. S Scott City, 2. _Ellis County_: Hays State College Campus, Hays, 1. =Geomys bursarius majusculus= Swenk _Geomys bursarius majusculus_ Swenk, Missouri Valley Fauna, 1:6, December 5, 1939; Hibbard, Trans. Kansas Acad. Sci., 47:74, 1944. _Geomys bursarius_, Baird, Expls. and surveys for a railroad route from the Mississippi River to the Pacific Ocean, pt. 1, Mammals, 377, 1857; Merriam, North Amer. Fauna, 8:120, January, 1895; Lantz, Trans. Kansas Acad. Sci., 19:175, 1905; Lantz, Kansas State Agric. College Bull., 129:335, April, 1905; Scheffer, Kansas State Agric. College Ento. and Zoöl. Dept. Bull., 172:199, September, 1910; Hibbard, Trans. Kansas Acad. Sci., 36:240, 1933; Allen, Kansas State Teachers College Emporia Bull. Inf. Stud. in Educ., 20 (no. 5):15, May, 1940. _Geomys bursarius bursarius_, Black, 30th Bienn. Rept. Kansas State Board Agric., 35:181, 1937. _Geomys breviceps_, Baird, Expls. and surveys for a railroad route from the Mississippi River to the Pacific Ocean, pt. 1, Mammals, 380, 1857. _Type locality._--Lincoln, Lancaster County, Nebraska. _Distribution in Kansas._--Northeastern Kansas, westward certainly to Clay and Marion counties and southward certainly to Greenwood County. _Description._--Color: Upper parts Mummy Brown in fresh appearing pelage of February but in more worn pelage of March more reddish being near (16') Prout's Brown; top of head and sometimes back darker than rest of upper parts; underparts usually with some whitish anteriorly; fore and hind feet and approximately distal half of tail white. Size: Large, total length averaging more than 280 mm. in males and 257 in females; hind foot averaging 35 mm. or more in males. Skull: Large; rostrum averaging more than twice as long as wide; sagittal crest high in males and barely present in females; occiput vertical when skull is laid top down; least width of braincase less than distance from alveolus of upper incisor to middle of lateral border of P^4 at alveolar border. _Comparisons._--From _Geomys bursarius lutescens_, _majusculus_ differs as follows: Color darker, Mummy Brown to Prout's Brown instead of Buckthorn Brown. In both sexes: head and body a fifth to a sixth longer; hind foot 5 to 6 per cent longer; skull averaging larger in all parts measured except that premaxillae (in each subspecies) extend equally far posteriorly to nasals; diastema longer in relation to basilar length; rostrum longer relative to its width; sagittal crest higher; rostrum often more depressed distally; angle of suture between maxilla and jugal more obtuse. From _G. b. bursarius_, according to Swenk (1939:6), _majusculus_ differs in larger size. From _G. b. illinoensis_, _majusculus_, according to Komarek and Spencer (1931:405), differs in brownish instead of slate-gray coloration and in two cranial characters as follows: Nasals straight-sided instead of shaped like an hour-glass, and superficial canals on palatine extending anteriorly beyond first molar, and from there anteriorly more or less separated. The first of these characters does not always hold; occasional individuals of _majusculus_, for example some from Douglas County, have the nasals shaped like an hour-glass. From _G. breviceps dutcheri_, _majusculus_ differs in larger size (hind foot more than 33 mm. in males, and 29 in females; basilar length more than 42 mm. in males and 36 in females); dorsal exposure of jugal longer than width of rostrum measured between ventral margins of infraorbital foramina. From _G. bursarius major_ of southcentral Kansas (for example Harvey County), _majusculus_ differs in slightly darker color, being Mummy Brown instead of Prout's Brown; size larger (in males total length more than 284 mm., hind foot 35 or more, basilar length of skull more than 42, and in females total length 265 or more, hind foot averaging 33 or more, and basilar length 40 or more). Skull: Averaging larger in all parts measured, except that premaxillae do not extend so far posteriorly to nasals in either males or females; interorbital constriction slightly narrower in adult females; temporal ridges forming a more prominent sagittal crest in adult males (sagittal crest barely present in some adult males of _major_ from Harper County). _Remarks._--In employing the subspecific name _majusculus_ we are following Swenk (1939:6) who on the basis of larger size differentiated the animals from southeastern South Dakota, the eastern parts of Nebraska and Kansas, and the western and southern parts of Iowa, from _G. bursarius bursarius_ to which he assigned a more northern geographic range. In the absence of comparative materials of the northern subspecies we cannot make an independent decision on the validity of _majusculus_ and recognize that if it is inseparable from _G. b. bursarius_ the latter name will apply to specimens from northeastern Kansas. We are the more uncertain about applying the name _majusculus_ to specimens from eastern Kansas because they average smaller than topotypes. Only at the northeasternmost locality in Kansas (3 mi. N Cummings, Atchison County) do specimens average as large as topotypes of _majusculus_. Farther southward they become progressively smaller in eastern Kansas, and we interpret this as intergradation with the still smaller subspecies _major_, to the southwest. The average external measurements of two adult males from Atchison County are: 321-99-35. Thirty-six miles farther south, in Douglas County, 16 adult males average 289-80-36. From Hamilton, Greenwood County, 80 miles farther southwest, nine adult males average 284-83-35. The maximum total length recorded at these three localities is: Atchison County, 342 (1 of 2 specimens), Douglas County, 308 (1 of 16 specimens), Greenwood County, 357 (in coll. of Dr. Glenn C. Rinker and 1 of 15 males of all ages involved). It will be seen, therefore, that although there is a trend to smaller average size toward the southward, the maximum of 357 millimeters total length at Hamilton exceeds the maximum of 352 millimeters recorded by Swenk (1939:3) among 86 males at Lincoln where the recorded average is largest. Four specimens from Salina (Debold Farm) are intermediate structurally, as they are also geographically, between _G. b. majusculus_ on the one hand and _Geomys bursarius lutescens_ and _Geomys bursarius major_ on the other hand. In color they agree with _majusculus_, as they do also in width of nasals posteriorly, in more obtuse angle of the rostrum and maxillary arm of the zygomatic arch. They agree with _G. b. lutescens_ in having the occiput inclined anterodorsally, and are intermediate between _majusculus_ and _lutescens_, but nearer the latter in size of skull and in length of the rostrum relative to its width. _Specimens examined._--Total number, 148, as follows: _Clay County_: 6 mi. SW Clay Center, 3. _Jackson County_: 10-1/2 mi. WSW Holton, 1; no locality more precise than county, 1. _Atchison County_: 3 mi. N Cummings, 2. _Jefferson County_: Oskaloosa, 1. _Leavenworth County_: Fort Leavenworth (Government Hill, 2; Engineer Hill, 1), 6; no locality more precise than county, 19. _Saline County_: Salina, Debold Farm, 4 (coll. of A. J. Kirn). _Morris County_: 1-1/2 mi. N Council Grove, 3. _Douglas County_: 1 mi. NW Midland, 2; 1 mi. N Lawrence, 1; 2-1/2 mi. W Lawrence, 2; 1 mi. W K. U. Campus, 2; 1 mi. W Lawrence, 2; 1/2 mi. W Lawrence, 2; "W K. U. Campus," 2; K. U. Campus, 4; Lawrence, 23; South Lawrence, 1; 1/2 mi. SW K. U. Campus, 2; Southwest K. U. Campus, 1; Haskell Institute, 1; 4-1/2 mi. S Lawrence, 1; 7 mi. SW Lawrence, 6; 7-1/2 mi. SW Lawrence, 1; 8 mi. SW Lawrence, 1; 10 mi. S Lawrence, 1; 11 mi. SW Lawrence, 3; no locality more precise than county, 15. _Marion County_: 1-1/2 mi. NE Lincolnville, 6; 4 mi. SE Lincolnville, 1; 6 mi. S Lincolnville, 1. _Greenwood County_: Hamilton, 1; 1/2 mi. S Hamilton, 4; 1 mi. S Hamilton, 4; 4 mi. S and 14 mi. W Hamilton, 6; 8 mi. SW Toronto, 1; 8-1/2 mi. SW Toronto, 5; no locality more precise than county, 6. =Geomys bursarius jugossicularis= Hooper _Geomys lutescens jugossicularis_ Hooper, Occas. Papers Mus. Zoöl., Univ. Michigan, no. 420: 1, June 28, 1940; Hibbard, Trans. Kansas Acad. Sci., vol. 47, p. 75, 1944. _Type locality._--Lamar, Prowers County, Colorado. _Distribution in Kansas._--Extreme southwestern part of state, northward certainly to Hamilton County and south certainly to Morton and Seward counties. _Description._--A yellowish-cinnamon colored animal, with body of medium size, zygomatic plate of maxilla deep and mastoid process small. _Comparisons._--Differs from _Geomys bursarius industrius_ in slightly lighter color; occiput not strongly inclined anterodorsally. From _G. b. lutescens_, _jugossicularis_ differs in less buffy coloration and deeper zygomatic plate of maxilla. _Remarks._--_G. bursarius jugossicularis_ and _G. bursarius industrius_ intergrade in the southern part of Meade County. Some specimens from this area show a coloration resembling that of _G. b. jugossicularis_; nevertheless, one specimen from Morton County has the occiput anterodorsally inclined as in _G. b. industrius_. Specimens examined from Hamilton County correspond closely to _G. b. jugossicularis_; they agree with it both in color and in cranial characters. _Specimens examined._--Total number, 20, distributed as follows: _Hamilton County_: 1 mi. E Coolidge, Conard Farm, 4. _Morton County_: 12 mi. NE Elkhart, 2; Cimarron River, 12 mi. N Elkhart, 4; no locality more precise than county, 6. _Seward County_: 1 mi. E Arkalon, 4. =Geomys bursarius industrius=, new subspecies _Geomys lutescens_ Merriam, North Amer. Fauna, 8:127, January 31, 1895. _Geomys breviceps llanensis_, Hibbard, Trans. Kansas Acad. Sci., 36:240, 1933; Black, 30th Bienn. Rept. Kansas State Board Agric., 35:181. 1937. _Geomys lutescens jugossicularis_ Hooper, Occas. Papers Mus. Zoöl., Univ. Michigan, 420:1, June 28, 1940. _Type._--Male, adult, skin and skull, no. 14083 Museum of Natural History, University of Kansas; from 1-1/2 miles north of Fowler, Meade County, Kansas; obtained December 30, 1941, by H. H. Hildebrand, original number 16. _Distribution in Kansas._--Southwestern Kansas from Meade County eastward certainly to Pratt and Clark counties; from Pawnee County southward probably to the Oklahoma boundary. _Diagnosis._--Size of body medium; color of upper parts Cinnamon Brown; skull with occiput strongly inclined anterodorsally in males. [Illustration: FIG. 2. Three views of the skull of the type specimen of _Geomys bursarius industrius_. A. Lateral view; B. Dorsal view; C. Ventral view. All natural size.] _Description._--Color: Upper parts Cinnamon Brown, slightly reddish, but in some specimens collected in September, in Pawnee County, near (15´ _i_) Ochraceous-Tawny; underparts usually Wood Brown, somewhat whitish anteriorly; forefeet white; hind feet and approximately distal half of tail whitish. Size: Medium (see measurements), total length averaging not more than 271 mm. in males and 254 in females; hind foot averaging not more than 35 mm. in males and less than 32 in females. Skull: In males, least width of braincase equal to distance from alveolus of incisor to anterior border of alveolus of first upper molar, occiput strongly inclined anterodorsally, temporal impressions usually united in a low sagittal crest, zygomatic arch heavy and curved at level of jugal bone. In adult females least width of braincase approximately equal to distance from alveolus of incisor to anterior border of alveolus of first upper molar (not premolar); occiput less inclined anterodorsally than in males; temporal ridges not forming a sagittal crest. In young females the width of the braincase is more than the distance between the alveoli of the incisor and first molar. _Comparisons._--_G. lutescens industrius_ differs from _G. lutescens lutescens_ in: Color darker; least width of braincase not equal to (usually more than) the distance from the alveolus of incisor to the anterior border of the alveolus of the first upper molar. _G. lutescens industrius_ differs from _G. lutescens jugossicularis_ in: Color slightly darker, the former being Cinnamon Brown instead of Vinaceous Cinnamon, with hairs basally Deep Neutral Gray in upper parts and underparts. Skull: Jugular part of zygomatic arch more curved (convex dorsally) and occiput far more inclined anterodorsally; lower part of mastoidal ridge more prominent. For comparison with _G. l. major_, see account of that subspecies. _Remarks._--Judging from the known specimens of this subspecies, it has the smallest geographic range of any of the subspecies in Kansas, but additional collecting in Hodgeman County and counties to the north and west of it may extend the known range in those directions; collecting in Comanche County and in adjoining parts of Oklahoma may extend the known range to the southward. The anterodorsal inclination of the occiput in males is the one cranial character in which _industrius_ differs from all of the subspecies with adjoining geographic ranges. The existence of this unique (among adjoining subspecies) cranial character is the principal reason for according subspecific status to this animal. Although it has other characters which are fairly uniform over a considerable geographic area, these other characters, namely, Cinnamon Brown color of the upper parts and medium size of the body, after all, are conditions intermediate between those in _jugossicularis_ to the west and those in the darker and larger animals assigned to _major_ to the eastward. Considering the intermediate geographic position of _industrius_, the color and size are approximately what a person would predict by study of only the animals to the west and those to the east. Therefore, the color and size probably are indicative of intergradation between _jugossicularis_ and _major_. Still, there is the anterodorsally inclined occiput in males--a character of a unique sort--and this influences us to give subspecific status to this animal with full recognition of the fact that it is a "weak" subspecies as compared with any one of the adjoining subspecies. Hooper (1940:2) in naming as new _Geomys lutescens jugossicularis_ referred to his new subspecies a skin-only from Meade County State Park. Our more abundant material from there shows the cranial conformation to be that of _industrius_ to which we accordingly assign the specimens. However, with only a skin available, we, too, would have used the name _jugossicularis_ because the color is paler than in other specimens of _industrius_ and this paleness indicates intergradation between the two named subspecies. Specimens from Pratt County are slightly darker than _industrius_ thereby indicating intergradation between _industrius_ and _major_. _Specimens examined._--Total number, 58, distributed as follows: _Pawnee County_: Jct. Pawnee and Arkansas rivers, Larned, 6; 1 mi. S and 1 mi. E Larned, 7. _Edwards County_: 1 mi. W and 3-1/2 mi. S Kinsley, 1. _Kiowa County_: Rezeau Ranch, 5 mi. N Belvidere, 2. _Pratt County_: Pratt, 14; no locality more precise than county, 1. _Meade County_: 3-1/2 mi. NE Fowler, 2; 2 mi. N Fowler, 2; 1-1/2 mi. N Fowler, 2; 1-1/4 mi. N and 3/4 mi. E Fowler, 2; 7 mi. N Meade, Cudahy Ash Pit, 2; 13 mi. SW Meade, 9; State Lake, 2; State Park, 4. _Clark County_: 7 mi. SW Kingsdown, E. A. Stephenson Ranch, 1; 6 mi. S Kingsdown, 1. =Geomys bursarius major= Davis _Geomys lutescens major_ Davis, Texas Agric. Exp. St., Bull. no. 590:32, August, 1940; Hibbard, Trans. Kansas Acad. Sci., 47:75, 1944. _Geomys lutescens_ Merriam, N. Amer. Fauna, 8:129, January 31, 1895. _Geomys breviceps llanensis_, Lantz, Trans. Kansas Acad. Sci., 20 (pt. 2): 215, 1907; Hibbard, Trans. Kansas Acad. Sci., 36:240, 1933; Black, 30th Bienn. Rept. Kansas State Board Agric., 35:182, 1937; Swenk, Missouri Valley Fauna, 2:12, February 1, 1940. _Type locality._--Eight miles west of Clarendon, Donley County, Texas. _Distribution in Kansas._--Southcentral Kansas, northward certainly to Ellsworth County, westward certainly to Stafford and Barber counties and eastward to Cowley County. _Description._--Color: Upper parts varying from Brussels Brown in some specimens to nearly Prout's Brown, especially in specimens from central part of state. Top of head, and sometimes back, darker than rest of upper parts, but no well defined black stripe; underparts varying from whitish to nearly Buffy Brown; fore and hind feet and approximately distal half of tail white. Size: Large (see measurements). Skull: Sagittal crest absent in females and barely present in males; least width of braincase more than distance from alveolus of incisor to middle of lateral border of P^4 at alveolar border. Length of auditory bulla (from anteroventral edge of paroccipital process of exoccipital to hamulus of peterygoid), in each sex, more than 8 mm.; occiput usually vertical when skull is laid top down; zygomatic arch broadly and squarely spreading, divergent anteriorly; rostrum averaging less than twice as long as wide. _Comparisons._--From _G. bursarius lutescens_, _major_ differs in color darker, premaxillae extending slightly farther posteriorly; temporal impressions usually forming a more well-marked sagittal crest in males; ventral side of zygomatic arch, at level of jugal bone, more curved. From _G. bursarius majusculus_, _major_ differs in slightly lighter color, smaller size of body; in males, total length less than 284 mm.; hind foot 34 or less; basilar length of skull less than 42; in females total length less than 264, hind foot no more than 33, and basilar length less than 39. From _G. bursarius industrius_, _major_ differs in color, being Prout's Brown, instead of Cinnamon Brown (less Fuscous); body averaging 10 per cent longer; total length in males from 9 to 9.7 per cent longer, hind foot 9.7 per cent longer on the average; skull averaging larger in all parts measured. Occiput less inclined anterodorsally; top nearly flat, less arched than that of _G. b. industrius_; auditory bulla averaging slightly larger and less inflated. _Remarks._--Specimens of this subspecies from Norman, Cleveland County, Oklahoma, and Canton, Dewey County, Oklahoma, and most of those from Kansas, are more Fuscous than topotypes and tend toward _G. bursarius majusculus_. Specimens from McPherson County have a darker dorsal stripe resembling that of _G. bursarius majusculus_. One adult from Little Salt Marsh, Stafford County, is pale, closely resembling topotypes. Most of the cranial characters, nevertheless, are constant in all available specimens, except that in specimens of each sex from the type locality the basilar length averages 4 to 5 per cent shorter. In the constancy of size of the relatively large auditory bullae and in the nearly flat dorsal profile of the cranial part of the skull, the specimens from Kansas agree with the specimens from the type locality. Specimens from Harper County have the occiput slightly inclined anterodorsally and thus are reminiscent of _industrius_ which has an even greater inclination of the occiput. Probably the appearance in dilute fashion of this character in Harper County is properly to be interpreted as intergradation with _industrius_. If so, the actual intergradation may be to the northwest _via_ Pratt County since specimens from Barber County, immediately west of Harper and lying between Harper County and the range of _industrius_, do not have the occiput so inclined. Of a pair of adults from eight miles west of Rosalia, Butler County, the female is indistinguishable in color from adults of _G. b. industrius_ from northern Meade County and from two specimens from eleven miles west of Clarendon, Donley County, Texas, near the type locality of _G. b. major_. The male from eight miles west of Rosalia is darker as compared either with _G. b. industrius_ or _G. b. major_ and the coloration of the upper parts resembles those in _G. b._ _majusculus_; the underparts are only slightly paler than the upper parts as in _majusculus_. Measurements of the skulls are intermediate between the averages for _G. b. majusculus_ and those for _G. b. major_. These specimens from eight miles west of Rosalia are intermediate structurally, and since they are intermediate geographically between _G. b. majusculus_ and _G. b. major_, they suggest intergradation of the two subspecies. The specimens in question are referred to _major_ because the size is nearer that of _major_. It is mainly the intermediate nature of these two specimens from Butler County, and the intermediate nature of the specimens from McPherson County, Kansas, that have caused us to treat _G. b. majusculus_ as only subspecifically distinct from the more western subspecies, _major_. _Specimens examined._--Total number, 77, as follows: _Ellsworth County_: 2 mi. S Ellsworth, 1. _McPherson County_: Smoky Hill River, 1 mi. S and 1/2 mi. W Lindsborg, 5; 1/2 mi. E McPherson, 1. _Stafford County_: Little Salt Marsh, 12; no locality more precise than county, 3. _Reno County_: 8 mi. N and 1 mi. E Haven, 2. _Harvey County_: 1 mi. E and 1/2 mi. N Halstead, 1; Halstead, 3. _Butler County_: 8 mi. W Rosalia, 2. _Barber County_: near South Bridge, Sun City, 1; 2 mi. S Sun City, 1; Wells Ranch, Aetna, 5; "1 mi. W Aetna," 3; near South Bridge, Aetna, 1; near Bridge, 1 mi. S Aetna, 2. _Harper County_: 4-1/2 mi. NE Danville, 8; 1 mi. N Harper, 11; 3 mi. S Harper, 1. _Cowley County_: 3 mi. SW Arkansas City, 4; 3 mi. SE Arkansas City, 9; 3 mi. S Arkansas City, 1. MEASUREMENTS OF ADULT MALES OF GEOMYS (In millimeters) Key for table headings in table on this page. N: Number of individuals averaged or catalogue number L: Total length T: Length of tail H: Length of hind foot B: Basilar length Na: Length of nasals Z: Zygomatic breadth M: Mastoid breadth Rb: Breadth of rostrum I: Interorbital constriction A: Alveolar length of maxillary tooth row E: Extension of premaxilla posterior to nasals S: Depth of skull Rl: Length of rostrum ======+===+====+====+====+====+====+====+====+===+===+===+====+===== N |L | T | H | B | Na | Z | M | Rb | I | A | E | S | Rl ------+---+----+----+----+----+----+----+----+---+---+---+----+----- _G. b. lutescens_; topotypes 5 ave.|266|82.0|34.2|40.0|17.7|30.5|26.8|11.5|6.7|8.6|3.9|17.1|20.8 min.|257|76.0|33.0|38.3|16.0|29.1|26.1|11.2|6.3|8.1|3.5|16.2|19.1 max.|276|91.0|36.0|42.4|20.3|31.7|27.5|11.9|6.9|9.2|4.2|17.7|23.6 2 mi. NE Ludell, Rawlins Co., Kansas 12088|272|92.0|35.0|43.2|19.1|32.3|27.7|11.3|6.6|8.4|2.8|18.0|22.1 _G. b. majusculus_; Douglas Co., Kansas | | | | | |[A] | | | | | | | 16 ave. |289|79.8|36.3|47.1|21.0|34.1|30.4|12.1|6.8|9.3|3.7|18.5|24.9 min. |273|70.0|32.0|44.7|18.9|30.5|27.5|11.1|6.5|8.2|2.9|17.3|22.9 max. |308|95.0|55.0|49.9|23.2|38.0|34.5|13.5|7.6|10.3|5.7|20.0|28.1 _G. b. jugossicularis_; Morton Co., Kansas 4 ave.|265|82.0|34.2|40.7|16.9|30.0|27.9|10.7|6.0|8.6|5.2|17.3|21.2 min.|250|68.0|30.0|38.5|16.1|29.0|27.5|10.5|5.5|8.2|4.7|16.4|20.2 max.|285|92.0|37.0|42.4|17.4|31.1|28.4|11.0|6.2|9.2|5.5|17.9|22.0 _G. b. industrius_; Meade Co., Kansas 8 ave.|265|82.0|35.0|40.9|18.1|30.0|28.0|11.0|6.2|8.8|4.3|17.7|21.8 min.|247|70.0|33.0|37.9|15.5|28.2|26.5| 9.9|5.7|8.0|2.9|16.8|19.5 max.|280|90.0|36.0|43.4|21.0|32.4|29.5|11.6|7.0|9.1|5.2|19.1|24.2 _G. b. major_; Wells Ranch, Aetna, Barber Co., Kansas 11724|256|66.0|34.0|41.0|18.3|31.6|28.2|10.6|6.1|9.0|4.0|17.0|21.3 1 mi. W Aetna, Barber Co., Kansas 11153|240|75.0|32.0|36.7|15.7|26.9|24.6| 9.9|5.9|8.8|4.0|15.0|19.5 11152|240|65.0|32.0|36.0|14.2|26.1|25.4|10.9|5.6|8.5|5.0|15.5|18.5 3 mi. SE Arkansas City, Cowley Co., Kansas | | | | |[E] | | | | | | | | 12870|246|76.0|32.0|42.1|16.0|33.7|29.7|11.5|6.3|9.4|4.5|17.6|21.3 3 mi. SW Arkansas City, Cowley Co., Kansas 12892|282|84.0|33.0|41.7|17.3|....|27.7|10.8|6.4|8.9|4.2|17.2|21.5 ------+---+----+----+----+----+----+----+----+---+---+---+----+----- MEASUREMENTS OF ADULT FEMALES OF GEOMYS (In millimeters) Key for table headings in table on this page. N: Number of individuals averaged or catalogue number L: Total length T: Length of tail H: Length of hind foot B: Basilar length Na: Length of nasals Z: Zygomatic breadth M: Mastoid breadth Rb: Breadth of rostrum I: Interorbital constriction A: Alveolar length of maxillary tooth row E: Extension of premaxilla posterior to nasals S: Depth of skull Rl: Length of rostrum ======+===+====+====+====+====+====+====+====+===+===+===+====+===== N | L | T | H | B | Na | Z | M | Rb | I | A | E | S | Rl ------+---+----+----+----+----+----+----+----+---+---+---+----+----- _G. b. lutescens_; topotypes 6 ave.|233|72.3|31.1|35.3|15.0|25.9|23.7|10.4|6.1|8.3|3.7|15.4|18.4 min.|215|63.0|30.0|33.5|13.9|24.6|21.8|10.1|5.6|8.1|2.9|14.8|17.3 max.|254|76.0|32.0|37.0|16.8|26.7|24.8|10.7|6.6|8.5|4.5|16.2|19.8 2 mi. NE Ludell, Rawlins Co., Kansas 11733|230|63.0|31.0|35.3|15.1|26.5|24.1| 9.3|6.1|7.5|2.4|15.0|18.2 12155|245|70.0|30.0|35.6|14.6|25.2|24.1|10.6|6.4|7.5|3.1|14.9|18.2 _G. b. majusculus_; Douglas Co., Kansas | | | |[B] |[B] |[A] | | | | | | | 17 ave. |265|78.6|32.8|40.6|17.2|28.6|26.4|10.9|6.5|9.1|3.6|16.6|21.0 min. |222|59.0|30.0|37.1|15.9|26.7|24.9|10.0|5.9|8.5|2.0|15.2|18.8 max. |304|92.0|35.0|47.0|20.1|33.4|29.1|12.3|7.3|10.0|5.9|19.1|24.1 _G. b. jugossicularis_; Morton Co., Kansas 5012|244|72.0|30.0|36.2|16.4|25.4|25.0|10.0|5.9|8.0|4.2|16.0|19.3 5395|230|72.0|30.0|34.6|13.9|24.7|24.8| 9.8|5.8|8.0|4.5|15.2|17.5 _G. b. industrius_; Meade Co., Kansas | |[C] | |[D] | | |[D] | 7 ave. |238|73.0|31.3|36.4|14.9|26.3|24.8|10.0|6.0|8.4|4.1|16.2|18.6 min. |231|65.0|30.0|35.4|14.0|25.8|24.5| 9.5|5.6|8.1|3.6|15.5|17.5 max. |256|75.0|32.0|37.8|16.1|27.8|25.9|10.3|6.5|8.7|4.7|17.6|19.9 _G. b. major_; 1 mi. S Aetna, Barber Co., Kansas 10069|257|95.0|32.0|37.0|16.4|26.4|25.5|10.8|6.2|9.0|3.4|16.4|19.4 Aetna, Barber Co., Kansas 10070|242|83.0|30.0|36.8|15.7|26.2|25.0|10.1|6.5|9.1|3.3|15.8|19.1 Wells Ranch, Aetna, Barber Co., Kansas 12238|239|65.0|31.0|34.2|14.5|24.6|23.7| 9.6|6.0|8.0|3.6|15.2|17.7 1 mi. S.Sun City, Barber Co., Kansas 11075|232|66.0|28.0|34.2|14.4|25.0|23.6| 9.9|5.9|8.0|3.4|15.0|17.0 3 mi. SW Arkansas City, Cowley Co., Kansas 12872|242|66.0|30.0|38.1|15.0|28.0|26.2|10.3|6.3|7.8|4.5|16.1|19.1 3 mi. SE Arkansas City, Cowley Co., Kansas 12894|230|82.0|30.0|38.5|15.5|28.0|25.6|10.0|6.7|8.7|4.0|16.6|19.5 12893|246|83.0|32.0|36.5|14.2|25.6|24.8| 9.6|6.6|8.7|4.6|15.4|18.1 ------+---+----+----+----+----+----+----+----+---+---+---+----+----- [A] 15 averaged. [B] 16 averaged. [C] 6 averaged. [D] 5 averaged. [E] approximate. SUBSPECIES OF THE SPECIES GEOMYS BURSARIUS If _Geomys lutescens major_ Davis is correctly judged to intergrade with _Geomys bursarius majusculus_ Swenk, the name for the full species will be _Geomys bursarius_ because _bursarius_ is the oldest name among those available. Some new combinations of names are required. According to our present understanding, the eleven kinds of pocket gophers named below are properly to be arranged as subspecies of the species _Geomys bursarius_: _Geomys bursarius bursarius_ (Shaw). Type from unknown locality in Upper Mississippi Valley. _Geomys bursarius majusculus_ Swenk. Type from Lincoln, Lancaster County, Nebraska. _Geomys bursarius hylaeus_ Blossom. Type from 10 mi. S Chadron, Dawes County, Nebraska. _Geomys bursarius levisagittalis_ Swenk. Type from Spencer, Boyd County, Nebraska. _Geomys bursarius vinaceus_ Swenk. Type from Scottsbluff, Scotts Bluff County, Nebraska. _Geomys bursarius lutescens_ Merriam. Type from Sandhills on Birdwood Creek, Lincoln County, Nebraska. _Geomys bursarius illinoensis_ Komarek and Spencer. Type from 1 mi. S Momence, Kankakee County, Illinois. _Geomys bursarius jugossicularis_ Hooper. Type from Lamar, Prowers County, Colorado. _Geomys bursarius industrius_ new subspecies. Type from 1-1/2 mi. N Fowler, Meade County, Kansas. _Geomys bursarius major_ Davis. Type from 8 mi. W Clarendon, Donley County, Texas. _Geomys bursarius llanensis_ Bailey. Type from Llano, Llano County, Texas. LITERATURE CITED ALLEN, J. A. 1874. Notes on the mammals of portions of Kansas, Colorado, Wyoming and Utah. Part I. On the mammals of middle and western Kansas. Bull. Essex Inst., 6 (no. 2):43-52. February, 1874. 1895. List of mammals collected in the Black Hills region of South Dakota and in western Kansas by Mr. Walter W. Granger with field notes by the collector. Bull. Amer. Mus. Nat. Hist., 7:259-274. August 21, 1895. ALLEN, P. 1940. Kansas mammals. Kansas State Teachers College, Emporia, Bull. Inf. Stud. in Educ., Number 20 (no. 5):l-62. May, 1940. BAKER, A. B. 1889. Mammals of western Kansas. Trans. Kansas Acad. Sci., 11:56-58 (for 1887-88). BAIRD, S. F. 1857. Explorations and surveys for a railroad route from the Mississippi River to the Pacific Ocean. War Department. Mammals, Part I, xxxii + 757, pls. 17-60, 35 figs. in text, 1857. BLACK, J. D. 1937. Mammals of Kansas. Thirtieth Bienn. Rept. Kansas State Board of Agric., 35:116-217. DAVIS, W. B. 1940. Distribution and variation of pocket gophers (Genus Geomys) in the southwestern United States. Texas Agric. Exp. Station, Bull., 590:1-38, 6 figs. in text. October 23, 1940. HIBBARD, C. W. 1933. A revised check list of Kansas mammals. Trans. Kansas Acad. Sci., 36:230-249. 1944. A checklist of Kansas mammals, 1943. Trans. Kansas Acad. Sci., 47:61-88. HOOPER, E. T. 1940. A new race of pocket gopher of the species Geomys lutescens from Colorado. Occas. Papers, Mus. Zoöl., Univ. Michigan, 420:1-3. June 28, 1940. KNOX, M. V. B. 1875. Kansas Mammalia. Trans. Kansas Acad. Sci., 4:18-22. KOMAREK, E. V. , and SPENCER, D. A. 1931. A new pocket gopher from Illinois and Indiana. Journ. Mamm., 12:404-408, 1 pl., 1 fig. in text. November 11, 1931. LANTZ, D. E. 1905. Kansas mammals in their relations to agriculture. Kansas State Agric. College Bull., 129:331-404. April, 1905. 1905. A list of Kansas mammals. Trans. Kansas Acad. Sci., 19:171-178. 1907. Additions and corrections to the list of Kansas mammals. Trans. Kansas Acad. Sci., 20 (pt. 2):214-217. MERRIAM, C. H. 1890. Descriptions of twenty-six new species of North American mammals. N. Amer. Fauna, 4: v + 60, 3 pls., 3 figs. in text. October 8, 1890. 1895. Monographic revision of the pocket gopher Family Geomyidae.... N. Amer. Fauna, 8:1-258, 19 pls. and frontispiece, 71 figs. in text, 4 maps. January 31, 1895. SCHEFFER, T. H. 1910. The pocket gopher. Kansas State Agric. Coll. Ent. and Zoöl. Dept., Bull., 172:197-233, illustrated. September, 1910. 1931. Habits and economic status of the pocket gophers. U. S. Dept. Agric., Tech. Bull., 224:1-27, 8 pls., 2 figs. in text. January, 1931. SWENK, M. H. 1939. A study of local size variations in the prairie pocket gopher (Geomys bursarius), with description of a new subspecies from Nebraska. Missouri Valley Fauna, 1:1-8. December 5, 1939. 1940. A study of subspecific variation in the yellow pocket gopher (Geomys lutescens) in Nebraska, and the geographical and ecological distribution of the variants. Missouri Valley Fauna, 2:1-12. February 1, 1940. _Transmitted May 30, 1947._ PRINTED BY FRED VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1947 21-8188 Transcriber Notes: Minor typographical errors were corrected without notice. Italic words and phrases are marked _like this_. Bold words and phrases are marked =like this=. Small caps are converted to all upper case, LIKE THIS. Superscripts in text are indicated by use of the caret, like this ^4. 
37317	----	UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Volume 9, No. 12, pp 363-384, 7 figs, in text, 1 table February 21, 1958 Geographic Variation in the Pocket Gopher, Thomomys bottae, in Colorado BY PHILLIP M. YOUNGMAN UNIVERSITY OF KANSAS LAWRENCE 1958 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson Volume 9, No. 12, pp. 363-384, 7 figs. in text, 1 table Published February 21, 1958 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1958 Geographic Variation in the Pocket Gopher, Thomomys bottae, in Colorado BY PHILLIP M. YOUNGMAN INTRODUCTION Two species of pocket gophers of the genus _Thomomys_ (Family Geomyidae) occur in Colorado, _Thomomys bottae_ (see fig. 1) in the low valleys in the south-central and southwestern parts of the state and _Thomomys talpoides_ mainly in the mountains and high valleys. _Thomomys bottae_ occurs primarily in the Piñon-juniper, Ponderosa Pine, and Short Grass zones of Daubenmire (1943) but in some localities is found in the Douglas Fir Zone. _Thomomys talpoides_ occupies primarily the Douglas Fir Zone and Engelmann Spruce-Subalpine Spruce Zone but is found also in the Piñon-juniper and Short Grass zones in some localities. The ranges of the two species do not overlap in the strict sense but interdigitate in a parapatric type of distribution. Two other pocket gophers, _Geomys bursarius_ and _Cratogeomys castanops_, also occur in Colorado--in the Upper Sonoran Life-Zone. _Geomys bursarius_ occupies much of the Great Plains, whereas _Cratogeomys castanops_ is found only on the plains in the southeastern part of the state. The objectives of the study, reported on here, were to learn the geographic distribution of _Thomomys bottae_ in Colorado, to find means for recognizing the different subspecies, and to describe individual and geographic variation. I am indebted to Mr. Sydney Anderson and Professor E. Raymond Hall for many helpful suggestions and for their critical reading of the manuscript, to Dr. Richard S. Miller, who made the collection of many of the specimens possible, and to Dr. Richard M. Hansen for numerous suggestions. I wish to express my appreciation also to the following for the loan of specimens in their care: Alfred M. Bailey and A. A. Rogers, Colorado Museum of Natural History, Denver, Colorado; David H. Johnson, United States National Museum, Washington, D. C; Robert W. Lechleitner, Colorado State University, Fort Collins, Colorado; and Robert Z. Brown, Colorado College, Colorado Springs, Colorado. METHODS Adults of approximately equal age were compared in the study of geographic variation. Three criteria of adulthood are: (a) suture obliterated between supraoccipital and exoccipital, (b) suture at least partly obliterated between basisphenoid and basioccipital, (c) supraorbital crests not widely separated and almost parallel. In males the crests encroach on the lateral borders of the interparietal; in females the crests approach the lateral borders of the interparietal but are more widely separated than in males. [Illustration: Fig. 1. Geographic distribution of _Thomomys bottae_ in southwestern Colorado. 1. _T. b. howelli_ 2. _T. b. aureus_ 3. _T. b. pervagus_ 4. _T. b. cultellus_ 5. _T. b. internatus_ 6. _T. b. rubidus_] In studying geographic variation, greater emphasis was placed on females than on males. As noted by Grinnell (1931:4), males vary more than females, especially in length of rostrum and associated nasal measurements. Color terms are those of Munsell (1954). Color measurements were standardized by the use of a single 100 watt General Electric blue daylight bulb in a 12 inch white reflector suspended 24 inches above the specimen. All other light was excluded. The individual hairs of _Thomomys bottae_ are either bicolored or tricolored. The darkness of a specimen often may be attributed to the presence of dark-tipped hairs. The color given in the description is the basic reddish or yellowish color of the hairs. The presence of a grizzled effect or a dark dorsal stripe, or any other pattern resulting from dark hairs, is noted in the remarks. Specimens examined are listed by counties in the following order: Mesa Montrose San Miguel Dolores Montezuma La Plata Archuleta Conejos Chaffee Fremont El Paso Pueblo Custer Huerfano Alamosa Las Animas Localities are listed from north to south within a county. If two localities lie on the same line of latitude, the western precedes the eastern. Localities omitted on the map in order to prevent overlapping of symbols are in Italics. Unless otherwise indicated, specimens are in the University of Kansas, Museum of Natural History. The following initials are used to designate specimens in other collections: CSU--Colorado State University, Fort Collins, Colorado. CMNH--Colorado Museum of Natural History, Denver, Colorado. ERW--E. R. Warren Collection, Colorado College, Colorado Springs, Colorado. USNM--United States National Museum, Washington, D. C. The following measurements of the skull are listed in the tables: _Condylobasal length._--The shortest distance between the anteriormost projections of the premaxillaries and a line touching the posterior surfaces of the exoccipital condyles. _Length of nasals._--The distance from the most anterior projection of the nasal bones to the most posterior projection of a nasal bone. _Zygomatic breadth._--The greatest distance across the zygomatic arches, at right angles to the long axis of the skull. _Squamosal breadth._--The greatest distance between the mastoidal processes of the squamosal. _Length of rostrum._--The shortest distance from the shallow notch that lies lateral to the hamulus of the lacrymal bone, to the tip of the nasal on the same side of the skull. _Breadth of rostrum._--The greatest width of the rostrum, anterior to the maxillae, transverse to the long axis of the skull. _Alveolar length of upper maxillary tooth-row._--Distance between the anterior margin of the alveolus of the first cheek-tooth and the posterior margin of the alveolus of the last upper cheek-tooth, on one side of the skull. _Least interorbital breadth._--The least distance across the frontal bones at the interorbital constriction as seen in dorsal view. PHYSIOGRAPHY _Thomomys bottae_ occurs in the Colorado Plateau Province (terminology of Fenneman, 1931), the Southern Rocky Mountain Province and a small part of the Great Plains Province. The Colorado Plateau Province, in the southwestern part of the state, is mostly above 5000 feet and is characterized by the great number of canyons cut by rivers and streams in the nearly horizontal strata. Prominent features of the landscape are cuestas, such as Mesa Verde, and laccoliths, such as Ute Peak. The Southern Rocky Mountain Province consists mainly of high granitic mountains running north and south, many of which extend to more than 14,000 feet above sea level. Included in this region are several large basins, such as North Park and South Park and the San Luis Valley. The San Juan Mountains, which separate the Colorado Plateau Province from the San Luis Valley, and the Sangre De Cristo and Wet mountains, which intervene between the San Luis Valley and the Great Plains, importantly influence the distribution of _Thomomys bottae_. The Great Plains Province is a broad highland that slopes gradually eastward from the Rocky Mountains. Of importance to the present study are two subdivisions of the Great Plains, the Colorado Piedmont and the Raton Section. The Colorado Piedmont is a much dissected fluviatile plain, roughly extending from the vicinity of the Arkansas River to the northern boundary of the state. In general the topography of the Colorado Piedmont is broadly rolling with greater relief than the high plains to the east; however, buttes and steep bluffs occur locally. The Raton Section imperceptibly blends into the southern boundary of the Colorado Piedmont and extends south into New Mexico and Texas. A trenched peniplane of greater relief and altitude than the Colorado Piedmont, it is characterized by high mesas, extensive dissected lava-capped plateaus, deep canyons, and mountains of volcanic origin. GEOGRAPHIC VARIATION Six subspecies of _Thomomys bottae_ occur in Colorado. _T. b. aureus_ and _T. b. howelli_ occupy the Colorado Plateau Province (see fig. 1) and are characterized by a yellowish color; nasals posteriorly truncate or rounded; posterior extensions of premaxillae long; basioccipital wide; and interpterygoid space U-shaped with a median spicule. _T. b. internatus_, _T. b. cultellus_, and a new subspecies from the vicinity of Cañon City described on page 376, inhabit the Sangre De Cristo and Wet mountains in the Southern Rocky Mountain Province and adjacent parts of the Colorado Piedmont and Raton Section of the Great Plains Province (see fig. 1). This group of closely related subspecies is characterized by reddish color; posterior margins of nasals forming a V; posterior extensions of premaxillae short; basioccipital narrow; and interpterygoid space V-shaped, lacking a median spicule. _T. b. pervagus_ occupies part of the San Luis Valley to the west of the Rio Grande (see fig. 1). In Colorado _T. b. pervagus_ is isolated from _T. b. internatus_ and _T. b. cultellus_ by the Sangre De Cristo and Culebra ranges and is separated from _T. b. aureus_ by the San Juan Mountains. _T. b. pervagus_ occupies an area geographically intermediate between _T. b. aureus_ to the west and _T. b. internatus_ and _T. b. cultellus_ to the east and has some characters in common with these subspecies. _T. b. pervagus_ resembles _T. b. aureus_ in having long posterior extensions of the premaxillae and in sometimes having rounded posterior margins of the nasals. _T. b. pervagus_ resembles _T. b. internatus_ and _T. b. cultellus_ in color, the presence of a V-shaped interpterygoid space, and a narrow basioccipital. Kelson (1951:69) has pointed out that in New Mexico the separation of the ranges of _T. b. pervagus_ and _T. b. cultellus_ is probably complete, but probably incomplete between _T. b. pervagus_ and _T. b. aureus_. Nevertheless, the similarities between _T. b. pervagus_ and _T. b. cultellus_ and _T. b. internatus_ suggest that _T. b. pervagus_ was originally derived from the more eastern stock. _T. b. aureus_ is a variable subspecies which, according to Durrant (1952:211), intergrades with _T. b. howelli_ in Utah. Specimens of _T. b. aureus_ showing the greatest amount of geographic variation cranially are from the ecotone between the Piñon-juniper and Douglas Fir zones at the edge of the range of the subspecies. _T. b. howelli_ is a markedly distinct subspecies that shows certain similarities to _T. b. aureus_, but the degree of cranial difference from _T. b. aureus_ suggests an isolation of long duration, or a rapid evolution from the parent stock. _T. b. internatus_ and _T. b. cultellus_ probably intergrade east of the Sangre De Cristo Range in the vicinity of the Colorado-New Mexico boundary. The amount of intergradation is obscured by the great amount of geographic variation occurring in _T. bottae_ at the edge of the plains and by the lack of specimens from this area. _T. b. internatus_ is a widespread subspecies showing its greatest variation at the edge of the plains. This area is an ecotone between the coniferous forest and the grassland and is by nature an area of change owing to the alternation of wet and dry periods such as the pluvial, interpluvial, and postpluvial periods. This seems to support Durrant's observation (1952:496) that "the greatest range of morphological variation is in animals from the least stable environments." Specimens from a small area north of the Arkansas River in the vicinity of Cañon City (see fig. 1) differ sufficiently from _T. b. internatus_ to be given nominal recognition. High mountains and the Arkansas River isolate the new subspecies found at Cañon City from populations of _T. b. internatus_ to the west and south; however there are no apparent geographic barriers between the newly named subspecies and populations of _T. b. internatus_ twelve miles to the north or from the vicinity of Pueblo to the east. This new subspecies is the most extreme of the variants occurring in the unstable environment at the edge of the plains. =Thomomys bottae aureus= Allen _Thomomys aureus_ Allen, Bull. Amer. Mus. Nat. Hist., 5:49, April, 1893; Warren, Colorado College Publ., 19:252, January, 1906; Warren, Colorado College Publ., 33:77, January, 1908; Warren, Mammals of Colorado, p. 79, 1910; Cary, N. Amer. Fauna, 33:136, August 17, 1911. _Thomomys bottae aureus_, Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Warren, Mammals of Colorado, p. 158, 1942. _Thomomys apache_ Bailey, Proc. Biol. Soc. Washington, 23:79, May 4, 1910. Holotype from Lake La Jara, 7500 feet, Rio Arriba County, New Mexico. _Thomomys perpallidus aureus_, Bailey, N. Amer. Fauna, 39:74, November 15, 1915. _Thomomys perpallidus apache_, Bailey, N. Amer. Fauna, 39:75, November 15, 1915. _Thomomys bottae apache_, Goldman, Proc. Biol. Soc. Washington, 48:157, October 31, 1935; Warren, Mammals of Colorado, p. 160, 1942. _Thomomys bottae optabilis_ Goldman, Jour. Washington Acad. Sci., 26:116, March 15, 1936. Holotype from Coventry, 6500 feet, Montrose County, Colorado; Warren, Mammals of Colorado, p. 159, 1942, part. _Holotype._--Adult female, skin and skull number 5243/4123, American Museum of Natural History, obtained at Bluff City, San Juan County, Utah, May 12, 1892, by Charles P. Rowley. _Distribution._--Colorado Plateau Province of southwestern Colorado (see fig. 1), northwestern New Mexico, southeastern Utah, and northeastern Arizona. _Distinctive characters._--Size large (see measurements); usually pale in western part of range, dark in eastern part; posterior extensions of premaxillae long, wide, and deeply serrated; posterior margins of nasals truncate or slightly rounded (see fig. 2); interpterygoid space U-shaped, with median spicule; basioccipital wide; bullae well inflated, rounded ventrally. _Comparisons._--For comparisons with _T. b. howelli_ and _T. b. pervagus_, see accounts of those subspecies. _Remarks._--_T. b. aureus_ is a variable subspecies, which differs considerably from _T. b. internatus_, _T. b. cultellus_, and _T. b. rubidus_ and includes several microgeographic races distinguishable to a taxonomist specializing in the group. These slightly varying populations are here not considered sufficiently distinct for nominal recognition. Characters such as color of the pelage and conformation of the bullae and zygomatic arches vary with the locality, and to some extent vary among specimens from a single locality. The name _Thomomys bottae optabilis_, given to specimens from Coventry by Goldman (1936:116), is here placed in synonymy under _T. b. aureus_ Allen. The characters originally used to describe _T. b. optabilis_ are of the type that vary between populations only a few miles apart, or often vary within a population. The skulls of specimens from Coventry are not lighter in structure than those of _T. b. aureus_. The premaxillae are not narrower, nor is the frontal region narrower or more constricted than in _T. b. aureus_. The name _Thomomys bottae apache_, given to specimens from Lake La Jara, New Mexico, by Bailey (1910:79), and later applied to specimens from Colorado by Bailey (1915:75), is here also placed in synonymy under _T. b. aureus_. Specimens from Lake La Jara, New Mexico, and nearby localities in Colorado may be separated from topotypes of _T. b. aureus_ on the basis of color only. The topotypes of _T. b. aureus_ are mostly pale; some, however, are dark. The number of pale specimens in any given series decreases gradually in a clinal pattern from west to east. Since there is no noticeable step in the cline and since all specimens show close cranial similarity, it is felt that nominal recognition of the darker specimens does not present a realistic picture of the relationships of the relatively unisolated populations in the Colorado Plateau Province. Since _Thomomys bottae_ in the Colorado Plateau Province is especially plastic, varying from locality to locality, emphasis is here placed on similarities that unite specimens from different localities. The individual and microgeographic variations are outlined below. Specimens from Bedrock have zygomatic arches that are heavy anteriorly. Specimens from Coventry are dorsally almost uniformly Strong Brown (7.5YR 5/6) and lack a strong dorsal stripe. The venters are Reddish Yellow (7.5YR 8/6). Specimens from 15 miles west of Cortez are the palest specimens of _T. b. aureus_ from Colorado, and closely resemble topotypes. The basic color varies from Reddish Yellow (7.5YR 7/6 and 6/6) to Strong Brown (7.5YR 5/6). Specimens are marked with a narrow dark dorsal stripe. The venters are white. Specimens from Ute Peak and Cortez have Reddish Yellow (7.5YR 6/6) flanks and are slightly darker dorsally. Many specimens from Mesa Verde are indistinguishable from specimens from Coventry and from Cortez. Others have dark diffuse dorsal stripes. The venters are Pink (7.5YR 7/4) or Pinkish White (7.5YR 8/2). Some specimens from the Mancos River have wide dorsal stripes. Specimens from three miles west of Durango have especially wide-spreading zygomatic arches posteriorly and have wide black dorsal stripes. The venters are Pink (7.5YR 7/4). One specimen from Florida is dark and grizzled and has a dark dorsal stripe. Another specimen is pale and has only a small dorsal stripe. Specimens from 12 miles west of Pagosa Springs have thin rostra and diffuse dorsal stripes. Specimens from Bondad have a V-shaped interpterygoid space and in it a small median spicule. One specimen is uniformly grizzled and lacks a dorsal stripe, giving an overall effect of Dark Yellowish Brown (10YR 3/3). Another specimen has Strong Brown (7.5YR 5/6) flanks and is only slightly darker dorsally. _Specimens examined._--Total 114. _Colorado_: Montrose Co.: West Paradox Valley, 5 (CMNH); Bedrock, 5150 ft., 5 (ERW); Coventry, 6800 ft., 14 (12 ERW, 2 USNM). San Miguel Co.: 19 mi. N Dove Creek, 6100 ft., 1. Montezuma Co.: _Ashbaugh's Ranch (T.36N, R.18W) 5350 ft._, 5 (4 ERW, 1 USNM); 15 mi. W Cortez (Sec. 2, T.35N, R.19W), 5400 ft., 8; Major Ranch, Cortez, 7 (CSU); _3 mi. SSW Cortez, 6400 ft._, 1; Ute Peak, 2 (CMNH); Four Corners, 1 (CMNH). Mesa Verde National Park: Upper Well, Prater Canyon, 7575 ft., 1; _3/4 mi. S, 1-3/4 mi. W Park Point, 8000 ft._, 3; _1/4 mi. N Middle Well 7500 ft._, 1; _Sec. 27, Head of E Fork, Navaho Canyon, 7900 ft._, 2; _1-1/4 mi. S, 1-3/4 mi. W Park Point, 8000 ft._, 1; _Middle Well, Prater Canyon, 7500 ft._, 9; _3 mi. N Rock Springs, 8200 ft._, 4; _1-1/2 mi. S, 2 mi. W Park Point, 8075 ft._, 1; _2-1/2 mi. N, 1/2 mi. W Rock Springs, 8100 ft._, 3; _2 mi. N, 1/4 mi. W Rock Springs, 7900 ft._, 2; _1/2 mi. N Far View Ruins, 7825 ft._, 1; _Far View Ruins, 7700 ft._, 1; _1 mi. NNW Rock Springs, 7500 ft._, 1; Rock Springs, 7400 ft., 1; Mancos River, 6200 ft., 9; _Mesa Verde_, 1 (USNM). La Plata Co.: 1 mi. N La Plata, 1; 3 mi. W Durango, 5; Florida, 6800 ft., 5; Bayfield, 1 (USNM); Bondad, 6 (CMNH); Archuleta Co.: 12 mi. W Pagosa Springs, 6700 ft., 2; Arboles, 1 (USNM). _New Mexico_: Rio Arriba Co.: La Jara Lake, 7500 ft., 2 (USNM). =Thomomys bottae howelli= Goldman _Thomomys bottae howelli_ Goldman, Jour. Washington Acad. Sci., 26:116, March 15, 1936; Warren, Mammals of Colorado, p. 161, 1942. _Thomomys aureus_, Cary, N. Amer. Fauna, 33:136, August 17, 1911, part. _Thomomys perpallidus aureus_, Bailey, N. Amer. Fauna, 39:74, November 15, 1915, part. _Holotype._--Adult female, skin and skull, number 75684, United States National Museum, obtained by Arthur H. Howell at Grand Junction, 4600 feet, Mesa County, Colorado, November 7, 1895. _Distribution._--Colorado Plateau Province of west-central Colorado and east-central Utah, in the Colorado River Valley east of the Green River (see fig. 1). _Distinctive characters._--Pale (Pinkish White 7.5YR 8/2); cranium flattened; nasals short and wide; posterior tongues of premaxillae long, thin, and attenuate (see fig. 3). _Comparisons._--Compared with _T. b. aureus_, _T. b. howelli_ differs as follows: paler; nasals shorter and wider; cranium more flattened; posterior extensions of premaxillae longer, thinner, and more acuminate. _Remarks._--_T. b. howelli_ most closely resembles _T. b. aureus_; however, since only one adult specimen of _T. b. howelli_ is known, it is impossible to appraise adequately its characters. Durrant (1952:211) records intergradation between _T. b. howelli_ and _T. b. osgoodi_, and between _T. b. howelli_ and _T. b. aureus_ in Utah. An attempt to collect specimens of _T. b. howelli_, in March, 1957, by Richard S. Miller and the writer was unsuccessful. _Specimens examined._--Total 2. Mesa Co.: Grand Junction, 4600 ft., 1 (USNM); Sieber Ranch, Little Doloris River, 1 (ERW). =Thomomys bottae pervagus= Merriam _Thomomys aureus pervagus_ Merriam, Proc. Biol. Soc. Washington, 14:110, July 19, 1901; Cary, Proc. Biol. Soc. Washington, 20:26, March 27, 1907; Warren, Colorado College Publ., 33:77, January, 1908; Warren, Mammals of Colorado, p. 79, 1910, part; Cary, N. Amer. Fauna, 33:137, August 17, 1911, part. _Thomomys bottae pervagus_, Goldman, Proc. Biol. Soc. Washington, 48:157, October 31, 1935. _Thomomys fulvus pervagus_, Bailey, N. Amer. Fauna, 39:82, November 15, 1915. _Holotype._--Adult male, skin and skull, number 58293, United States National Museum, Espanola, Rio Arriba County, New Mexico, obtained by J. Alden Loring, January 4, 1894. _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 acuminate; nasals long, thin, posterior margins usually forming a wide V (see fig. 4); bullae rounded ventrally; interpterygoid space 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 space 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). =Thomomys bottae internatus= Goldman _Thomomys 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. _Thomomys aureus pervagus_, Warren, Mammals of Colorado, p. 80, 1910, part; Cary, N. Amer. Fauna, 33:137, August 17, 1911, part. _Thomomys 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 space 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 Pass 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 assigned 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 Cañon 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 Cañon 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. =Thomomys bottae cultellus= Kelson _Thomomys bottae cultellus_ Kelson, Univ. Kansas Publ., Mus. Nat. Hist., 5:64, October 1, 1951. _Thomomys 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. _Thomomys 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). [Illustration: Figs. 2-7. Dorsal views of skulls of _Thomomys bottae_. × 1. Fig. 2. _Thomomys b. aureus_, 3 mi. W Durango, La Plata Co., Colorado. No. 72967, Female. Fig. 3. _Thomomys b. howelli_, holotype, Grand Junction, 4600 ft., Mesa Co., Colorado. No. 75684 USNM, Female. Fig. 4. _Thomomys b. pervagus_, Espanola, 5000 ft., Rio Arriba Co., New Mexico. No. 133614 USNM, Female. Fig. 5. _Thomomys b. cultellus_, Fishers Peak, 8000 ft., Las Animas Co., Colorado. No. 129285 USNM, Female. Fig. 6. _Thomomys b. internatus_, Salida, 7050 ft., Chaffee Co., Colorado. No. 2757 ERW, Female. Fig. 7. _Thomomys b. rubidus_, holotype, 2-9/10 mi. E Cañon City, Fremont Co., Colorado. No. 72954, Female.] =Thomomys bottae rubidus= new subspecies _Holotype._--Adult female, skin and skull, number 72954, Museum of Natural History, University of Kansas, trapped by Richard S. Miller and Phillip M. Youngman, original number 253 (PMY), 2-9/10 miles east of Cañon City, 5344 feet, Fremont County, Colorado, March 17, 1957. _Distribution._--Known only from Garden Park in Cañon City and from the type locality (see fig. 1). _Distinctive characters._--Dark (Reddish Brown 5YR 3/3); size large (see measurements); skull large; rostrum wide; zygomatic arches rounded and broadly spreading (see fig. 7); alveolar length of upper maxillary tooth-row small. _Comparisons._--From topotypes of _T. b. internatus_, _T. b. rubidus_ differs as follows: uniformly darker; skull averages larger in all measurements, except alveolar length of upper maxillary tooth-row, which is smaller; rostrum proportionately wider and tapered anteriorly; zygomatic arches more rounded; bullae more rounded in lateral view. Specimens of _T. b. rubidus_ differ from topotypes of _T. b. pervagus_ in darker color; rostrum wider posteriorly; posterior extensions of premaxillae shorter; bullae smaller, proportionately more inflated posteriorly; zygomatic arches more rounded; wider across squamosals; alveolar length of upper maxillary tooth-row greater. From topotypes of _T. b. cultellus_, _T. b. rubidus_ differs as follows: paler; larger in all measurements taken; rostrum proportionately wider; zygomatic arches more rounded, less angular; angle formed by zygomatic arch and rostrum greater; bullae proportionately smaller, not so pointed anteriorly; alveolar length of upper maxillary tooth-row shorter. _Remarks._--The range of _T. b. rubidus_ is surrounded by the range of _T. b. internatus_; nevertheless, intergradation has not been found. For a discussion of the geographic relation of _T. b. rubidus_ to _T. b. internatus_ see page 374. _Specimens examined._--Total 7. Fremont Co.: Garden Park, Cañon City, 5344 ft., 1; _2-9/10 mi. E Cañon City, 5344 ft._, 6. SUMMARY A study of 249 specimens of _Thomomys bottae_ from Colorado reveals six subspecies in the state. _T. b. aureus_ and _T. b. howelli_ occupy the Colorado Plateau Region in the western and southwestern parts of the state. _T. b. internatus_, _T. b. cultellus_, _T. b. pervagus_, and the newly named _T. b. rubidus_ occupy part of the Southern Rocky Mountain Region and a narrow strip of the Great Plains. The greatest amount of geographic variation, in _Thomomys bottae_ in Colorado, occurs in the ecotone between the grassland and coniferous forest at the edge of the Great Plains, and in the ecotone between the Piñon, juniper, and sage of the Colorado Plateau and the Coniferous forest of the southern Rocky mountains. TABLE 1. MEASUREMENTS, IN MILLIMETERS, OF THOMOMYS BOTTAE Unless otherwise noted, specimens are adults from Colorado Key to Headings: A: Catalog number or number of individuals averaged B: Total length C: Tail D: Hind foot E: Condylobasal length F: Nasal length G: Zygomatic breadth H: Squamosal breadth I: Length of rostrum J: Breadth of rostrum K: Alveolar length of upper max. tooth-row L: Least interorbital breadth =============================================================== Sex| [A] |[B]|[C]|[D]| [E]| [F]| [G]| [H]| [I]| [J]|[K]|[L] ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae howelli_, holotype ---+---------+---+---+---+----+----+----+----+----+----+---+--- F | 75684[1]| | | | | | | | | | | | sad. |219| 71| 29|37.3|11.1|23.7|20.0|14.5| 8.5|7.7|6.6 | +---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae aureus_, Bedrock | +---+---+---+----+----+----+----+----+----+---+--- F | 2982[2] |217| 59| 31|40.4|13.8|24.3|20.6|16.7| 8.6|9.2|6.8 F | 3013[2] |210| 60| 29|38.7|13.0|24.4|20.4|15.7| 8.1|8.9|7.0 | | | | | | | | | | | | M | 2997[2] |242| 73| 33|44.7|15.4|28.4|22.8|15.7|10.1|9.0|7.2 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Coventry | +---+---+---+----+----+----+----+----+----+---+--- F | 6 av. |222| 61| 31|39.0|12.1|25.4|20.3|15.2| 7.8|8.2|6.8 | Max. |229| 63| 33|40.0|12.8|25.8|20.6|15.6| 8.2|8.5|7.0 | Min. |217| 58| 30|38.3|11.4|25.0|19.3|14.7| 7.5|8.0|6.6 | | | | | | | | | | | | M | 3 av. |259| 70| 35|46.5|15.0|29.3|22.7|17.8| 9.2|9 5|6.7 | Max. |270| 76| 36|48.3|16.0|31.9|23.7|18.0| 9.3|9.6|6.9 | Min. |250| 65| 35|45.5|14.4|27.6|22.2|17.6| 9.2|8.0|6.4 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Ashbaugh's Ranch and 15 mi. W Cortez | +---+---+---+----+----+----+----+----+----+---+--- F | 7 av. |225| 67| 28|39.0|13.7|24.4|20.2|16.1| 8.0|8.3|6.3 | Max. |238| 75| 31|40.6|14.7|25.0|20.7|16.5| 8.5|8.7|6.8 | Min. |216| 55| 26|37.8|12.9|23.6|19.7|15.5| 7.8|7.9|6.1 | | | | | | | | | | | | M | 4 av. |247| 73| 31|44.2|15.9|27.7|22.1|18.6| 9.2|8.4|6.4 | Max. |252| 80| 34|45.2|16.7|28.8|22.3|19.8| 9.6|8.8|6.7 | Min. |244| 67| 30|43.7|15.5|27.0|21.7|18.0| 8.8|8.0|6.2 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Cortez | +---+---+---+----+----+----+----+----+----+---+--- F | 5120[3] |224| 56| 28|38.1|12.3|....|19.5|15.4| 7.5|7.6|6.5 | 5121[3] |220| 68| 31|38.3|11.6|24.2|19.6|15.1| 7.6|8.0|6.7 | | | | | | | | | | | | M | 5124[3] |257| 81| 33|44.4|15.4|29.5|22.2|18.6| 8.9|8.6|6.5 M | 5119[3] |215| 62| 28|42.0|14.0|27.9|22.1|17.9| 8.2|8.6|6.4 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Mesa Verde (combined) | +---+---+---+----+----+----+----+----+----+---+--- F | 5 av. |221| 63| 30|39.0|12.6|24.7|20.2|16.0| 8.0|8.2|6.7 | Max. |235| 66| 32|40.4|13.7|25.6|21.1|17.3| 8.7|8.5|7.1 | Min. |212| 61| 28|38.1|12.0|24.1|19.5|15.0| 7.7|7.9|6.4 | | | | | | | | | | | | M | 3 av. |246| 74| 32|43.7|14.9|27.8|22.3|18.3| 8.8|8.9|6.6 | Max. |252| 79| 33|45.0|15.2|28.4|23.0|18.5| 9.0|9.0|6.8 | Min. |238| 69| 31|42.0|14.7|27.5|21.2|18.2| 8.7|8.9|6.3 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 1 mi. N La Plata | +---+---+---+----+----+----+----+----+----+---+--- M | 72966[4]|236| 70| 31|45.4|15.6|29.4|23.3|20.2| 8.8|8.5|6.5 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 3 mi. W Durango | +---+---+---+----+----+----+----+----+----+---+--- F | 3 av. |225| 65| 28|40.1|13.1|25.7|21.0|16.6| 8.1|8.3|6.5 | Max. |230| 67| 29|40.4|13.5|25.8|21.2|16.8| 8.4|8.5|6.6 | Min. |219| 63| 28|39.9|13.0|25.7|20.6|16.5| 8.4|8.1|6.4 | | | | | | | | | | | | M | 70054[4]|262| 87| 35|45.0|15.6|27.9|22.7|19.7| 9.3|9.8|6.4 M | 70055[4]|248| 79| 31|43.3|14.0|27.6|22.1|17.1| 8.7|8.2|6.2 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 12 mi. W Pagosa Springs | +---+---+---+----+----+----+----+----+----+---+--- F | 72971[4]|217| 65| 27|39.1|12.8|....|20.0|15.4| 7.4|8.7|6.2 | | | | | | | | | | | | M | 72970[4]|238| 70| 29|42.7|15.0|27.5|21.8|17.2| 8.8|8.3|6.5 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae pervagus_, Antonito | +---+---+---+----+----+----+----+----+----+---+--- F |133668[1]| | | | | | | | | | | | sad. |208| 69| 29|37.3|12.9|23.1|18.2|15.8| 7.5|8.0|6.9 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | Espanola, New Mexico | +---+---+---+----+----+----+----+----+----+---+--- F |133616[1]|249| 82| 38|41.1|....|24.6|20.0|16.3| 8.2|8.1|7.1 F |133619[1]|216| 65| 32|40.6|....|24.9|19.3|....| 8.0|8.0|6.8 | | | | | | | | | | | | M | 58293[1]|244| 76| 31|44.0|16.1|26.9|21.2|18.3| 8.8|8.1|6.6 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae internatus_, Salida | +---+---+---+----+----+----+----+----+----+---+--- F | 11 av. |219| 67| 31|38.6|13.4|23.2|19.5|15.4| 7.6|7.8|6.5 | Max. |242| 80| 34|40.4|14.2|25.0|20.2|16.2| 8.1|8.4|6.9 | Min. |196| 45| 29|37.6|12.9|21.9|18.8|14.8| 7.3|7.0|6.3 | | | | | | | | | | | | M | 3 av. |247| 74| 32|42.9|16.1|25.1|20.9|18.0| 8.2|8.0|6.3 | Max. |248| 74| 33|43.7|16.3|26.4|21.7|18.1| 8.8|8.1|6.4 | Min. |247| 74| 32|42.2|15.9|25.8|20.5|17.9| 7.9|7.9|6.3 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 12 mi. N Cañon City | +---+---+---+----+----+----+----+----+----+---+--- F | 72945[4]|230| 81| 28|38.1|13.0|22.6|19.4|15.0| 7.9|8.0|6.7 F | 72947[4]|228| 74| 27|38.7|14.0|23.6|19.8|15.9| 8.2|8.1|6.8 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 1 mi. W Coaldale | +---+---+---+----+----+----+----+----+----+---+--- F | 70042[4]|224| 70| 30|38.1|13.1|23.5|19.5|15.6| 7.7|7.5|6.6 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 5 mi. S Cotopaxi | +---+---+---+----+----+----+----+----+----+---+--- F | 72932[4]|224| 65| 27|39.1|13.8|24.3|20.4|15.5| 7.7|7.5|6.5 | | | | | | | | | | | | M | 72925[4]|250| 74| 29|44.0|16.2|27.5|22.8|18.7| 9.0|8.1|6.1 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 9 mi. SSW Colorado Springs | +---+---+---+----+----+----+----+----+----+---+--- F | 72942[4]|225| 77| 29|38.8|14.1|23.3|20.2|15.4| 7.8|8.3|6.7 | 72943[4]|219| 70| 28|37.7|13.5|23.0|19.7|14.8| 7.6|8.4|6.8 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 2-1/2 mi. S Wetmore | +---+---+---+----+----+----+----+----+----+---+--- M | 70053[4]|250| 81| 30|42.5|16.7|26.3|22.3|17.7| 8.5|7.9|5.9 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 200 yards E St. Charles River, 8 mi. W Pueblo | +---+---+---+----+----+----+----+----+----+---+--- F | 73497[4]|226| 69| 30|39.3|13.9|24.9|20.5|15.7| 7.7|7.9|7.2 F | 73498[4]|216| 64| 29|38.0|12.9|24.2|20.1|15.1| 7.7|7.4|6.7 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | St. Charles Mesa | +---+---+---+----+----+----+----+----+----+---+--- F | 4860[3] |222| 70| 29|38.2|13.5|....|19.3|15.9| 8.2|7.5|6.5 M | 4864[3] |240| 72| 33|43.1|15.8|....|21.4|17.6| 9.2|7.9|6.7 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 11 mi. WNW Gardner | +---+---+---+----+----+----+----+----+----+---+--- F | 70052[4]|227| 64| 28|37.9|13.0|22.5|18.8|14.8| 7.3|8.0|6.7 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 1-1/2 mi. S Redwing | +---+---+---+----+----+----+----+----+----+---+--- F | 72940[4]|227| 73| 28|39.0|13.1|23.1|18.8|15.6| 7.8|8.0|6.8 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | 1 mi. E La Veta | +---+---+---+----+----+----+----+----+----+---+--- M | 70049[4]|254| 88| 32|42.4|15.1|27.5|21.8|17.3| 8.4|8.2|6.5 M | 70044[4]|239| 80| 32|42.3|16.5|27.8|22.0|17.9| 8.7|8.1|6.4 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae cultellus_, Fishers Peak | +---+---+---+----+----+----+----+----+----+---+--- F |129285[1]| | | | | | | | | | | | sad. |214| 64| 27|37.2|13.0|....|19.0|15.3| 7.7|7.6|6.5 ---+---------+---+---+---+----+----+----+----+----+----+---+--- | | _Thomomys bottae rubidus_, holotype and topotypes | +---+---+---+----+----+----+----+----+----+---+--- F | 72952[4]|233| 80| 28|40.6|14.2|25.1|20.8|16.7| 8.8|7.5|6.9 F | 72954[4]|225| 80| 28|40.3|14.2|24.6|20.6|16.6| 9.2|7.2|6.9 | | | | | | | | | | | | M | 3 av. |261| 89| 31|44.7|15.7|27.8|22.6|18.6|10.1|7.4|6.9 | Max. |270| 94| 32|45.1|15.9|28.1|22.7|18.8|10.4|7.6|7.0 | Min. |255| 85| 30|44.2|15.5|27.5|22.5|18.5| 9.8|7.2|6.8 ---+---------+---+---+---+----+----+----+----+----+----+---+--- sad. denotes subadult. 1. United States National Museum. 2. E. R. Warren Collection. 3. Colorado State University. 4. Museum of Natural History, University of Kansas. LITERATURE CITED BAILEY, V. 1910. Two new pocket gophers of the genus _Thomomys_. Proc. Biol. Soc. Washington, 23:79-80, May 4. 1915. Revision of the pocket gophers of the genus Thomomys. U. S. Dept. Agric., Bur. Biol. Surv., N. Amer. Fauna, 39:1-136, 8 pls., 10 figs, in text, November 15. DAUBENMIRE, R. F. 1943. Vegetational zonation in the Rocky Mountains. Bot. Rev., 9:325-393, June. DURRANT, S. D. 1952. Mammals of Utah. Univ. Kansas Publ., Mus. Nat. Hist., 6:1-549, 91 figs. August 10. FENNEMAN, N. M. 1931. Physiography of western United States. McGraw Hill Book Co., New York, xiii + 534 pp., 173 figs., 1 map in cover pocket. GOLDMAN, E. A. 1936. _New pocket gophers of the genus_ Thomomys. Jour. Washington Acad. Sci., 26(3):111-120, March 15. GRINNELL, J. 1931. A new pocket gopher from southeastern California. Univ. California Publ. Zool., 38(1):1-10, 2 pls., October 17. KELSON, K. R. 1951. Two new subspecies of Thomomys bottae from New Mexico and Colorado. Univ. Kansas Publ., Mus. Nat. Hist, 5(6):59-71, 1 fig. in text, October 1. MUNSELL, A. H. 1954. Munsell soil color charts. Munsell Color Co., Inc., Baltimore. _Transmitted November 14, 1957._ 27-1765 
40282	----	Transcriber's note: Text enclosed by underscores is in italics (_italics_). Text enclosed by equal signs is in bold face (=bold=). Throughout, an asterisk (*) before a name denotes extinct genera/species. * * * * * UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Vol. 16, No. 6, pp. 473-579, 9 figures in text August 5, 1968 Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae BY ROBERT J. RUSSELL UNIVERSITY OF KANSAS LAWRENCE 1968 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Frank B. Cross, J. Knox Jones, Jr. Volume 16, No. 6, pp. 473-579, 9 figs. Published August 5, 1968 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY ROBERT R. (BOB) SANDERS, STATE PRINTER TOPEKA, KANSAS 1968 [Illustration: Look for the Union label] 31-4628 Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae BY ROBERT J. RUSSELL CONTENTS PAGE INTRODUCTION 477 MATERIALS AND ACKNOWLEDGMENTS 477 TAXONOMIC CHARACTERS 478 Prismatic character of molars 478 Character of enamel patterns 479 Grooving of incisors 480 Masseteric ridge and fossa 480 Basitemporal fossa 481 Specializations of skull 481 FOSSIL RECORD 484 Miocene 485 Pliocene 486 Pleistocene 490 Thomomys 492 Zygogeomys 496 Geomys 496 Pappogeomys 503 Orthogeomys 504 HISTORY OF CLASSIFICATIONS 505 CLASSIFICATION 512 Family Geomyidae 512 Subfamily *Entoptychinae 513 Genus *_Pleurolicus_ 514 Genus *_Gregorymys_ 514 Genus *_Grangerimus_ 514 Genus *_Entoptychus_ 514 Subfamily Geomyinae 514 Tribe *Dikkomyini 515 Genus *_Dikkomys_ 516 Genus *_Pliosaccomys_ 517 Tribe Thomomyini 518 Genus _Thomomys_ 518 Subgenus *_Pleisothomomys_ 519 Subgenus _Thomomys_ 520 Tribe Geomyini 521 Genus *_Pliogeomys_ 522 Genus _Zygogeomys_ 523 Genus _Geomys_ 525 Genus _Orthogeomys_ 528 Subgenus _Orthogeomys_ 529 Subgenus _Heterogeomys_ 530 Subgenus _Macrogeomys_ 531 Genus Pappogeomys 532 Subgenus _Pappogeomys_ 534 Subgenus _Cratogeomys_ 535 PHYLOGENY OF THE GEOMYIDAE 536 Primitive Morphotype 537 Entoptychid Radiation 540 Phyletic Trends in Subfamily Geomyinae 542 Plio-Pleistocene Radiation of Geomyini 558 Morphotype 559 Specializations in Genera 560 Zygogeomys 564 Geomys 565 Orthogeomys 568 Pappogeomys 569 LITERATURE CITED 572 INTRODUCTION When C. Hart Merriam wrote his monograph of the subfamily Geomyinae in 1895, he had no opportunity to examine fossil specimens. No doubt his phylogenetic conclusions and classification would have been greatly influenced had he enjoyed that opportunity because study of fossil geomyids reveals the historic sequence of phyletic development, and this sequence provides a firm basis for distinguishing specialized from primitive characters. The history of the Geomyinae has been characterized by the evolution of specializations. These evolutionary trends begin, as we presently know them, with a generalized ancestral stock in the early Miocene. The direction, degree, and rate of change, beginning with the primitive morphotype of the subfamily, has not been the same in the various lineages. The classification within the subfamily is based upon the phyletic interpretations of available data and the relationships they disclose. In turn, a new, and I hope more realistic, phylogeny and classification is offered. MATERIALS AND ACKNOWLEDGMENTS Recent specimens were studied of all the known genera, subgenera and 29 of the 36 living species. Most of the species not studied are monotypic and have restricted geographic ranges. They are: _Geomys colonus_, _G. fontanelus_, and _G. cumberlandius_, _Orthogeomys cuniculus_ and _O. pygacanthus_ of the subgenus _Orthogeomys_, and _O. dariensis_ and _O. matagalpae_ of the subgenus _Macrogeomys_. Examination of these modern species would not radically change the estimation of the degree of phyletic development of the genera and subgenera involved. All of the major polytypic and widespread species were studied. Specimens of the extinct genera _Dikkomys_, _Pliosaccomys_, _Pliogeomys_, _Nerterogeomys_, and _Parageomys_ also were studied, as were examples of the extinct species _Geomys quinni_, _Geomys tobinensis_, and _Orthogeomys onerosus_. Considerable fossil material of living species, especially of the genera _Geomys_ and _Pappogeomys_, was used. Inasmuch as the present account concerns mainly structural changes in the subfamily Geomyinae at the level of subgenera and above, and the temporal sequence of those changes, no attempt is made in the present account to revise taxonomy below the level of subgenera. Considerable modification of the classification below that level (for species and subspecies) is to be expected in _Orthogeomys_ and Pleistocene taxa of _Geomys_ when available specimens are studied. I thank Prof. Robert W. Wilson for his assistance in securing fossil geomyids for study, and those in charge of the paleontological collections at the California Institute of Technology, Prof. Bryan Patterson, formerly of the Field Museum of Natural History, and Prof. Claude W. Hibbard of the University of Michigan, Museum of Zoology. For their kindness in lending Recent species, I thank Mr. Hobart M. Van Duesen of the American Museum of Natural History, Dr. David H. Johnson of the U. S. National Museum, and Dr. Oliver P. Pearson of the California Museum of Vertebrate Zoology, the late Colin C. Sanborn of the Field Museum of Natural History, and Profs. Emmet T. Hooper and William H. Burt of the University of Michigan Museum of Zoology. I am especially grateful to Prof. E. Raymond Hall for his guidance and helpful criticisms with the manuscript. For assistance with paleontological problems, I thank Drs. Robert W. Wilson and William A. Clemens. Several persons have offered helpful suggestions and encouragement in the course of my study. For assistance of various sorts I especially thank Drs. J. Knox Jones, Jr., Rollin H. Baker, A. Byron Leonard, Sydney Anderson, James S. Findley, Robert L. Packard, and Robert G. Anderson. Advice concerning the drawings of the dentitions was generously given by Mr. Victor Hogg, and the drawings were done by Mrs. Lorna Cordonnier under his direction and by Mr. Thomas H. Swearingen. For assistance with secretarial tasks I thank Valerie Stallings, Violet Gourd, Ann Machin, Toni Ward, Sheila Miller, and my wife, Danna Russell. TAXONOMIC CHARACTERS Morphological features of the fossils and their stratigraphic provenience provide the information upon which phylogenetic interpretations are based. Although the most critical sequences of the fossil record are lacking, and although the existing fossils are mostly fragmentary and therefore seldom furnish ideally suitable data for the interpretations that have been made, phylogenetic conclusions drawn from fossil materials are superior to those drawn on other bases. The especially relevant characters are those disclosing primary trends in the evolution of the modern assemblages. The higher systematic categories recognized in the following account are based primarily upon such characters. The most important characters found are in the teeth, although several structural changes in the lower jaw, especially those associated with the insertion of cranial musculature, are almost as important. _Prismatic Character of Molars_ In primitive geomyines the molar consisted of two columns united at their mid-points and forming a figure 8 or H-pattern (see Fig. 4B). Both labial and lingual re-entrant folds were formed between the two columns. The primitive pattern is retained in the premolars of all known Geomyinae. Therefore, in the earliest (Miocene) members of the subfamily, the pattern of the molars was essentially like that of the premolars. In Pliocene Geomyinae the two columns of the molars tend to merge into one. This is evident on the worn occlusal surface of the teeth; the lateral re-entrant folds are shallow vertically and progressively recede laterally until only a slight inflection remains. In the final stages of attrition, the inflection disappears and the tooth is a simple elliptical column. In the Pleistocene the monoprismatic pattern appears at earlier stages of wear owing to the decrease in depth of the re-entrant folds, and in Geomyinae of Recent time the initial stages of wear on the enamel cap of infants erase the last vestiges of two columns in the molar teeth. The general trend in evolution, therefore, has been from a bicolumnar to a monocolumnar pattern. The particular patterns of wear characterizing each genus are described in detail beyond. The third upper molar has evolved less rapidly than the first and second and in one of the modern lineages (tribe Geomyini) tends to retain at least a vestige of the primitive bicolumnar pattern in the final stage of wear. Therefore, the loss of any trace of the bicolumnar pattern in M3 is considered to be a much specialized condition. Unfortunately, the fossil record of the third upper molar is less complete than that for the first molar and second molar; the tooth drops out of its alveolus more often than does any one of the other molariform teeth and is seldom recovered. _Character of Enamel Patterns_ In the primitive genera the enamel pattern is bilophate and the enamel loop (see Fig. 4B) is continuous on the occlusal surface of a worn molar. Concomitant with the union of the double columns, the bilophodont pattern is reduced to a single loph, but the enamel still completely encircles the dentine. In the molars of modern geomyines, the enamel loop is not continuous but is interrupted on the sides of the crown by vertical tracts of dentine that are exposed at the occlusal surface of the tooth during early stages of wear. Therefore, a continuous enamel band is to be found only in a juvenal individual whose teeth have been subjected to only slight attrition on the enamel cap. In molars lacking enamel on the labial and lingual sides, anterior and posterior enamel plates, or blades, are found on each molar. The premolar also has an enamel plate on the anterior surface and another on the posterior surface, and in addition both re-entrant angles are protected by a V-shaped investment of enamel. One or the other of the various plates can be reduced or lost accounting for the several distinctive tooth-patterns of the modern geomyines. If loss occurs, it usually is the anterior plate in the lower dentition and the posterior plate in the upper dentition, including the upper premolar. When reduction of the posterior plate of the upper cheek teeth occurs, enamel is first lost from the labial side of the tooth, thus leaving only a short vestigial plate on the lingual end of the crown. _Grooving of Incisors_ The incisors are smooth with no trace of a groove in the ancestral lineage. In the specialized assemblage (tribe Geomyini) pronounced grooves are always developed on the anterior face of the upper incisor. The pattern of grooving is constant in each species and thus provides characters of taxonomic worth for grouping species into genera. The only inconstancy noted was an incisor of _Geomys_ from the Tobin local fauna of the middle Pleistocene which has three grooves rather than the normal two (No. 6718 KU). The extra groove is an obvious abnormality, and the tooth was associated with others of the same species from the same quarry that were normally grooved. Grooves on the lower incisors are unknown. The functional significance of grooving has been debated on numerous occasions in the literature. Grooves appear in a number of only distantly related rodents and in lagomorphs. The grooving occurs always in small herbivorous mammals, and in some way may be related to feeding habits. The grooves provide a serrated cutting edge on the occlusal edge of the upper incisor. In the genus _Geomys_, for example, the two incisors, including the slight space between them, present a total of five serrations, which may facilitate cutting and piercing tuberous and fibrous roots upon which _Geomys_ feeds. Also the sulci would perform the same function as the longitudinal groove on the side of a bayonet, and would aid the animal in extracting its upper incisors from coarse, fibrous material. In gathering food, the gopher sinks its upper incisors into a root, and then, with the upper incisors firmly anchored, slices off small chunks by means of the lower incisors. Therefore, in pocket gophers, grooving may be an adaptation for feeding on fibrous or woody material. Finally, grooves increase the enamel surface of the incisor without additional broadening of the tooth itself. There could be a selective advantage for sulcation if the extra enamel and the serrate pattern strengthen the incisors, which are under heavy stress while penetrating or prying off pieces of coarse material. Few broken incisors of pocket gophers are found. _Masseteric Ridge and Fossa_ This ridge and fossa are on the lateral surface of the ramus. The crest on the ridge begins at the base of the angular process and terminates slightly anterior to the plane of the lower premolar. The masseteric fossa receives the insertion of the rostral or superficial division of the masseter muscle. The mental foramen lies immediately anterior, or anteroventral, to the fossa. In the ancestral lineage, the ridge is distinct but relatively low; the masseteric fossa is shallow and is a poorly developed area for attachment of the superficial masseter muscle. In modern Geomyinae the ridge is massive and forms a high crest, especially anteriorly, and the masseteric fossa is a deep, prominent cup along the dorsal side of the crest. The elaboration of the crest and fossa evidently is associated with an increase in size of the superficial masseter muscle, which enlarges and provides increased power for the propalinal type of mastication. A high crest has evolved independently in both modern lineages, Thomomyini and Geomyini. _Basitemporal Fossa_ The name basitemporal fossa is suggested here to denote the deep pit that lies between the lingual base of the coronoid process and the third lower molar. The basitemporal fossa receives the insertion of the temporal muscle. The fossa, which until now has not been named, is a unique feature in advanced Geomyinae, being unknown in either primitive Geomyinae or in other rodents. The temporal is one of several muscles holding the occlusal surface of the lower molariform dentition firmly against the upper cheek teeth during mastication. In primitive geomyines that masticate food by a planing action, the temporal muscle also moves the mandible posteriorly and food is ground between the enamel plates when the lower jaw is retracted as well as when it is moved forward. The basitemporal fossa appears in late Pliocene geomyines and increases the attachment surface of the temporal muscles that powers the planing action important in utilizing woody and fibrous foods. The basitemporal fossa developed in only one of the modern lineages (tribe Geomyini), the same lineage in which grooved incisors evolved. Both features probably are adaptations for feeding on coarse food. The fossa is not greatly developed in either the ancestral tribe Dikkomyini or the modern tribe Thomomyini, although in some specimens a slight depression marks the site of the basitemporal fossa. [Illustration: FIG. 1. Types of skulls in the subfamily Geomyinae. � 1. A. and B. Generalized type of skull. _Geomys bursarius lutescens_, adult, male, No. 77955 KU, 10 mi. N Springview, Keya Paha Co., Nebraska. A. Dorsal view of skull. B. Ventral view of lower jaw. C. and D. Dolichocephalic type of skull. _Orthogeomys_ (_Orthogeomys_) _grandis guerrerensis_, adult, female, No. 39807 KU, 1/2 mi. E La Mira, 300 ft., Michoacán, México. C. Dorsal view of skull. D. Ventral view of lower jaw. E. and F. Platycephalic type of skull. _Pappogeomys_ (_Cratogeomys_) _gymnurus tellus_, adult, female, No. 33454 KU, 3 mi. W Tala, 4300 ft., Jalisco, México. E. Dorsal view of skull. F. Ventral view of lower jaw. ] _Specializations of Skull_ The skull in most geomyines is generalized, being neither extremely long and narrow nor short, broad and flat as in specialized skulls (see Fig. 1). In Pleistocene lineages of the modern tribe Geomyini, long skulls and broad skulls evolved and have been termed dolichocephalic and platycephalic specializations, respectively by Merriam (1895:88-101). He correlated them with two diametrically different mechanical methods of mastication. In animals with dolichocephalic skulls the principal movements of the mandible in the masticatory process are anteroposterior. The resulting propalinal action of enamel plates in opposition to each other characterizes also animals with a generalized skull, and evidently is the method of mastication in the primitive geomyines, but in animals with a dolichocephalic skull the method is developed to a high degree by elongation of the cranium, mandible, and teeth. Both the mandibular and maxillary tooth-rows are relatively longer than in the generalized skull, providing a longer block for the planing action of the lower molariform teeth. All teeth, especially P4 and M3, are longer. In M3 the heel (posterior loph) in particular is elongated. Both the anterior and posterior enamel plates usually are retained in M1 and M2. The superficial (or rostral) masseter muscle, originates on the side of the rostrum and inserts in the masseteric fossa and on the masseteric ridge. The deep masseter, especially the zygomatic part having its origin along the zygomatic arch, inserts on the angular process of the lower jaw. These two divisions of the masseter muscle have a longer pull (forward) in the dolichocephalic skull than in a non-dolichocephalic skull. The temporal and diagastric muscles retract the lower jaws. Other, secondary, modifications of the dolichocephalic skull are shortening of the angular process of the mandible, broadening of the rostrum, and narrowing of the cranium and zygomata. Depth of the posterior part of the skull is unchanged. The skull appears to be deep and of nearly equal breadth from nasals to occiput. A good example of a dolichocephalic skull is that of _Orthogeomys_ (see Fig. 1, C and D). In the platycephalic skull, the principal masticatory movement of the mandible is anterooblique, to one side and then to the other. The oblique passage of the enamel blades of the lower teeth across those of the upper teeth produces a shearing rather than planing action (Fig. 1E, F). The anterooblique movement of the lower jaw is possible because of major architectural changes in the cranium and mandible. These changes include: (1) Broadening of the postrostral part of the skull, especially the occiput (mastoidal breadth equals or exceeds zygomatic breadth in skulls of some taxa); (2) flattening of the skull; (3) anteroposterior compression of the molariform teeth, especially the molars. Therefore, the entire maxillary tooth-row is relatively shorter than in the dolichocephalic skull. Only a vestige of the heel ordinarily remains on M3. The loss of the posterior enamel blades of P4, M1, and M2 eliminates unnecessary friction, and each of these teeth is wider than long. The distance between the posterior ends of the lower jaws is increased approximately in proportion to the extent that the occiput is widened. As a result of the flattening of the skull the angular processes of the lower jaws are lateral to the zygomatic arches, and approximately on the same vertical level with them. Consequently the insertions of masticatory muscles are shifted laterally. This is especially true of the zygomatic division of the deep masseter, which inserts on the angular process. Contraction of that muscle division of one side of the skull moves the lower jaws obliquely forward. The diagastric and temporal muscles of course retract the lower jaws. The platycephalic skull is the most specialized skull in the Geomyinae and is a result of the new (for the Geomyinae) method of mastication. The subgenus _Cratogeomys_ (see Fig. 1, E and F) has a platycephalic skull. The trend toward platycephalic specialization has been the major feature of evolution in _Cratogeomys_. FOSSIL RECORD The fossil record of the subfamily Geomyinae begins in the early Miocene of western North America. No geomyids have been recovered from beds of the late Miocene age. Beginning with the early Pliocene the fossil record becomes progressively more complete, and geomyines are relatively abundant in deposits of late Pliocene and Pleistocene age. Although pocket gophers of the subfamily Geomyinae are rare in lower Miocene deposits, members of the subfamily Entoptychinae are relatively common and highly diversified. Four genera and a number of species have been described (see Wood, 1936:4-25), and the subfamily ranged widely in western North America. I interpret this to mean that the geomyines were indeed uncommon in the early Miocene and their distribution restricted since so few of their remains have been recovered in comparison with entoptychines and the known records are only from the northern part of the Great Plains. On the other hand, entoptychines enjoyed a widespread distribution in western North America (see discussion beyond). Probably the geographic range of the geomyines was largely allopatric to that of the more specialized entoptychines. The zone of fossoral adaptation for herbivorous rodents is ecologically narrow, and as a result competition is severe. As a rule, the outcome of episodes of intergroup competition is geographic exclusion. If these rodents were fossorial in the early Miocene--their morphology suggests they were at least semi-fossorial--mutually exclusive patterns of distribution are to be expected. Miocene _Dikkomys_ is the only genus of the Geomyinae known from the early and middle Miocene. _Dikkomys matthewi_ was described by Wood (1936) on the basis of isolated teeth from lower Harrison deposits (Arikareean in age) near Agate, Sioux County, Nebraska. Later, Galbreath (1948:316-317) described the features of an almost complete mandible recovered from the younger upper Rosebud deposits, now considered by MacDonald (1963:149-150) to be middle Miocene, near Wounded Knee, Shannon County, South Dakota. More recently Black (1961:13) has described a new species, _Dikkomys woodi_, from the Deep River Formation, Meagher County, Montana. The Deep River Formation is late Hemingfordian (middle Miocene) in age. No remains of _Dikkomys_ have been identified in the extensive rodent fauna of the John Day beds of the lower Miocene of Oregon, although entoptychines are abundant in these deposits. In the present account, _Dikkomys_ is regarded as the ancestor from which the Pliocene and modern geomyines were derived. These probably did not evolve from the subfamily Entoptychinae because the dentition of entoptychines, especially the premolars and third molars, was already highly specialized by Miocene time. The numerous records of _Thomomys_ and especially _Geomys_ reported from supposed Miocene or Pliocene deposits are without foundation (see Matthew, 1899:66; 1909:114, 116, 119; 1910:67, 72; 1923a:369; 1924:66; Matthew and Cook, 1909:382; Cook and Cook, 1933:49; and Simpson, 1945:80). Most of the records of _Geomys_ date back to the description of _Geomys bisculcatus_ Marsh (1871:121) from the Loup Fork beds of Nebraska (near Camp Thomas on the Middle Loup River). At first Marsh and other investigators thought these beds were of the late Miocene age. Subsequently the Loup Fork fauna was determined by Matthew (1923b) to be mostly early Pliocene (Clarendonian), but with a later Pleistocene element. Recently, Schultz and Stout (1948:560) have shown that the various Loup River faunas and also those from along the Niobrara River (Hay Springs, Rushville, Gordon local faunas) are of middle Pleistocene age, the fossil-bearing beds occurring just below the Pearlette Ash. These beds are those termed the Loup Fork or North Prong of Middle Loup by the earlier workers who supposed them to be of Miocene or Pliocene age. Both _Geomys_ and _Thomomys_ have been recovered from most of these deposits, but they are no older than middle Pleistocene. This is not surprising in view of the primitive structure of the geomyids known from Miocene and Pliocene beds, but the supposed early appearance of _Geomys_ and _Thomomys_ led to much confusion concerning geomyid evolution in the late Tertiary. The dearth of geomyines in the Miocene is counterbalanced by the relatively abundant and highly differentiated gophers of the subfamily Entoptychinae. They reached the zenith of their development in this period. Four genera and a number of species are known from the western part of the United States, mostly from beds along the Pacific Coast and in the northern part of the Great Plains. The great diversification of the group in a relatively short period suggests prior movement into a new adaptive zone and subsequent specialization in different subzones and therefore an episode of radial adaptation. The radiation of the entoptychines is discussed elsewhere in the account of geomyid phylogeny, but it should be noted here that both the Geomyinae and the Entoptychinae appear in the fossil record at about the same time in the early Miocene. The principal distinguishing features of each of the two lineages were well developed at the time of their first occurrence, and the entoptychines were the more successful in early Miocene. The Entoptychinae are known only from the early and middle Miocene, unless the earlier deposits of the John Day Formation of Oregon from which mammals have been recovered are considered to be latest Whitneyian (latest Oligocene); for correlations, see Wilson (1949:75). Both lineages likely had an earlier history extending back to their divergence in the Oligocene. Pliocene The oldest and most primitive Pliocene geomyine is _Pliosaccomys dubius_ Wilson (1936:20) from the Smith Valley local fauna of middle Pliocene (Hemphillian) age in Nevada. According to Wilson (_op. cit._:15) the beds probably were deposited near the middle of Hemphillian time. Shotwell (1956:730) recorded _Pliosaccomys dubius_ from the McKay Reservoir and from the Otis Basin (1963:73) local faunas of the middle Pliocene (Hemphillian) of Oregon, and Green (1956:155) has recovered remains of _Pliosaccomys_ (cf. _dubius_) from the Wolf Creek local fauna, uppermost part of the lower Pliocene (late Clarendonian in age), of Shannon County, South Dakota. Recently, James (1963:101) has described a second species, _Pliosaccomys wilsoni_, of this primitive genus. The new species was found in early Pliocene deposits (late Clarendonian) from the Nettle Spring local fauna (Apache Canyon), in the Cuyama Valley, Ventura County, California. _Pliosaccomys wilsoni_ does not differ greatly from _P. dubius_; however, the few differences in dental characters seem to warrant specific recognition. The reduction of cusps on the metalophid of p4 from three (_dubius_) to two (_wilsoni_) and the lack of accessory cuspules on the protolophid of p4 in _wilsoni_ are probably specializations, suggesting that _P. dubius_ even though the more recent in age is the less advanced of the two. _P. wilsoni_ is known only from a lower jaw of a young individual that had dp4 in place, along with m1 and m2. The permanent premolar was in the process of erupting, and the deciduous tooth was removed so that the unworn surface of p4 could be examined. _Pliosaccomys_ occurred geographically in the area that the Entoptychinae had occupied in the early Miocene. The Smith Valley material includes dentitions in almost all stages of wear and the chronological sequences in the development of the patterns of wear can be reconstructed. An understanding of the dental patterns of the primitive geomyines is based mostly on the interpretation of the stages of wear in _Pliosaccomys_. No other pocket gopher is known from the area in which _Pliosaccomys_ occurred, and it is unknown after middle Hemphillian age. _Pliosaccomys_ has closer affinities with _Dikkomys_ of the early Miocene than with any geomyid of the modern assemblage and gives no clue to the origin of the lineage culminating in the modern pocket gophers of the tribe Geomyini. _Pliogeomys buisi_ Hibbard (1954:353) was found in the Buis Ranch local fauna, of latest middle Pliocene, on the west side of Buckshot Arroyo, Beaver County, Oklahoma. The original material included a right ramus bearing the premolar and first two molars (the holotype) and five isolated premolars and molars. One of the molars is slightly worn and from an immature individual. One premolar is a deciduous tooth. Hibbard (_op. cit._:342) identified the beds from which he obtained the Buis Ranch local fauna as from the lowermost part of the Upper Pliocene. Moreover, he judged the Buis Ranch local fauna to be only slightly older than the Saw Rock Canyon local fauna of Seward County in southwestern Kansas. Previously (Hibbard, 1953:408-410), the Saw Rock Canyon local fauna had been assessed as older than the Rexroad local faunas (latest late Pliocene) and, therefore, representative of the early part of the late Pliocene. More recently, Hibbard (1956:164) identified the Buis Ranch beds as part of the Ogallala Formation, which here occurs unconformably just beneath the Rexroad Formation (composed of strata nearly all of late Pliocene age). Therefore, he regarded the Buis Ranch beds as latest middle Pliocene in age. Hibbard (1954:356) suggested that pocket gopher remains from the Saw Rock Canyon local fauna were referable to _Pliogeomys buisi_, and, in effect, tentatively assigned them to _Pliogeomys_ (in his description of the genus Hibbard remarked that the upper incisor is bisulcate as in _Geomys_, and the only upper incisor that he mentions was one of the Saw Rock Canyon fossils and not part of the Buis Ranch material). _Pliogeomys_ has closer affinities with modern pocket gophers of the tribe Geomyini than it does with the middle Pliocene genus _Pliosaccomys_. The pocket gopher fauna known from the late Pliocene was more varied than the faunas known from any earlier time. In addition to the extinct _Pliogeomys_, which occurs in early late Pliocene (see discussion above), the living genera _Zygogeomys_, _Geomys_, _Pappogeomys_ (in the sense used on p. 534), and _Thomomys_ first appear in the late Pliocene. The only other living genus, _Orthogeomys_, makes its first appearance in the late Pleistocene. The earliest record of the genus _Thomomys_ is based on a fragment of a left mandibular ramus bearing p4 and m1, _Thomomys gidleyi_ Wilson (1933b:122), from the Hagerman local fauna of Twin Falls County, Idaho. Wilson (_loc. cit._) was uncertain as to age (late Pliocene or early Pleistocene) but subsequently (1937:38 and 67-70) settled on the middle part of the late Pliocene. Hibbard (1958:11) later considered the age as early Pleistocene (suggesting that the deposits accumulated in the Aftonian interglacial interval) but subsequently (Hibbard _et al._, 1965:512), on the basis of potassium argon age determinations, also settled on late Pliocene. Remains of _Nerterogeomys_ [=_Zygogeomys_] have been found in the Benson local fauna, Cochise County, Arizona, and the Rexroad local fauna of Kansas. This early Blancan gopher first was described as _Geomys minor_ by Gidley (1922:123), and was later referred by Gazin (1942:487) to his new genus _Nerterogeomys_. Hibbard (1950:138) identified specimens from the Fox Canyon locality, one of the localities of Meade County, Kansas, where the Rexroad local fauna is preserved, as _Nerterogeomys_, and tentatively referred them to the species _N. minor_. _Nerterogeomys_ cf. _minor_ has been recovered also from Locality 3 of the Rexroad local fauna (Hibbard, 1950:171) of Meade County, Kansas. Apparently these are also the small gophers about which Franzen (1947:58) wrote. She assigned them to the genus _Geomys_, and they may actually be a primitive form of _Geomys_ that represents an intermediate stage in the development of the enamel pattern from the uninterrupted loops of the ancestor to the discontinuous pattern of modern _Geomys_. I favor this interpretation; the evidence, however, is inconclusive, and I have, therefore, reluctantly allocated them, along with the other specimens of _Nerterogeomys_, to the genus _Zygogeomys_. In an early paper, Hibbard (1938:244) erroneously referred the same specimens, two upper premolars of a young individual, to the genus _Thomomys_, and the same material was identified with the genus _Geomys_, also without specific assignment, in a later paper (Hibbard, 1941b:278). _Thomomys_ is unknown from the late Pliocene of the Great Plains. The specimens previously referred to _Nerterogeomys_ are assigned to the genus _Zygogeomys_ for the first time in this report; for a discussion of the systematic arrangement see the accounts beyond. The type and paratype of _Nerterogeomys_ from the Benson local fauna of Arizona have no indication of enamel reduction. Specimens of the genus _Geomys_ from the late Pliocene were referred to the large _Geomys quinni_ McGrew, first by Franzen (1947:55) and later by Hibbard and Riggs (1949:835) and Hibbard (1950:171). _Geomys quinni_ has been obtained from the Fox Canyon locality and Locality 3 of the Rexroad local fauna. At Locality 3, both _Zygogeomys_ (cf. _minor_) and _Geomys quinni_ have been found together, but _Geomys quinni_ can be distinguished by its much larger size and the advanced enamel pattern of the cheek teeth (see systematic accounts beyond). All age classes are represented among the specimens of _Geomys quinni_; therefore, it seems unlikely that the smaller gophers referred to _Zygogeomys_ are actually the young of _Geomys quinni_. Hibbard (personal communication, May, 1966) informed me that specimens of _Geomys_ from the late Pliocene (Fox Canyon and Rexroad Locality 3) are erroneously referred to _G. quinni_. According to Hibbard, this material represents instead two distinct undescribed species, descriptions of which have been submitted by him for publication. Allocation of late Pliocene specimens of _Geomys quinni_ to other species will restrict _quinni_ to the early Pleistocene. _Cratogeomys bensoni_ Gidley (1922:123) was of medium size. The name was based on an upper incisor bearing a single median sulcus and an associated lower jaw containing all of the cheek teeth from the Benson local fauna, Cochise County, Arizona. Additional lower jaws carrying various teeth also were recovered. The specimens might just as well have been assigned to the genus _Pappogeomys_ since the lower dentitions of all the genera of the tribe Geomyini have the same enamel pattern, and the subgenera _Pappogeomys_ and _Cratogeomys_ have upper incisors with median grooves. The specimens are too fragmentary to warrant more than generic identification. Mainly because of their late Pliocene age and primitive traits the specimens are here regarded as early representatives of the subgenus _Pappogeomys_. Discovery of the upper molariform dentition would make a more precise assignment possible. Pleistocene Numerous specimens of geomyids from many localities and horizons are available from the Pleistocene of North America. Specimens of the genera _Geomys_ and _Thomomys_ are especially common. Few specimens are known of the genera _Orthogeomys_ and _Pappogeomys_, especially from the early and middle Pleistocene, owing, probably, to slight knowledge of the early Pleistocene of México where these two genera are thought to have evolved (see map, Figure 2). This lack of knowledge about early Pleistocene deposits in México is a handicap in the present instance since the center of differentiation for several of the modern genera is judged to have been in México, probably on, and at the edge of, the Central Plateau. The relative abundance of the remains of _Geomys_ and _Thomomys_ from Pleistocene deposits farther north, and the marked absence of other genera, may mean that _Orthogeomys_ and _Pappogeomys_ did not range northward from southern and central México in most of the Pleistocene. One species of _Pappogeomys_ eventually ranged into the southwestern United States in the late Pleistocene (toward the end of the Wisconsin) and it occurs there today, but the genus is essentially Mexican. The fossil record of _Zygogeomys_, as the genus is here understood, evidently continued in the United States will into the Middle Pleistocene, depending upon the stratigraphic interpretation of the age of the Curtis Ranch local fauna from southeastern Arizona. Hibbard (1958:25) regarded the Curtis Ranch local fauna as Irvingtonian in age, a local fauna that lived either in the late Kansan glacial or the Yarmouthian interglacial, and his correlation is tentatively followed here. In deposits laid down later than those of Irvingtonian age no remains of _Zygogeomys_ have been found. Today a single species exists as a relic in the mountains of central México and _Zygogeomys_ may have retreated southward to its present refugium in the late Pleistocene. Perhaps, _Zygogeomys_ occurred in northern México and the southwestern United States in the early and middle Pleistocene (see Fig. 2), occupying the area between the ranges of _Pappogeomys_ to the south and _Geomys_ to the north. Competition with _Pappogeomys_, and especially _Geomys_, during Irvingtonian time may have extirpated _Zygogeomys_ over most of this area, and by late Pleistocene (Sangamon) much of the former range of _Zygogeomys_ came to be occupied by one or the other of its competitors. The occurrence of _Geomys garbanii_ in southern California (see White and Downs, 1961) and the unidentified species of _Geomys_ in Aguascalientes (Mooser, 1959; for faunal correlation, see Hibbard and Mooser, 1963), both from deposits of Irvingtonian age, supports this suggestion. [Illustration: FIG. 2. Probable distribution of the Subfamily Geomyinae in the early Pleistocene (late Blancan), depicting major areas of differentiation of the modern genera. 1. _Thomomys_ 2. _Geomys_ 3. _Zygogeomys_ 4. _Pappogeomys_ 5. _Orthogeomys_ ] _Thomomys_ The earliest Pleistocene records of _Thomomys_ are mostly isolated teeth. Although they can be identified as genus _Thomomys_, most of the materials are too fragmentary to be identified to species. In _Thomomys_ two distinct patterns of occlusal surfaces of the molars can be recognized: the generalized elliptical pattern in the subgenus _Pleisothomomys_, not unlike the pattern in other geomyids, and the pear-shaped pattern in the subgenus _Thomomys_, which results from constriction of the upper molars on the labial side and constriction of the lower molars on the lingual side. Some fossils assigned to _Thomomys_ were not examined with this distinction in mind by the persons who made the assignments. Consequently some of the identifications now in the literature may be subject to change. Three occurrences of _Thomomys_ are from the early and middle Pleistocene, with a possible fourth (depending upon the age of the Hay Springs local fauna of Nebraska). The earliest Pleistocene record is from the Broadwater-Lisco beds along the North Platte River in Morrill County, western Nebraska. Possibly the specimen from there was misidentified. Those beds are Lower Pleistocene, and are regarded by Schultz and Stout (1948:560-561, 573) and by Hibbard (1958:11), as having been deposited mostly during the Aftonian interglacial. There is also some indication that some of the strata were deposited late in the Nebraskan glaciation. There are no other early Pleistocene records of _Thomomys_. Savage (1951:228) reported the genus from the Irvington local fauna, Alameda County, California. The specimens were not identified to species, although they were described as indistinguishable from _Thomomys bottae_. Paulson (1961:137) recorded specimens from the Cudahy local fauna, Meade County, Kansas. These fragmentary specimens are referable to the subgenus _Thomomys_, owing to the strong constriction of the molars, but have not been identified to species. The Cudahy is an Irvingtonian local fauna, and is considered to have been deposited during the late Kansan glaciation. The stratum containing the Cudahy local fauna immediately underlies the Pearlette Ash. The Cudahy material includes five isolated molars and a fragmentary ramus bearing only the premolar. The genus _Thomomys_ has been recovered also from the Hay Springs local fauna in Sheridan County, northwestern Nebraska, by Shultz and Tanner (1957:71). The Hay Springs local fauna is considered to have been deposited in late Kansan glaciation or in early Yarmouth interglacial by Shultz and Tanner (_op. cit._:69), or of Irvingtonian age; however, Hibbard (1958:25) regarded the beds containing this fauna as Illinoian (thus post-Irvingtonian in age), and equivalent in age to the Berends local fauna of Oklahoma and the Butler Springs and Mt. Scott local faunas of Kansas. The _Thomomys_ from Hay Springs local fauna has not been referred to species. The relative abundance of _Geomys_, and rarity of _Thomomys_, in Great Plains fossil beds of early and middle Pleistocene is probably due to allopatric distributions of the two genera. The Great Plains area was evidently the center of distribution and differentiation of _Geomys_. Perhaps _Thomomys_ evolved earlier to the west, in the Great Basin and Pacific Coastal regions, and not on the Great Plains. Upper Pleistocene records of _Thomomys_ are more common. The genus was widespread in beds identified with the Illinoian and Sangamon and extended its range eastward to the Atlantic Coast. Stephens (1960:1961) reported _Thomomys_ from the Doby Springs local fauna, Harper County, northwestern Oklahoma. The material (34 isolated teeth) was too fragmentary to permit assignment to species. The molars are constricted on one side, indicative of the subgenus _Thomomys_, like the Cudahy specimens reported by Paulson (see discussion above). Stephens erroneously mentioned that the enamel plate on the posterior face of the upper premolar is unique in _Thomomys_; this plate occurs also in _Zygogeomys_. The Doby Springs local fauna was recovered from beds that have been identified as Illinoian deposits, and it is correlated with the Berends local fauna in Beaver County, Oklahoma, and the Butler Springs local fauna in Meade County, Kansas (see Stephens, _op. cit._: 1700). Local faunas in Maryland and Florida of Rancholabrean age include _Thomomys_, in every instance referable to the subgenus _Pleisothomomys_ on the basis of unconstricted molars. _Thomomys potomacensis_ (Gidley and Gazin, 1933), from Cumberland Cave local fauna, Allegany County in western Maryland, is the type of the genus _Pleisothomomys_ Gidley and Gazin (1933:354). _Pleisothomomys_ is here regarded as a subgenus. The material used in the original description included four lower jaws, one with a complete dentition. Hibbard (1958:25) pointed out that the Cumberland Cave assemblage is a composite fauna including both glacial and interglacial forms. He placed the stratigraphic position of the fauna as definitely Upper Pleistocene, probably deposited in both Illinoian glaciation and during the Sangamon interglacial. _T. potomacensis_ is significantly larger than _T. orientalis_ Simpson (1928:6), from the Saber-tooth Cave local fauna, Citrus County, Florida. Simpson's material included a rostral fragment with an incisor, premolar, and first molar. The Saber-tooth Cave local fauna is regarded by Kurten (1965:219) as having been recovered from Sangamon deposits. _Thomomys_ is unknown from Wisconsin deposits in the eastern United States, and today the genus does not occur east of the Great Plains. _Thomomys_ of Rancholabrean provincial age from the western United States and México is known only from Wisconsin beds. Three extinct species of _Thomomys_, all referable to the subgenus _Thomomys_, have been described. _Thomomys microdon_ Sinclair (1905:146), based on the rostral portion of a skull without a mandible, is from the Potter Creek Cave local fauna, Shasta County, California, and has been recovered also from Samwel Cave, Shasta County, California. _T. microdon_ closely resembles _Thomomys monticola_ that lives in the area today. _Thomomys scudderi_ Hay (1921:614) is from the Fossil Lake (or Christmas Lake) local fauna in central Oregon. Elftman (1931:10-11) referred these specimens to _Thomomys townsendii_, and he considered _T. scudderi_ to be a synonym of _T. townsendii_. Davis (1937:156-158) disagreed with Elftman concerning the taxonomic status of _T. scudderi_, which he regarded as a valid species. According to Davis, _T. scudderi_ is more closely allied to _Thomomys bottae_ than to _T. townsendii_. Cope (1878:389; 1889:160-165) had referred the same specimens to _Thomomys clusius_ (now _Thomomys talpoides clusius_). Cope considered the beds to be Pliocene in age. In all accounts of the Fossil Lake local fauna up to Hay (1921), the specimens of _Thomomys_ were referred to the species _clusius_, _talpoides_, or _bulbivorus_ (see Elftman, _loc. cit._). The Fossil Lake local fauna is currently considered as being of Rancholabrean provincial age, probably dating from the Wisconsin glacial maximum when the lake reached its greatest size. The third extinct species described from the Wisconsin is _Thomomys vetus_ Davis (1937:156), also from the Fossil Lake local fauna in Lake County, Oregon. Davis pointed out that _T. vetus_ differs from _T. scudderi_ Hay, of the same fauna, in larger size and other cranial details, and that it is closely allied to the living species _Thomomys townsendii_, and not to _Thomomys talpoides_, which is the only species of _Thomomys_ living in the area today. _Thomomys townsendii_ was recovered by Gazin (1935:299) from the American Falls beds (probably Wisconsin deposits) in Idaho. _Thomomys talpoides_ is reported from the Howard Ranch local fauna in Hardeman County, western Texas, by Dalquest (1965:69-70), who referred the isolated teeth to _T. talpoides_ on geographic grounds, apparently on the erroneous assumption that _T. talpoides_ was the species of _Thomomys_ nearest geographically to Hardeman County. Hay (1927:259) reported _Thomomys fuscus_ [= _Thomomys talpoides_] from late Pleistocene beds near Wenatchee, Chelan County, Washington. Hibbard (1951:229) recorded _Thomomys talpoides_ from late Pleistocene deposits in Greeley County, Kansas, and Walters (1957:540) reported the same species from late Pleistocene deposits in Clark County, Kansas. According to Hibbard (1958:14) other remains reported as _T. talpoides_ have been recovered from numerous areas of Wisconsin glacial drift in western North America. _Thomomys bottae_ has been identified from Wisconsin age deposits in western North America, as follows: Burnet Cave, Gaudalupe Mt., New Mexico (Schultz and Howard, 1935:280); Carpinteria Asphalt, California (Wilson, 1933a:70); McKittrick Asphalt, Kern County, California (J. R. Schultz, 1938:206); Rancho La Brea, Los Angeles County, California (Dice, 1925:125--specimens described as a new subspecies, _T. b. occipitalis_); Papago Springs Cave, Santa Cruz County, Arizona (Skinner, 1942:150 and 158--probably _bottae_, but possibly _umbrinus_ on the assumption that the two are specifically instead of subspecifically distinct); Isleta Cave, Bernalillo County, New Mexico (Harris and Findley, 1964:115--some of these fossils may be post-Wisconsin in age); Potter Creek Cave and Samwel Cave, Shasta County, California (Sinclair, 1905:146--identified as _T. leucodon_, now a subspecies of _T. bottae_; also see Hay, 1927:214-215). _Thomomys umbrinus_ has been reported from San Josecito Cave, Nuevo León, México (Russell, 1960:542); Upper Bercerra, México (Hibbard, 1955a:51--identified only as _Thomomys_ sp., but undoubtedly referable to _T. umbrinus_). Post-Wisconsin remains of _Thomomys umbrinus_ are reported by Alvarez (1964:6) from capa II and capa III of the Cueva La Nopalera, southwestern Hidalgo. Hay (1927:222-223) reported specimens of the genus _Thomomys_ from Wisconsin deposits in Hawver Cave, Eldorado County, California, but did not assign them to species. Gilmore (1947:158) found the remains of _Thomomys umbrinus_ in cave deposits near Quatro Ciénegas in central Coahuila. These cave deposits may have been laid down during the Wisconsin, but more likely accumulated in the post-Wisconsin. _Zygogeomys_ Remains found in the Curtis Ranch local fauna, Cochise County, in southeastern Arizona are regarded as of middle Pleistocene age. See Gazin (1942:481-484), Wilson (1937:39-40), Hibbard (1958:25), and Hibbard _et al._ (1965:510-511). Although some question as to the exact age of the Curtis Ranch local fauna still seems to exist, most authorities on the Pleistocene agree that the age is not Pliocene and that it is older than Rancholabrean. Gidley (1922:122) described the pocket gopher found in the Curtis Ranch beds as _Geomys parvidens_, which is preoccupied by _Geomys parvidens_ Brown (1908:194), a name proposed for the pocket gopher from the Conard Fissure of Arkansas; therefore, Hay (1927:136) proposed the name _Geomys persimilis_ for the Curtis Ranch species to replace _Geomys parvidens_ Gidley. _Geomys persimilis_ Hay became the type species of Gazin's genus _Nerterogeomys_ (1942:507). In this paper, _Nerterogeomys_ is considered to be a junior synonym of _Zygogeomys_. _Zygogeomys persimilis_ is represented by a rostral fragment bearing all the cheek teeth on the left side and the upper incisors. In addition, two lower jaws, one with the first three cheek teeth, are referred to the species (see Gazin, 1942:507). The fossils identified as _Geomys_ from the Arroyo San Francisco, Cedazo fauna, in Aguascalientes, México, by Mooser (1959:413) may be referable instead to _Zygogeomys_. I have not seen the specimens and no figures are available; Mooser states that a cranium was recovered. If either the upper premolar or third molar is in place, generic identification could be made with reasonable certainty. No other fossils of _Zygogeomys_ have been uncovered in late Pleistocene deposits and the significance of the absence of _Zygogeomys_ has been discussed in an earlier paragraph of this section. _Geomys_ has not been found so far south as Aguascalientes, but _Zygogeomys_ occurs farther south now and presumably had a more extensive range on the plateau to the north in the Pleistocene. _Geomys_ _Geomys_ is common in Pleistocene deposits, especially on the Great Plains. Certainly the center of differentiation for _Geomys_ was in this region, although at times, probably when conditions were favorable, _Geomys_ expanded its range into adjacent areas, reaching the Pacific Coast in Irvingtonian times and the Atlantic Coast at the time of the Illinoian glaciation. The earliest Pleistocene records of the genus are from the Great Plains. McGrew (1944:49) described _Geomys quinni_ from the Sand Draw local fauna, Brown County, Nebraska, considered by Hibbard (1958:11) to be Nebraskan in age. As mentioned in the account of Pliocene geomyids, _Geomys quinni_ occurs also in the late Pliocene deposits of southwestern Kansas. Also, _Geomys quinni_ occurs in the Broadwater-Lisco local fauna of Morrill and Garden counties, western Nebraska (Barbour and Schultz, 1937:3; Schultz and Stout, 1948:560-563; Schultz _et al._, 1951: table 1). The Broadwater-Lisco is currently regarded as Aftonian deposits (Schultz and Stout, _loc. cit._; Hibbard, 1958:11). Hibbard (1956:174) identified _Geomys quinni_ from the Deer Park local fauna, probably deposited during the early Aftonian interglacial, of Meade County, Kansas. Strain (1966:36) described _Geomys paenebursarius_ on the basis of fossils obtained from early Pleistocene deposits of the Hudspeth local fauna from western Hudspeth County in the Trans-Pecos of Texas. The Hudspeth fossils were probably deposited during the Aftonian interglacial. From Kingman County, Kansas, Hibbard (_op. cit._: 164) recovered isolated teeth of _Geomys_ from the Dixon local fauna, regarded by him (_op. cit._:153-154) as deposited during the latest Nebraskan glaciation, and correlated by him with the Sand Draw local fauna of Nebraska. Hibbard (1958:11) later regarded the Dixon as a transitional fauna between Nebraskan and Aftonian. The remains of _Geomys_ from the Dixon are known only from isolated teeth. The teeth are small, and suggest that a smaller species of _Geomys_ may have occurred along with the more common and larger _G. quinni_ during the early Pleistocene (see discussion beyond of the Saunders _Geomys_). _Geomys quinni_ was widespread and common throughout the central Great Plains from the late Pliocene (Rexroad fauna) through the early Pleistocene (Nebraskan and Aftonian deposits). Hibbard (1956:179) referred the pocket gopher remains taken from the Saunders local fauna in Meade County, Kansas, to _Geomys tobinensis_, a small species having continuous enamel bands around the lower premolar in younger specimens. The Saunders local fauna was deposited in the late Aftonian and is younger than the Deer Park local fauna discussed above. Paulson (1961:138) later pointed out that the Saunders _Geomys_ is distinct from _Geomys tobinensis_; hence, the small pocket gopher from the Saunders local fauna is probably an unnamed species, perhaps more closely allied to _paenebursarius_ than to _quinni_. The small _Geomys_ reported from the Aftonian Broadwater-Lisco local fauna of Nebraska (Schultz and Stout, 1948:563) may also be the same as the Saunders pocket gopher, but the smaller adult specimens occurring in the same bed with larger specimens probably are females and the larger specimens males. In all living Geomyini females have smaller skulls than males. The Irvingtonian provincial age is currently regarded as Middle Pleistocene and includes the late Kansan glaciation (that part occurring after the glacial maximum) and the Yarmouthian interglacial (see Hibbard _et al._, 1965:512-514). The Irvingtonian provincial age, therefore, follows the late Blancan provincial age of the early Pleistocene and is succeeded by the Rancholabrean provincial age of the late Pleistocene. No specimen of an Irvingtonian _Geomys_ is referable to any living species. Two Irvingtonian species have been described. Hibbard (1944:735) named _Parageomys tobinensis_ [= _Geomys tobinensis_] from the Tobin local fauna of Russell County, Kansas. This species since has been reported from the Cudahy local fauna of Meade County, Kansas (Paulson, 1961:137). Hibbard (1956:183) also identified as _Geomys tobinensis_ the pocket gopher recovered from the Saunders local fauna, a late Aftonian deposit of Meade County, Kansas, and reduced the technical name _Parageomys_ from generic to subgeneric rank. Paulson (_op. cit._:138) pointed out that the Saunders specimens differ from _G. tobinensis_, and he, therefore, restricted the name to the small _Geomys_ of the Cudahy and Tobin local faunas of Irvingtonian provincial age. _G. tobinensis_ is markedly smaller than the Blancan _G. quinni_. The Cudahy and Tobin local faunas are of approximately the same age, and presently both are included in one unit, the Cudahy fauna. The Cudahy fauna is considered to have been deposited in late Kansan as it occurs in strata immediately below the Pearlette ash. Recently, White and Downs (1961:8) described a new Irvingtonian species, _Geomys garbanii_, from the middle Pleistocene Vallecito Creek local fauna of San Diego County, California. Many well preserved fossils of the new species were recovered. _Geomys garbanii_ is of medium size (approximately the size of one of the larger subspecies of _G. bursarius_), and significantly larger than the Irvingtonian _Geomys tobinensis_ of the Great Plains. The Vallecito Creek occurrence of _Geomys_ is the first authenticated record from the Pacific Coast region. Matthew (1902:320) erroneously referred remains of _Thomomys_ to the genus _Geomys_ in his revised list of Cope's earlier report on the Fossil Lake (or Silver Lake) fauna (see discussion of _Thomomys_ above). A number of Irvingtonian fossil remains of _Geomys_ have not been identified with particular species. Hibbard (1941a:206) found _Geomys_ in the Borchers local fauna (deposited in the time of the Yarmouthian interglacial) of Meade County, Kansas. Also, _Geomys_ has been reported from several sites in Nebraska. Schultz and Tanner (1957:67) reported _Geomys_ from the Angus fossil quarry in Nuckolls County, south-central Nebraska. The Angus fossils were found in sediments of the Sappa Formation considered by Schultz and Tanner to be a Yarmouthian deposit. Fossil quarries (Hay Springs, Rushville, and Gordon) along the south side of the Niobrara River Valley in Sheridan County, Nebraska, have also provided records of geomyids. Both a large and small species of _Geomys_ have been reported from the more recently excavated Rushville and Gordon sites (Schultz and Stout, 1948:562-567, and table 3). In view of the great disparity in size owing to sex, these may actually be males and females of the same species, as mentioned above. The name Hay Springs has been used in reference to all three sites. The ages of the Hay Springs sites are approximately the same, but their correlation is presently under debate. Schultz and Tanner (1957:68-71) maintain that the fossils are distinctly middle Pleistocene, and that they were deposited during late Kansan glaciation, or perhaps from early Yarmouthian into early Illinoian, with the largest concentration coming from the Sappa sands of pre-Illinoian (Yarmouth) age. Hibbard (1958:25), basing his opinion on the presence of _Microtus pennsylvanicus_, and the stage of evolution of other species in the assemblage, regards the Hay Springs sites as probably Illinoian deposits, but certainly no older than that. Mooser (1959:413) identified as _Geomys_ the pocket gopher from Irvingtonian deposits in Arroyo San Francisco (loc. no. 5) near the city of Aguascalientes, México. As suggested elsewhere in this account, these fossils may be referable to _Zygogeomys_ rather than _Geomys_. The Irvingtonian provincial age of this fauna was established by Hibbard and Mooser (1963:245-250). Other alleged occurrences have recently been compiled by Alvarez (1965:19-20). Maldonado-Koerdell (1948:20) noted four fossil occurrences of the genus _Geomys_ in México. Two of these from San Josecito Cave in Nuevo León have since been identified with the genera _Orthogeomys_ and _Pappogeomys_ (Russell, 1960:543-548); the third listed by Maldonado-Koerdell from "near Ameca, Jalisco," was based on Brown's (1912:167) mention of some bones supposedly of the family "Geomyidae," and the fourth refers to pocket gopher remains from the "Hochtals von Mexiko" listed as _Geomys_ by Freudenberg (1921:139). His generic identification is doubtful and the specimens should be compared with Mexican genera of the Geomyinae. Upper Pleistocene records of _Geomys_ also are common. Upper Pleistocene is here understood to include late Illinoian, Sangamon and Wisconsin deposits; all are considered to be of Rancholabrean provincial age (see Hibbard _et al._, 1965:512-515) and post-Irvingtonian. The presence of remains of _Bison_ and/or _Microtus pennsylvanicus_ are currently considered mammalian index fossils of Rancholabrean faunas. In the Illinoian, _Geomys_ extended its range to the Atlantic Coast in the southeastern United States. The eastern and western species-groups evidently were isolated throughout much of the late Pleistocene, and, therefore, evolved separately. Of the two, the eastern, or _pinetis_, species-group seems to have remained somewhat more generalized, and the western, or _bursarius_, species-group has become more specialized. The Rancholabrean _Geomys_ from deposits in the southeastern United States are referable (see Ray, 1963:325) to _Geomys pinetis_. Marsh (1871:121) described _Geomys bisulcatus_ from the North Prong of the Loup River (near Camp Thomas), Nebraska. These beds are also termed the Loup Fork or Loup River fossil beds (see discussion on p. 485), and they lie along the upper reaches of the Middle Loup River in Thomas County (near Senea), Hooker County (near Mullen), and southeastern Cherry County (probably the North Prong beds northwest of Mullen). These beds were at first thought to be of Miocene age, but later were regarded as early Pliocene (see Schultz and Stout, 1948:562-566 for a historical account of expeditions to these fossil sites). Schultz and Tanner (1957:71-72) pointed out that the principal fossiliferous beds in the Middle Loup region are of middle to late Pleistocene age, with most of the fossils coming from the Crete sand and silt beds which are probably early Illinoian deposits, and, therefore, younger than the Hay Springs faunas. Some fossils may have come from the Sappa deposits dated by Schultz and Tanner (_loc. cit._) as mostly Yarmouthian deposits. _Geomys bisulcatus_, judging from the original description and Hibbard's discussion of the cotypes (1954:357), does not differ significantly from _Geomys bursarius_. However, _Geomys bisulcatus_ is tentatively retained as a valid species. Based on the evidence cited above it seems unlikely that _Geomys bisulcatus_ occurred in pre-Irvingtonian times as often suggested in the literature. The genus _Geomys_ has been identified in several faunas of Illinoian age, all from the Great Plains. Stephens (1960:1961) reported the genus from the Doby Springs local fauna in Harper County, Oklahoma, and Starrett (1956:1188) reported it from the Berends local fauna in Beaver County, Oklahoma. Schultz (1965:249) assigned 21 isolated teeth, including six incisors, from Butler Springs local fauna (considered by him to be late Illinoian, following the glacial maximum) to _Geomys_ cf. _bursarius_. Hibbard and Taylor (1960:167) reported a baculum tentatively identified as that of _Geomys_ from the early Illinoian Butler Springs local fauna (including the Adams fauna) of Meade County, Kansas. Hibbard (1963:206) recorded the genus _Geomys_ from the Mt. Scott local fauna (late Illinoian deposits) of Meade County, Kansas; the specimens probably are referable to the living species _bursarius_. From McPherson County, Kansas, Hibbard (1952:7) reported the genus _Geomys_ from the Kentuck Assemblage, which he (1958:25) regarded as a composite of Illinoian and Sangamon species. Specific identification of the Illinoian pocket gophers is uncertain, primarily due to the fragmentary nature of the material. On the basis of dental characters alone most specimens could be referred to _G. bursarius_; however the taxonomic status of _G. bisulcatus_ is in doubt, and more complete material may indicate that the Illinoian gophers are specifically distinct from the living species. Consequently, most authors, including myself, have made no attempt to refer these specimens to species. Nevertheless, the Illinoian _Geomys_ from the Great Plains is more closely allied to the living species of _Geomys_ than it is to the earlier Irvingtonian species. _Geomys bursarius_ has been collected from a number of Sangamon fossil sites on the Great Plains. Although specific identification of specimens of _Geomys_ from Illinoian faunas is uncertain, the Great Plains _Geomys_ from Sangamon and later deposits probably is referable to the living species as Hibbard and Taylor (1960:165) pointed out. They found no difference between _Geomys_ recovered from the Cragin Quarry local fauna (early Sangamon) of Meade County, Kansas, and the living species _Geomys bursarius_. Isolated teeth of the same species were collected from the Jinglebob local fauna of Meade County, Kansas (Hibbard, 1955b:206), a fauna of the late Sangamon. Hibbard (1943:240) also recorded the genus _Geomys_ (referable to _G. bursarius_) from the Rezabek local fauna of Lincoln County, Kansas. According to Schultz _et al._ (1951:6 and table 1) the genus _Geomys_ occurs in buried or "fossil" soils of Sangamon age, lying just above the Loveland Loess, in Nebraska. No specific localities were given by them, nor were any particular specimens mentioned. Dalquest reported _Geomys bursarius_ from two Sangamon faunas in northern Texas. The species is represented in the Ward Quarry local fauna of Cooke County, Texas (1962a:42), and the Good Creek local fauna of Foard County, Texas (1962b:575). _Geomys bursarius_ has been reported from Wisconsin fossil deposits of the Great Plains and adjacent areas as follows: Jones local fauna, Meade County, Kansas (Hibbard and Taylor, 1960:64-66); Two Creeks Forest beds of the third interstadial soils formed between Cary and Mankato glaciations, late Wisconsin (Schultz _et al._, 1951:8 and table 1); Cita Canyon local fauna in the northern part of the Panhandle of Texas (Johnson and Savage, 1955:39); Howard Ranch local fauna of Hardeman County in northwestern Texas (Dalquest, 1965:70); Quitaque local fauna of Motley County, Texas (Dalquest, 1964:501); Clear Creek local fauna of Denton County in north-central Texas (Slaughter and Ritchie, 1963:120); Ben Franklin local fauna, of late Wisconsin beds along the North Sulphur River in Delta County, NE Texas (Slaughter and Hoover, 1963:137); Bulverde Cave (Hay, 1920:140; 1924:247) and Friesenhahn Cave (Tamsitt, 1957:321), both in Bexar County, south-central Texas; Alton, Illinois (Hay, 1923:338-339); Wisconsin drift of Illinois, without mention of specific locality (Bader and Techter, 1959:172); Wisconsin drift of southwestern Wisconsin and northeastern Iowa (Hay, _op. cit._:343); Wisconsin drift near Galena, Illinois, and mouth of Platte River in eastern Nebraska (Leidy, 1869:406). Brown (1908:194) described _Geomys parvidens_ from the Conard Fissure, in northern Arkansas. Hibbard (1958:25) concluded that the Conard Fissure fauna represents a glacial stage, probably the Illinoian, and Hibbard _et al._ (1965:510-511) regarded the fauna as a composite including both Irvingtonian and Rancholabrean elements. White and Downs (1961:21) considered _G. parvidens_ to be a subspecies of _Geomys bursarius_. The first Pleistocene occurrence of _Geomys_ in the southeastern United States is from the Reddick I deposits reported by Gut and Ray (1963:325), who found the remains of _Geomys pinetis_ among the fossils comprising the "rodent beds" of Marion County, Florida. Gut and Ray tentatively identified the beds as Illinoian, but Kurten (1965:219) regarded the Reddick I fauna as early Sangamon. Simpson (1928:2) reported _Geomys floridanus_ [= _pinetis_] from Saber-tooth Cave deposits of Citrus County, Florida. The Saber-tooth Cave (or Lecanto Cave) local fauna is considered by Kurten (_op. cit._:219) also to be a Sangamon deposit. _Geomys floridanus_ [= _pinetis_] was reported from the Seminole Field deposits by Simpson (1929:563); both Simpson and Kurten (_op. cit._:221) agreed that the Seminole Field fauna is mainly late Wisconsin, although sub-Recent fossils occur at the tops of the beds. Ray (1958:430) collected remains of _Geomys pinetis_ from the Melbourne Bone Bed of Brevard County, Florida. The Melbourne local fauna is considered to be from Wisconsin deposits by Kurten (_op. cit._:220). The eastern species of _Geomys_ were probably derived from Great Plains stock that reached the southeastern Coastal Plains in early Rancholabrean (Illinoian) time. Presently there is no contact between the eastern and western populations of the genus, and it is assumed that disjunction occurred as a result of Wisconsin glaciation. It is interesting to note that the genus _Thomomys_ occurred in this region at approximately the same time; both genera occur in Saber-tooth Cave deposits. _Pappogeomys_ The genus _Pappogeomys_ is not known from Pleistocene deposits older than the Wisconsin glaciation, but a pre-Pleistocene occurrence in the Benson beds of Arizona (see discussion of the Pliocene above) shows that _Pappogeomys_ had been differentiated by late Pliocene time. The absence of _Pappogeomys_, beginning in the early Pleistocene and continuing well into the late Pleistocene, is attributed to the southern distribution of the genus, where its range probably was centered on the Central Plateau of México. The paucity of early and middle Pleistocene deposits from this critical region prevents any definite statements about phyletic development within the genus. All of the late Pleistocene records pertain to the subgenus _Cratogeomys_ (long in use as a generic name but in the present paper reduced to subgeneric rank in the genus _Pappogeomys_). Schultz and Howard (1935:280) found _Cratogeomys_ [= _Pappogeomys_] _castanops_ in Burnett Cave in the Guadalupe Mountains of south-central New Mexico. The Burnett deposits are probably late Wisconsin (see Schultz and Tanner, 1957:75, for discussion of the age of these deposits based on carbon-14 tests). These writers (_loc. cit._) also referred the mandible of a small pocket gopher to the genus _Pappogeomys_ [= subgenus _Pappogeomys_]. However, neither genera nor subgenera of the tribe Geomyini can be distinguished on the basis of their inferior dentitions. Judging from the distribution of the modern geomyines, it seems unlikely that the subgenus _Pappogeomys_ has occurred beyond its present range in the late Pleistocene; therefore the small mandible is most likely that of a young individual of _Pappogeomys castanops_. Russell (1960:543) referred specimens collected at San Josecito Cave in Nuevo León, México, to the group of small subspecies _Cratogeomys_ [= _Pappogeomys_] _castanops_. Also, Russell (_loc. cit._) identified a rostral fragment as of the genus _Cratogeomys_ [= subgenus _Cratogeomys_] although the fragment had a combination of features different than in any named species of the genus; he did not name the fragment as a new species, preferring to wait for additional material that could clarify its taxonomic relationships. Hibbard (1955a:52-53) identified _Cratogeomys_ [= _Pappogeomys_] _tylorhinus_ from the Becerra Superior deposits in the valley of Tequixquic in the northern part of the state of México. The Wisconsin age of these beds suggests an earlier Pleistocene derivation of the _gymnurus_-group of species. Several specimens of the subgenus _Cratogeomys_ have been reported from beds of latest Wisconsin (certainly after the glacial maximum) or post-Wisconsin age. Gilmore (1947:158) found fossil remains of _Cratogeomys_ [= _Pappogeomys_] _castanops_ commonly in Quaternary cave deposits on the mountain slopes in the vicinity of Cuatro Ciénegas, in central Coahuila. These deposits actually may be of post-Wisconsin origin (see discussion above). Alvarez (1964:8) obtained fragments of _Cratogeomys_ [= _Pappogeomys_] _tylorhinus_ from sub-Recent deposits of Capa III in the Cueva La Nopalera in southwestern Hidalgo, México. _Pappogeomys merriami_ lives in the area today. Mayer-Oakes (1959:373) reported remains of _Cratogeomys_ [= _Pappogeomys_] _merriami_ from levels eight and eleven of the excavations at El Risco II, in the northern part of Mexico City. The ages of these deposits are unknown to me, but they probably are no older than late Wisconsin with most of the beds dating from the post-Wisconsin. _Orthogeomys_ This genus is not known from the Pleistocene, except for its occurrence in the San Josecito cave deposits of southwestern Nuevo León, México (Russell, 1960:544). Although _Orthogeomys_ does not occur in the immediate vicinity of the cave at the present time, the northern limits of its range is nearby in southern Tamaulipas. The _Orthogeomys_ from San Josecito Cave differs from living species, and has been named _Heterogeomys_ [= _Orthogeomys_] _onerosus_ Russell (_loc. cit._), and is evidently referable to the subgenus _Heterogeomys_. As mentioned before, the San Josecito Cave local fauna represents deposits of Wisconsin glaciation. HISTORY OF CLASSIFICATION The account of the Tucan or Indian mole by Hernandez (sometimes listed as Fernandez) in 1651 probably is the earliest published one of a geomyid (see Merriam, 1895:201; Coues, 1877:607-608). Linnaeus in 1758 did not mention geomyids. In 1772, Kerr described Hernandez's Tucan under the name _Sorex mexicana_ on the basis of Hernandez's account without having seen any specimens. Lichtenstein in 1827 applied the technical name _Ascomys mexicana_ to three specimens collected by Deppe from unknown localities on the tableland of México. Merriam (_loc. cit._) pointed out that the name _mexicanus_ of Lichtenstein in 1827 is a _nomen nudum_, and that it is preoccupied by _mexicanus_ used by Kerr in 1792. The latter can not be technically identified with any particular species of geomyid. Bartram in 1791 wrote of the pocket gopher of Florida, without formally describing it. The first available technical name is _Mus bursarius_ of Shaw in 1800. Rafinesque in 1817 proposed the first generic names for the geomyids when he described _Geomys_ and _Diplostoma_. In 1839, Waterhouse referred the genus _Geomys_ to his family Arvicolidae, considered by him to be a subgroup of muroids. In 1841, he suggested that _Geomys_ was related to _Bathyergus_ and _Spalax_. Waterhouse in 1848 (p. 8) treated the pocket gophers as a subgroup of rodents under the group name Saccomyina, in which he included the genera _Heteromys_, _Saccomys_, _Perognathus_, and _Dipodomys_. Hence, Waterhouse was the first to recognize the relationship between the heteromyids and geomyids. In the next year Gervais erected the family Pseudostomidae for a group of specialized squirrels to include _Geomys_ and _Thomomys_ and the same genera (at least in part) of heteromyids that Waterhouse classified in the "family" Saccomyina. In 1839 the name _Thomomys_ was proposed by Maximilian (Wied-Neuwied). All of the generic names previously proposed for pocket gophers were considered by subsequent authors to be synonyms of _Geomys_. A third family name, Sciurospalacoides, was proposed by Brandt (1855:188) who referred _Geomys_ and _Thomomys_ to that family. He placed his new family phylogenetically between the family Sciuridae and the family Spalacoides (a group in which Brandt included the genera _Spalax_, _Sipheus_, and _Ellobius_). Brandt took exception to the classification of Waterhouse (1848), who united the geomyids and heteromyids in one family. Brandt placed the heteromyid genera in other groups: _Perognathus_ in the Muridae, and _Macrocolus_ [= _Dipodomys_] in the Macrolini, a subfamily of the family Dipodoides. Modern classification of the pocket gophers begins with Baird in 1858. The important classifications are summarized in Table 1; a few that do not depart essentially from those listed have been omitted owing to limited space for the tabular arrangement, but are discussed in the following account. Baird probably was strongly influenced by the arrangement proposed by Waterhouse in 1848, but was opposed to separating geomyids from heteromyids as was done by Brandt. Baird was convinced of the close relationship of the geomyids and heteromyids, and referred both groups to one family, the Saccomyidae, as Waterhouse had done earlier. In order to recognize the morphological specializations he used two subfamilies, Geomyinae and the Saccomyinae. In the 20 years that followed, some authors followed Brandt and others followed Baird. Gill, in 1872 (p. 71), proposed a classification essentially like Baird's of 1858, but Gill raised Baird's subfamilies to the rank of family (see Table 1). In referring all pocket gophers to the Geomyidae, Gill used that name as a family term for the first time. Also he established the superfamily Saccomyoidea to include his two families, Geomyidae and Saccomyidae; therefore, the Saccomyoidea was equivalent to the group Saccomyina of Waterhouse (1848) and the Saccomyidae of Baird (1858). Coues (1877), in his classic monograph of the Geomyidae followed the arrangement proposed by Gill in treating the pocket gophers as a family. Alston in 1876 proposed another classification based on Baird (1858), with two subfamilies, the Geomyinae and the Heteromyinae, united together in the family Geomyidae; thus, he recognized that the genus _Saccomys_ Frédéric Cuvier, 1823, was a synonym of _Heteromys_ Desmarest, 1817, as had been pointed out by Gray (1868:201) and Peters (1874:356). Coues (1877:487-490) acknowledged the invalidity of the genus _Saccomys_, but refused to give up the name in supergeneric classification. Winge, first in 1887 and subsequently in 1924, classified the geomyids and heteromyids together in the family Saccomyidae as did Baird in 1858, and like Coues, Winge too ignored the synonymy of _Saccomys_ with _Heteromys_ and insisted on retaining the technical terms Saccomyidae and Saccomyini. Up to the time of Merriam's classic revision of the Recent Geomyidae in 1895 all the known species of living pocket gophers were referred to two genera, _Geomys_ and _Thomomys_. Merriam described much new material, especially from México and Central America, and proposed seven new genera (see Table 1). His complete and detailed study of the dentitions and osteology of the skull remains today as the definitive work on this subject, and is the point where most studies of the Geomyidae must begin. His treatment of the Recent genera survived for 52 years without change until Hooper (1946:397) arranged _Platygeomys_ as a synonym of _Cratogeomys_. However, Merriam's genera have been recognized in all subsequent classifications except for the current review (see Table 1). Cope described the first known fossil geomyids in 1878, and published an excellent review of the two genera, _Pleurolicus_ and _Entoptycus_, in 1884 (pp. 855-870, pl. 64, figs. 1-9). Both genera were recovered from the John Day Miocene deposits of Oregon. Cope did not propose a new systematic arrangement of these geomyids, but referred them to the family Saccomyidae and mentioned that the Saccomyidae was equivalent to the family Geomyidae of Alston. Winge, in 1887, followed Cope in referring _Pleurolicus_ and _Entoptycus_ to the Saccomyidae along with the living genera _Thomomys_ and _Geomys_. Miller and Gidley (1918), in their synopsis of the supergeneric groups of rodents, proposed a new subfamily, Entoptychinae, to include the divergent Miocene pocket gophers. Miller and Gidley also revived the old subfamily Geomyinae of Baird (1858), but restricted its application to the modern pocket gophers and their immediate ancestors. In 1936, A. E. Wood revised the taxa of the subfamily Entoptychinae, and described the first Miocene genus, _Dikkomys_, of the Geomyinae. He followed the supergeneric classification of Miller and Gidley (1918). The recent classifications of Simpson (1945) and Wood (1955) have combined the classifications of Merriam (1895) and Wood (1936). Wood (1955) brought up to date the list of genera, including those that were described after the publication of Simpson's classification (1945). In Table 1, the list of genera is principally from Simpson (1945) but generic names used by Wood (1955) are included. This is the currently accepted classification. The new classification proposed in this paper (see Table 1) includes three tribes proposed as vertical units; they are intended to stress the phyletic trends in the known evolutionary sequences by placing immediate ancestors together with their descendants. _Pliogeomys_ is placed in the same tribe (Geomyini) as _Zygogeomys_, _Geomys_, _Orthogeomys_, and _Pappogeomys_. That tribe includes the most specialized Geomyinae. _Zygogeomys_, _Geomys_, _Orthogeomys_, and _Pappogeomys_ are lineages resulting from a Pleistocene radiation in which all the lineages diverged from a common Pliocene ancestor. The radiation of the Geomyini was well under way by the close of the late Pliocene. Although _Pliogeomys_ may not be the actual ancestor, it closely resembles the primitive morphotype. TABLE 1.--History of the classification of the Superfamily Geomyoidea ===============+==============+==================+================ Baird 1858 | Gill 1872 | Winge 1887 | Merriam 1895 | Coues 1877 | and 1924 | Ellerman 1940 ---------------+--------------+------------------+---------------- Family | Family | Family | Family Saccomyidae | Geomyidae | Saccomyidae | Geomyidae ---------------+--------------+------------------+---------------- Subfamily | | "Group" | Geomyinae | | Geomyini | -- -- -- -- -- +-- -- -- -- --+-- -- -- -- -- -- +-- -- -- -- -- - | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | _Thomomys_ | _Thomomys_ | _Thomomys_ | _Thomomys_ | | | | | | | | | | | | | | | | | | _Zygogeomys_ | | | | | | _Geomys_ | _Geomys_ | _Geomys_ | _Geomys_ | | | | | | _Orthogeomys_ | | | _Heterogeomys_ | | | _Macrogeomys_ | | | | | | _Pappogeomys_ | | | _Cratogeomys_ | | | _Platygeomys_ -- -- -- -- -- +-- -- -- -- --+-- -- -- -- -- -- +-- -- -- -- -- - | | | | | | | | | | | *_Pleurolicus_ | | | | | | | | | *_Entoptychus_ | ---------------+--------------+------------------+---------------- | | | | | | | | | | | "Group" | | | Gymnoptychine** | | | _Gymnoptychus_ | ---------------+--------------+------------------+---------------- Subfamily | Family | "Group" | Saccomyinae | Saccomyidae | Saccomyini | -------------+-------------+------------------+---------------- =====================+=====================+=================== Wood 1935 | Simpson 1945 | Names used in Wood 1936 | Wood 1955 | present paper ---------------------+---------------------+------------------- Family | Family | Family Geomyidae | Geomyidae | Geomyidae ---------------------+---------------------+------------------- Subfamily | Subfamily | Subfamily Geomyinae | Geomyinae | Geomyinae -- -- -- -- -- -- -- +-- -- -- -- -- -- -- +-- -- -- -- -- -- - | | Tribe | | Dikkomyini | | *_Dikkomys_ | *_Dikkomys_ | *_Dikkomys_ | *_Pliosaccomys_ | *_Pliosaccomys_ | | | | Tribe | | Thomomyini | | *_Pleisothomomys_ | *_Pleisothomomys_ | } _Thomomys_ | _Thomomys_ | } _Thomomys_ | | | | Tribe | | Geomyini | | | *_Pliogeomys_ | *_Pliogeomys_ _Zygogeomys_ | _Zygogeomys_ | } | *_Nerterogeomys_ | } _Zygogeomys_ | | _Geomys_ | _Geomys_ | } | *_Parageomys_ | } _Geomys_ _Orthogeomys_ | _Orthogeomys_ | } _Heterogeomys_ | _Heterogeomys_ | } _Orthogeomys_ _Macrogeomys_ | _Macrogeomys_ | } | | _Pappogeomys_ | _Pappogeomys_ | } _Cratogeomys_ | _Cratogeomys_ | } _Pappogeomys_ _Platygeomys_ | _Platygeomys_ | } -- -- -- -- -- -- -- +-- -- -- -- -- -- -- +-- -- -- -- -- -- - Subfamily | Subfamily | Subfamily Entoptychinae | Entoptychinae | Entoptychinae | | *_Pleurolicus_ | *_Pleurolicus_ | *_Pleurolicus_ *_Gregorymys_ | *_Gregorymys_ | *_Gregorymys_ *_Grangerimus_ | *_Grangerimus_ | *_Grangerimus_ *_Entoptychus_ | *_Entoptychus_ | *_Entoptychus_ ---------------------+---------------------+------------------- | Geomyidae | Geomyidae | _incertae sedis_ | _incertae sedis_ | | | | *_Gidleumys_ | *_Diplolophus_ | *_Diplolophus_ | *_Griphomys_ | *_Griphomys_ ---------------------+---------------------+------------------- Family | Family | Family Heteromyidae | Heteromyidae | Heteromyidae ---------------------+---------------------+------------------- * Denotes extinct genera. ** Winge included in his family Saccomyidae the "group" Gymnoptychine and the contained genus _Gymnoptychus_ Cope, 1873, which genus currently is placed in the family Eomyidae. The type of _Gymnoptychus_ Cope, 1873, is synonymous with _Ischyromys_ Leidy, 1856, and the valid name for the genus is _Adjidaumo_ Hay, 1899. _Pliosaccomys_, on the other hand, represents the terminal stages of a long trend that began with the _Dikkomys_-like Geomyinae of the early Miocene. In this lineage, the rate of evolution in the dentition and the skull was slow; therefore, the differences between early Miocene (_Dikkomys_) and middle Pliocene (_Pliosaccomys_) are not great and the two are united into the tribe Dikkomyini. The Dikkomyini is the ancestral geomyinen trunk from which the modern groups have diverged. The Pliocene ancestor of _Thomomys_ is unknown but probably resembled _Pliosaccomys_, with which it may have been a contemporary. _Thomomys_ is the least specialized of the modern Geomyinae, and, consequently, shows the most resemblance to the ancestral tribe. The specializations of _Thomomys_, however, clearly preclude its reference to the tribe Dikkomyini; therefore, it is set apart in the monotypic tribe Thomomyini. That tribe has not undergone an adaptive radiation comparable to that of the tribe Geomyini or that of the Entoptychinae in the early Miocene. Here, for the first time, _Thomomys_ is set apart in classification from the other living pocket gophers. Merriam's genera _Orthogeomys_, _Heterogeomys_, and _Macrogeomys_ are closely related. Each of these taxa is retained as a subgenus of a single genus, _Orthogeomys_. Some species of _Macrogeomys_ seem to be more closely allied to the subgenus _Orthogeomys_ and others to the subgenus _Heterogeomys_. A revision of the genus is needed; it might show that the currently recognized subgenera are artificial, and that a different arrangement of the species would more clearly express their evolutionary relationships. The subgenus _Heterogeomys_ seems to be the most nearly uniform of the subgenera, and it is the least specialized. Radiation within the genus may have begun relatively recently, but the many special adaptations for tropical environments suggest that the genus has been in the Neotropical Zone a long time. Therefore, discovery of an early dichotomy from the common ancestral stock of the tribe would come as no surprise. _Nerterogeomys_ Gazin here is arranged as a junior synonym of _Zygogeomys_. Both are less specialized than any of the other Geomyini, except _Pliogeomys_. The single living species (_Zygogeomys tricopus_) is obviously a relic. Its range is small. The two subspecies differ only in minor features. The living species does have a few unique characteristics, only to be expected in the surviving species of a long phyletic lineage. Some of these are specializations. Otherwise, _Zygogeomys_ and _Nerterogeomys_ are closely related and the latter is best placed as a synonym of the former. Both are admittedly closely related to _Geomys_. _Zygogeomys_ and _Geomys_ share several characters, particularly primitive ones; there is considerable parallelism, especially marked in Irvingtonian species of _Geomys_. Nevertheless, _Geomys_ is more specialized, particularly in the dentition, and it has developed some _Pappogeomys_-like specializations. _Zygogeomys_ has retained more of the primitive characters of the tribe. A strong case could be made for recognizing only one genus, _Geomys_, containing _Zygogeomys_ as one of two subgenera. Nevertheless, the characters separating _Zygogeomys_ and _Geomys_ are of considerable importance and I consider the two kinds to be distinct genera. The species of _Geomys_, both living and extinct, form a distinct and well-marked group. The genus is less primitive in most respects than _Zygogeomys_ and _Orthogeomys_ and it is less specialized than _Pappogeomys_, excluding the ancestral stock (subgenus _Pappogeomys_). Some specimens of species of Irvingtonian age (_Geomys tobinensis_ and _Geomys garbanii_, especially the former) retain primitive enamel plates as does _Zygogeomys_; but this is true of only a small percentage of the individuals. Also the adult dental pattern developed somewhat later in ontogeny in these middle Pleistocene species of _Geomys_ than in either Recent or late Pliocene and early Pleistocene representatives (_Geomys paenebursarius_, _Geomys quinni_) of the genus. Whether these features represent a stage in the evolution of the late Pleistocene and Recent species or a terminal stage in members of a sterile and primitive branch of the main line of evolution of _Geomys_ is uncertain. At present I favor the latter explanation, and view _G. paenebursarius_ and _G. quinni_ as early progressive species that evolved dental specializations that were maintained in the main line of phylogeny. Hibbard proposed the generic name _Parageomys_ (1944:55), but later regarded it as a subgenus of _Geomys_ (1956:182) that includes those species retaining continuous enamel bands until relatively late in ontogeny; no other differences have been noted. When the early phylogeny of _Geomys_ is better understood, _Parageomys_ may serve as a subgeneric taxon in which the primitive species of _Geomys_ can be grouped, but as of now _Parageomys_ is arranged as a synonym of _Geomys_. _Pappogeomys_ and _Cratogeomys_ also form a natural group. Their close relationship is best reflected in formal taxonomy by including them in the same genus. Their dissimilarities are of the sort that separate a primitive ancestral lineage from a divergent and progressively more specialized assemblage. The fossil record is inadequate, and I can only speculate that _Cratogeomys_ diverged from primitive _Pappogeomys_-stock in the earlier Pleistocene, at least before the end of the Irvingtonian. _Cratogeomys_ probably originated on the Mexican Plateau and probably underwent its subsequent evolution there. The living species of the subgenus _Pappogeomys_ are evidently relics of the ancestral stock of the genus. Hooper (1946:397), I think correctly, considered _Platygeomys_ as congeneric with _Cratogeomys_, although the highest degree of specialization of the genus is attained in those species formerly classed in the genus _Platygeomys_. Even so, in my opinion, the differences are insufficient to warrant even subgeneric recognition. CLASSIFICATION Family GEOMYIDAE Gill, 1872 Rodents of the superfamily Geomyoidea specialized for completely fossorial life (early Pliocene to Recent); specialized earlier (late? Oligocene and early Miocene) for semi-fossorial habits; body thickset, fusiform without apparent neck (in modern geomyids); legs short; forelegs especially stout; eyes and ears small (pinna reduced to inconspicuous crest concealed beneath pelage); tail tactile, shorter than head and body; lips closing behind incisors; cheek pouches external, fur-lined; baculum rodlike, arched, having expanded quadriform platelike base; pelage long, soft without underfur, covering body in thick coat (in some species of _Orthogeomys_ scant, harsh or scattered bristles); color varying from pale tints of buffy (almost white) to metallic black. Skull thick-walled, massive, angular, relatively broad, and flattened; distinctly murine form, but having zygomasseteric structure of advanced sciuromorphs, including small infraorbital canal (that transmits no part of masseter muscle) and well-developed, broad zygomatic plate; zygomata massive and widely flaring, jugals stout; rostrum robust, relatively broad and deep, and without evidence of transverse canal (as in Heteromyidae); anterior projection of nasals only slightly exceeding that of upper incisors; interorbital region usually constricted, narrower than rostrum; anterior opening of infraorbital canal far forward on side of rostrum, about half way between zygomatic plate and upper incisor and just behind premaxillary-maxillary suture, its opening countersunk in oblique sulcus (for protection from muscle contraction); postorbital process lacking, except for rudimentary knoblike projection in subgenus _Macrogeomys_; palate relatively narrow, its deeply sculptured surface sloping steeply downward posteriorly causing region supporting maxillary tooth-row to be markedly depressed; palatine bone reduced, forming, on two abruptly different levels, posterior margin of hard palate behind tooth-rows; parietals compressed and narrow, and most of cerebral cavity roofed by squamosals (in some species squamosals overlap lateral parts of parietals); tympanic bullae completely inferior in position and fully ossified, external meatus being developed laterally as elongated tube; mastoid not inflated, but broadly exposed at posterolateral margin of the skull; occiput large, its surface usually rugose, and paroccipital processes large and flangelike, at least in advanced groups (early Pliocene to Recent); ramus relatively short and stout, having distinct crest and ridges for muscle attachments; coronoid process well developed, erect; articular condyle prominent; angular process prominent, reflected laterally, and in modern groups lateral extension protruding from posterior border of ramus nearly at right angle; capsule for root of lower incisor, prominent between angular process and articular condyle. Anterior surface of incisors broad and flat, always smooth on lower teeth, but either smooth or grooved on upper teeth depending on taxon; cheek teeth hypsodont, becoming progressively higher crowned in modern groups, rooted in primitive groups (late? Oligocene to middle Pliocene), rootless and ever-growing in modern groups (late Pliocene to Recent); upper and lower premolars persistently bicolumnar; upper and lower molars bicolumnar only in primitive groups (late? Oligocene and early Miocene), becoming progressively monocolumnar in advanced groups (early Pliocene to Recent), primitive bicolumnar pattern being retained on occlusal surface only in early stages of ontogeny and in third molar throughout life; enamel pattern of occlusal surface of cheek teeth based on sextituberculate prototype (see Wood and Wilson, 1936:388-391), having cusps arranged in two transverse rows of three cusps each, excepting three anterior cusps of premolars that are arranged in trefoil, especially on p4 (sometimes only one or two, rather than three, cusps develop in a particular set, especially in p4), conules absent; protostyle and endostyle in upper teeth and protostylid and hypostylid in lower teeth formed from cingulum; cusps of each row uniting with wear into transverse enamel lophs (or lophids), each tooth having two lophs, one on anterior column, protoloph and protolophid, and one on posterior column, hypoloph and hypolophid, that unite with additional wear forming continuous enamel band; enamel lacking on sides of each column in advanced lineages, thereby restricting enamel to anterior and posterior walls; with extreme reduction, posterior plates of upper teeth and, more commonly, anterior plates of lower molars, missing. Dental formula: 1/1, 0/0, 1/1, 3/3. Key to the Subfamilies of Geomyidae A Angular process of ramus mostly below alveolar level of mandibular tooth-row; pattern of premolar like that of molars, consisting of two subequal crests united at one or both margins of tooth; molars persistently bicolumnar; molariform teeth always rooted. Subfamily Entoptychinae p. 513 A´ Angular process of ramus mostly above level of mandibular tooth-row; pattern of permolar unlike that of molars, consisting of two prisms differing in size and united at their mid-points but never at either margin; molars progressively monocolumnar, except for early Miocene forms; molariform teeth rooted only in primitive genera (late? Oligocene to middle Pliocene), and rootless and ever-growing in later genera (late Pliocene to Recent). Subfamily Geomyinae p. 514 Subfamily ENTOPTYCHINAE Miller and Gidley, 1918 Anterior face of upper incisor usually smooth, sometimes bearing faint groove in center or near medial margin of tooth, at least in _Gregorymys_; cheek teeth hypsodont, medium to high crowned, and rooted in all but _Entoptychus_ (has rootless, ever-growing teeth); cheek teeth identical in form, premolars resembling molars and lower cheek teeth mirror images of upper teeth; crowns biprismatic, having two columns joined at edge of protomeres (for description of term, see discussion of primitive morphotype on page 537) and with persistent lateral fissure between them; lateral re-entrant fold deep, penetrating at least half width of crown, from external side in upper teeth and internal side in lower teeth (in specialized genus _Entoptychus_ lophs, upon additional wear, join also at edge of parameres, thus uniting columns at both ends and thereby enclosing interior part of lateral fissure as a transverse fossette in center of tooth); enamel investment of prisms usually complete, including inflection bordering re-entrant folds, occlusal pattern becoming interrupted with wear only in _Entoptychus_, where enamel disappears first from sides of crowns (following union of anterior and posterior columns at both sides) and later, in final stages of attrition, from anterior wall of lower molars and posterior wall of upper molars. Maxillary bone without pronounced vertical depth in part supporting cheek teeth, its inferior border only slightly lower than inferior border of premaxillary and alveolar lips of molariform teeth consequently approximately level with, or slightly below, alveolar lip of upper incisor; squamosal without lateral expansion, therefore, meatal tube of auditory bulla separated from zygomatic process of squamosal by deep, well-developed postglenoid notch; angular part of mandible below alveolar level of mandibular cheek teeth; angular process only slightly reflected laterally; coronoid process low, tip only slightly above condyle. For information concerning the structure and relationships of the known genera, and for accounts of species, see Wood (1936). A list of the named genera in order of specialization is as follows: *_Pleurolicus_ Cope, 1878. Proc. Amer. Phil. Soc., 18:66. *_Gregorymys_ Wood, 1936. Amer. Mus. Novit., 866:9. *_Grangerimus_ Wood, 1936. Amer. Mus. Novit., 866:13. *_Entoptychus_ Cope, 1878. Proc. Amer. Phil. Soc., 18:64. Five new species have been described since Wood's (1936) revision. They are: _Pleurolicus clasoni_ MacDonald (1963:180); _Gregorymys kayi_ Wood (1950:335); _Gregorymys montanensis_ Hibbard and Keenmon (1950:198); _Grangerimus dakotensis_ MacDonald (1963:182); _Grangerimus sellardsi_ Hibbard and Wilson (1950:623). Subfamily GEOMYINAE Baird, 1858 Anterior face of upper incisor primitively smooth, grooves consistently developed only in one modern lineage (Geomyini); cheek teeth hypsodont, primitively rooted and having crown of medium height (late Oligocene to middle Pliocene), being higher crowned, rootless and ever-growing in modern lineages (late Pliocene to Recent); primitively crowns of cheek teeth biprismatic, having two columns joined at mid-points by narrow isthmus and entire crown sheathed in continuous band of enamel; premolars retaining primitive biprismatic form, anterior and posterior columns never uniting at edge of protomeres or parameres, and with both lateral re-entrant folds persistent throughout life; primitive biprismatic pattern becoming decidedly modified in molars (except in M3), having two prisms progressively uniting into one column by reduction and loss of lateral inflections, primitive biprismatic patterns being retained only in early stages of ontogeny; third upper molars retaining, at least partially, primitive bicolumnar pattern (except in Thomomyini), with relatively broad isthmus and horizontally shallow re-entrant folds, lingual fold sometimes wanting; enamel pattern becoming discontinuous (late Pliocene to Recent) owing to loss of enamel from sides of each column; remaining enamel restricted to anterior and posterior plates, or cutting blades, and enamel bordering lateral inflections in premolars (considering both sides together, these plates constitute essentially two transverse cutting blades); enamel pattern of M3 varying, depending on taxon; with specialization, anterior plates of lower molars and posterior plates of upper premolar and molars may be reduced or lost; except in primitive species (early Miocene), no enamel fossettes retained in adult dentitions. Maxillary bone having pronounced vertical depth in part supporting cheek teeth, inferior border arching downward well below inferior border of premaxillary; consequently, alveolar lips of molariform teeth decidedly below level of alveolar lip of upper incisor; squamosal with marked lateral expansion at expense of postglenoid notch; notch compressed and reduced between meatal tube of auditory bulla and zygomatic process of squamosal; angular part of mandible mostly above alveolar level of mandibular cheek teeth; angular process reflected laterally at right angles to axis of ramus and developed into heavy knoblike projection; coronoid process well developed, tip decidedly higher than condyle; fossorial specializations remarkably well developed in advanced lineages, degree of specialization of primitive Miocene species unknown but probably only semi-fossorial as in Entoptychinae. Key to the Tribes of the Geomyinae A Enamel investment complete and uninterrupted, even in final (adult) stages of wear; cheek teeth rooted, with crowns of medium height; third lower molar biprismatic, the two columns separated by inner and outer re-entrant folds as in lower premolar. Tribe Dikkomyini p. 515 A´ Enamel investment incomplete and discontinuous, reduced, at least in final (adult) stages of wear, to interrupted enamel plates; cheek teeth rootless and ever-growing (except in extinct genus _Pliogeomys_), crowns of maximum height; third lower molar monoprismatic, without trace of inner and outer re-entrant folds as in first and second lower molars. B Upper incisors smooth, occasionally with a fine indistinct groove near inner margin of tooth; form of third upper molar same as M1 and M2, monoprismatic, anteroposteriorly compressed, and having transverse enamel plates on both anterior and posterior faces, and without suggestion of either labial or lingual re-entrant folds; basitemporal fossa absent (except for a shallow depression in one Recent species, _T. townsendii_); forefoot small and narrow with claws not elongated for digging. Tribe Thomomyini p. 518 B´ Upper incisors grooved, bearing either one or two sulci; form of third upper molar distinctly different from M1 and M2, fully or partially biprismatic (with a few exceptions discussed beyond), without marked anteroposterior compression (either subtriangular, elongated, suborbicular or quadriform in cross-section, but not elliptical as in M1 and M2), and having typical transverse anterior plate and two lateral plates (varying in their development, depending on taxa), but no posterior plate, and with lateral re-entrant folds usually developed, especially labial inflection (although sometimes minute in a few species, as described beyond); basitemporal fossa well-developed, although occasionally shallow or absent (primitive species of _Zygogeomys_); forefoot large and broad, with elongated claws for digging. Tribe Geomyini p. 521 Tribe DIKKOMYINI, new tribe _Genotype._--_Dikkomys_ Wood, 1936. _Chronologic and geographic range._--Early to Middle Pliocene (early Arikareean to mid-Hemphillian) in western United States. Known from Miocene fossil sites in Montana, South Dakota, and Nebraska and Pliocene sites in South Dakota, Oregon, Nevada, and southern California. For precise localities see accounts of _Dikkomys_ and _Pliosaccomys_ beyond. _Diagnosis._--Small Geomyinae; lacking specializations of more advanced tribes; upper incisors smooth, at least in _Pliosaccomys_; molariform teeth always rooted and having crowns of medium height; enamel investment of cheek teeth complete and uninterrupted in all stages of wear; crowns of molars primitively biprismatic, having two columns united at mid-points, thus forming narrow isthmus separating lateral re-entrant folds as in premolars, and, with wear, also uniting secondarily at protomeres (with exception of third lower molars), consequently, isolating remnant of that inflection as shallow fossette (columns uniting first at protomeres in _Pliosaccomys_); anterior and posterior columns of first and second molars, both above and below, becoming progressively united into one column in advanced Dikkomyini (early and middle Pliocene), but m3 (M3 unknown) retaining primitive biprismatic pattern, with columns joined at centers but never at protomeres (for details of dentition see generic accounts); mandible stout, its angle mostly above mandibular tooth-row; masseteric ridge low; basitemporal fossa barely discernable in some fragments of _Pliosaccomys_; postcranial skeleton unknown. Key to the Genera of the Tribe Dikkomyini A Molars biprismatic throughout life; anterior and posterior lophs of first and second molars in pre-final stages of wear uniting first at their mid-points and later at edge of protomeres; anterior lophid of lower premolar having distinct anteroexternal inflection. Genus _Dikkomys_ p. 516 A' First and second molars becoming monoprismatic in final (adult?) stages of wear, biprismatic only in pre-final stages of wear; third molars persistently biprismatic; anterior and posterior lophs of first and second molars uniting first at edge of protomeres; anterior lophid of lower premolar lacking anteroexternal inflection. Genus _Pliosaccomys_ p. 517 Genus =Dikkomys= Wood 1936. _Dikkomys_ Wood, Amer. Mus. Novit., 866:26, July 2. _Type._--_Dikkomys matthewi_ Wood, 1936, from Lower Harrison deposits near Agate, Sioux County, Nebraska. _Chronologic range._--Early Miocene, from early Arikareean (Lower Harrison local fauna of Nebraska) to middle Miocene, late Hemingfordian (Upper Rosebud local fauna, South Dakota, and the Deep River Formation, Montana). According to MacDonald (1963:149-150), the Upper Rosebud is middle Miocene rather than early Miocene. _Description._--Size small, about as in small kinds of _Thomomys_; known only from fragmentary mandible, including molariform dentition in place, and isolated cheek teeth, including M1 (see Wood, 1936:26-28 and fig. 32; Galbreath, 1948:316-317 and fig. 1; and Black, 1961:13-14 and fig. 58); upper incisors unknown; cheek teeth hyposodont, persistently rooted, and having crowns of medium height compared with Recent geomyids; enamel investment complete and uninterrupted in all molariform teeth in all stages of wear; P4 unknown, but probably formed like p4; p4 persistently biprismatic, two crowns joined at mid-points by relatively narrow isthmus separating lateral re-entrant folds; anterior lophid of p4 having distinct anteroexternal inflection; molars also biprismatic throughout life; two lophids of lower molars first uniting at mid-points as in p4, and, with additional wear, m1 and m2 secondarily uniting at edge of protomeres and forming isolated enamel fossette between point of connection (detailed description of stages of wear discussed in account of phylogeny of subfamily); m3 permanently joined at mid-point only, without lateral union at edge of protomeres; upper molars, judging by M1 (M2 and M3 unknown), having same pattern as lower molars, but first union of lophs decidedly on lingual side of center, consequently, lingual re-entrant fold small; M1 probably developing U-pattern in advanced stages of wear by union of protomeres, with minute lingual fossette developing in transition as lophs secondarily become united at lingual edge of columns; mandible stout and geomyidlike; masseteric ridge weakly developed; basitemporal fossa absent. Evidently, _Dikkomys matthewi_ is more primitive than _Dikkomys woodi_. The modified H-pattern in m1 and m2, with the metalophid and hypolophid joined at both their mid-points and also at their protomeres (by union of the protostylid and hypostylid in the lower dentition), is persistent throughout life. Therefore, the enclosed enamel fossette is not eradicated with wear. In m1 and m2 of _Dikkomys woodi_, the fossette is shallower, and, at least in advanced stages of wear, it would disappear, therefore, forming a U-pattern on the occlusal surface, as in M1 and M2, but lateral inflection horizontally shallow rather than deep as in entoptychines. Specimen (No. P 26284 FMNH) reported as _Dikkomys matthewi_ by Galbreath (1948:316) is referable to the recently described species _Dikkomys woodi_ Black, 1961. _Specimens examined._--One, no. P 26284, Field Mus. Nat. Hist., from upper Rosebud, Shannon Co., South Dakota. _Referred species._--two: _Dikkomys matthewi_ Wood, 1936. Amer. Mus. Novit., 866:26, July. Type from early Arikareean Lower Harrison deposits (early Miocene) near Agate, Sioux County, Nebraska. _Dikkomys woodi_ Black, 1961. Postilla, Yale Peabody Museum, 48:13, January 16. Type from Deep River Formation, late Hemingfordian (middle Miocene), Meagher County, Montana; also known from Upper Rosebud deposits (middle Miocene) near Wounded Knee, Shannon County, South Dakota. Genus =Pliosaccomys= Wilson 1936. _Pliosaccomys_ Wilson, Carnegie Inst. Washington Publ., 473:20, May 21. _Type._--_Pliosaccomys dubius_ Wilson, 1936, from Smiths Valley local fauna in Lyon County, Nevada. _Chronologic range._--Early Pliocene, late Clarendonian (Wolf Creek local fauna, South Dakota, and Nettle Springs local fauna, California) to Middle Pliocene, middle part of Hemphillian (Smiths Valley local fauna, Nevada, and McKay Reservoir and Otis Basin local faunas, Oregon). _Description._--Size small (alveolar length of mandibular tooth-row measuring 6.0 in holotype), about as in _Thomomys monticola_; upper incisor relatively broad and flat, having anterior face smooth, without trace of grooving; crowns of cheek teeth of medium height and rooted; enamel investment continuous and uninterrupted in all stages of wear; premolars permanently, biprismatic; P4 having anterior prism subtriangular and decidedly smaller that sub-crescentic posterior prism, and joined near centers by narrow, obliquely oriented isthmus; p4 having anterior prism subovate, posterior prism strongly compressed anteroposteriorly, and joined at mid-points by relatively broad and straight isthmus; first and second molars, both above and below, monoprismatic in final (?adult) stage of wear, derived ontogenetically from primitive bilophate pattern by coalescence of two columns into one; M1 and M2 mirror images of m1 and m2 in pre-final stages of wear, two columns first uniting at edge of protomeres forming U-pattern, and primitive H-pattern never developing in either series (for detailed description of stages of wear, see account of phylogeny, p. 546); m3 (M3 unknown, but probably with same form as in Geomyini, see p. 552) persistently biprismatic, two columns joined by relatively broad isthmus at centers, consequently, forming H-pattern of primitive ancestors; rostrum heavy and broad as in modern geomyids; palate narrow and strongly ribbed; mandible stout; masseteric ridge and fossa well developed; basitemporal fossa absent. _Specimens examined._--Six, nos. 1796 (holotype)--1799, 1804 and 1806 (CIT) now in the Los Angeles County Museum, all from Smiths Valley local fauna, Middle Pliocene, Nevada. _Referred species._--two: *_Pliosaccomys dubius_ Wilson, 1936. Carnegie Inst. Washington Publ., 743:20, May 21. Known from early and middle Pliocene faunas including Wolf Creek local fauna (late Clarendonian), Shannon County, South Dakota; McKay Reservoir local fauna and Otis Basin local fauna (Hemphillian), Oregon; type from Smiths Valley local fauna (probably middle Hemphillian), Lyon County, Nevada. *_Pliosaccomys wilsoni_ James, 1963. Univ. California Publ. Geol. Sci., 45:101, June 26. Type from Nettle Springs local fauna of late Clarendonian (early Pliocene), Ventura County, California. Tribe THOMOMYINI, new tribe _Type._--_Thomomys_ Wied-Neuwied, 1839. _Chronologic and geographic range._--Known from late Pliocene (early Blancan) to Recent. Known primarily from western North America from southern Canada south to Central México in Pliocene, Pleistocene and Recent and in middle and late Pleistocene of Maryland and Florida. _Diagnosis._--Size small to medium (basilar length exclusive of _T. bulbivorus_, measuring from approximately 24 to 45, including both males and females); upper incisors without grooving, excepting fine, indistinct sulcus rarely near inner margin (grooving more common in _T. monticola_ than in other Recent species); crowns of cheek teeth high, rooted and ever-growing; all molars, including M3, monoprismatic and anteroposteriorly compressed, sometimes (especially in subadults) having slight inflection on labial side in upper teeth and lingual side in lower teeth; molars bicolumnar in pre-final stages of wear (seen in juvenal teeth only), patterns of wear in both upper and lower molars resembling those of _Pliosaccomys_, except that crowns of m3 and M3 unite into single column in final stages of wear; enamel pattern interrupted in all cheek teeth, loss occurring only at sides of each column; transverse enamel blade completely covering posterior face of both P4 and p4; all upper and lower molars with two transverse enamel blades, one on anterior surface and one on posterior surface, of each tooth, including M3; small third plate sometimes persistent on broad side of tooth, labial side in upper molars and lingual side in lower molars (_T. bulbivorus_); skull generalized, neither unusually narrow and deep or broad and flat; usually without marked cresting or rugosity; masseteric ridge well developed and massive; basitemporal fossa absent, sometimes shallow depression forming in _T. townsendii_; pelage soft, never harsh or hispid, covering body with thick coat of hair; forefoot exceptionally small for fossorial mammal, claws not especially long; body form remarkably fossorial. The tribe Thomomyini is monotypic, including only the genus _Thomomys_. Genus =Thomomys= Wied-Neuwied 1839. _Thomomys_ Wied-Neuwied, Nova Acta Phys. Med. Acad. Caesar. Leop.-Carol., 19(1):377. 1836. _Oryctomys_ Eydoux and Gervais (in part), Mag. de Zool., 6:20, pl. 21. Type: _Oryctomys_ (_Saccophorus_) _bottae_, from coast of California, probably near Monterey. 1903. _Megascapheus_ Elliot, Field Columb. Mus., Publ. 76, Zool. Ser., 3(11):190, July 25. Type: _Diplostoma bulbivorum_ Richardson, from Columbia River, probably near Portland, Ore. 1933. _Pleisothomomys_ Gidley and Gazin, Jour. Mamm. 14:354. Type: _Pleisothomomys potomacensis_ Gidley and Gazin, from Pleistocene, Cumberland Cave local fauna, Allegany County, Maryland. _Chronologic range._--Known from late Pliocene to Recent. _Description._--Same as that given for the tribe Thomomyini above. _Discussion._--Features characterizing _Thomomys_ and the tribe Thomomyini are more advanced than those characterizing the tribe Dikkomyini. Also, the Thomomyini retain more of the primitive features of the Geomyinae than do the more specialized tribe Geomyini. Specializations are few, but include the third molar being a single column both above and below, enamel plates, and a masseteric ridge. Key to the Subgenera of _Thomomys_ A Molars sub-crescent or ovate in cross-section, not becoming abruptly narrower at one end of tooth. Subgenus _Pleisothomomys_ p. 519 A´ Molars pear-shaped, not sub-crescent or ovate, in cross-section, crown becoming abruptly narrow at one end of tooth. Subgenus _Thomomys_ p. 520 Subgenus =Pleisothomomys= Gidley and Gazin 1933. _Pleisothomomys_ Gidley and Gazin, Jour. Mamm., 14:354, November 13. _Type._--_Pleisothomomys potomacensis_ Gidley and Gazin, 1933. _Chronologic range._--Late Pliocene (Hagerman local fauna, Idaho) to late Pleistocene. The latest records are from the fauna of Saber-tooth Cave, Florida, a late Pleistocene assemblage that probably was deposited in the Sangamon. The middle and late Pleistocene records are from the eastern United States, suggesting that the subgenus _Pleisothomomys_ was restricted to that region while the subgenus _Thomomys_ occupied the western United States and parts of Canada and México as it does today. _Description and Comparison._--Separated from subgenus _Thomomys_ only on basis of sub-crescentic shaped molars (only jaw fragments and isolated teeth known), seemingly a primitive feature of the genus. This dental structure continued into the late Pleistocene; none of the Recent species expresses this feature of the molars, although the molars of _Thomomys vetus_ of the late Pleistocene (Wisconsin deposits), referred to the subgenus _Thomomys_ on the basis of its alleged relationship to _Thomomys townsendii_ (see Davis, 1937:156-158), are less distinctly pear-shaped, and are more sub-crescentic, than in any other known species of the subgenus _Thomomys_. _Pleisothomomys_ Gidley and Gazin (_loc. cit._) was proposed as a genus but is here considered as of no more than subgeneric worth, and is recognized because of the apparent constancy of the sub-crescentic molars in the earlier members of the genus and in those populations of _Thomomys_ occurring in Pleistocene times in the eastern United States. _Referred species._--Three (all extinct): *_Thomomys gidleyi_ Wilson, 1933. Carnegie Inst. Washington Publ. 440:122, December. Type from Hagerman beds, late Pliocene, Idaho. *_Thomomys potomacensis_ Gidley and Gazin, 1933. Jour. Mamm., 14:354, November 13. Type from Cumberland Cave, middle and late Pleistocene, Maryland. *_Thomomys orientalis_ Simpson, 1928. Amer. Mus. Novit., 328:6, October 26. Type from Saber-tooth Cave, late Pleistocene, Florida. Subgenus =Thomomys= Wied-Neuwied 1839. _Thomomys_ Wied-Neuwied, Nova Acta Phys.-Med. Acad. Caesar. Leop. Carol., 19(1):377. 1903. _Megascapheus_ Elliot, Field Columb. Mus., Publ. 76, Zool. Ser., 3 (11):190, July 25. Type: _Diplostoma bulbivorum_ Richardson, from Columbia River, probably near Portland, Oregon. _Type._--_Thomomys rufescens_ Wied-Neuwied, 1839. _Chronologic range._--Early Pleistocene (Broadwater-Lisco local fauna, Nebraska) to Recent. Numerous records, mostly isolated teeth, from nearly all stratigraphic levels of the Pleistocene (for details, see account of fossil record). _Description._--Molars pear-shaped in cross-section, becoming abruptly narrow at one end of the tooth. The teeth of the late Pleistocene species _Thomomys vetus_ are less distinctly pear-shaped than other referred species (see remarks in the description of the subgenus _Pleisothomomys_). Essentially on the basis of its significantly larger size and details of the skull, Elliott (1903:190) proposed subgeneric recognition of _Thomomys bulbivorus_ and described the subgenus _Megascapheus_ to include it. Also the molars of _Thomomys bulbivorus_ usually have a small enamel plate, both above and below, bordering the persistent inflection on the protomere end of the tooth; each lateral plate is isolated from the transverse plates on the anterior and posterior walls of the tooth. In my opinion these features do not warrant subgeneric recognition; however, these characters do distinctly separate _Thomomys bulbivorus_ from other groups of species, and the character of the molars suggests retention of a primitive trait. Therefore, I propose that the unique structure of this species be recognized by setting it apart in the _bulbivorus_ species-group. _Referred species._--Ten species, three extinct, placed in three species-groups (the numerous subspecies of this genus are listed in Miller and Kellogg, 1955:276-332, and Hall and Kelson, 1959:412-447). _bulbivorus_ species-group _Thomomys bulbivorus_ (Richardson, 1829). Fauna Boreali-Americana, 1:206. Type from Columbia River, probably near Portland, Oregon. _umbrinus_ species-group *_Thomomys scudderi_ Hay, 1921. Proc. U. S. Nat. Mus., 49:614. Type from Fossil Lake beds, late Pleistocene, Oregon. _Thomomys umbrinus_ (Richardson, 1829). Fauna Boreali-Americana, 1:202. Type from southern México, probably near Boca de Monte, Veracruz. _Thomomys bottae_ (Eydoux and Gervais, 1836). Mag. de Zool., Paris, 6:23. Type from coast of California, probably near Monterey. *_Thomomys vetus_ Davis, 1937. Jour. Mamm., 18:156, May 12. Type from Fossil Lake beds, late Pleistocene, Oregon. _Thomomys townsendii_ (Bachman, 1839). Jour. Acad. Nat. Sci. Philadelphia, 8:105. Type probably from near Nampa, Canyon Co., Idaho (erroneously given as "Columbia River"). _talpoides_ species-group *_Thomomys microdon_ Sinclair, 1905. Bull. Dept. Geol. Univ. California, 4:145-161. Type from Potter Creek Cave, late Pleistocene, California. _Thomomys monticola_ J. A. Allen, 1893. Bull. Amer. Mus. Nat. Hist., 5:48, April 28. Type from Mt. Tallac, 7500 ft., El Dorado Co., California. _Thomomys talpoides_ (Richardson, 1828). Zool. Jour., 3:518. Type locality fixed at near Fort Carlton (Carlton House), Saskatchewan River, Saskatchewan, Canada. _Thomomys mazama_ Merriam, 1897. Proc. Biol. Soc. Washington, 11:214, July 15. Type from Anna Creek, 6000 ft., near Crater Lake, Mt. Mazama, Klamath Co., Washington. Tribe GEOMYINI, new tribe _Genotype._--_Geomys_ Rafinesque, 1817. _Chronologic and geographic range._--Known from late middle Pliocene deposits to Recent. The range of living members extends from extreme southern Manitoba and the southeastern United States south to southern Panamá, and probably northern Colombia, South America. _Diagnosis._--Size small to large (condylobasal length of skull 33.0 to 73.0 in adults, including both sexes); sexual dimorphism marked, sometimes strongly, females being smaller than males, especially in cranial dimensions; upper incisors invariably grooved, number and position of grooves varying according to genus; cheek teeth high-crowned and ever-growing, except in one primitive genus (_Pliogeomys_); all three lower molars and M1 and M2 monoprismatic, and elliptical in cross-section in final stages of wear (teeth of young, subadult, and adult animals); primitive biprismatic patterns (as known from Recent specimens) occurring only in pre-final stages of wear (teeth of juveniles only); biprismatic patterns of lower molars as in _Dikkomys_, and upper molars as in _Pliosaccomys_ (for detailed description of these patterns, see account beyond of the phylogeny of the Geomyinae); m3 becoming monoprismatic, anteroposteriorly compressed and elliptical in cross-section like m1 and m2, but M3 remaining, with rare exceptions (see accounts of _Geomys_ and _Pappogeomys_ beyond), at least partially biprismatic throughout life, having one or both lateral inflections usually persisting (with exceptions) and developing various occlusal shapes (subtriangular, elongate, obcordate, suborbiculate, or quadriform) but never elliptical. Enamel of cheek teeth reduced to interrupted plates, with exception of p4 in _Pliogeomys_; plate on posterior wall of P4 variable, occurring completely across posterior surface in primitive members, but progressively reduced to lingual side only or completely lost in modern genera (see generic accounts beyond for detailed description); both anterior and posterior plates usually retained in M1 and M2, posterior plate sometimes reduced to lingual side or completely lost (as in _Pappogeomys_) but anterior plate always completely retained; M3 usually having three plates, one anterior and two lateral; posterior plate wanting (sometimes lingual plate moved to posterior position); plates retained completely across posterior walls of all lower cheek teeth with no reduction, but anterior plates of m1-3 always lacking, except in primitive genus _Pliogeomys_ (only Geomyini having both anterior and posterior enamel plates on lower molars). Skull primitively generalized, but becoming specialized towards either dolichocephaly (_Orthogeomys_) or platycephaly (_Pappogeomys_) in two modern genera; skull highly specialized for fossorial life; mandible stout and deep, angular process being high and diverging laterally at right angles to ramus; masseteric ridge and fossa weakly developed in primitive members, becoming well developed and massive in modern genera; basitemporal fossa absent in primitive forms (_Pliogeomys_ and early members of _Zygogeomys_); pelage usually soft, but harsh and hispid in some genera; forefeet broad and massive, claws long and stout for digging; body form remarkably fossorial. The tribe Geomyini includes the most highly specialized members of the subfamily Geomyinae. Key to the Genera of the Tribe Geomyini A Cheek teeth rooted; p4 with uninterrupted enamel loop; enamel plates on both anterior and posterior walls of m1 and m2; masseteric ridge weakly developed, low, not massive. Genus _Pliogeomys_ p. 522 A´ Cheek teeth rootless, ever-growing; p4 with enamel investment interrupted at ends of columns, consequently, forming four isloted plates; enamel plate retained only on posterior wall of m1 and m2, anterior wall without trace of enamel (except rarely in pre-final stage of wear in _Geomys tobinensis_ of middle Pleistocene); masseteric crest strongly developed and massive. B Enamel plate on posterior wall of P4, but usually restricted to lingual end of tooth (usually absent in subgenus _Orthogeomys_ of genus _Orthogeomys_); M3 conspicuously bicolumnar, longer than wide owing to elongation of posterior loph. C Upper incisor bisulcate; skull generalized; rostrum relatively narrow; length of labial enamel plate of M3 decidedly less than length of lingual plate; pelage soft and thick. Genus _Zygogeomys_ p. 523 C´ Upper incisor unisulcate; skull strongly dolichocephalic; rostrum remarkably broad and massive; length of lingual plate of M3 approximately equal to, or greater than, length of labial plate; pelage harsh, often hispid and scant. Genus _Orthogeomys_ p. 528 B´ Posterior wall of P4 without trace of enamel; M3 not strongly bicolumnar, having shallow re-entrant fold on labial side, and crown no longer than wide owing to shortness of posterior loph. D Upper incisor bisulcate; skull generalized; both anterior and posterior walls of M1 and M2 having complete enamel plates. Genus _Geomys_ p. 525 D´ Upper incisor unisulcate; skull generalized or tending towards platycephaly; enamel plate on posterior wall of M1 usually reduced to lingual side or absent (complete only in one species, _Pappogeomys bulleri_); enamel plate on posterior wall of M2 also absent in advanced species (subgenus _Cratogeomys_). Genus _Pappogeomys_ p. 532 Genus =Pliogeomys= Hibbard 1954. _Pliogeomys_ Hibbard, Michigan Acad. Sci., Arts and Letters, 39:353. _Genotype._--_Pliogeomys buisi_ Hibbard, 1954, from Buis Ranch local fauna (middle Pliocene), Beaver County, Oklahoma. _Chronologic range._--Latest Middle Pliocene, known only from the highest part of the Hemphillian mammalian fauna (Buis Ranch local fauna, Oklahoma). Professor Hibbard informs me (personal communication) that he found the type, a right ramus, lying on the surface near the base of the fossil beds. The isolated teeth of small geomyids from the Saw Rock Canyon local fauna (see Hibbard, 1953:392) may also be referable to this genus. The Saw Rock Canyon local fauna may also be middle Pliocene in age but is considered to be from the later part of the late Pliocene, and, therefore, somewhat younger than the Buis Ranch local fauna (Hibbard, _op. cit._:342). _Description and discussion._--The size of members of this small genus of the Geomyinae is about the same as in smaller adults of _Geomys bursarius_. According to Hibbard (_op. cit._:353), the holotype is smaller than specimens from the Rexroad local fauna referred to _Geomys quinni_ and larger than specimens referred to _Zygogeomys_ cf. _minor_. The cheek teeth are rooted, and the crowns are as high as those of living geomyids. The upper incisor is bisulcate, and the inner groove is fine and indistinct in places. Of the molariform dentition only the lower premolar and first two lower molars are known. The enamel investment of p4 is complete, and would not be subject to interruption at any stage of wear; the two prisms are joined at their mid-points, and the isthmus of dentine is relatively broad (as in _Pliosaccomys_) when compared with modern pocket gophers of this tribe. Also, the re-entrant folds, rather than having parallel sides, diverge broadly to the sides. The divergence is especially noticeable in the labial fold. The lower deciduous premolar would have formed essentially the same enamel pattern with wear as observed in _Nerterogeomys_ [= _Zygogeomys_] cf. _minor_ (see Hibbard, 1954:fig. 5, A and B) and _Pliosaccomys dubius_ (see Wilson, 1936; pl. 1, fig. 1). Each molar is a single column in the final stages of wear; pre-final stages are unknown. Anterior and posterior enamel plates are present on m1 and m2 (m3 has not been recovered). The dentine tracts of m1 are exposed over a relatively wide surface; therefore, the enamel plates are distinctly separated. The tracts of dentine of m2 are much narrower than in m1 and the enamel plates are barely separated at the anterolateral margin of the tooth. Possibly the enamel band of m2 was continuous in an earlier stage of wear. The mandible is stout and its general construction not unlike that in modern geomyines. The capsule at the base of the angular process that receives the terminal end of the lower incisor is well developed. The base of the angular processes is preserved, and suggests that the process was short and decidedly smaller than in living examples of the tribe. The masseteric ridge is distinct but weakly developed, and not at all massive as in living pocket gophers. The mental foramen is immediately anterior, and slightly ventral, to the anterior extension of the crest. The basitemporal fossa is absent as such, but its position is marked by a slight depression. _Specimens examined._--Two rami; nos. 29147 (holotype) and 33446; several isolated teeth 30194 and 30195, including an upper incisor and a dp4 (deciduous lower premolar), all from Univ. Michigan Mus. Paleo. _Referred species._--One. *_Pliogeomys buisi_ Hibbard, 1954. Papers Michigan Acad. Sci., Arts, and Letters, 39:353. Type from Buis local fauna, latest middle Pliocene, Beaver County, Oklahoma. Genus =Zygogeomys= Merriam 1895. _Zygogeomys_ Merriam, N. Amer. Fauna, 8:195, January 31. 1942. _Nerterogeomys_ Gazin, Proc. U. S. Nat. Mus., 92:507 (type, _Geomys persimilis_ Hay, 1927). _Type._--_Zygogeomys trichopus_ Merriam, 1895, from Nahuatzen, Michoacán. _Chronologic range._--Late Pliocene (Benson and Curtis Ranch local faunas, Arizona, and ?Rexroad Formation, Kansas) to Recent. _Description and discussion._--The size is small to medium for the subfamily Geomyinae. This genus is distinguished principally by the retention of primitive features. In the living species, the skull is generalized, rather than specialized toward either extreme dolichocephaly or platycephaly. The angular process is short, barely exceeding the lateral extensions of the mastoid process of the squamosal. The rostrum is remarkably narrow in relation to its length. The jugal is reduced and displaced ventrally, causing the maxillary arm of the zygomata to articulate with the squamosal arm of the zygomata along the dorsal border of the zygomatic arch (a feature observed also in _Orthogeomys cherriei costaricensis_). The upper incisor, recovered in material from the late Pliocene and middle Pleistocene, is bisulcate as in the genus _Geomys_ and the primitive genus _Pliogeomys_. The enamel plate across the posterior wall of P4 is either complete (late Pliocene to late Pleistocene) or restricted to the lingual half of the tooth (always restricted in living species). The Pliocene specimens of the Rexroad local fauna referred to _Nerterogeomys_ cf. _minor_ by Hibbard (1950:138-139) are exceptional. In these specimens the length and position of the posterior enamel plate is variable; however, all but one specimen had persistant enamel. Evidently, in approximately 43 per cent of the specimens, a complete enamel blade was present (see Paulson, 1961:139), and in the others (except the one without any enamel) the plate was restricted to a small area of the ventral surface, usually on the lingual side of the loph. Hibbard suggested that the decrease in size of the plate, and its restriction to the lingual side, may be a function of age. Hence, most adults would be characterized by the reduced posterior plate on the upper premolar. Although age may be the important factor, intragroup variation cannot be ruled out. It is of interest to note that in all specimens from the Benson (type series of _P. minor_) and Curtis Ranch local faunas, the former of late Pliocene age and the latter of middle Pleistocene age, the enamel plates are complete on the posterior face of the upper premolar. As mentioned before, the specimens from Kansas may actually represent the transitional stages of the early evolution of _Geomys_ in which the posterior plate of P4 is entirely lost. The enamel pattern of p4 is like that in other members of the tribe (excepting the genus _Pliogeomys_). The re-entrant angles of P4 and p4 are widely open (obtuse) in the examples recovered from late Pliocene and middle Pleistocene deposits, representing retention of a trait that is primitive in the Geomyini (see account of phylogeny). M1 and M2 are elliptical in cross-section and each has an enamel plate on both the anterior and posterior surface. In the living species (_Z. trichopus_), the posterior enamel plate fails to reach the labial margin of the tooth and is restricted to the lingual two-thirds of the posterior surface; however, the enamel plates are complete in the late Pliocene species (_Z. minor_) and the middle Pleistocene species (_Z. persimilis_), being only slightly separated from the anterior plate by narrow tracts of dentine on the ends of the tooth. M3 is partly biprismatic in the living species, the two incompletely divided lophs being separated by a distinct outer sulcus. The posterior loph is elongated and forms a conspicuous heel paralleling the evolution of this trait in the genus _Orthogeomys_; therefore, the crown is longer than wide. The posterior part of the tooth is protected by two lateral enamel plates; of the two, the lingual plate is especially long and extends to the end of the heel. M3 has not been recovered in the Pliocene species, but in the middle Pleistocene species (_Z. persimilis_) M3 is subtriangular, no longer than wide, and the lateral inflections are weakly developed. The trend towards elongation of M3 evidently occurred in late Pleistocene evolution of the genus. All three of the inferior molars are elliptical, and only the posterior enamel plate is present (as in all other genera of the tribe except _Pliogeomys_). The masseteric ridge of the mandible is well developed. In the late Pliocene species _Z. persimilis_ and _Z. minor_ the mental foramen is directly beneath the anterior extension of the masseteric ridge, but in the living species, _Z. trichopus_, the foramen lies well anterior to the ridge. The basitemporal fossa in the living species is well developed and deep; in the Pliocene species it is usually distinct but shallow (late Pliocene specimens of _Z. minor_). _Referred species._--Three (two extinct and one living; the last has two subspecies): *_Zygogeomys minor_ (Gidley), 1922. U. S. Geol. Surv. Prof. Paper, 131:123, December 26. Type from Benson local fauna (late Pliocene), Cochise County, Arizona; also known from the Rexroad local fauna, Meade County, Kansas. *_Zygogeomys persimilis_ Hay, 1927. Carnegie Inst. Washington Publ., 136. Originally described by Gidley, 1922 (U. S. Geol. Surv. Prof. Papers, 131:123, December 26) as _Geomys parvidens_ which was preoccupied by _G. parvidens_ Brown, 1908. Type from Curtis Ranch local fauna (middle Pleistocene), Cochise County, Arizona. _Zygogeomys trichopus trichopus_ Merriam, 1895. N. Amer. Fauna, 8:196, January 31. Type from Nahuatzen, Michoacán. _Zygogeomys trichopus tarascensis_ Goldman, 1938. Proc. Biol. Soc. Washington, 51:211, December 23. Type from 6 mi. SE Pátzcuaro, 8,000 ft., Michoacán. Genus =Geomys= Rafinesque 1817. _Geomys_ Rafinesque, Amer. Monthly Mag., 2(1):45, November. 1817. _Diplostoma_ Rafinesque, Amer. Monthly Mag., 2(1):44-45, November. Included species: _Diplostoma fusca_ Rafinesque [= _Mus bursarius_ Shaw] and _Diplostoma alba_ Rafinesque [= _Mus bursarius_ Shaw] from the Missouri River region. 1820. _Saccophorus_ Kuhl, Beitr. Zool. und Vergl. Anat., pp. 65, 66. Type: _Mus bursarius_ Shaw, from upper Mississippi Valley. 1823. _Pseudostoma_ Say, Long's Expd. Rocky Mts., I, pp. 406. Type: _Pseudostoma bursaria_ [= _Mus bursarius_ Shaw], from upper Mississippi Valley. 1825. _Ascomys_ Lichtenstein, Abh. K. Akad. Wiss. Berlin (1822), p. 20., fig. 2. Type: _Ascomys canadensis_ Lichtenstein [= _Mus bursarius_ Say], probably from upper Mississippi Valley. 1944. _Parageomys_ Hibbard, Bull. Geol. Soc. Amer., 55:735, June. Type: _Parageomys tobinensis_ Hibbard, from Pleistocene, Cudahy (Tobin) local fauna, Russell Co., Kansas. _Type._--_Geomys pinetis_ Rafinesque, 1817, restricted to Screven County, Georgia, in region of the pines. _Chronologic range._--Late Pliocene faunas of Blancan age (Rexroad, Kansas, and Sand Draw, Nebraska, local faunas) to Recent. Reported from numerous Pleistocene deposits of all stratigraphic levels, especially from the Great Plains, where common today. _Description and discussion._--Pocket gophers of this genus are medium-sized geomyids; none is so small as the average-sized _Thomomys_. The skull is generalized and lacks the dolichocephalic and platycephalic specializations seen in the genera _Orthogeomys_ and _Pappogeomys_, respectively. _Geomys_ closely resembles _Zygogeomys_, but retains fewer of the primitive characters of the ancestral stock. At the same time, _Geomys_ has several specializations. Even so, a considerable amount of parallelism is evident in the phyletic trends of the two genera. The upper incisor of _Geomys_ is bisulcate as in _Pliogeomys_ and _Zygogeomys_; the deeper grove is medial and the shallower grove lies near the inner border of the tooth. The premolar, above and below, is bicolumnar; and two columns are joined at their mid-points (deep re-entrant angles separate the columns at the sides). A permanent enamel plate protects the anterior face of the anterior loph, and enamel bands outline each of the re-entrant folds. In p4 a complete enamel plate covers the posterior surface of the posterior loph. All of the enamel bands are interrupted by tracts of dentine, except in the initial stages of wear of the occlusal surface of the newly erupted tooth. For a short time in living _Geomys_, the enamel bands are continuous as observed in juveniles of _Geomys bursarius major_ (KU 5628, 8531, and 41540). But, the enamel cap is thin and the dentine tracts, which are high on the sides of the tooth, are soon revealed by a minimum of wear on the crown. Therefore, the adult, or final, pattern characterized by interrupted enamel plates emerges early in life and remains throughout the life of the individual. Evidence from fossil _Geomys_, especially from specimens from early and late Pleistocene deposits, suggests that the final adult pattern appears later, ontogenetically, than in Recent specimens. Some of the fossil premolars in initial stages of wear have continuous and uninterrupted bands of enamel. _Geomys quinni_ of the late Pliocene and early Pleistocene has the interrupted pattern seen in late Pleistocene and Recent _Geomys_. Also, in late Pliocene and early Pleistocene species, the re-entrant folds diverge laterally and form "open" angles. In later taxa (middle Pleistocene to Recent) the folds are compressed and parallel-sided, and the "open" folds are found only in the early stages of wear. The posterior enamel plate of P4 disappears in the final stages of wear as the interrupted enamel pattern is formed. In the late Pleistocene and Recent _Geomys_, the loss of the posterior plate occurs early in life, usually in the first phases of wear on the occlusal surface of the newly erupted tooth, but in fossils of _Geomys_ of corresponding ontogenetic age from the early and middle Pleistocene, the posterior plate is retained in some individuals until a later phase of wear, thereby delaying the appearance of the final pattern. Indeed, in five or fewer per cent of the individuals (see Paulson, 1961:138-139; and White and Downs, 1961:18) a vestige of enamel is retained throughout life or at least until late in adulthood. In _Geomys tobinensis_, for example, a thin, but transversely complete, plate of enamel occurs all the way down to the base of the loph (Paulson, _loc. cit._) and would persist throughout life. In _Geomys garbanii_, a vestige on the lingual side of the posterior surface of a fully adult specimen was noted by White and Downs (_loc. cit._). Vestiges of the posterior plate occur less frequently in living geomyids. Paulson (_loc. cit._) found a posterior plate in one of 75 specimens of _Geomys bursarius dutcheri_. A young (suture present between exoccipitals and supraoccipital) female of _Geomys pinetis austrinus_ (KU 23358) has a vestige of the posterior plate on the lingual side of the tooth as White and Downs (_loc. cit._) observed in a specimen of _Geomys garbanii_. The enamel, I suspect, tends to be thicker on the lingual than on the labial side of the loph and extends farther down the lingual surface in some individuals; therefore, wear on the occlusal surface erodes it down to the dentine more rapidly on the labial than on the lingual side. The tendency of enamel to be retained is a primitive feature. A lower molar of _Geomys_ is a single elliptical column, and enamel is restricted to the posterior surface as in _Zygogeomys_, _Orthogeomys_, and _Pappogeomys_. Paulson (_loc. cit._) found a thin enamel plate on the anterior surfaces of the lower molars in about five per cent of the individuals of _Geomys tobinensis_ from the Cudahy local fauna (middle Pleistocene, deposits of the late Kansan glaciation). An anterior plate is unknown in other members of the tribe Geomyini, except in the primitive genus _Pliogeomys_ of the middle Pliocene. Occurrence of the plate in _Geomys tobinensis_ is an atavistic trait. Primitive dental patterns occur occasionally in geomyids, as pointed out above, but the frequency of occurrence in _G. tobinensis_ is higher than would be expected. M1 and M2, like the lower molars, are elliptical in cross-section. Complete enamel plates on the anterior and posterior surfaces are separated by tracts of dentine on the sides of each tooth. M3 is usually suborbicular (sometimes subtriangular) in cross-section. The tooth is not especially elongated posteriorly and usually has no definite heel; therefore, it is not significantly longer than wide. Living species of _Geomys_ rarely have a well defined outer re-entrant fold on M3; less than 10 per cent of the individuals (and usually only one side in each individual in which it occurs) have it, although a shallow inconspicuous groove occurs more frequently. The biprismatic molar characteristic of the ancestral morphotype is less often found in _Geomys_ than in any other living member of the tribe Geomyini. The outer re-entrant fold and biprismatic pattern are more often present in the extinct species _Geomys garbanii_ of the Middle Pleistocene than in other species. Less than 24 per cent of the third upper molars in _Geomys garbanii_ lack a tract of the re-entrant fold and more than 38 per cent have a well developed outer fold (see White and Downs, 1961:13, 18). The bicolumnar pattern, although incomplete, would be clearly evident in those teeth having a well marked re-entrant fold; the pattern occurs less frequently in those teeth with no fold or only a slight one. M3 of geomyids is not usually recovered and, therefore, the occlusal pattern of M3 is unknown in most extinct kinds of _Geomys_. In Recent _Geomys_ the fold is more common in the eastern _pinetis_ species-group than in the western _bursarius_ species-group. The masseteric ridge on the outer side of the mandible is well developed in all species of the genus. The position of the mental foramen relative to the anterior part of the ridge varies with individuals and according to species. The basitemporal fossa is always present, but is shallower in the late Pliocene and Pleistocene species than in Recent species. The angular process is short. _Referred species._--The twelve species, five of which are extinct, are as follows: _quinni_ species-group *_Geomys quinni_ McGrew, 1944. Geol. Ser., Field Mus. Nat. Hist., 9 (546):49, January 20. Type from Sand Draw local fauna (late Pliocene), Brown County, Nebraska; also known from Broadwater-Lisco local faunas (early Pleistocene), Morrill and Garden counties, Nebraska, Deer Park local fauna (early Pleistocene), Meade County, Kansas. *_Geomys paenebursarius_ Strain, 1966. Bull. Texas Memorial Mus., 10:36. Type from Hudspeth local fauna (early Pleistocene), Hudspeth County, Texas. *_Geomys tobinensis_ Hibbard, 1944. Bull. Geol. Soc. Amer., 55:736. Type from Tobin local fauna (middle Pleistocene), Russell County, Kansas; also known from Cudahy local fauna (middle Pleistocene), Meade County, Kansas. *_Geomys garbanii_ White and Downs, 1961. Contrib. Sci., Los Angeles Co. Mus., 42:1-34, June 30. Type from Vallecito Creek local fauna (middle Pleistocene), San Diego County, California. *_Geomys bisulcatus_ Marsh, 1871. Amer. Jour. Sci., 3:121. Type from Loup River fossil beds, near Camp Thomas, Nebraska (probably late Pleistocene). _bursarius_ species-group *_Geomys parvidens_ Brown, 1908. Mem. Amer. Mus. Nat. Hist., 9:194. (An extinct subspecies of _Geomys bursarius_ according to White and Downs, 1961:6). Type from Conard Fissure local fauna (late Pleistocene), northern Arkansas. _Geomys bursarius_ (Shaw, 1800). Trans. Linn. Soc. London, 5:227. Type from somewhere in Upper Mississippi Valley, North America. _Geomys arenarius_ Merriam, 1895. N. Amer. Fauna, 8:139, January 31. Type from El Paso, El Paso County, Texas. _Geomys personatus_ True, 1889. Proc. U. S. Nat. Mus., 11:159, January 5. Type from Padre Island, Cameron County, Texas. _pinetis_ species-group _Geomys pinetis_ Rafinesque, 1806. Amer. Monthly Mag., 2 (1):45, November. Type locality restricted to Screven County, Georgia. _Geomys colonus_ Bangs, 1898. Proc. Boston Soc. Nat. Hist., 28:178, March. Type from Arnot Plantation, about 4 mi. W St. Marys, Camden County, Georgia. _Geomys cumberlandius_ Bangs, 1898. Proc. Boston Soc. Nat. Hist., 28:180, March. Type from Stafford Place, Cumberland Island, Camden County, Georgia. _Geomys fontanelus_ Sherman, 1940. Jour. Mamm., 21:341, August 13. Type from 7 mi. NW Savannah, Chatham County, Georgia. Genus =Orthogeomys= Merriam 1895. _Orthogeomys_ Merriam, N. Amer. Fauna 8:172, January 31. 1895. _Heterogeomys_ Merriam, N. Amer. Fauna 8:179, January 31 (type, _Geomys hispidus_ Le Conte, 1862). 1895. _Macrogeomys_ Merriam, N. Amer. Fauna 8:185, January 31 (type, _Geomys heterodus_ Peters, 1865). _Type._--_Geomys scalops_ Thomas, 1894, from Tehuantepec, Oaxaca, México. _Chronologic range._--Late Pleistocene Wisconsin deposits (San Josecito Cave local fauna, Nuevo León, México) to Recent. _Description and discussion._--Species of this genus are of medium to large size. The skull is strongly dolichocephalic in most species; the posterior part of the skull is especially narrow. The angular processes are remarkably short, especially in relation to the length of the mandible. The nasals and rostrum are relatively broad and heavy. The pelage is coarse, and often hispid. In some species the hairs are so sparsely distributed that the body appears almost naked, and none has so dense a covering of hair as do other genera. The genus occurs entirely within the tropical life-zones, and most of the external features seem to be associated with adaptation to tropical conditions. The upper incisor is unisulcate; the sulcus is usually near the inner border of the tooth, but in some species (subgenus _Orthogeomys_) it is more medial, and in a few individuals with an extremely wide groove the outer lip of the sulcus may actually reach the middle of the tooth. The groove is compressed or open. The premolar is a double column united at the mid-point. The two prisms are of approximately equal size, and the lateral re-entrant folds are so compressed that their sides are parallel. Enamel plates cover the anterior surface and border the re-entrant angles in both upper and lower premolars. As in other members of the tribe, the lower premolar has a fourth enamel plate on the posterior surface of the posterior lophid. In the upper premolar, the enamel plate is reduced to a narrow blade on the lingual side of the loph as in the living species of the genus _Zygogeomys_. In the subgenus _Orthogeomys_ the posterior plate is usually absent, and otherwise is narrow and near the lingual border of the tooth. Each lower molar, in the final stage of wear, consists of a single elliptical column having an enamel plate only on the posterior surface. The first and second upper molars are single elliptical columns having one enamel plate on the anterior surface and another on the posterior surface. The plates are separated by a tract of dentine on each side of the tooth. The third upper molar is partly bilophodont, and the two lophs are separated by a deep outer re-entrant fold. In many of the species an inner re-entrant fold also is retained, but in the adult tooth it is less distinct than the outer. In all of the species the posterior loph is long and forms a conspicuous heel; consequently the crown is significantly longer then wide. Moreover, the posterior loph has an enamel plate on each side. The labial plate always borders the outer re-entrant fold, and in the subgenus _Orthogeomys_ is infrequently separated into two small plates. The mandible is relatively long. Its masseteric ridge is well developed and massive. The basitemporal fossa is usually deep and well defined; it tends to be shallow in the subgenus _Orthogeomys_, and in young individuals is hardly more than a slight depression. Key to the Subgenera of _Orthogeomys_ A Frontal wide and greatly inflated; no interorbital constriction; enamel plate on posterior wall of P4 usually absent, although sometimes having small plate, restricted to lingual end of wall. Subgenus _Orthogeomys_ p. 529 A´ Frontal narrow and not greatly inflated; interorbital region decidedly constricted; enamel plate on posterior wall of P4 always present but short and restricted to lingual end of wall. B Anterior margin of mesopterygoid fossa even with plane of posterior wall of M3; postorbital bar weakly developed; anteroposterior occlusal length of M3 equal to, or less than, combined length of M1 and M2. Subgenus _Heterogeomys_ p. 530 B´ Anterior margin of mesopterygoid fossa decidedly behind plane of posterior wall of M3; postorbital bar strongly developed; anteroposterior occlusal length of M3 more than combined length of M1 and M2. Subgenus _Macrogeomys_ p. 531 Subgenus =Orthogeomys= Merriam 1895. _Orthogeomys_ Merriam, N. Amer. Fauna, 8:172, January 31. _Type._--_Geomys scalops_ Thomas, 1894, from Tehuantepec, Oaxaca, México. _Chronologic range._--Known only from the Recent. _Description._--Skull elongated and narrow (many skulls of nearly uniform breadth throughout), being extreme in dolichocephalic specializations; mandibles long and narrow, rami not spreading laterally, being more nearly parallel-sided than in other subgenera; angular processes short; breadth across zygomata not significantly exceeding breadth across mastoid processes (in many skulls considerably less); interorbital area remarkably broad, lacking deep constriction; frontals between orbits greatly inflated laterally, postorbital prominence inconspicuous; mesopterygoid fossa extending to level of posterior margin of M3; I having sulcus broader than in other subgenera, mostly on inner half of anterior surface but sometimes overlapping mid-line; enamel plate lacking from posterior wall of P4, rarely retaining narrow vestige near lingual border of posterior loph; M3 having distinct heel, bicolumnar pattern with inner re-entrant fold usually minute, occlusal length less than in other subgenera, length less than combined lengths of M1-2; hair generally coarse, sometimes hispid, sparse, in lowland forms, so sparse as to impart appearance of nakedness. _Referred species and subspecies._--Fourteen taxa: _Orthogeomys grandis alleni_ Nelson and Goldman, 1930. Jour. Mamm., 11:156, May 9. Type from near Acapulco, 2000 ft., Guerrero. _Orthogeomys grandis annexus_ Nelson and Goldman, 1933. Proc. Biol. Soc. Washington, 46:195, October 26. Type from Tuxtla Gutierrez, 2600 ft., Chiapas. _Orthogeomys grandis carbo_ Goodwin, 1956. Amer. Mus. Novit., 1757:5, March 8. Type from Excurano, 2500 ft., Cerro de San Pedro, 20 km. W Mixtequilla, Oaxaca. _Orthogeomys grandis felipensis_ Nelson and Goldman, 1930. Jour. Mamm., 11:157, May 9. Type from Cerro San Felipe, 10 mi. N Oaxaca, Oaxaca. _Orthogeomys grandis huixtlae_ Villa, 1944. Anal. Inst. Biol. Univ. Nac. México, 15:319. Type from Finca Lubeca, 12 km. NE Huixtla, 850 m., Chiapas. _Orthogeomys grandis grandis_ (Thomas, 1893). Ann. Mag. Nat. Hist., ser. 6, 12:270, October. Type from Dueñas, Guatemala. _Orthogeomys grandis latifrons_ Merriam, 1895. N. Amer. Fauna, 8:178, January 31. Type from Guatemala, exact locality unknown. _Orthogeomys grandis nelsoni_ Merriam, 1895. N. Amer. Fauna, 8:176, January 31. Type from Mt. Zempoaltepec, 8000 ft., Oaxaca. _Orthogeomys grandis pluto_ Lawrence, 1933. Proc. New England Zool. Club, 13:66, May 8. Type from Cerro Cantoral, north of Tegucigalpa, Honduras. _Orthogeomys grandis scalops_ (Thomas, 1894). Ann. Mag. Nat. Hist., ser. 6, 13:437, May. Type from Tehuantepec, Oaxaca. _Orthogeomys grandis soconuscensis_ Villa, 1949. Anal. Inst. Biol. Univ. Nac. México, 19:267, April 8. Type from Finca Experanza, 710 m., 45 km. (by road) NW Huixtla, Chiapas. _Orthogeomys grandis guerrerensis_ Nelson and Goldman, 1930. Jour. Mamm., 11:158, May 9. Type from El Limón, in valley of Río de las Balsas approximately 20 mi. NW La Unión, Guerrero. _Orthogeomys cuniculus_ Elliot, 1905. Proc. Biol. Soc. Washington, 18:234, December 9. Type from Zanatepec, Oaxaca. _Orthogeomys pygacanthus_ Dickey, 1928. Proc. Biol. Soc. Washington, 41:9, February 1. Type from Cacaguatique, 3500 ft., Dept. San Miguel, El Salvador. Subgenus =Heterogeomys= Merriam 1895. _Heterogeomys_ Merriam, N. Amer. Fauna, 8:179, January 21. _Type._--_Geomys hispidus_ Le Conte, 1852, from near Jalapa, Veracruz. _Chronologic range._--Late Pleistocene, Wisconsin deposits (San Josecito Cave local fauna, Nuevo León) to the Recent. _Description._--Skull dolichocephalic (less so than in the other subgenera); zygomata more widely spreading than in _Orthogeomys_; ramus and angular process short; interorbital area noticeably constricted; frontals between orbits neither exceptionally broad or inflated; mesopterygoid fossa extending to level of posterior margin of M3; I having sulcus on inner third of anterior surface usually narrower than in subgenus _Orthogeomys_; enamel plate on posterior wall of P4 restricted to lingual half of loph; M3 distinctly biprismatic, posterior loph usually circumscribed by shallow inner re-entrant fold and outer deep fold well developed in all members of genus; posterior loph forming conspicuous heel longer than in subgenus _Orthogeomys_; occlusal length equal to or slightly less than combined lengths of M1-2; hair coarse and hispid but never so sparse as to impart appearance of nakedness. _Referred species and subspecies._--Eleven taxa: *_Orthogeomys onerosus_ (Russell, 1960). Univ. Kansas Publ., Mus. Nat. Hist., 9 (21):544, January 14. Type from San Josecito Cave local fauna, Upper Pleistocene, Nuevo León. _Orthogeomys hispidus cayoensis_ (Burt, 1937). Occ. Papers Mus. Zool., Univ. Michigan, 365:1, December 16. Type from Mountain Pine Ridge, 12 mi. S El Cayo, British Honduras. _Orthogeomys hispidus chiapensis_ (Nelson and Goldman, 1929). Proc. Bio. Soc. Washington, 42:151, March 30. Type from Tenejapa, 16 mi. NE San Cristobal, Chiapas. _Orthogeomys hispidus concavas_ (Nelson and Goldman, 1929). Proc. Biol. Soc. Washington, 42:148, March 30. Type from Pinal de Amoles, Querétaro. _Orthogeomys hispidus hispidus_ (Le Conte, 1852). Proc. Acad. Nat. Sci. Philadelphia, 6:158. Type from near Jalapa, Veracruz. _Orthogeomys hispidus latirostris_ (Hall and Alvarez, 1961). Anal. Escuela Nac. Ciencias Biol., 10:121, December 20. Type from Hacienda Tamiahua, Cabo Rojo, Veracruz. _Orthogeomys hispidus negatus_ (Goodwin, 1953). Amer. Mus. Novit., 1620:1, May 4. Type from Gomez Ferias, 1300 ft., about 45 mi. S Ciudad Victoria, 10 km. W Pan American Highway, Tamaulipas. _Orthogeomys hispidus tehuantepecus_ (Goldman, 1939). Jour. Washington Acad. Sci., 29:174, April 15. Type from mountains 12 mi. NW Santo Domingo and about 60 mi. N Tehuantepec, 1600 ft., Oaxaca. _Orthogeomys hispidus torridas_ (Merriam, 1895). N. Amer. Fauna, 8:183, January 31. Type from Chichicaxtle, Veracruz. _Orthogeomys hispidus yucatanensis_ (Nelson and Goldman, 1929). Proc. Biol. Soc. Washington, 42:150, March 30. Type from Campeche, Campeche. _Orthogeomys lanius_ (Elliot, 1905). Proc. Biol. Soc. Washington, 18:235, December 9. Type from Xuchil, Veracruz. Subgenus =Macrogeomys= Merriam 1895. _Macrogeomys_ Merriam, N. Amer. Fauna, 8:185, January 31. _Type._--_Geomys heterodus_ Peters, 1865, from Costa Rica, exact locality unknown. _Chronologic range._--Known only from the Recent. _Description._--Skull dolichocephalic in varying degree (overlapping subgenera _Orthogeomys_ and _Heterogeomys_ in this respect); mandibles elongated, not spreading far laterally; angular processes decidedly short; breadth across zygomata in no instance significantly exceeding mastoid breadth; interorbital area strongly constricted; frontals between orbits slightly inflated laterally (especially in forms having more strongly dolichocephalic skulls); postorbital prominence conspicuous; anterior margin of mesopterygoid fossa terminating well behind M3; I having narrow and deep sulcus entirely on inner third of anterior surface; enamel plate on posterior wall of P4 restricted to inner half of loph; M3 bilophodont (outer and inner re-entrant folds each circumscribing a loph), posterior loph remarkably elongated and forming pronounced heel, length of crown more than combined lengths of M1-2; hair wooly in some individuals, harsh in others but seldom hispid, never so sparse as in subgenus _Orthogeomys_; some species having white markings, especially on lumbar region and head. _Referred species and subspecies._--Eleven taxa: _Orthogeomys heterodus cartagoensis_ (Goodwin, 1943). Amer. Mus. Novit., 1227:2, April 22. Type from Paso Ancho, Province Cartago, Costa Rica. _Orthogeomys heterodus dolichocephalus_ (Merriam, 1895). N. Amer. Fauna, 8:189, January 31. Type from San José, Costa Rica. _Orthogeomys heterodus heterodus_ (Peters, 1865). Monatsb. preuss. Acad. Wiss., Berlin, 1865:177. Type from Costa Rica, exact locality unknown. _Orthogeomys cavator nigrescens_ (Goodwin, 1943). Amer. Mus. Novit., 1227:3, April 22. Type from El Muneco (Río Navarro), 10 mi. S Cartago, 4000 ft., Province Cartago, Costa Rica. _Orthogeomys cavator pansa_ (Bangs, 1902). Bull. Mus. Comp. Zool., 39:44, April. Type from Bogava (= Bugaba), 600 ft., Chiriquí, Panamá. _Orthogeomys dariensis_ (Goldman, 1912). Smithsonian Misc. Coll., 60(2):8, September 20. Type from Cana, 2000 ft., mountains of eastern Panamá. _Orthogeomys underwoodi_ (Osgood, 1931). Field Mus. Nat. Hist., Publ. 295, Zool. Ser., 185:143, Aug. 3. Type from Alto de Jabillo Pirris, between San Geronimo and Pozo Azul, western Costa Rica. _Orthogeomys cherriei carlosensis_ (Goodwin, 1943). Amer. Mus. Novit., 1227:3, April 22. Type from Cataratos, San Carlos, Alajuela, Costa Rica. _Orthogeomys cherriei cherriei_ (J. A. Allen, 1893). Bull. Amer. Mus. Nat. Hist., 5:337, December 16. Type from Santa Clara, Costa Rica. _Orthogeomys cherriei costaricensis_ (Merriam, 1895). N. Amer. Fauna, 8:192, January 31. Type from Pacuare, Costa Rica. _Orthogeomys matagalpae_ (J. A. Allen, 1910). Bull. Amer. Mus. Nat. Hist., 28:97, April 30. Type from Peña Blanca, Matagalpa, Nicaragua. Genus =Pappogeomys= Merriam 1895. _Pappogeomys_ Merriam, N. Amer. Fauna, 8:145, January 31. 1895. _Cratogeomys_ Merriam, N. Amer. Fauna, 8:150, January 31. Type: _Geomys merriami_ Thomas. 1895. _Platygeomys_ Merriam, N. Amer. Fauna, 8:162, January 31. Type: _Geomys gymnurus_ Merriam; Hooper, Jour. Mamm., 27:397, November 25, 1946. _Type._--_Geomys bulleri_ Thomas, 1892, from near Talpa, west slope Sierra de Mascota, 8500 ft. (actually about 5000 ft.), Jalisco. _Chronologic range._--Late Pliocene, from deposits of early Blancan age (Benson local fauna, Arizona) to the Recent. However in the Pleistocene, only late Pleistocene records are known, and _Pappogeomys_ has not been found in early (late Blancan) or middle (Irvingtonian) Pleistocene local faunas. Presumably the genus was restricted to México during the Pleistocene until post-Wisconsin time. _Description and discussion._--The size ranges from as little as in the smaller kinds of _Thomomys_ to the maximum attained in the subfamily and matched elsewhere perhaps in only a few of the larger subspecies of _Orthogeomys grandis_. Depending on the species and subgenus, the form of the skull varies from generalized to specialized. The generalized skulls are short and not especially narrow; the zygomatic arches are spread laterally so far that the breadth across them exceeds the breadth across the mastoid processes. The most specialized skulls are platycephalic and the breadth across the mastoid processes equals or exceeds the breadth across the zygomatic arches (even so, the zygomatic arches are still relatively widespread). In correlation with the great breadth of the posterior part of the cranium, the rami of the mandibles diverge widely posteriolaterally and the angular processes are remarkably elongated. The rostrum is moderately broad in most species, but not nearly so broad and heavy as in _Orthogeomys_. The single deep, median sulcus on the outer surface of the upper incisor is slightly displaced to the inner side of the tooth. The posterior surface of P4 lacks enamel (small vestige found on lingual end of posterior wall in only two adult individuals--UA 3260 and KU 100442, of the subgenus _Pappogeomys_); the other three plates are fully developed as usual. The p4 is provided with four fully developed enamel plates, in the pattern characteristic of the tribe Geomyini. In the p4 of the late Pliocene species (_P. bensoni_) the re-entrant angles are open (obtuse), a trait that is evidently primitive in the Geomyini. All three lower molars are single, compressed, elliptical columns with enamel on only the posterior surfaces. M1 and M2 are also elliptical in cross-section and decidedly anteroposteriorly compressed, like the lower molars. Nevertheless, the enamel pattern is variable; enamel plates may be retained completely across both the anterior and posterior walls of M1 and M2 or only the anterior plate may be retained without reduction and the posterior plate may be reduced so that only a vestige is retained on the lingual fourth of the tooth or the posterior plate may be completely lost. M3 tends to remain at least incompletely bilophodont by reason of retaining a permanent labial re-entrant fold in most species (with exceptions in _Pappogeomys bulleri_ and some old adults of _P. castanops_). Primitively the occlusal surface of M3 is subtriangular (subgenus _Pappogeomys_), but in the _castanops_ species-group of the advanced subgenus _Cratogeomys_, the posterior loph usually is reduced and the occlusal surface is quadriform or obcordate. Curiously, the trend towards reduction of the posterior loph is reversed in one subspecies (_P. merriami fulvescens_) and, the loph has elongated into a pronounced heel in some specimens, resembling the condition in _Orthogeomys_. The entire range of variation occurs in _P. m. fulvescens_. The subtriangular pattern is retained in the most specialized species of _Cratogeomys_ where that pattern is associated with extreme platycephaly in the _gymnurus_ species-group. In most species the posterior loph supports two lateral plates, the outer one always bordering the labial re-entrant fold. In _Pappogeomys bulleri_ and in the _castanops_ species-group, the outer re-entrant fold of M3 tends to be obsolete, and the tooth becomes quadriform or suborbiculate in some individuals and loses the bilophodont pattern that characterizes other species. The lingual enamel plate is displaced to the posterior surface of the tooth, and one or both plates may disappear with advancing age. Consequently, only the anterior enamel plate remains in some adults, and constitutes the maximum degree of reduction of enamel on M3 in the Geomyinae. In many adults of _Pappogeomys bulleri_, the enamel investment of the posterior loph is complete and the two lateral plates are connected, without interruption around the posterior apex of the tooth, evidently representing the retention of a primitive character of the ancestral lineage. The m3 of _P. bensoni_ from the late Pliocene is distinguished by minute lateral inflections suggesting the primitive biprismatic pattern. Also the posterior enamel plates of m1 and m2 are remarkably long, extending around the ends of the tooth. The associated upper incisor was unisulcate as in the modern species, and the basitemporal fossa of the mandible is well developed and deep. The lower jaw is stout and relatively short. The masseteric ridge is well developed and has an especially thick crest. The basitemporal fossa is deep. In most living species, the pelage is soft and dense, but in one species, _Pappogeomys fumosus_, the hairs are coarse and hispid somewhat as in _Orthogeomys_. Key to the Subgenera of _Pappogeomys_ A Enamel plates completely developed across posterior walls of M1 and M2, except in one species (_P. alcorni_) having enamel restricted to lingual fourth in M1; sagittal crest lacking owing to impressions of temporal muscles remaining separated (even in old adults); zygomata slender, and without platelike expansion at lateral angle. Subgenus _Pappogeomys_ p. 534 A´ Enamel lacking on posterior walls of M1 and M2; pronounced sagittal crest developed in adults of both sexes by union of temporal impressions at middorsal line; zygomata stout and wide, with lateral angle expanded into broad plate. Subgenus _Cratogeomys_ p. 535 Subgenus =Pappogeomys= Merriam 1895. _Pappogeomys_ Merriam, N. Amer. Fauna, 8:145, January 31. _Type._--_Geomys bulleri_ Thomas, 1892, from near Talpa, west slope Sierra de Mascota, 8500 ft. (actually about 5000 ft.), Jalisco. _Chronologic range._--Late Pliocene (Benson local fauna, Arizona) to Recent, but no specimens known from Pleistocene. _Description._--Small, approximately same size as small subspecies of _Thomomys umbrinus_ but forefeet larger and claws longer; skull of generalized shape, broad, relatively short, smoothly rounded, not especially compressed dorso-ventrally; zygomatic breadth great but not exceeding mastoid breadth; zygomata relatively slender for geomyid and lacking platelike expansions at lateral angles; rostrum relatively narrow; sagittal crest lacking, owing to impressions of temporal muscles remaining separated; angular process of mandible not especially elongated; enamel plates extending completely across posterior wall of M1 and M2, except in one species, _P. alcorni_, where posterior plate of M1 remains only on lingual fourth of posterior wall (remainder of plate lacking); with wear, plates sometimes exceptionally thin completely across posterior face of M2 and especially M1 in a few individuals of _P. bulleri_ much as Paulson (1961:138-139) describes in extinct _Geomys tobinensis_; one or both plates rarely disappear in final stages of attrition in old individuals resulting in same dental pattern found in _Cratogeomys_; M1 and M2 retaining enamel plate on anterior wall throughout life; M3 usually subtriangular in cross-section but sometimes suborbiculate or ovoid, crown slightly bilophodont owing to shallowness of labial re-entrant angle in modern species; posterior loph of M3 not especially elongated and crown not significantly longer than wide; both lateral enamel plates of M3 usually well developed and approximately equal in length, occasionally plates reduced in length and rarely one or both plates are lost with wear in old individuals; patch of whitish or buffy hairs surrounding nose of most individuals. The primitive character of the lower dentition, as described in the species account above, suggest that _Cratogeomys_ [= _Pappogeomys_] _bensoni_ Gidley should be referred to the subgenus _Pappogeomys_ rather than _Cratogeomys_. Only the upper dentition would make positive identification possible; however, reference to the subgenus _Pappogeomys_ seems to be the best arrangement at this time. _Referred species._--Three (one extinct): *_Pappogeomys bensoni_ (Gidley), 1922. U. S. Geol. Surv. Prof. Papers, 131:123. Type from Benson local fauna (late Pliocene), Cochise County, Arizona. _Pappogeomys alcorni_ Russell, 1957. Univ. Kansas Publ. Mus. Nat. Hist., 9(11):359. Type from 4 mi. W Mazamitla, Jalisco. _Pappogeomys bulleri_ Thomas, 1892. Ann. Mag. Nat. Hist., Ser. 6, vol. 10:196, August. Type from "near Talpa," west slope of Sierra Madre de Mascota, Jalisco. Subgenus =Cratogeomys= Merriam 1895. _Cratogeomys_ Merriam, N. Amer. Fauna, 8:150, January 31. 1895. _Platygeomys_ Merriam, N. Amer. Fauna, 8:162, January 31. Type: _Geomys gymnurus_ Merriam, 1892. _Type._--_Geomys merriami_ Thomas, 1893, from "Southern México," probably in Valley of México. _Chronologic range._--Late Pleistocene, from Wisconsin deposits (San Josecito Cave, Nuevo León, Upper Bercerra, México, and Burnet Cave, New Mexico, local faunas) to the Recent. _Description._--Size medium to large; skull becoming angular and rugose with age, and tending towards platycephaly and dorso-ventral compression; zygomata stout, each bearing platelike expansion at anterolateral angle into which anterior end of jugal becomes morticed; breadth across zygomata great relative to length of skull; rostrum relatively broad; squamosals expanding medially with age eventually growing over lateral parts of parietals, and sometimes also expanding laterally displacing postglenoid notch; sagittal crest well developed in adults of both sexes, but especially high and bladelike in males; lambdoidal crest prominent in all but young animals, having dorsal outline broadly convex posteriorly in most species but strongly sinuous in _gymnurus_-group; enamel plate on posterior wall of P4 absent; enamel plates present only on anterior walls of M1 and M2; M3 variform in occlusal shape (as described in species account), either subtriangular (_gymnurus_-group), quadriform or obcordate (_castanops_-group, with exceptions as noted before); lateral plates of M3 usually present in all species, labial plate approximately as long as lingual plate in _gymnurus_-group (like that in subgenus _Pappogeomys_) or distinctly shorter in _castanops_-group (labial plate scarcely extending beyond border of labial re-entrant fold); one or both lateral plates tending to disappear with wear in _castanops_-group, with lingual plate usually disappearing first; breadth across angular processes clearly more than breadth across zygomatic processes, especially in _gymnurus_-group. _Remarks._--In the species of the _castanops_-group the skulls can be spoken of as generalized and the least platycephalic of the subgenus. Indeed, the species of the _castanops_-group are hardly more specialized in this respect than is the subgenus _Pappogeomys_. In these skulls the breadth across the squamosal processes is less than that across the zygomatic arches, although the two dimensions are almost equal in some examples of _P. merriami_ of the _castanops_-group (where squamosal breadth varies from 85 to 98% of zygomatic breadth). In the species having marked platycephalic skulls (_gymnurus_ species-group) the breadth across the squamosal processes equals or exceeds the breadth across the zygomatic arches (squamosal breadth rarely 97 to 99% of zygomatic breadth), except in _P. zinseri_ and _P. tylorhinus zodius_. The variable character of the third upper molar as between species suggests that this tooth is presently undergoing active evolution. The structure of this tooth, although differing between taxa, is remarkably stable in other kinds of Geomyini. The most remarkable modification of M3 in _Cratogeomys_ is the obcordate pattern developed in _P. merriami_ of the _castanops_-group. The posterior loph and entire tooth is shortened somewhat resembling in shape that of _Thomomys_. Moreover, the posterior loph is twisted labially; consequently, its posterior surface now forms the labial border of the weakly defined posterior loph. Owing to the torsion, the lingual enamel plate has been rotated to the posterior surface of the tooth. Therefore, the tooth is provided with two transverse enamel plates, including the plate on the anterior wall of the tooth. The labial plate is greatly reduced, its total surface being restricted to the small labial inflection. The highly specialized obcordate M3 is not found in the most specialized platycephalic skulls characteristic of the _gymnurus_ species-group. Instead the _gymnurus_-group retains the primitive subtriangular pattern without significant modification. _Referred species._--Seven: _castanops_ species-group _Pappogeomys castanops_ (Baird, 1852). Report Stanbury's Exp'd. to Great Salt Lake, p. 313, June. Type from "Prairie road to Bent's Fort," near present town of Las Animas, Colorado. _Pappogeomys merriami_ (Thomas, 1893). Ann. Mag. Nat. Hist., ser. 6, 12:271, October. Type from "southern Mexico," probably Valley of México (see Merriam, 1895:152). _gymnurus_ species-group _Pappogeomys fumosus_ (Merriam, 1892). Proc. Biol. Soc. Washington, 7:165, September 29. Type from 3 mi. W Colima, Colima. _Pappogeomys gymnurus_ (Merriam, 1892). Proc. Biol. Soc. Washington, 7:166, September 29. Type from Zapotlan (Ciudad Guzman), Jalisco. _Pappogeomys neglectus_ (Merriam, 1902). Proc. Biol. Soc. Washington, 15:68, March 22. Type from Cerro de la Calentura, about 8 mi. NW Pinal de Amoles, Querétaro. _Pappogeomys tylorhinus_ (Merriam, 1895). N. Amer. Fauna, 8:167, January 31. Type from Tula, Hidalgo. _Pappogeomys zinseri_ (Goldman, 1939). Jour. Mamm., 20:91, February 15. Type from Lagos, Jalisco. PHYLOGENY OF THE GEOMYIDAE The fossil record of the Geomyidae provides a sequence of morphotypes, each representing a stage in the phyletic development of the family. Most of the preserved specimens probably represent the stufenreihe rather than the ahnenreihe, as Simpson (1953:219-220) points out. Even so, the stufenreihe closely approximates the general trend of evolution, and the level of structural organization in the different stages of phyletic development may be ascertained. The actual ancestral series of most lineages probably will remain unknown, but hopefully some of the existing gaps will be filled by future discoveries. From the established record, several clearly defined lineages can be distinguished; in fact the sequence of origin, pattern of evolution, and specializations, of the principal lineages are reasonably well expressed. Primitive Morphotype In the earliest known geomyids from the Upper Oligocene and Lower Miocene, the premolars and molars are biprismatic and bilophodont. In rodents, this is itself a specialized pattern, and is thought to have evolved from a more primitive sextituberculate prototype by the union of individual cusps, and probably also cuspules, forming the two transverse enamel lophs. The primitive, common ancestor of the Geomyidae and Heteromyidae with sextituberculate teeth in the early Tertiary is unknown. As soon as geomyids attained the early bilophodont stage of evolution, the basic morphological structure of the family was established. The family probably first became clearly distinguished from other Geomyoidea at this stage. In the early bilophodont stages of evolution, owing to the relatively deep valley between them, the two columns probably failed to unite in the normal cycle of wear, as they do in all later geomyids. _Griphomys_ described by Wilson (1940:93) from the late Eocene of California, has a bilophate pattern in which the anterior and posterior lophs are separated by a persistent transverse valley. The occlusal pattern of _Griphomys_ closely resembles a stage through which the ancestors of the early Miocene geomyids must have passed in their pre-Miocene evolution, as Wilson suggests (1949:115-116). Although he (1940:95; 1949:110-118) tentatively referred _Griphomys_ to the superfamily Geomyoidea and Simpson (1945:80) went so far as to refer it to the family Geomyidae, with a notation of _incertae sedis_, its exact relationship to the pocket gophers is uncertain. However, the structure of the molariform dentition of _Griphomys_ does not exclude it from the phyletic ancestry of the Geomyidae. In subsequent stages of evolution the anterior and posterior columns become united. Thereby part of the valley floor between the transverse prisms was progressively elevated, to the stage where attrition on the occlusal surface would unite the two columns. On the unworn enamel cap of living geomyids the two transverse enamel folds are separated by a shallow but well defined valley, briefly reflecting the ancient ancestral pattern. Union of the lophs may have been either at the mid-points of the two columns or at the edge of their protomeres. [A protomere is the half of a tooth containing the protocone or protoconid--lingual side of upper tooth and labial side of lower tooth. The paramere is the opposite half of a given tooth--labial side of upper tooth and lingual side in lower tooth. See Miller and Gidley, 1918:434.] Union of the columns at the mid-points would have produced the figure-8 occlusal pattern (or H-pattern), which is characteristic of the early Miocene Geomyinae (_Dikkomys_). Union of the two columns at the protomeres would have produced the U-shaped pattern of the Entoptychinae, which also occurred in the early Miocene and were contemporary with the earliest Geomyinae. Since pre-Miocene geomyids are unknown, the actual phyletic development of the dentition is a matter of speculation. Probably the development of the two divergent lineages, one leading to the Entoptychinae and the other to the subfamily Geomyinae, occurred in the Oligocene (as depicted in Fig. 3). Of the two lineages, the subfamily Geomyinae, in my view, is the more primitive and less specialized. Support for this view is furnished by a reconstruction of the pattern of occlusal wear in _Dikkomys_ and _Pliosaccomys_, especially on the first and second molars. In _Dikkomys_, the anterior and posterior column first unite near their mid-points in the first stages of wear thus producing a figure-8 shaped (H-shaped) occlusal pattern in the premolar and all three molars. Evidently in the first two upper molars, the columns unite closer to their lingual margins than their mid-points, but at any rate both outer and inner re-entrant folds are evident at this stage of wear. With continued attrition on m1 and m2 of _Dikkomys_, the anterior and posterior columns secondarily unite at the edge of their labial margins thus enclosing a fossette of enamel in the labial half of the tooth. The lateral coalescence at the ends of the protomeres occurs because of the shallow vertical depth of the labial re-entrant fold, and the fossette itself does not reach the base of the crown and with continued wear it too would disappear, but not until the last stages of wear, at least in _Dikkomys matthewi_. The lingual re-entrant fold is deep, and therefore, persistent through all stages of wear. Although the amount of wear required for its effacement would be great, the occlusal configuration of the first and second lower molars in _Dikkomys_ could be eventually ground down to a U-pattern as in the entoptychids. Only one upper molar of _Dikkomys_, the first, has been recovered (see Wood, 1936:23, fig. 32B). Although the tooth is in an early stage of wear, the lingual valley is minute. Less attrition than required in m1 and m2 would progressively reduce the lingual fold until it too would essentially form a U-pattern, perhaps retaining a slight lingual inflection. Hence, the first upper molar becomes a mirror image of the first lower molar, and the second upper molar probably had the same pattern as the first (at least it does so in _Pliosaccomys_). Both of the lateral re-entrant folds of the premolar are deep vertically, and consequently would not disappear with occlusal wear. Therefore, the H-pattern of the premolars is retained throughout life. The m3 (M3 unknown for _Dikkomys_ or _Pliosaccomys_) also has deep lateral folds; hence, it too retains the H-pattern in all stages of attrition, although the isthmus between the two prisms may become wider in the final phases of wear (as it does in _Pliosaccomys_). In _Pliosaccomys_, the stages of wear are essentially the same as those described for _Dikkomys_, except that the anterior and posterior loph of the first and second molars tend to unite closer to one side of the tooth, lingual side in upper molars and labial in lower. Only a slight inflection of the re-entrant fold is evident on the side of union, and the inflection disappears in the first phases of wear as the columns unite. Concomitant with the lateral shift in the initial point of coalescence of the transverse lophs, the occlusal penetration of the re-entrant fold from the opposite side increases in horizontal depth, and the fold extends medially more than half way across the occlusal surface, thus forming a pattern essentially like that of the entoptychids. The U-pattern in _Pliosaccomys_ appears in the initial stages of wear without going through an earlier H-pattern as is the case in its Miocene ancestors of the genus _Dikkomys_, unless the minute inflection is considered as indicative of that stage. The two columns of the premolar and m3 are joined near their mid-points as in _Dikkomys_; therefore, they retain their primitive H-pattern, a feature unique to the Geomyinae. The evolutionary trend toward an ontogenetically earlier U-pattern in the first two molars in the primitive lineage of the Geomyinae suggests that the U-pattern characteristic of the Entoptychinae was simply an earlier tendency toward the same specialization that occurred later in the subfamily Geomyinae. If so, early entoptychines would have been characterized by an H-pattern in the first stages of attrition, like _Dikkomys_, and later developed union at the edge of the protomeres. However, in the entoptychines, all the molariform dentition, and not merely the first and second molar, became specialized; consequently the U-pattern was produced on the occlusal surfaces of each of the cheek teeth. As in _Pliosaccomys_, the transitional phase, in which the two columns were united at their mid-points, was eventually eliminated from the pattern of wear and only the U-pattern, that now appeared in the initial stages of wear, was retained. In the entoptychines of the early Miocene there is no suggestion of the H-pattern that characterizes the Geomyinae, except in the position of the cusps before wear in the lower molars of _Pleurolicus sulcifrons_, which, according to Wood (1936:6), suggests the H-pattern. In earlier unknown Oligocene stages of evolution, the prisms possibly united first at their mid-points, and the columns may have joined at the side of the tooth only in the terminal stages of wear. The U-pattern of pre-Miocene entoptychines, therefore, may have become the dominant occlusal pattern only in the later stages of phyletic development. According to the recently expressed views of several paleontologists, the Entoptychinae constitute the primitive lineage of the family and the early Geomyinae constitute a specialized offshoot of the entoptychine ancestral assemblage. The structure of the Entoptychinae, especially of the less advanced genera, closely approximates that of the hypothetical primitive morphotype. But, according to my view, the subfamily Geomyinae constitutes the ancestral assemblage and its structure is essentially that of the primitive morphotype of the family. At any rate the structure of the early geomyines more closely approximates the structure of the ancestral stock than the more divergent entoptychines. Therefore, the genus _Dikkomys_ of the early Miocene, the first known geomyine, is considered to be a generalized geomyid, and, although it is a contemporary of the more specialized entoptychid assemblage, is considered to be more closely allied to the ancestral stock. The entoptychines were the dominant and most highly differentiated geomyids of the early and middle Miocene. Nevertheless, they became extinct in the middle Miocene, and the geomyines of that time survived and later gave rise to the modern pocket gophers. Therefore, the early history of the family Geomyidae is characterized by an early radiation and trend toward specialization, followed by survival of the less specialized Geomyinae and extinction of the more specialized Entoptychinae. Entoptychid Radiation The most abundant geomyids of the early and middle Miocene, the Entoptychinae, consisted of at least 24 species (see Wood, 1936:4-25) classified in four genera: _Pleurolicus_, _Gregorymys_, _Grangerimus_, and _Entoptychus_. The genera were essentially contemporaneous (see Figure 3). Even so, the subfamily was morphologically varied, pointing to an earlier origin in the Oligocene (actually a part of the John Day Fauna, including _Pleurolicus_ may be correlated with late Oligocene Whitneyian age) followed by a relatively rapid radiation including all four genera in the early Miocene. Two genera, _Pleurolicus_ and _Gregorymys_, continued into the Middle Miocene (Hemingfordian). This divergence, specialization, and subsequent radiation suggest that the entoptychines evolved into a new major adaptive zone, in the sense described by Simpson (1945:199-206). The radiation is correlated geographically and temporally with the southward retreat of the Neotropical flora of the Tertiary from the western United States and southward movement of the Arctic flora of the Tertiary (see Axlerod, 1950; Berry, 1937:31-46; Chaney, 1947:139-148; and Kendeigh, 1961:280-283). In the early Tertiary the Neotropical-tertiary geoflora occurred northward to at least 49° latitude in western North America, and the boreal Arctic-tertiary flora was restricted to a circumpolar zone. The southward and eastward shift of the Neotropical-tertiary flora, associated with the drying and chilling of the continent, began in the middle or late Oligocene and was concurrent with the divergence and radiation of the Entoptychinae. Beginning in late Oligocene and continuing at least into middle Miocene, most of the region in which the entoptychines occurred was occupied by the Arcto-tertiary geoflora of which the temperate forest division contributed the dominate plant associations. The maples, chestnuts, dogwoods, beeches, walnuts, oaks, elms, birches, and sycamores of that flora were the forerunners of today's eastern deciduous forest. It is my view that the entoptychines became adapted to the conditions of this paleoecological environment and radiated rapidly in the Arikareean when the major change occurred in climax vegetation. The ancestral stock of the Geomyinae was not so successful in the Arcto-tertiary climax, and most of it probably was displaced southward along with the tropical flora. The skeleton in the entoptychines is not so strongly fossorial as in the modern geomyids (Wilson, 1949:117), and these early geomyids probably were semi-fossorial with somewhat the same burrowing habits as those of the living mountain beaver (_Aplodontia_). Inasmuch as the morphology and taxonomy of the entoptychines were discussed in detail by Cope (1884) and reviewed later by Wood (_loc. cit._), there is no need to recount the details here. According to Wood (_op. cit._, 27-28), _Pleurolicus_ occupied a central position in the entoptychid radiation and perhaps appeared slightly earlier than the other genera. Wilson (1949) suggested that the lower part of the John Day may actually be Upper Oligocene rather than Lower Miocene, and this arrangement is followed here. Also, _Pleurolicus_ is less specialized than the other genera and occurs in deposits of both the Great Plains and the Pacific Coast. _Gregorymys_, also little specialized, occurred only on the Great Plains. The more specialized genera, _Grangerimus_ and _Entoptycus_, evidently appeared somewhat later than _Pleurolicus_ and evolved from it. Except for a record from southern Texas reported recently by Hibbard and Wilson (1950:621-623) and the new species described by MacDonald (1963:182) from the Sharps Formation of South Dakota (early Arikareean), _Grangerimus_ is known only from the Pacific coast. _Entoptycus_ was restricted to the Pacific Coast (John Day fauna). _Entoptycus_ is the most specialized of the known genera; it has pronounced fossorial adaptations, especially in the skull. Its molariform teeth are rootless and ever-growing as in the modern geomyines. Moreover, the continuous enamel bands on only moderately worn teeth become separated in the final stages of wear into anterior and posterior enamel plates by tracts of dentine that extend toward the crown on the sides of each tooth. This extension was made possible by the union of the two columns at both the lingual and labial margins of the tooth forming an O-pattern, and the crown is essentially monoprismatic save for the isolated enamel fossette in the center of the tooth. The fossette is all that remains of the lateral re-entrant fold that characterized the preceding U-pattern of the earlier stages of wear. Late in the sequence of wear, the anterior enamel plate is lost in the lower molars and the posterior plate in the upper molars. The U-pattern characterizes the final stages of attrition in the other genera of the Entoptychinae; none developed the dental specializations seen in _Entoptycus_. Rootless, ever-growing cheek teeth, discontinuous enamel patterns, and monoprismatic molars were not evolved in the subfamily Geomyinae until the late Pliocene. Phyletic Trends in Subfamily Geomyinae The subfamily Geomyinae is made up of three groups, recognized taxonomically for the first time in this account as tribes--Dikkomyini, Thomomyini, and Geomyini (for full discussion of classification, see previous account). The phylogeny proposed by me is illustrated in Figure 3. The tribe Dikkomyini is characterized by generalized and primitive features that together form the basic structural foundation of the subfamily. Evolution within the Dikkomyini resulted in the acquisition and perfection of fossorial adaptations. The Thomomyini and Geomyini are considerably more specialized than the ancestral Dikkomyini from which they evolved. The Geomyini are clearly more specialized than the Thomomyini, suggesting closer affinity between the Thomomyini and the Dikkomyini than between the Geomyini and the Dikkomyini. The specializations in the dentition and the associated changes in the skull of the Thomomyini and Geomyini permit more efficient mastication of fibrous vegetation. Along with these specializations, fossorial adaptations inherited from the Dikkomyini are retained without noteworthy modification. _Dikkomys_, the earliest known genus of the tribe Dikkomyini, can be taken as a starting point of evolution for the subfamily Geomyinae. The Pliocene genus _Pliosaccomys_ is the only other known geomyine having primitive features closely resembling those of _Dikkomys_. The relatively close but previously unrecognized relationship between _Dikkomys_ and _Pliosaccomys_ can be understood when patterns of wear on the occlusal surfaces of the cheek teeth are taken into account. It appears that _Pliosaccomys_ descended from _Dikkomys_-like stock, if not _Dikkomys_ itself. Although _Dikkomys_ is towards the beginning of this phyletic sequence and _Pliosaccomys_ towards the end of the sequence, the primitive features shared by the two provide a generalized morphotype for the subfamily Geomyinae. In the molariform dentition, an almost complete series of stages of wear in _Pliosaccomys_ has been preserved, and those of _Dikkomys_ can be reconstructed with reasonable accuracy from those that are known (see Fig. 4): (1) In the initial stage of wear in _Dikkomys_ the anterior and posterior columns are separated by an intervening valley (Fig. 4A), and the occlusal surface of each column bears a loph of dentine surrounded by a ring of enamel: protoloph on the anterior column and metaloph on the posterior column of the upper teeth (protolophid and hypolophid in corresponding positions in the lower teeth). Actually this stage is not preserved in the known material of _Dikkomys_, but does occur in both geomyines and entoptychines in all stages of evolution, and it must have also occurred in _Dikkomys_ in order for the next two stages, which are preserved, to have developed. (2) The occlusal surfaces are ground down to a level where the enamel loops of the two columns join at their mid-points, thus forming an H-shaped pattern (Fig. 4B), or more exactly a pattern resembling a figure 8. Probably this was the primitive pattern in the final stage of wear in the geomyid ancestor of the Oligocene. [Illustration: FIG. 3. Diagram depicting geologic range and probable phyletic relationships of the family Geomyidae. Dashed lines represent parts of lineages that are not represented by fossil records, and solid lines represent parts of lineages verified by actual specimens. Question marks indicate uncertainty of suggested ancestry of known taxa. The relationships within the subfamily Entoptychinae are modified after Wood (1936), and the temporal range of the Miocene geomyids have been adjusted to agree with current stratigraphic correlations. Hence, _Pleurolicus_, _Gregorymys_ and _Dikkomys_ are illustrated as ranging into the Hemingfordian, rather than being confined to the Arikareean (see MacDonald, 1963, and Black, 1961).] (3) In the pre-final stage of wear, the anterior and posterior lophs of the first and second molars unite secondarily at the edge of their protomeres (labial side in the lower and lingual in the upper), thus enclosing an isolated enamel fossette (Fig. 4C). Lateral union occurs in the lower teeth because the vertical depth of the labial re-entrant angle is less than the depth of the lingual re-entrant fold. In the upper teeth the reverse is true. The re-entrant angle on one side of the premolar is as deep vertically as the angle on the other side of that tooth, and both reach the base of the crown; therefore, they do not disappear at any stage of attrition. The same pertains in the third lower molar. (4) In the final stage of wear (Fig. 4D), the enamel fossette disappears as a result of continued attrition on the occlusal surface in the upper series. The fossette may vary somewhat in vertical depth in m1 and m2, but the amount of wear required for its effacement would be greater than in the upper teeth. Therefore, upon wear, the U-pattern would become characteristic of the final stage in M1 (and probably also M2), but the modified H-pattern described in Fig. 4C would prevail in m1 and m2. Perhaps, in extremely worn teeth, the labial fossette of m1 and m2 would disappear. If this advanced stage of effacement is obtained, then the two columns would be united across the entire surface of their protomeres from the center of the crown to its labial edge, and the occlusal pattern would be in the shape of a U. The occlusal pattern, at least in M1 and M2, in the final stages of wear in _Dikkomys_ resembles that in the subfamily Entoptychinae, but the U-pattern develops on only the first and probably the second molar in _Dikkomys_ and not on all of the cheek teeth as it does in the entoptychines. Judging from the material that has been described, the U-pattern did not develop in the lower teeth of _Dikkomys_ until the Hemingfordian (_D. woodi_), upper Rosebud, and specimens of _D. matthewi_ from the earlier Arikareean, lower Harrison, suggest that the modified H-pattern, with secondary coalescence at the edge of the protomeres, persisted throughout life, without developing the U-pattern in the final stages of wear. Essentially the same patterns of wear characterize the genus _Pliosaccomys_, except that the earlier stages were telescoped and the second stage was omitted while another (final) stage was added. The stages are reconstructed in sequence in figure 4, and all are based on preserved dentitions, as follows: (1) The first phases of wear produced the pattern (Fig. 4E and I) described for _Dikkomys_ in the previous account (Fig 4A). (2) A small additional amount of wear produced the 2nd stage (Fig. 4F and J) characterized by a U-pattern, formed by union of the anterior and posterior columns at the edge of the protomeres of the first and second molars, both above and below, without first forming an H-shaped pattern. Union at the mid-points thus was omitted from the sequence of wear in these two teeth. In the premolars and third molars the primitive H-pattern did form, as in _Dikkomys_. The pattern of wear in the first two molars is the same as in the entoptychines of the early Miocene. The trend of evolution through which the _Pliosaccomys_ lineage passed must have featured a progressively earlier union at the edge of the tooth until the lateral coalescence occurred simultaneously with the median union. At that stage, emphasis was shifted to the union at the edge of the tooth, and eventually the teeth failed to unite at their mid-points and the U-pattern developed directly. Therefore, the horizontally deep re-entrant fold that separates the two lophs of the U-pattern is equivalent to one fold plus the apex of the opposite fold. (3) The horizontal re-entrant fold of the U-pattern was remarkably shallow vertically and disappeared with little additional wear. Thus the two parts of M1, and also of M2, are united into a single column except for a slight inflection on the labial side and this is true also of m1 and m2 except for a slight inflection on the lingual side (Fig. 4G and K). The inflection appears to have persisted in the upper teeth (Fig. 4H), but evidently with slight wear, disappeared in the lower teeth (Fig. 4L). The final monocolumnar pattern was attained early ontogenetically, evidently before the permanent premolar had fully erupted; hence, the earlier stages occurred only in transition, persisted for only a brief interval in the teeth of juveniles, and the final stage developed in the young animal and lasted throughout the rest of its life in _Pliosaccomys_. In _Dikkomys_ the two columns never united into a single column, and a bilophodont occlusal pattern persisted throughout life. The early phyletic development of the subfamily Geomyinae took place in the tribe Dikkomyini from the early Miocene into the early Pliocene. Compared with the rapid evolution of the specializations that distinguish the Entoptychinae, the structural changes in the early Geomyinae occurred at a remarkably slow rate. In fact the lineage changed but little from _Dikkomys_ to _Pliosaccomys_, in parts of the animal that can be compared, as illustrated by the low-crowned and rooted cheek teeth, the continuous enamel bands, the lack of grooving of the upper incisor, the retention of the primitive H-pattern, both above and below, in the premolar and third lower molar, and the ridges and fossae of the mandible to which the muscles of mastication attach. The only major changes detected in the known fragments are in the pattern of wear and the final configuration of the first and second molars, as described above. The unification of the two lophs in each of these two teeth into a single column was a significant step in the evolution of the Geomyinae, and is a stage between the primitive bilophodont pattern of the early and middle Miocene geomyines having continuously bicolumnar teeth and the monolophodont pattern in the modern pocket gophers of both lineages in which these teeth consist of a single column in all but the initial stages of wear. The monocolumnar structure of the first and second molars in the final stages of wear, therefore, is closer to that in the lineage of _Thomomys_ than it is to that of _Dikkomys_. Other specializations in the dentition of _Pliosaccomys_, especially in m1 and m2 where the H-pattern has been completely eliminated from the sequence of wear, are too far advanced for _Pliosaccomys_ to have given rise to the tribe Geomyini. The teeth in the immediate ancestor of the Geomyini must have been less specialized in m1 and m2, perhaps about as in _Dikkomys_. In the m1 and m2 of the tribe Geomyini, the H-pattern is formed in the initial stages of wear; therefore, in the early Pliocene ancestor, presently unknown in the fossil record, the H-pattern probably was present. Even so, the ancestor of the Geomyini and that of _Pliosaccomys_ probably were closely allied otherwise, and both probably had attained the highly specialized fossorial adaptations characterizing all modern pocket gophers, before the divergence of _Pliosaccomys_ and the Geomyini took place. The evidence points to a major divergence of the geomyines that lived in the latest Miocene or the early Pliocene (probably the latter) and that gave rise to the two modern lineages, Thomomyini and Geomyini (see Fig. 3). One, the most primitive of the two, gave rise to the Thomomyini lineage that eventually evolved into _Thomomys_. _Pliosaccomys_ is closely allied to the ancestry of this lineage, although it is probably not the actual ancestor, as mentioned previously. Aside from the aforementioned specializations of the first and second molars, the features of the Thomomyini are less advanced than in the other specialized lineage (tribe Geomyini). Primitive traits retained in the tribe Thomomyini (and also characteristic of the ancestral tribe Dikkomyini) are: (1) Small size, in general no larger than the ancestral morphotype; (2) lack of grooving on the upper incisor (although a slight rudimentary groove is developed rarely in some living species); (3) retention of anterior and posterior enamel plates in lower and upper cheek teeth; (4) premolars having widely open re-entrant folds; (5) smooth and generalized skull lacking marked angularity, regosity or cresting (neither the sagittal nor the lambdoidal crest are ordinarily well developed except in _Thomomys bulbivorus_); (6) forefoot small, less modified for digging than in the Geomyini. [Illustration: FIG. 4. Drawings of the molariform dentitions of _Dikkomys_ and _Pliosaccomys_ (Tribe Dikkomyini) depicting the patterns of wear on the occlusal surfaces. Ontogenetically, the stages of wear are arranged from left to right in each row. Stages not represented by actual specimens have been carefully reconstructed from information provided by known stages in the sequence of wear and the dentitions of other geomyines. � 5. A-D. _Dikkomys woodi_, right lower tooth-row, including p4-m3. Patterns based on No. P26284 (FMNH) from Upper Rosebud (Middle Miocene), Shannon Co., South Dakota (B above). E-H. _Pliosaccomys dubius_, left upper tooth-row, including P4-M2 (M3 unknown). Patterns based on Nos. 1798 and 1799 (LAM) from Smiths Valley (Middle Pliocene), Lyon Co., Nevada. I-L. _Pliosaccomys dubius_, right lower tooth-row, including p4-m3. Patterns based on Nos. 1796 (holotype), 1804, and 1806 (LAM) from Smiths Valley (Middle Pliocene), Lyon Co., Nevada. ] The lineage of the Thomomyini is essentially rectilinear and without the major branching seen in the tribe Geomyini. The one genus, _Thomomys_, appears first in the Upper Pliocene (early Blancan time), and the specializations characterizing the lineage had already developed by that time. Evidently, the early stages of divergence from the ancestral stock resulted in the development of rootless, ever-growing, more hypsodont cheek teeth, simplification of M3, and enlargement of the masseteric ridge on the mandible. The enamel investment on the sides of the molariform teeth is interrupted owing to intrusion of tracts of dentine on the sides of each column. Even so, complete anterior and posterior plates are retained on all of the cheek teeth (Fig. 5, K and L) and there is no trend toward additional loss of enamel as in the Geomyini. The enamel on the sides of the column has little functional value, and its elimination probably reduces friction during the anteroposterior movements of the lower jaw, thereby increasing the efficiency of the cutting blades on the anterior and posterior wall of the tooth. The simplification of M3 was achieved by union of the two columns of the primitive pattern into a single column and obliteration of both the labial and lingual re-entrant folds in the first stages of wear. The adult tooth (see Fig. 5L) is without trace of the bilophate pattern and is not elongated; therefore, its structure is essentially the same as that of the first and second upper molars. In the Thomomyini, the two lophs of the unworn molars unite entirely across the width of their surfaces with the first traces of wear (see Fig. 5, I and J), owing to the shallow and uniform depth of the transverse valley. In the molars, the final pattern is acquired, therefore, before the deciduous premolar has been replaced by the permanent tooth. A relatively shallow re-entrant inflection between the ends of the parameres sometimes is retained, although it also will disappear with slight additional wear. Therefore, both lophs tend to unite completely with the first stages of wear in the Thomomyini, thus omitting both U and H patterns from the sequence of wear. This is the highest degree of specialization attained in the Geomyidae in regard to the patterns of wear, since a sequence of bilophodont patterns appear in both the Dikkomyini and Geomyini before the monoprismatic pattern is developed. [Illustration: FIG. 5. Drawings of molariform dentitions representative of the tribes Geomyini and Thomomyini depicting patterns of wear on the occlusal surface. A-D represent, in ontogenetic sequence from left to right, upper tooth-rows of the tribe Geomyini. E-H represent, in the same sequence of stages, lower tooth-rows of the tribe Geomyini. I-L represents both upper and lower tooth-rows of both pre-final and final stages of wear in the tribe Thomomyini. All � 5. A and E. _Geomys bursarius majusculus_, No. 2948 (KU), Douglas Co., Kansas. Right upper (A) including DP4-M3; lower left (E) including dp4-m3. B and F. _Pappogeomys bulleri burti_, No. 100444 (KU), 10 mi. NNW Barra de Navidad, Jalisco. Right upper (B) including P4-M3; right lower (F) including p4-m3 (both P4 and p4 with unworn enamel caps). C and G. _Pappogeomys bulleri albinasus_, No. 31044 (KU), 10 mi. S and 8 mi. W Guadalajara, Jalisco. Right upper (C) including P4-M3; right lower (G) including p4-m3. D and H. _Pappogeomys bulleri albinasus_, No. 31002 (KU), W side La Venta, 13 mi. W and 4 mi. N Guadalajara, Jalisco. Right upper (D) including P4-M3; right lower (H) including p4-m3. I and J. _Thomomys talpoides bridgeri_, No. 6865 (KU), 2 mi. up Mink Creek, Pocatella, Bannock Co., Idaho. Left upper (I), DP4-M3; left lower (J), dp4-m3. K and L. _Thomomys talpoides fossor_, No. 13205 (KU), Wasson Ranch, 3 mi. E Creede, Mineral Co., Colorado. Right lower (K), p4-m3; left upper (L), P4-M3. ] Relationship of the Geomyini with the ancestral Dikkomyini is most clearly demonstrated in the sequence of wear on the occlusal surfaces of the molars. As in all geomyids, the upper part of the crown is biprismatic in the newly erupted tooth, and the two columns are separated by an intervening valley. With slight attrition on the unworn enamel cap, the weakly developed cusps merge and form a transverse enamel loop on each of the two columns (see third molar in Fig. 5, A and E), each loop enclosing a core of dentine that had become exposed. The valley between the two columns is shallow, and upon further wear of the tooth, the two loops unite. The two columns become joined at different points in the upper and lower molars depending on the varying depth of the valley in different teeth. Therefore, upper and lower molars develop distinctly different occlusal configurations. In the lower molars, the pattern characteristic of _Dikkomys_ (Fig. 4C) is preserved without significant modification, as illustrated in an immature specimen of _Geomys_ (see Fig. 5E). The H-pattern and modified H-pattern are developed in the same sequence of wear in the Geomyini. A juvenal female (not illustrated), KU 2931, provides an example of the intermediate H-pattern. In this specimen, the protolophid and hypolophid of the left m2 are united only at their mid-points, indicating that the pattern of wear occurs in the same sequence in the Geomyini as it did in the Miocene genus _Dikkomys_. After the two columns have become united at their mid-points, a secondary union is formed at the edge of their protomeres, thus enclosing the enamel fossette as illustrated in Figure 5E (this is the modified H-pattern mentioned above). However, the fossette itself is shallow and soon disappears with slight wear. At this stage, the occlusal configuration would be in a U-pattern (m1 in Fig. 5E). The lingual re-entrant fold is also shallow in vertical depth; therefore, it is obliterated by wear following the eradication of the labial fossette. Consequently, the two columns are united into one. In m3 (see Figs. 5E, F, and G), the two columns merge by progressive lateral expansion of the medial isthmus. In the first and second upper molars, the two columns unite across the entire surface of their protomeres from near the lingual edge of the crown to near its center. A minute inner inflection may be temporarily retained in some teeth. At this stage (see Fig. 5B), the parameres are still separated by the labial fissure, and the occlusal pattern is in the shape of a U, resembling, but not exactly duplicating, the pre-final pattern of Ml and M2 in the genus _Pliosaccomys_ (see Fig. 4H). The labial fissure is shallow, and, with further wear, the inflection is worn away and the parameres also unite, thereby forming a monoprimatic crown in the final stage. In M3, the two lophs first become united near the edge of their protomeres (see Fig. 5B), therefore forming a U-pattern similar to that developed in Ml and M2 of _Pliosaccomys_. The connection of the two lophs is not directly at the end of the protomere; consequently a shallow lingual inflection remains. The lingual edge of the valley is also shallow, and, with continued wear a second union of the two lophs takes place near the ends of their parameres, and the deeper, interior part of the valley remains as an isolated enamel fossette (see Fig. 5C). The two primary lophs of the tooth are now joined near both sides, having shallow lingual and labial re-entrant angles on the sides and the enamel island in the center. With continued effacement of the occlusal surface, the fossette will be eradicated, and the pattern of the occlusal surface will become the partially biprismatic pattern of the final stages (adult) of wear (see Fig. 5D). M3's of _Dikkomys_ and _Pliosaccomys_ are not known; however, it seems reasonable to assume that the pattern of wear in the M3 of Dikkomyini was not essentially different from that of the Geomyini, except that it is likely that the U-pattern of the second stage of wear in the Geomyini was probably the final stage in the genus _Dikkomys_. Judging from the pre-final stages of wear, the dentition of the Geomyini provides a curious combination of patterns that resemble in part the Miocene genus _Dikkomys_ and in part the early and middle Pliocene genus _Pliosaccomys_. There is no significant variation in the premolars or third molars (at least in the lower teeth) of the Geomyinae from the early Miocene to late Pliocene; therefore, deviations of major significance are in the character of the first and second molars. In the Geomyini, the patterns of wear of m1 and m2 are the same as those of _Dikkomys_, and are distinctly different from those of _Pliosaccomys_ where the two columns first unite at the edge of their protomeres to form a U-pattern, rather than at their mid-points to form an H-pattern. Even though the intermediate stages of ontogeny in m1 and m2 of _Pliosaccomys_ and the Geomyini are entirely different, the bicolumnar crowns of both eventually unite, upon wear, into a single column. On the other hand, the patterns of M1 and M2 in the Geomyini most closely resemble those of _Pliosaccomys_, rather than _Dikkomys_. In this regard it should be pointed out that the upper molars of _Dikkomys_ are presently represented by only one tooth, an M1 in an early stage of wear. As described already, the patterns of M1-2 evidently would be mirror images of m1-2 in corresponding stages of wear. However, the initial union of the two columns, in the M1 that is known, is somewhat to the lingual side of center and the relatively small lingual valley does not reach the base of the crown, indicating, that eventually with wear, the two columns of _Dikkomys_ might have become united across the entire surface of their protomeres as in _Pliosaccomys_. Even so, the two columns of M1 do initially join closer to their mid-points than they do in _Pliosaccomys_, and, if they did actually unite across their protomeres, the union would have occurred with subsequent wear. That is, the first occlusal pattern would be H-shaped (but with the connection closer to the lingual than the labial side), as in m1 and m2, and it would become U-shaped only after additional wear. This sequence of patterns of M1 and M2, as already pointed out, does not pertain in _Pliosaccomys_ or the Geomyini, since the U-pattern is formed with the first union of the two columns at the edge of their protomeres, and the primitive H-pattern is never developed, unless one counts the slight lingual inflection, that occasionally is formed just after the two columns unite, as being indicative of the primitive pattern. As in the lower teeth, the bicolumnar crowns of early ontogeny in both _Pliosaccomys_ and the Geomyini become eventually united, with wear, into a single column. Based upon the foregoing evidence, it would seem likely that the Geomyini evolved from an early Pliocene (perhaps late Miocene) Dikkomyini ancestor that had evolved the specializations of M1 and M2 that characterize its relative, _Pliosaccomys_, but had not also evolved the specializations of m1 and m2 that distinguish _Pliosaccomys_. Therefore, the ancestor of the Geomyini differed from the _Pliosaccomys_-Thomomyini lineage in its retention, unmodified, of the primitive patterns in m1 and m2 that characterized the earliest known Geomyines (_Dikkomys_). The same patterns are preserved in m1 and m2 of its modern descendents, the living Geomyini. In the _Pliosaccomys_-Thomomyini lineage the pattern of m1 and m2 are entirely different, as described above. The earliest record of the Geomyini is the extinct genus _Pliogeomys_ (see Fig. 6) in the latest Hemphillian (middle Pliocene) and earliest Blancan (late Pliocene). _Pliogeomys_ is more primitive than any modern genus of the Geomyini, seems to have been a late survivor of the primitive stock, but was itself probably a collateral lineage and not on the direct line of descent. The cheek teeth in _Pliogeomys_ are rooted and less hypsodont than in the late Pliocene examples of the modern genera, and the anterior enamel plate of the lower molars shows no indication of reduction, as would be expected if _Pliogeomys_ were in the direct line of evolution. Separation of _Pliogeomys_ from the main stem of the Geomyini probably occurred after several specializations had already been achieved by the Geomyini. Two inheritances might have been grooving on the upper incisors and some reduction in amount of enamel on the sides of the cheek teeth. The dentine tracts on the sides of the cheek teeth of _Pliogeomys_ are narrow (see Fig. 7A) and barely separate the enamel blades and there is no discernible reduction in the anterior enamel blades on its lower molars. Those blades evidently were lost in the main lineage before the Pleistocene radiation of the living genera took place. _Pliogeomys_ is in an intermediate stage in evolution, and was not so advanced as was the main lineage at the time _Pliogeomys_ died out. Its structure does provide clues as to phyletic development that took place in the main lineage. Specialized trends in the early phylogeny of the Geomyini included: development of rootless, ever-growing cheek teeth and an increase in hypsodonty; loss of the bicolumnar structure of the first and second molars, and, consequently, the formation of a single elliptical column in the final stage of wear; interruption of the enamel investment of the molariform teeth and formation of anterior and posterior enamel plates; and enlargement of the masseteric ridge and fossa. Each of these trends occurred independently in the Thomomyini, and each is an example of parallelism in the phyletic evolution of the two lineages. Three additional specializations lacking in the Thomomyini are the grooving on upper incisors, loss of anterior enamel plate in lower molars, and development of a basitemporal fossa on the mandible. Evidently, two grooves evolved in the ancestral incisors in the same bisculcate pattern preserved in _Pliogeomys_, _Zygogeomys_ and _Geomys_. The innermost groove is weakly developed in _Pliogeomys_, suggesting that this character was in an intermediate stage of evolution in the ancestral lineage at the time that _Pliogeomys_ split off. Numerous other specializations in the Geomyini appeared later, but evolved in the different genera that diverged from the ancestral lineage and are discussed separately in the next account. Only two of the major features characterizing the Dikkomyini are retained in the Geomyini: the H-pattern on the occlusal surface of the m1 and m2 developed during the initial stages of wear, and the bicolumnar pattern of M3. Adaptive radiation produced the living genera of the Geomyini in the late Pliocene and early Pleistocene (see Fig. 6) and subsequent specialization of the ancestral morphology followed. Parallelism in the molars of later geomyines and the Entoptychinae is illustrated by the lateral interruption of the enamel investment and loss of enamel plates and by the omission of the H-pattern stage in the first and second molars (in _Pliosaccomys_). Resemblance of dentitions in certain stages of wear in _Pliosaccomys_ and in entoptychines led some investigators, for instance, Hibbard (1953:357), to suggest that _Pliosaccomys_ descended from one of the less specialized entoptychines, possibly _Grangerimus_ but probably _Gregorymys_. Actually, the highly specialized upper and lower premolars and third molars of the entoptychines rule them out as ancestors of the later geomyines. The evolution of entoptychine-like features in _Pliosaccomys_ is regarded as an example of iteration, a pattern of parallelism (see Simpson, 1953:248-253) where an allochronic and independent lineage undergoes the same evolutionary trend that phyletically characterized an earlier lineage, usually after the latter has become extinct. In this case, the lineage giving rise to _Pliosaccomys_ passed through the same phyletic stages in its evolution in the early Pliocene (and possibly the late Miocene) as did the entoptychines in the late Oligocene and early Miocene. Another parallelism by iteration, occurring in the middle and late Pliocene in both the Thomomyini and Geomyini, is the loss of enamel from the lateral surfaces of the cheek teeth, and, in the Geomyini only, the eventual loss of the anterior plate in the lower teeth and the posterior plate in the upper teeth. Both features were evolved more than an epoch earlier in the specialized entoptychid genus _Entoptychus_ of the lower Miocene. In _Entoptychus_, only the posterior plate of the lower molars and the anterior plate of the upper molars remained in the final stages of attrition, although a central enamel fossette, a remnant of the re-entrant fold, remained throughout life. Iteration is also expressed in the subfamily Geomyinae by the development of grooving on the upper incisor and the formation of the basitemporal fossa. A shallow but distinct basitemporal fossa occurs between the coronoid process and the third lower molar in the genus _Entoptychus_ and a sulcated upper incisor, a single shallow groove usually near the median border of the tooth, is found in the genus _Gregorymys_ of the subfamily Entoptychinae. Both features are regarded as advanced specializations in the tribe Geomyini, even though each was evolved in the entoptychines of the Lower Miocene. The postcranial skeleton of living genera of pocket gophers, as befits animals that spend most of their life within underground burrows, are highly specialized for a fossorial life. Elements of the postcranial skeleton recovered from Lower Miocene deposits indicate that the entoptychines were only semi-fossorial (see Cope, 1884:857; Wood, 1936:4-5; Wilson, 1949:117-118). One of the basic trends of the entoptychines was towards greater fossorial adaptation; the skeleton of _Entoptychus_ shows a greater degree of fossorial adaptation than earlier genera of the subfamily. There is no reason to suppose that the geomyine genus _Dikkomys_, which lived at the same times as the entoptychines, had acquired any more advanced fossorial adaptations than had the entoptychines. The most pronounced fossorial adaptations seem to have evolved only in the ancestral lineage of the modern geomyines, probably in the latter part of the Miocene and in the early Pliocene, before the modern Thomomyini and Geomyini diverged. Extreme fossorial adaptations in herbivorous rodents, such as those characteristic of the modern pocket gophers and their immediate ancestors, are thought to have evolved only in response to pronounced arid conditions. The Entoptychinae and evidently the early geomyines lived in environments that were either tropical or temperate, and under conditions more mesic than I would consider necessary to bring about selection pressure resulting in fossorial specializations. In late Oligocene and early Miocene, according to Axelroad (1958:433-509), arid conditions did not exist in the United States, and the only xerophytic environments in North America occurred on the Central Plateau of México. Moreover (Axelroad, _loc. cit._), arid conditions did not develop in the western United States until the early Pliocene. Geomyids evidently became extinct in this region at the close of the Middle Miocene, and none appear in fossil deposits in the western United States until the latest Lower Pliocene (Clarendonian). The reappearance of geomyids, _Pliosaccomys_, in the western United States coincides with a trend toward aridity and the northward movement of the Madro-tertiary geoflora into the Great Basin and Great Plains from its place of origin on the Central Plateau of México (Axelroad, _loc. cit._). Later, in the middle and later Pliocene, the Madro-tertiary geoflora gave rise to the modern xerophytic plants that now characterize the desert vegetation of North America. The Madro-tertiary climax does not appear as a major flora until the Miocene, but probably originated earlier. According to Axelroad (_loc. cit._), this xerophytic flora evolved from elements of the Neotropical-tertiary geoflora that became adapted to arid conditions that developed in the rain shadow of the high mountains flanking the Central Plateau of México. Originally, the Madro-tertiary flora consisted of small trees, shrubs, and grasses. Although some elements of this flora moved northward in the late Miocene, the major part of it remained in México until the early Pliocene. In the western United States, mountain formation increased in intensity in the Pliocene and continued on into the early Pleistocene. As the mountains became more elevated, especially the Sierra Nevada and Cascade ranges, they blocked the prevailing winds from the Pacific Ocean and extensive aridity developed on their leeward side. As xeric conditions became widespread, the Madro-tertiary flora successfully occupied the drier regions of southern California, the Great Basin, and the western parts of the Great Plains. While the Entoptychinae probably evolved in response to the Arcto-tertiary flora, the late Tertiary geomyines probably evolved in response to the Madro-tertiary geoflora on the Central Plateau of México. Some of these early geomyines, especially ancestors of the modern lineages, probably were pushed southward by competition with the more specialized entoptychines. Most geomyines were pushed out of the northern area of distribution, except for _Dikkomys_ that survived in association with the entoptychids throughout the early and middle Miocene. During this time, and probably continuing on into the late Miocene, the geomyines occurring to the south in México became adapted to the arid environments of the Madro-tertiary geoflora. Of course, information is lacking about climates in several parts of the late Miocene and early Pliocene. When such information becomes available it conceivably could modify the hypothesis outlined immediately above. The principal trend of evolution in these semi-fossorial rodents was toward more complete fossorial adaptation, and the pronounced fossorial features characteristic of the modern pocket gophers were perfected. This trend continued in response to the intense selection pressures in this arid environment. The principal structural characters effected were in the postcranial anatomy, especially in the skeletal and muscular systems. Consequently, it is not surprising that in skull and dentition, _Pliosaccomys_ differs but little from _Dikkomys_. Therefore, most of the basic structural specializations so far developed for subterranean existence probably had evolved by the time geomyines moved back north in the early Pliocene. Both modern lineages, the tribes Thomomyini and Geomyini, have essentially the same fossorial features, and it seems unlikely that these features were acquired independently in the relatively short period of time available to them after their divergence; probably they were inherited from a common ancestor. These probabilities indicate that the evolution of the fossorial specialization was in the later phyletic development of the tribe Dikkomyini. Plio-Pleistocene radiation of Geomyini Unlike the lineage of the Thomomyini that remained essentially rectilinear through out its history, the Geomyini in the late Pliocene and the early Pleistocene underwent adaptive radiation in a degree comparable to the earlier radiation of the Entoptychinae, and all of the later history of the tribe is dominated by the radiation--the resulting structural diversity. At least four lineages were produced by the Plio-Pleistocene radiation (see Fig. 6); each originated at essentially the same time (late Pliocene) presumably from the same ancestral stock. Each of these lineages within the Geomyini has given rise to one of the four modern genera: _Zygogeomys_, _Geomys_, _Orthogeomys_, and _Pappogeomys_. [Illustration: FIG. 6. Plio-Pleistocene radiation of the Tribe Geomyini.] _Morphotype_ The immediate, unknown, ancestor probably lived on the Central Plateau of México. After the radiation began the ancestors of _Geomys_ and _Zygogeomys_ extended their ranges northward. Features of the hypothetical morphotype, that would permit derivation of the modern genera would include the following: (1) Skull generalized, neither excessively long and narrow or short and broad; (2) skull smoothly rounded, without pronounced angularity, rugosity or cresting (sagittal crest probably lacking, even in old individuals); (3) zygomata slender, without lateral platelike expansions; (4) rostrum moderately broad; (5) upper incisors bisulcate, two grooves in pattern found in _Pliogeomys_, _Zygogeomys_ and _Geomys_; (6) lateral re-entrant angles of premolars obtuse; (7) p4 having four enamel plates (one on anterior wall, one on posterior wall, and two lateral plates) and lower molars having one enamel plate on the posterior wall of tooth (anterior plate is lacking); (8) P4 having four enamel plates, in same pattern as described for p4, M1 having two enamel plates (one anterior and one posterior), M2 same as M1, M3 having three plates (one anterior, two lateral on sides of posterior loph, none posterior); (9) M3 subtriangular in cross-section, distinctly bicolumnar, two columns marked by shallow re-entrant folds and connected by broad isthmus; (10) masseteric ridge large, forming high crest bordering masseteric fossa; (11) basitemporal fossa shallow; (12) angular process of mandible short, its lateral projection barely exceeding that of zygomatic arch. _Specializations in Genera_ In relation to the primitive morphotype, increase in size, simplification of dentition, and changes in shape of skull are regarded as specializations. Considerable parallelism between the four lineages is seen. But each lineage is distinguished by a combination of specialized features, and three by a few unique specializations. Among trends resulting in simplification of the dentition, reduction of enamel on the posterior wall of the upper cheek teeth has occurred in various degrees in all lineages of the Geomyini even to loss of all enamel on the posterior wall of the premolars and molars in two genera. Loss of some enamel is more common on P4 than on M1-2, and has occurred in all genera (see Figs. 7 and 9.) In evolutionary sequence loss of enamel from M1 and M2 usually occurs after, but never preceding, the reduction of enamel on P4. Loss of enamel plates from the posterior face of M1 and M2 is associated with the evolution of an efficient anterotransverse shearing action of the teeth. On the anterior wall of those teeth no reduction of the cutting blade has been observed; a complete anterior plate is retained in all living Geomyini. Presence of both the posterior and anterior plates decreases the efficiency of transverse shearing, by providing two upper plates (anterior plate of one tooth and posterior plate of the preceding tooth) over which the lower cutting blade _simultaneously_ must pass with each movement. The advantages of shearing over the more common mechanics of planing are largely lost unless the posterior plates are eliminated. Also, none of the living Geomyini have retained a definitive posterior enamel plate on M3, the last upper molar; but two well-developed lateral plates, that extend almost all of the way back to the posterior apex of M3, have been retained, and, together function as a posterior plate. Loss of either or both of the lateral plates of M3 is rare, and occurs only in old individuals. Their loss in the final stages of wear may represent the beginning of a new trend in those species where it occurs (the _castanops_-group of the subgenus _Cratogeomys_). In any case, reduction of enamel takes place by transverse shortening of the plate through the complete loss of enamel on one end, the diminution beginning first on the labial end and proceeding by progressive atrophy to the lingual end of the plate. Evidently, when enamel has been eliminated from the labial end of a plate, the rate of loss decreases markedly, and the last stages of evolution, terminating in complete loss of an enamel plate, occurs more slowly. Evolution may be arrested before complete loss has occurred, and that part of the enamel that remains forms a short, vestigial plate restricted to the lingual one-fourth or one-third of the wall. The enamel pattern of the lower dentition is the same in all of the diverging lineages, with no evidence of additional loss of enamel from that which had already occurred in their common ancestor (see Figs. 7 and 9). Reduction and loss of enamel plates began and was terminated in the lower dentition before reduction began in the upper dentition. Other dental specializations have occurred in the shape of the third upper molar and in the pattern of grooving in the upper incisor. Unlike M3 of the Thomomyini, that of the Geomyini differs in shape from M2, and its enamel investment differs from that of M2. Primitively, M3 was probably subtriangular in cross-section, and the posterior loph evidently projected posteriorly as a short, rudimentary heel that formed the apex of the triangle. Other shapes of M3 are considered to be specializations that have been derived from the primitive form. In addition to the primitive subtriangular pattern, the M3 of living Geomyini may be suborbicular, quadriform, elongate, or obcordate in shape. Usually each lineage is characterized by only one pattern, but in one genus (_Pappogeomys_) all patterns occur. Of the different forms, the elongate and obcordate seem to be the most highly specialized deviations from the triangular-shaped tooth. The bicolumnar pattern is accentuated in the elongate type (Fig. 7D, F, H) by deep lateral re-entrant folds, on both the lingual and labial sides, and by the elongation of the posterior loph into a pronounced heel. Teeth having this pattern have been illustrated by Merriam (1895:76-82) in Figures 27 (6 and 7), 28 (c and d), 34 (7 through 15), and 35 (8). [Illustration: FIG. 7. Molariform dentitions of the Tribe Geomyini. Drawings illustrating enamel patterns characteristic of _Pliogeomys_, _Zygogeomys_, and the subgenera of _Orthogeomys_ (_Orthogeomys_, _Heterogeomys_ and _Macrogeomys_). � 5.       A. _Pliogeomys buisi_, No. 29157 (UMMP), holotype, Buis Ranch (Upper Middle Pliocene), Beaver Co., Oklahoma. Right lower, p4-m2 (m3 unknown). B and C. _Zygogeomys trichopus trichopus_, adult female, No. 51971 (FMNH), Mt. Tancítaro, 10,500 ft., Michoacán. Left upper (B), P4-M3; right lower (C), p4-m3. D and E. Subgenus _Orthogeomys_. _Orthogeomys grandis guerrerensis_, adult female, No. 39807 (KU), 1/2 mi. E La Mira, 300 ft., Michoacán. Left upper (D), P4-M3; right lower (E), p4-m3. F and G. Subgenus _Heterogeomys_. _Orthogeomys hispidus hispidus_, adult female, No. 23975 (KU), 4 km. W Tlapacoyan, 700 ft., Veracruz. Left upper (F), P4-M3; right lower (G), p4-m3. H and I. Subgenus _Macrogeomys_. _Orthogeomys heterodus cartagoensis_, adult female, No. 60664 (KU), Rancho Redando, Volcán Lrozá, Prov. San José, Costa Rica. Left upper (H), P4-M3; right lower (I), p4-m3. ] The subcordate form is characterized by pronounced anteroposterior compression, and retention of a distinct labial re-entrant fold. The posterior loph apparently has been rotated in such a way that what was previously its posterior border now lies on the outer margin of the tooth; therefore, the axis of the posterior loph is strongly oblique in relation to the anteroposterior bearing of the maxillary tooth-row, and the median enamel plate also has been rotated and so lies transversely across the posterior wall of the tooth. Owing to the rotation of the posterior loph, the apex of the obcordate tooth is at its lingual side. The subcordate type is illustrated by Merriam (_loc. cit._) in Figures 27 (3 and 4), 28 (a and b), 34 (3 and 4), and 35 (5, 6, and 7). The suborbicular and quadriform types are less specialized than the two described above. Both are characterized by reduction, often obliteration, of the bicolumnar pattern of the subtriangular ancestral form, especially marked by the decrease in depth of the lateral re-entrant folds and the decrease in length of the posterior projection of the posterior loph. With these changes, the tooth becomes essentially monocolumnar, its occlusal surface oval in outline in one and squarish in shape in the other. Occlusal views of the suborbicular form are presented by Merriam (_loc. cit._) in Figure 33 (1, 5, 6, 7, 11, and 12) and the quadriform tooth is depicted in Figure 29. Grooved upper incisors are characteristic of the living Geomyini, but variation occurs in the number of grooves, and, if only one groove is present, its position on the anterior face of the tooth varies. Except for the previously mentioned (p. 480) abnormal tooth having three grooves, incisors with no more than two grooves are found in these pocket gophers, and this number of grooves is taken to be primitive. Loss of one or the other of the two grooves of the bisulcate pattern, therefore, is regarded as specialization. However, complete loss of both grooves never occurs in the Geomyini. Each of the four major lineages is characterized by one of the three patterns of grooving, and the particular groove-pattern is remarkably stable in each group. Shape of skull varies from dolichocephalic to platycephalic. The morphology of each has been described in foregoing accounts. The dolichocephalic skull is highly specialized for planing, a grinding action of the teeth; whereas, the platycephalic skull is highly specialized for shearing, a slicing action of the teeth. Of course, concomitant specializations of the dentition, as described above, are closely associated with both specialized trends in the skull. Most kinds of living Geomyini have generalized skulls that show no tendency toward either of the specialized conditions. Increase in size of body and skull is seen in most Pleistocene lineages of the Geomyini. Judging from the smallness of the skull in late Pliocene species, representing the base of three of these lineages, the ancestral species of the living assemblage were no larger than the living species of the subgenus _Pappogeomys_ or the smaller subspecies of _Geomys bursarius_. The recorded range of variation in condylobasal length is 36.1 to 45.5 in _Pappogeomys bulleri_, including both adult males and females. Probably the skulls of the ancestral species were not significantly larger. Maximum dimensions of males in living species are 74.5 (subgenus _Cratogeomys_) and 75.0 (subgenus _Orthogeomys_). These are more than twice the minima observed in _Pappogeomys bulleri_. Zygogeomys This is the least specialized and most primitive of the four lineages, has a generalized type of skull, two grooves on the anterior face of each upper incisor, an enamel plate on the posterior wall of P4, open or divergent lateral re-entrant angles on the premolars, and a bicolumnar and elongated M3. All of these features are primitive and essentially as in the ancestral morphotype. No other modern genus retains so much of the primitive structure. Phyletic trends in _Zygogeomys_ are not well documented in the fossil record; and only a few fossils are known and they are fragmentary as discussed before. The genus is represented in the late Pliocene (_Z. minor_), middle Pleistocene (_Z. persimilis_), and Recent (_Z. trichopus_). The living species is a relict population in the mountains of Central México. Judging from the known material, the phyletic trends in the genus have been increase in size, reduction of enamel on the posterior face of P4 (occurring only in the living species) where a short enamel plate is retained on the lingual side of the tooth (see Fig. 7B), loss of the outer fourth of the enamel blade on the posterior wall of M1 and M2 (also occurring only in the living species), development of a more pronounced heel on the M3 by progressive elongation of the posterior loph, reduction in size of the jugal and its displacement ventrally, which allows the maxillary and squamosal bones to meet along the dorsal border of the zygomatic arch. The last specialization is seen in at least one taxon of _Orthogeomys_ (_Orthogeomys cherriei costaricensis_). In my opinion, too much weight has been given to this feature in past classifications. Reduction of enamel in the upper dentition evidently occurred in the late Pleistocene, since the posterior plates on the upper cheek teeth were complete in specimens from the middle Pleistocene (_Z. persimilis_). Geomys _Geomys_, slightly more specialized than _Zygogeomys_, must also be regarded as one of the most primitive of the living genera. Primitive features that have been retained are the generalized type of skull, the bisulcate pattern of grooves on the upper incisor, and the retention of enamel plates on both the anterior and posterior walls of M1 and M2 (see Fig. 9A). All of these primitive features are shared with _Zygogeomys_. In addition, three other trends, or specializations, in evolution characterize the phyletic development of _Geomys_. One major trend is toward loss of the enamel plate from the posterior wall of P4. No trace of enamel remains on the posterior wall of this tooth in late Pleistocene or Recent species of _Geomys_, and at least one of the earlier species (_quinni_) was also characterized by loss of this enamel plate. Secondly, M3 retains only a vestige of the primitive bicolumnar pattern after the initial stages of wear. In most Recent specimens, especially of the species _G. bursarius_, the lateral re-entrant fold and the heel of M3 are small, and the re-entrant inflection is hardly evident. The lateral fold is more frequently well-developed in Irvingtonian species than in living species (White and Downs, 1961:13), illustrating progressive loss of the bicolumnar pattern in Pleistocene evolution. A third trend involves the modification of the lateral folds of the premolars. Primitively the angles of these folds are broadly open or divergently V-shaped, and some of the earliest species of _Geomys_, for example _G. quinni_, have retained this feature throughout life. Nevertheless, the main trend is toward progressive compression of the folds resulting in their walls being more nearly perpendicular, and parallel, to the long axis of the tooth. Obtuse re-entrant angles persist in premolars of young individuals of Irvingtonian species, but the adults are characterized by well-compressed folds, as in Recent species. Remains of _Geomys_ are abundant, especially from Pleistocene deposits of the Great Plains, but in most instances specific assignment is difficult or impossible since only isolated teeth or fragments of skulls have been preserved. Estimates of phyletic relationships of the known species of _Geomys_ are depicted in Figure 8; those estimates are useful in discussing the phyletic development of the genus. One of the earliest known species, _Geomys quinni_, ranges from Upper Pliocene to the later stages of the Lower Pleistocene (Aftonian interglacial deposits). The dentition of _G. quinni_ is essentially the same as in the living species except that open lateral re-entrant angles are retained in the premolars. _Geomys paenebursarius_, also of the early Pleistocene, is a smaller species and seems to be more directly in the line of evolution of the modern species. As yet unnamed smaller species of _Geomys_ from the Rexroad fauna (late Pliocene) and Saunders fauna (latest Aftonian) may also be on the main line of evolution. Surprisingly, _Geomys tobinensis_ and _Geomys garbanii_ of later Irvingtonian provincial age are less specialized than either _Geomys quinni_ or _Geomys paenebursarius_. It is likely that _G. tobinensis_ and the unnamed species from the Dixon are closer to the main line of descent than _G. paenebursarius_ suggesting that the direct ancestral lineage of the living species of _Geomys_ was more conservative and less specialized than _Geomys paenebursarius_ of the Lower Pleistocene. _Geomys quinni_ and _G. paenebursarius_ seem to have acquired specialized dental features in the early Pleistocene. _Geomys quinni_ was successful on the Great Plains, and persisted into the late Blancan. The main line may be represented in the early Pleistocene by _Geomys paenebursarius_ from the Hancock formation of the Texas Trans-Pecos. The structure of _G. paenebursarius_ indicates that it is in or close to the main line of descent, and probably evolved from one of the more primitive late Pliocene species of _Geomys_ from the Rexroad fauna. [Illustration: FIG. 8. Tentative arrangement of species of the genus _Geomys_, depicting phylogenetic trends and probable relationships within the genus.] Isolated teeth, to which the name _Geomys bisulcatus_ probably applies, from Illinoian deposits on the Great Plains, show that the dentition characteristic of the living _Geomys_ had been developed by that time. Actually, the Illinoian material is too fragmentary to show clearly its taxonomic or phyletic affinities with the species of the later Pleistocene. Even so, the two main stocks of living _Geomys_, _G. bursarius_ and _G. pinetis_, had certainly been differentiated by Sangamon time. The other living species evidently evolved from one or the other of these two stocks in a period of isolation from the main population, probably in either the Wisconsin or post-Wisconsin. For example, _Geomys arenarius_ clearly differentiated from populations of _Geomys bursarius_ that were isolated by the eastward retreat of the main population from the southwestern United States as that region became more arid in the post-Wisconsin. In review, it seems that the Recent species, represented basically by _bursarius_ and _pinetis_, evolved from Illinoian species (_Geomys bisulcatus?_), which descended in turn from the more primitive species of the early Pleistocene, possibly _Geomys paenebursarius_ or possibly from descendants of the Saunders species. Actually the Saunders species may prove to be _Geomys paenebursarius_. At any rate, three trends that took place during the Pleistocene stage of evolution, in the direction of the modern species, were an increase in size, progressive loss of the posterior enamel plate on P4, and a decrease in the vertical depth of the enamel cap as a result of which the dentine is reached in the initial phases of attrition on the tooth of a juvenile. _Geomys garbanii_, occurring at the periphery of the range of the genus, is regarded as a sterile offshoot of the primitive _tobinensis_-line of evolution. Orthogeomys This is one of the more specialized genera of the Geomyini. Save for one record in the late Pleistocene (_Orthogeomys onerosus_), there is no fossil history of the genus upon which to reconstruct its phylogeny; therefore, its phyletic development must be estimated by comparing it and the primitive morphotype of the tribe. Results of that comparison suggest that _Orthogeomys_ has closer affinities with _Zygogeomys_ than with any of the other genera, and that _Orthogeomys_ may have originated in an early dichotomy of primitive _Zygogeomys_ stock instead of descending from the ancestral stock of the tribe. Except for the unisulcate incisors and the longer posterior loph on the third upper molars, the teeth of the two genera do not differ significantly. As in _Zygogeomys_, the enamel blade on the posterior wall of P4 has been reduced to a short plate restricted to the lingual third of the tooth (see Fig. 7F and H). In _Orthogeomys_, the trend in reduction of enamel is carried to its extreme only in the subgenus _Orthogeomys_, where this plate has been completely lost in most taxa (see Fig. 7D). The most significant trends in _Orthogeomys_, and the principal basis for recognizing the genus, are the dolichocephalic specializations of the skull, as described elsewhere, and the adaptive traits that have equipped the genus for living in tropical environments. The dolichocephalic features are more sharply defined in the subgenera _Orthogeomys_ and _Macrogeomys_, and are less developed in the subgenus _Heterogeomys_. Aside from the general dolichocephalic specializations, trends in _Orthogeomys_ include: Increase in size; loss of the median one of the two grooves on the anterior face of the upper incisor in the ancestral stock; increase in the anteroposterior length of each of the cheek teeth, as well as the aforementioned elongation of the posterior loph of M3; compression of the lateral angles of the premolars; and the remarkable increase in the size of the rostrum. Pappogeomys The genus _Pappogeomys_, as it is conceived of in this study, is comprised of two subgenera; one, _Pappogeomys_, is generalized and primitive, and the other, _Cratogeomys_, is specialized, and includes the most highly specialized of the modern pocket gophers. The subgenus _Pappogeomys_ is regarded as the ancestral lineage, and the subgenus _Cratogeomys_ is regarded as an early offshoot, probably in the early Pleistocene, that became progressively more specialized in the course of its subsequent evolution. In the same period of time, the subgenus _Pappogeomys_ changed little. It is known only from late Pliocene fragments and from the living species. The ancestral morphotype is preserved in _Pappogeomys_. Primitive characters are: (1) Small size; (2) skull generalized and smoothly rounded; (3) temporal ridges separate (not uniting into a sagittal crest); (4) enamel plates retained on both anterior and posterior walls of M1 and M2; (5) M3 bilophate, its posterior loph short. Basic specializations are few and include loss of the inner groove from the anterior face of the upper incisor; anteroposterior compression of the lateral re-entrant folds of the premolars; and loss of enamel from the posterior wall of P4. All three features have been perpetuated in the advanced subgenus _Cratogeomys_, suggesting that they were already developed in the early evolution of the subgenus _Pappogeomys_ before _Cratogeomys_ diverged. Agreement with _Geomys_ is demonstrated by the lack of enamel on the posterior wall of P4 (see Fig. 9) and by retention of the posterior enamel plate on M1 and M2. In _Pappogeomys (Pappogeomys) alcorni_ the enamel from the posterior face of M1 has been lost from all but the lingual fourth or so of the posterior wall (Fig. 9E). Reduction of enamel in M1 provides an example of parallelism with the more advanced subgenus _Cratogeomys_, discussed below. There is no record as yet of the early evolution of the subgenus _Cratogeomys_. The features that characterize the subgenus were already well developed in the first known fossils which are from Wisconsin deposits of the late Pleistocene. _Cratogeomys_ is not a homogenous assemblage; instead it is composed of two groups of living species, the generalized _castanops_ group and the specialized _gymnurus_ group. The _castanops_ group may be survivors of the ancestral lineage that diverged in two different stages in the phyletic development of the main line. Even so, the _castanops_ group has acquired its peculiar specializations. Indeed, _P. merriami_ of the _castanops_ group differs from the hypothetical stem more than does _P. castanops_. Judging from the structure of the living species of the subgenus _Cratogeomys_ and from the primitive subgenus _Pappogeomys_, the subgenus _Cratogeomys_ featured five major trends: (1) Increase in size; (2) formation of sagittal crest by union of the temporal impressions; (3) increase in rugosity and angularity of the skull; (4) progressive development of platycephalic specializations, including the elongation of the angular process of the mandible; (5) complete loss of enamel plates from the posterior wall of M1 and M2. Each trend is thought to be adaptive. [Illustration: FIG. 9. Molariform dentitions of the Tribe Geomyini. Drawings illustrating enamel patterns characteristic of _Geomys_ and _Pappogeomys_ (including the subgenera _Pappogeomys_ and _Cratogeomys_). � 5. A and B. _Geomys bursarius bursarius_, adult female, No. 46275 (KU), Elk River, Sherborne Co., Minnesota. Left upper (A), P4-M3; right lower (B), p4-m3. C and D. Subgenus _Pappogeomys_. _Pappogeomys bulleri albinasus_, adult female, No. 31002 (KU), W side La Venta, 13 mi. W and 4 mi. N Guadalajara, Jalisco. Left upper (C), P4-M3; right lower (D), p4-m3. E and F. Subgenus _Pappogeomys_. _Pappogeomys alcorni_, adult female, No. 31051 (KU), holotype, 4 mi. W Mazamitla, 6600 ft., Jalisco. Left upper (E), P4-M3; right lower (F), p4-m3. G and H. Subgenus _Cratogeomys_. _Pappogeomys gymnurus tellus_, adult female, No. 31051 (KU), 1 mi. NE Tala, 4400 ft., Jalisco. Left upper (G), P4-M3; right lower (H), p4-m3. ] Loss of enamel is a trend common to all living genera of the tribe Geomyini, but the greatest loss has occurred in _Cratogeomys_. It has lost the plates on the posterior walls of M1 and M2 (Fig. 9G). If the lateral plates of M3 are considered as one functional plate and the lateral plates on either side of P4 together as two transverse plates, then, the transverse cutting blades in _Cratogeomys_ number seven in the upper and seven in the lower cheek teeth compared with 10 in the upper and seven in the lower in the primitive morphotype. Indeed, in some species of the subgenus, one or both of the lateral plates on M3 is also lost, usually in old age, resulting in even greater reduction of enamel. Loss of enamel from the posterior walls of the upper molars may be associated with changes in the mechanics of mastication from anteroposterior planing to anterotransverse shearing, as discussed elsewhere. Merriam (1895:95-96) argues convincingly that the posterior cutting blades of the upper molars would hinder efficient shearing action of the teeth; hence, selection would favor their reduction and eventual loss. Changes in the shape of the skull also seem to be correlated with the shift from a planing to a shearing type of mastication. More efficient shearing action, which depends upon lateral movement of the jaw, can be developed if the functional muscles insert farther laterally than is possible in the generalized type of skull. Therefore, platycephalic specializations involved lateral expansion of the braincase and mandible. Pronounced lateral expansion has been developed only in the _gymnurus_ group of species, suggesting that the dental specializations evolved earlier in the evolution of the subgenus than did the platycephalic specializations of the skull, and that the _castanops_ group separated from the _gymnurus_ group before the common ancestor had developed the more extreme trends in platycephaly. 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Hagerups Forlag, Copenhagen, 321 pp. WOOD, A. E. 1935. Evolution and relationship of the heteromyid rodents. Ann. Carnegie Mus., 24:73-262, May 13. 1936. Geomyid rodents from the Middle Tertiary. Amer. Mus. Novit., 866:1-31, July 2. 1950. A new geomyid rodent from the Miocene of Montana. Ann. Carnegie Mus., 31:335-338, 1 fig. 1955. A Revised classification of rodents. Jour. Mamm., 36:165-187, May 26. WOOD, A. E., and WILSON, R. W. 1936. A suggested nomenclature for the cusps of the cheek teeth of rodents. Jour. Paleo., 10:388-391, 2 figs., July. _Transmitted May 29, 1967._ [] * * * * * Transcriber's note: All obvious typographical errors were corrected. Minor changes were made to standardize the text to match the most prevalent form used. Typographical Corrections Page Correction ==== ============ 477 cumberlandicus => cumberlandius 535 breath => breadth 
39164	----	Archive. UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY VOLUME 1 1946-1950 EDITORS E. RAYMOND HALL DONALD S. FARNER DONALD F. HOFFMEISTER H. H. LANE A. BYRON LEONARD EDWARD H. TAYLOR ROBERT W. WILSON MUSEUM OF NATURAL HISTORY UNIVERSITY OF KANSAS LAWRENCE, KANSAS 1950 MUSEUM OF NATURAL HISTORY UNIVERSITY OF KANSAS LAWRENCE, KANSAS PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1950 23-2413 CONTENTS 1. The pocket gophers (genus Thomomys) of Utah. By Stephen D. Durrant. Pp. 1-82, 1 figure in text. August 15, 1946. 2. The systematic status of Eumeces pluvialis Cope, and noteworthy records of other amphibians and reptiles from Kansas and Oklahoma. By Hobart M. Smith. Pp. 85-89. August 15, 1946. 3. The tadpoles of Bufo cognatus Say. By Hobart M. Smith. Pp. 93-96, 1 figure in text. August 15, 1946. 4. Hybridization between two species of garter snakes. By Hobart M. Smith. Pp. 97-100. August 15, 1946. 5. Selected records of reptiles and amphibians from Kansas. By John Breukelman and Hobart M. Smith. Pp. 101-112. August 15, 1946. 6. Kyphosis and other variations in soft-shelled turtles. By Hobart M. Smith. Pp. 117-124, 3 figures. July 7, 1947. 7. Natural history of the prairie vole (Mammalian genus Microtus). By E. W. Jameson, Jr. Pp. 125-151, 4 figures in text. October 6, 1947. 8. The postnatal development of two broods of great horned owls (Bubo virginianus). By Donald F. Hoffmeister and Henry W. Setzer. Pp. 157-173, 5 figures in text. October 6, 1947. 9. Additions to the list of the birds of Louisiana. By George H. Lowery, Jr. Pp. 177-192. November 7, 1947. 10. A check-list of the birds of Idaho. By M. Dale Arvey. Pp. 193-216. November 29, 1947. 11. Subspeciation in pocket gophers of Kansas. By Bernardo Villa R. and E. Raymond Hall. Pp. 217-236, 2 figures in text. November 29, 1947. 12. A new bat (Genus Myotis) from Mexico. By Walter W. Dalquest and E. Raymond Hall. Pp. 237-244, 6 figures in text. December 10, 1947. 13. Tadarida femorosacca (Merriam) in Tamaulipas, Mexico. By Walter W. Dalquest and E. Raymond Hall. Pp. 245-248, 1 figure in text. December 10, 1947. 14. A new pocket gopher (Thomomys) and a new spiny pocket mouse (Liomys) from Michoacán, México. By E. Raymond Hall and Bernardo Villa-R. Pp. 249-256, 6 figures in text. July 26, 1948. 15. A new hylid frog from eastern Mexico. By Edward H. Taylor. Pp. 257-264, 1 figure in text. August 16, 1948. 16. A new extinct emydid turtle from the Lower Pliocene of Oklahoma. By Edwin C. Galbreath. Pp. 265-280, 1 plate. August 16, 1948. 17. Pliocene and Pleistocene records of fossil turtles from western Kansas and Oklahoma. By Edwin C. Galbreath. Pp. 281-284, 1 figure in text. August 16, 1948. 18. A new species of heteromyid rodent from the Middle Oligocene of northeast Colorado with remarks on the skull. By Edwin C. Galbreath. Pp. 285-300, 2 plates. August 16, 1948. 19. Speciation in the Brazilian spiny rats (Genus Proechimys, Family Echimyidae). By João Moojen. Pp. 301-406, 140 figures in text. December 10, 1948. 20. Three new beavers from Utah. By Stephen D. Durrant and Harold S. Crane. Pp. 407-417, 7 figures in text. December 24, 1948. 21. Two new meadow mice from Michoacán, México. By E. Raymond Hall. Pp. 423-427, 6 figures in text. December 24, 1948. 22. An annotated check list of the mammals of Michoacán, México. By E. Raymond Hall and Bernardo Villa-R. Pp. 431-472, 2 plates, 1 figure in text. December 27, 1949. 23. Subspeciation in the kangaroo rat, Dipodomys ordii. By Henry W. Setzer. Pp. 423-573, 27 figures in text, 7 tables. December 27, 1949. 24. Geographic range of hooded skunk, Mephitis macroura, with description of a new subspecies from Mexico. By E. Raymond Hall and Walter W. Dalquest. Pp. 575-580, 1 figure in text. January 20, 1950. 25. Pipistrellus cinnamomeus Miller 1902 referred to the genus Myotis. By E. Raymond Hall and Walter W. Dalquest. Pp. 581-590, 5 figures in text. January 20, 1950. 26. A synopsis of the American bats of the genus Pipistrellus. By E. Raymond Hall and Walter W. Dalquest. Pp. 591-602, 1 figure in text. January 20, 1950. Index pp. 605-638. The Pocket Gophers (Genus Thomomys) of Utah BY STEPHEN D. DURRANT University of Kansas Publications Museum of Natural History Volume 1, No. 1, pp. 1-82, 1 figure in text August 15, 1946 UNIVERSITY OF KANSAS LAWRENCE 1946 The Pocket Gophers (Genus Thomomys) of Utah BY STEPHEN D. DURRANT University of Kansas Publications Museum of Natural History Volume 1, No. 1, pp. 1-82, 1 figure in text August 15, 1946 UNIVERSITY OF KANSAS LAWRENCE 1946 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Donald S. Farner, Donald F. Hoffmeister Volume 1, No. 1, pp. 1-82, 1 figure in text. Published AUGUST 15, 1946 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1946 21-2786 The Pocket Gophers (Genus Thomomys) of Utah By STEPHEN D. DURRANT Contribution from the Department of Biology, University of Utah, and the Museum of Natural History, University of Kansas. INTRODUCTION The history of pocket gophers of Utah begins with J. A. Allen's mention in 1874 of mounds of these animals. For them he employed the name "_Thomomys rufescens?_" (1874:65). Actual specimens were reported upon a year later by Elliot Coues (1875:251, 256), who used the name _Thomomys talpoides_ for specimens from "Utah" but later in the same paper listed specimens from Provo as _Thomomys talpoides bulbivorus_. Even as the great variation in Utah pocket gophers has been perplexing to modern workers, so it was also to Coues seventy years ago who left the problem with the statement that animals from Provo "exhibit among themselves such variations that their labelling becomes a matter of indifference"! In the same year in another report, Coues and Yarrow (1875:112) used the name _Thomomys talpoides umbrinus_ for animals from Provo. In 1877, Coues again referred these same animals to _Thomomys talpoides bulbivorus_, using the name _umbrinus_ for the animals of only southern Utah (Coues, 1877:627, 628). The two names _Thomomys bottae_ and _Thomomys talpoides_, now applicable to gophers in Utah, were synonomized under the name _Thomomys talpoides bulbivorus_ by Coues (1875:256; 1877:627). After this beginning only three other papers, all by J. A. Allen, appeared in the next twenty years. They were reports on collections of mammals made by Walter W. Granger and Charles P. Rowley. One of these contained the description of _Thomomys aureus_. Likewise, in the ensuing twenty years there were only three papers, one in 1901 by C. Hart Merriam in which he described _Thomomys uinta_, one by Allen (1905:119), and Vernon Bailey's (1915) "Revision of the pocket gophers of the genus _Thomomys_" in which he summarized the information then available on these animals within the state. Barnes (1922 and 1927) reprinted the information summarized by Bailey. Since 1927 approximately twenty-five papers, mostly taxonomic, have been published in which reference is made to Utah gophers, and especially since 1930 much information has been accumulated about the distribution and speciation of this genus within the state. Specimens to the number of 1,045 have been available for this study. Whereas Bailey (_loc. cit._) listed only four kinds belonging to four different species, thirty-five kinds are now known from Utah. Seven of these are herein described as new. The thirty-five kinds are found to belong to only two instead of four full species. Inasmuch as the literature is scattered and since names have been applied in different ways at different times, I have attempted to give a synonomy as complete as possible for each form found within the state. The bibliographies of Hayward (1936 and 1941) and Miller's (1924) "List of North American mammals" have been of great use. Capitalized color terms in the accounts are after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912. In the lists of specimens examined, the localities are listed by counties from west to east, beginning at the northwestern corner of the state, and within each county from north to south. When two localities are on the same latitude, the westernmost is listed first. I am deeply indebted to Professor R. V. Chamberlin, of the University of Utah, for encouragement and support in my investigation. I also acknowledge critical assistance in the preparation of this paper from Professor E. Raymond Hall of the University of Kansas. For the loan of specimens I am grateful to the following: Clinton G. Abbott and Lawrence M. Huey, Natural History Museum of San Diego, San Diego, California; Harold E. Anthony and J. Eric Hill, American Museum of Natural History, New York City, New York; Seth B. Benson, Museum of Vertebrate Zoölogy, University of California, Berkeley, California; William H. Burt, Museum of Zoölogy, University of Michigan, Ann Arbor, Michigan; J. Kenneth Doutt, Carnegie Museum, Pittsburgh, Pennsylvania; Ross Hardy, Dixie Junior College, St. George, Utah; C. Lynn Hayward and Vasco M. Tanner, Brigham Young University, Provo, Utah; H. H. T. Jackson and Viola S. Schantz, United States Fish and Wildlife Service, U. S. National Museum, Washington, D. C.; Remington Kellogg and Alexander Wetmore, U. S. National Museum, Washington, D. C.; J. S. Stanford, Utah State Agricultural College, Logan, Utah. Unless otherwise indicated, specimens are in the Museum of Zoölogy, University of Utah, Salt Lake City, Utah. In lists of specimens examined, abbreviations are employed as follows: (A. M. N. H.) American Museum of Natural History. (N. H. M. S. D.) Natural History Museum of San Diego. (M. V. Z.) Museum of Vertebrate Zoölogy, University of California. (U. M.) Museum of Zoölogy, University of Michigan. (C. M.) Carnegie Museum. (R. H.) Collection of Ross Hardy. (B. Y. U.) Brigham Young University. (U. S. N. M.) United States National Museum. (U. S. A. C.) Utah State Agricultural College. (K. U.) Museum of Natural History, University of Kansas. [Illustration: FIG. 1. Map showing the distribution of species and subspecies of pocket gophers in Utah.] Guide to subspecies: 1. _T. t. gracilis_ 2. _T. t. wasatchensis_ 3. _T. t. oquirrhensis_ 4. _T. t. uinta_ 5. _T. t. pygmaeus_ 6. _T. t. ravus_ 7. _T. t. ocius_ 8. _T. t. moorei_ 9. _T. t. fossor_ 10. _T. t. parowanensis_ 11. _T. t. levis_ 12. _T. b. aureiventris_ 13. _T. b. robustus_ 14. _T. b. minimus_ 15. _T. b. nesophilus_ 16. _T. b. stansburyi_ 17. _T. b. albicaudatus_ 18. _T. b. bonnevillei_ 19. _T. b. centralis_ 20. _T. b. sevieri_ 21. _T. b. convexus_ 22. _T. b. tivius_ 23. _T. b. contractus_ 24. _T. b. lenis_ 25. _T. b. levidensis_ 26. _T. b. osgoodi_ 27. _T. b. howelli_ 28. _T. b. wahwahensis_ 29. _T. b. dissimilis_ 30. _T. b. aureus_ 31. _T. b. birdseyei_ 32. _T. b. virgineus_ 33. _T. b. planirostris_ 34. _T. b. absonus_ 35. _T. b. alexandrae_ GENUS =Thomomys= Wied All pocket gophers of Utah belong to the genus _Thomomys_. There are only two species within the state, _Thomomys bottae_ with twenty-four subspecies and _Thomomys talpoides_ with eleven subspecies. Due to marked mutational capacities and ready response to environmental pressures and sedentary habits, pocket gophers differentiate readily into numerous subspecies. It is well known that Utah by its highly varied topography and climate possesses widely different types of habitats. The aforementioned plasticity of these animals and possibly the fact that both species are at the extreme limits of their ranges in Utah account for the numerous forms found within the state. The genus may be characterized as follows: Highly specialized fossorial rodents, with heavy, thick bodies; all four legs of approximately equal length, but front legs more muscular for digging, and feet provided with long claws; external fur-lined cheek pouches; small eyes, short ears and tail; upper incisors long and projecting external to lips. Skull: Stout and flattened; zygomatic arches well developed and usually widely spreading; all teeth with permanent pulp cavities; incisors superficially smooth, but fine median groove present on anterior face of each upper incisor; dental formula, i. 1/1, c. 0/0, p. 1/1, m. 3/3; external auditory canal long; stapedial artery small and enclosed within an osseous canal. =Thomomys talpoides= (Richardson) _Thomomys talpoides_ is a northern species that in Utah approaches the southern limits of its range. The animals of this species inhabit the mountains and high valleys. In the southward extension of their range, as in Utah, they are found at higher elevations which zonally represent lower elevations at more northern latitudes. The specific characters are: Sphenorbital fissure absent; incisive foramina anterior to infraorbital canal; anterior prism of P4 triangular; interparietal relatively large; lambdoidal suture concave posteriorly in region of interparietal, in Utah specimens. =Thomomys talpoides gracilis= Durrant _Thomomys quadratus gracilis_ Durrant, Bull. Univ. Utah, 39 (No. 6):3, February 28, 1939. _Thomomys talpoides gracilis_ Durrant, Bull. Univ. Utah, 30 (No. 5):6, August 24, 1939; Goldman, Journ. Mamm., 25:414, December 12, 1944. _Thomomys quadratus fisheri_ Hall, Univ. California Publ. Zoöl., 37:4, April 10, 1931. _Thomomys uinta_ Bailey, N. Amer. Fauna, 39:114, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):83, April, 1922; Bull. Univ. Utah, 17 (No. 12):104, June, 1927. _Type._--Male adult, skin and skull; No. 44866, Museum of Vertebrate Zoölogy, University of California; Pine Canyon, 6,600 ft., 17 mi. NW Kelton, Box Elder County, Utah; July 12, 1930; collected by Annie M. Alexander; original number 676. _Range._--Mountainous regions of extreme northwestern Utah. _Diagnosis._--Size medium (see measurements). Color: Upper parts Buckthorn Brown grading over the sides and flanks to Light Buff on the underparts; chin white; nose and postauricular patches grayish black. Claws on front feet long and slender. Skull: Long and slender; rostrum long and narrow; zygomatic and mastoidal breadths slight; palatal pits deep; upper incisors narrow; basioccipital wide. _Comparisons._--Compared with topotypes of _Thomomys talpoides fisheri_, _gracilis_ is of approximately the same size. Upper parts darker and underparts lighter; postauricular patches larger and darker; claws on front feet longer and slenderer. Skull: Generally longer and narrower; nasals and rostrum longer; basioccipital wider. As compared with _T. t. uinta_, _gracilis_ is of approximately the same size but differs as follows: Color: Lighter throughout; postauricular patches markedly smaller and lighter; inguinal and pectoral regions much lighter. One characteristic difference is in the ear. In _uinta_ the external opening of the ear is much larger; the pinna of the ear is larger, more rounded at the tip, and lacks most of the pigmentation on the inner margin. Skull: Generally narrower and longer; nasals longer; zygomatic arches weaker and less angular; upper incisors narrower. This form is easily distinguished from _bridgeri_ by smaller size, and by the skull being longer, narrower and less angular. From _Thomomys talpoides oquirrhensis_ to the southeast, _T. t. gracilis_ can be distinguished by: Total length and ear shorter. Color: Generally lighter, except the underparts which are about the same; postauricular patches larger and more deeply pigmented. Skull: Braincase less inflated; nasals truncated posteriorly as opposed to rounded; zygomatic and mastoidal breadths less; rostrum shorter but narrower; upper incisors narrower and shorter. For comparisons with _wasatchensis_ see comparisons under that form. In general, this mountain form can be distinguished from all other _talpoides_ in Utah by lighter color, narrow, slender, "graceful" skull whence the name _gracilis_ is derived. _Remarks._--In Utah, _gracilis_ is limited to the extreme northwestern corner of the state. This part of the state is in the Snake River drainage. The main part of the range of this race lies in south-central and southwestern Idaho and northeastern Nevada. The center of its range might be considered to be in the Jarbidge Mountains area of Nevada. The south slopes of these mountains are in the Humboldt River drainage, while the north slopes are in the Snake River drainage, and this subspecies occurs as far north as the Snake River and south and west almost to central Nevada. No specimens are available from the area in Utah between the Raft River Mountains inhabited by _gracilis_ and the Wasatch Mountains in central Utah inhabited by _wasatchensis_. Judging from the nature of the terrain, the range of _gracilis_ does not extend eastward much beyond the Raft River Mountains. The type locality for a gopher of a different species, _Thomomys bottae aureiventris_, is in the first valley east of these mountains. Furthermore, all valleys to the east and south, as far as known, are inhabited by gophers of the _bottae_ group. Also, all mountain ranges in this area, as far east as the Wasatch Mountains are inhabited by members of the _bottae_ group. No specimens from Utah indicate intergradation between _gracilis_ and _wasatchensis_, the form to the east, but specimens from farther north at Albion, Cassia County, Idaho, do show intergradation. Bailey (1915:116), Hall (1931:4), and Durrant (1939:6) have reported on these specimens which at the present time seem best referred to _T. t. gracilis_. _Specimens examined._--Total, 24, distributed as follows: _Box Elder County_: Yost, 4 (U. S. A. C.); Pine Canyon, 6,600 ft., 17 mi. NW Kelton, 7 (M. V. Z.): Lynn Canyon, Raft River, 4; Park Valley, 3 (U. S. A. C.); Etna, 4 (U. S. A. C.); Raft River Mountains, Clear Creek Camp of Minnedoka National Forest, 1 (R. H.); Raft River Mountains, 1,500 feet above Clear Creek Camp of Minnedoka National Forest, 1 (R. H.). =Thomomys talpoides wasatchensis= new subspecies _Thomomys quadratus uinta_ Hall, Univ. California Publ. Zoöl., 37:4, April 10, 1931. _Thomomys talpoides uinta_ Goldman, Journ. Mamm., 20:234. May 14, 1939. _Thomomys uinta_ Bailey, N. Amer. Fauna, 39:114, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):83, April, 1922; Bull. Univ. Utah, 17 (No. 12):104, June, 1927; Stanford, Journ. Mamm., 12:360, November 11, 1931. _Type._--Male, adult, skin and skull, No. 1604, Museum of Zoölogy, University of Utah; Midway, 5,500 ft., Wasatch County, Utah; September 1, 1936; collected by S. D. Durrant; original number 1049. _Range._--Wasatch Mountains and neighboring high valleys as far south as Spanish Fork Canyon, Utah County. _Diagnosis._--Size medium (see measurements). Color: Upper parts Snuff Brown, finely mixed with black; sides and flanks Sayal Brown; underparts overlaid with Cinnamon Buff, with suffusion of black on underfur; postauricular patches black, extending around ear; ears pointed and covered with black hairs; nose, cheeks, chin and top of head dusky; front feet, hind feet and distal part of tail white; tail covered proximally with light brown hairs. Skull: Moderately heavy and ridged; nasals long, wide posteriorly and not markedly dilated distally; posterior ends of nasals emarginate; zygomatic arches fairly widely spreading and angular, being nearly straight in adults, but tending to bow out slightly at posterior ends in young; zygomatic processes of maxillae heavy; interparietal small and variously shaped, but always wider than long; interorbital region fairly wide; well marked dorsal depression in frontals posterior to ends of nasals; interpterygoid space narrowly V-shaped; tympanic bullae large; occipital condyles large and widely separated; foramen magnum large and higher than wide; basioccipital wide; dentition light. _Comparisons._--From topotypes of _Thomomys talpoides moorei_, _wasatchensis_ differs as follows: Size slightly larger; ears longer and more pointed. Color: Generally darker throughout; postauricular patches smaller. Skull: Zygomatic arches not as widely spreading; zygomatic processes of squamosals dip farther ventrally; premaxillae less extended posterior to nasals; nasals wider posteriorly and less dilated distally; median dorsal depression of frontals present; tympanic bullae generally larger, but less inflated ventrally; foramen magnum larger especially in dorsoventral dimension; occipital condyles farther apart; basioccipital wider; alveolar length of upper molar series less; molariform teeth smaller; upper incisors wider and shorter. Topotypes of _wasatchensis_ differ from topotypes and near topotypes of _Thomomys talpoides uinta_ as follows: Size larger in every measurement taken. Color: Darker throughout; ears longer and more pigmented; opening of external ear smaller; postauricular patches larger. Skull: In females larger throughout, more massive and angular; nasals longer, wider and not so dilated distally; rostrum longer but wider; zygomatic arches wider, more angular and less widely spreading posteriorly; extension of premaxillae posterior to nasals less; tympanic bullae larger, but less inflated ventrally; foramen magnum larger and more ovoid; width across occipital condyles greater; basioccipital wider; molariform teeth smaller; upper incisors shorter and wider. Topotypes of _wasatchensis_ can be distinguished from those of _Thomomys talpoides oquirrhensis_ as follows: Size larger; tail longer; ears longer. Color: Slightly darker on sides and underparts. Skull: Heavier, more ridged and angular; nasals more dilated distally; posterior ends of nasals more deeply emarginate; zygomatic arches heavier and more widely spreading, but more nearly parallel and less divergent posteriorly; zygomatic processes of maxillae much heavier; braincase and tympanic bullae larger; pterygoid hamulae shorter; interpterygoid space more narrowly V-shaped; wider across occipital condyles; foramen magnum larger and more ovoid. From topotypes of _Thomomys talpoides gracilis_, _wasatchensis_ differs as follows: Size larger; hind foot longer; ears longer and more pointed. Color: Darker throughout; postauricular patches relatively smaller. Skull: Larger, heavier and more angular; nasals emarginate posteriorly as opposed to truncate; rostrum heavier; zygomatic arches heavier and more widely spreading; zygomatic processes of maxillae much heavier and more angular; mastoid breadth greater; interparietal relatively smaller; extension of premaxillae posterior to nasals actually as well as relatively less; palatal pits deeper; tympanic bullae larger; interpterygoid space more narrowly V-shaped; foramen magnum more ovoid; upper incisors wider. Topotypes of _wasatchensis_ can be readily distinguished from those of _Thomomys talpoides levis_ and _parowanensis_ by larger size; more massive, ridged, angular skulls; larger tympanic bullae; large, ovoid foramen magnum; and relatively smaller interparietal. _Remarks._--Specimens from Mount Timpanogos and environs are intergrades between _moorei_ and _wasatchensis_. They resemble _moorei_ in the shape and size of the tympanic bullae, and are intermediate in the size and shape of the foramen magnum. In the majority of characters they resemble _wasatchensis_ to which they are here referred. The animals from east of Salt Lake City in Salt Lake County are intergrades between _oquirrhensis_ and _wasatchensis_ and show some characters of _uinta_, but are referable to _wasatchensis_. Animals from Morgan County and western Summit County are intergrades between _wasatchensis_ and _uinta_. They resemble _uinta_ in size, shape of nasals and size of tympanic bullae. The remainder of the cranial details place them with _wasatchensis_. Morphologically the animals from Wellsville, Cache County, were the closest to the topotypes of any obtained and are nearly indistinguishable from them. Like the topotypes of _wasatchensis_ this population inhabits a high valley. The remaining specimens from Cache County resemble those from Morgan and Summit counties. _Specimens examined._--Total, 119, distributed as follows: _Cache County_: Logan Canyon, Beaver Basin, Utah-Idaho Line, 2 (U. S. A. C); Logan Canyon, Tony Grove Camp, 6 (U. S. A. C); Logan Canyon, Green Camp, 3 (U. S. A. C); Logan Canyon, 3 (U. S. A. C); Logan Mountains, 20 mi. E Logan, 3 (U. S. A. C); Logan Peak area, 13 (U. S. A. C); near Providence Peak, Logan Mountains, 1 (U. S. A. C.); Wellsville, 10 (U. S. A. C); Hardware Ranch, Blacksmith Fork, 1 (U. S. A. C); Avon, 1 (U. S. A. C); 1 mi. E Avon, 1 (U. S. A. C); 7-8 mi. E Avon, 1 (U. S. A. C). _Weber County_: South Fork, Ogden River, 18 mi. E Ogden, 4 (M. V. Z.). _Morgan County_: East Canyon, 18 mi. NW Park City, 6,000 ft., 1. _Davis County_: 8 mi. NE Salt Lake City, 1. _Salt Lake County_: Mouth of Dry Canyon, 1 mi. NE Salt Lake City, 1; 4 mi. above mouth City Creek Canyon, 5,000 ft., 1; mouth of Emigration Canyon, 1; mouth of Millcreek Canyon, 1; Lambs Canyon, 13 mi. SE Salt Lake City, 2 (C. M.); mouth of Big Cottonwood Canyon, 1. _Summit County_: Park City, 1 (U. S. N. M.). _Wasatch County_: Midway, 5,500 ft., 29. _Utah County_: Mt. Timpanogos, 1 mi. N Aspen Grove, 7,500 ft., 20; Aspen Grove, Mt. Timpanogos, 5 (1, U. S. A. C.; 4, B. Y. U.); Head of Grove Creek, Mt. Timpanogos, 4 (B. Y. U.). _Additional Records_: _Weber County_: Ogden, 6. _Salt Lake County_: Parleys Canyon, 1 (Bailey, 1915:114). =Thomomys talpoides oquirrhensis= Durrant _Thomomys talpoides oquirrhensis_ Durrant, Bull. Univ. Utah, 30 (No. 5):3, October 24, 1939. _Type._--Male, adult, skin and skull; No. 2605, Museum of Zoölogy, University of Utah; Settlement Creek, Oquirrh Mountains, 6,500 ft., Tooele County, Utah; June 11, 1938; collected by S. D. Durrant; original number 1461. _Range._--Known only from the Oquirrh Mountains, which are in Salt Lake, Tooele and Utah counties, Utah. _Diagnosis._--Size medium (see measurements); ear long; tail short, claws of front feet long and slender. Color: Upper parts Buckthorn Brown, mixed with black, grading over the sides and flanks to Pinkish Buff on the ventral surface; feet white; nose grayish black; postauricular patches medium in size and black; chin and throat with varying amounts of white; proximal two-thirds of tail dark brown, distal third white. Skull: Long and slender, but relatively wide across mastoidal region; nasals long and rounded posteriorly; rostrum long and narrow; zygomatic arches weak and not widely spreading, tending to be slightly bowed out posteriorly, but in the main roughly parallel to the sides of the skull; outer margin of zygomatic arch slightly concave, and zygomatic arch dips deeply ventrad; dorsal surface of skull smooth, with weakly defined parietal crests; parietal crest nearly parallel, but bowed medially, in parietal region, and flaring widely posteriorly to pass lateral to interparietal; tympanic bullae large, truncate anteriorly and markedly inflated ventrally; upper incisors short and fairly robust. _Comparisons._--From _Thomomys talpoides uinta_, _oquirrhensis_ may be differentiated as follows: Color: Darker throughout; postauricular patches larger and darker; ears longer and more pointed; inner margin of pinna heavily pigmented; external opening of ear smaller. Skull: Nasals rounded posteriorly rather than deeply emarginate, and less flaring distally; zygomatic arches weaker and markedly less widely spreading; pterygoid hamulae weaker; basisphenoid narrower; upper incisors shorter and wider. For comparisons between _oquirrhensis_ and _Thomomys talpoides gracilis_, and _oquirrhensis_ and _wasatchensis_, see comparisons under those forms. Topotypical specimens of _oquirrhensis_ can be distinguished from those of _Thomomys talpoides moorei_ as follows: Color generally darker, due to greater admixture of black; terminal bands of hair actually lighter; postauricular patches larger and darker; ears longer, more pointed and with more heavily pigmented pinnae; tail shorter. Skull: About the same size; smoother; zygomatic arches weaker and less widely spreading; nasals rounded posteriorly as opposed to emarginate; mastoid breadth less; pterygoid hamulae weaker; upper incisors wider. _Remarks._--This race is limited to the Oquirrh Mountains, a high mountain range that lies parallel to, and just west of the Wasatch Mountains, in Utah, Salt Lake and Tooele counties. These mountains were connected in past times to the Wasatch Mountains by the Transverse Range, and by a sand and gravel bar deposited by Pleistocene Lake Bonneville. The Jordan River in its course from Utah Lake to the Great Salt Lake has cut a channel through the aforementioned bar. This channel has been cut to the level of the surrounding valleys as is indicated by the meandering nature of the stream through this part of its course. As a result the Oquirrh Mountains are relatively isolated. Although separated from the Wasatch Mountains by the Jordan River Valley only a few miles wide, the pocket gophers are distinct on each mountain. A population of _T. bottae_ is interposed between the two mountain ranges as is indicated by specimens from Riverton, six miles north of the Transverse Range. The populations of _bottae_ are subspecifically the same on the two sides of the Jordan River. On the east side of the Oquirrh Mountains, pocket gophers collected from the Jordan Valley up Rose Canyon to about 5,000 feet elevation were all of the species _T. bottae_. Between 5,000 and 6,000 feet there is an area in which the ranges of _bottae_ and _talpoides_ overlap. When trapping, it is possible to predict what species will be taken by the types of burrows and soil. Gophers of the _bottae_ group have their burrows in the areas of the deepest soil and heaviest vegetation, whereas the areas of shallow, rocky soil covered with sparse vegetation are the habitat of _talpoides_. Above 6,000 feet the only gopher encountered is _talpoides_. Along Settlement Creek on the west side of the Oquirrh Mountains, which is the type locality of _oquirrhensis_, _bottae_ and _talpoides_ have essentially the same vertical distribution as in Rose Canyon. On this mountain the two species appear to be in competition. The available information, based on collections, indicates that the Oquirrh Mountains are the only mountains west of the Wasatch Range upon which _talpoides_ occurs. In Utah, all other mountains to the west, as far as known, are inhabited by subspecies of of _Thomomys bottae_. _Specimens examined._--Total, 41, as follows: _Tooele County_: Settlement Creek, Oquirrh Mountains, 6,500 ft., 14. _Salt Lake County_: Rose Canyon, Oquirrh Mountains, 5,650 ft., 27. =Thomomys talpoides uinta= Merriam _Thomomys uinta_ Merriam, Proc. Biol. Soc. Washington, 14:112, July 19, 1901; Bailey, N. Amer. Fauna, 39:113, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):83, April, 1922; Bull. Univ. Utah, 17 (No. 12):104, June, 1927; Stanford, Journ. Mamm., 12:360; November 11, 1931; Goldman, Journ. Washington Acad. Sci., 28:333, July 15, 1938; Davis, The Recent mammals of Idaho, pp. 239, 259, The Caxton Printers, Ltd., Caldwell, Idaho, April 5, 1939. _Thomomys talpoides uinta_ Goldman, Journ. Mamm., 20:234, May 14, 1939. _Thomomys quadratus uinta Hall_, Univ. California Publ. Zoöl., 37:4, April 10, 1931. _Type._--Male, adult, skin and skull, No. 22501/30051, U. S. National Museum (Biological Surveys Collection); north base Gilbert Peak, Uinta Mountains, 10,000 ft., Summit County, Utah; June 6, 1890; collected by Vernon Bailey; original number 1262 (after Merriam, type not seen). _Range._--Uinta Mountains in Duchesne County, eastern Wasatch and Summit counties, and western Uintah County south to the Roan, Brown and Book cliffs in Carbon County. _Diagnosis._--Size medium (see measurements). Color: Upper parts Snuff Brown finely mixed with black, paling over sides and flanks to near Pinkish Buff on underparts; postauricular patches relatively small and dusky; external opening of ear large; pinnae usually lightly pigmented; hind feet white; front feet usually white only at base of toes; distal third to half of tail white; tail usually light below, with proximal dorsal half covered with darker hairs; nose, chin, cheeks and top of head dusky; usually considerable white on throat. Skull: Small, slender, and not heavily ridged; nasals short and dilated distally; posterior margins of nasals emarginate; zygomatic arches moderately widely spreading, widest posteriorly; interparietal pentagonal or subquadrangular; interpterygoid space V-shaped; tympanic bullae well inflated ventrally; upper incisors long and narrow. _Comparisons._--For comparisons with other subspecies of _Thomomys talpoides_, see accounts of those forms. _Remarks._--The range formerly ascribed to _uinta_ (Bailey, 1915:114; Barnes, 1922:83, 1927:104) is now known to be inhabited by animals belonging to three distinct subspecies. The range of _uinta_ as now understood is restricted to the southern and western parts of the Uinta Mountains and their environs. Three specimens from the Book Cliffs, Sunnyside, Carbon County, are not typical, but in a majority of their characters agree with _uinta_ to which they are here referred. I have seen only one specimen from the type locality. It is one of the series on which Merriam (1901:112) based his original description. In addition, I have studied several large series of near topotypes. From the material at hand, and from Merriam's description (_loc. cit._), I regard the animals on which the name _uinta_ was based as intergrades between _Thomomys talpoides ravus_, the race to the northeast, on the one hand and the animals of the western and southern parts of the Uinta Mountains on the other hand. The affinities of the type series are with the animals from the latter area which are here all referred to _uinta_. _Specimens examined._--Total, 41, distributed as follows: _Summit County_: 2 mi. S junction Bear River and Haydens Fork, 2 (C. M.); N base, Gilbert Peak, 10,000 ft., 1 (U. S. N. M.); Smith and Moorehouse Creek, 2; Bald Peak, 25 mi. NE Kamas, 15 (8, M. V. Z.; 6, C. M.). _Duchesne County_: Petty Mountain, 15 mi. N Mountain Home, 9,500 ft., 6 (C. M.). _Wasatch County_: Wolf Creek Pass, 18 mi. NW Hanna, 1 (U. S. A. C.); Lost Lake, Uinta Mountains, 10 (B. Y. U.); Current Creek, Uinta Mountains, 1 (U. S. N. M.). _Carbon County_: Forks, Sunnyside, 9,000 ft., 3. _Additional records._--_Summit County_: Uinta Mountains, 6 (see Bailey, 1915:114). =Thomomys talpoides pygmaeus= Merriam _Thomomys pygmaeus_ Merriam, Proc. Biol. Soc. Washington, 14:115. July 19, 1901. _Thomomys talpoides pygmaeus_ Davis, The Recent mammals of Idaho, p. 252, The Caxton Printers, Ltd., Caldwell, Idaho, April 5, 1939. _Type._--Male, adult, skin and skull, No. 55251, U. S. National Museum (Biological Surveys Collection); 10 mi. NE Montpelier, in open sagebrush of Transition Zone, 6,600 ft., Bear County, Idaho; July 29, 1893; collected by Vernon Bailey: original number 4150 (after Merriam, type not seen: see, also, Bailey, 1915:109). _Range._--Limited to Daggett County. _Diagnosis._--Size: Small (see measurements). Color: Upper parts near Bister slightly mixed with black, grading over sides and flanks to Ochraceous Buff on underparts; postauricular patches small and dusky; hind feet white; front feet dusky, being white only at base of claws; chin and nose dusky; tail brown, lighter below and tipped with white. Skull: Very small, slender and smooth; nasals short and slender; zygomatic arches weak and not widely spreading; rostrum narrow; extension of premaxillae posterior to nasals short; parietal ridges hardly noticeable; interparietal large; extension of supraoccipital posterior to lambdoidal suture long; tympanic bullae actually small, but relatively large; basioccipital narrow; interpterygoid space narrow and acutely angled; upper incisors markedly recurved; molariform teeth relatively large. _Comparisons._--This small pocket gopher can be distinguished from all other members of _Thomomys talpoides_ occurring in Utah by remarkably small size, and slender, weak, small skull with strongly recurved upper incisors. _Remarks._--The specimens used in this study were those recorded by Svihla (1931:261). She reports that they were obtained in the flood-plain banks of the streamsides, and preferred the pine belt. This shows probably an extension of range with reference to life zones, as heretofore the main reported localities of capture have been in sagebrush in the Transition Life-zone. Insofar as I am aware, Mrs. Svihla's specimens are the only ones of this subspecies ever obtained in Utah. Additional work is necessary in southwestern Wyoming to outline accurately the geographic distribution of this subspecies. In comparison with topotypes, the specimens from Utah are lighter in color and some specimens have slightly larger skulls, suggesting slight intergradation with _Thomomys talpoides uinta_. _Specimens examined._--Total, 18 (all in Museum of Zoölogy, University of Michigan), distributed as follows: _Daggett County_: Sheep Creek, 4; 1 mi. W Summit Springs, 4; Beaver Creek, 22 mi. S Manila, 9; Granite Park, 24 mi. S Manila, 1. =Thomomys talpoides ravus= new subspecies _Type._--Male, adult, skin and skull, No. 13690, Carnegie Museum; Vernal-Manila Highway, 19 mi. N Vernal, 8,000 ft., Uintah County, Utah; August 22, 1937; collected by J. K. and M. T. Doutt; original number 4718. _Range._--Uinta Mountains in Daggett, northern Uintah and northern Summit counties. _Diagnosis._--Size large (see measurements); ears relatively narrow; hind foot relatively small. Color: Upper parts between Drab and Light Drab, darkest along middorsal line due to mixture of hairs tipped with light brown; sides and flanks Light Drab; entire underparts creamy white; front and hind feet, ventral surface of tail and end of tail white; proximal two-thirds of tail covered dorsally with light brown hairs; nose and cheeks dusky; postauricular patches black. Skull: Large, heavy and ridged; rostrum long and narrow; nasals long, moderately dilated distally and with a distal hump; posterior ends of nasals emarginate; parietal and lambdoidal crests well developed; zygomatic arches moderately heavy and widely spreading, widest posteriorly; zygomatic processes of maxillae moderately heavy and flaring abruptly from base of rostrum; marked middorsal depression in frontals present; interparietal pentagonal; extension of premaxillae posterior to nasals long; posterior tongues of premaxillae long, slender and rounded proximally; braincase high, vaulted and relatively narrow; tympanic bullae well inflated ventrally, and ridged in old animals; pterygoid hamulae long; interpterygoid space narrowly V-shaped; upper incisors long and narrow; molariform teeth medium. _Comparisons._--Compared with topotypes of _Thomomys talpoides bridgeri_, _ravus_ differs as follows: Size larger; hind foot smaller; ears narrower. Color: Lighter throughout, grayish as opposed to brown. Skull: Smaller, narrower, less angular and less massive; nasals, rostrum, zygomatic processes of maxillae, ascending branches of premaxillae and posterior tongues of premaxillae all narrower; extension of premaxillae posterior to nasals longer; interparietal wider; braincase higher and narrower; tympanic bullae approximately the same size, but more inflated ventrally; interpterygoid space more narrowly V-shaped; upper incisors narrower; molariform teeth weaker. Compared with topotypes and near topotypes of _Thomomys talpoides uinta_, _ravus_ differs as follows: Size larger in every measurement taken. Color: Lighter throughout, being grayish as opposed to brown. Skull: Larger in every measurement taken; rostrum and nasals actually as well as relatively longer; extension of premaxillae posterior to nasals longer; upper incisors longer and wider; molariform teeth larger. There is only one other gray subspecies of _Thomomys talpoides_ in Utah, _Thomomys talpoides ocius_. Topotypes of _ravus_ differ from it as follows: Size markedly larger in every measurement taken. Color: Darker, more brown hairs. Skull: Larger in every measurement taken; premaxillae extended farther posteriorly to nasals; extension of supraoccipital posterior to lambdoidal suture markedly less; tympanic bullae actually as well as relatively smaller; upper incisors longer and more procumbent. This new subspecies can be readily distinguished from all other subspecies of _Thomomys talpoides_ occurring in Utah by markedly greater size and paler, more grayish color. _Remarks._--The range of this form appears to be limited to the north slopes of the Uinta Mountains, except in Daggett County where it occurs also on the south slopes. Intergradation in color and in cranial details with _bridgeri_ is shown by animals from the East Fork of Blacks Fork, thirty-one miles SSW Fort Bridger, and by those from Henrys Fork, 8,300 ft., both in Summit County. Due to the grayish color and the narrower, weaker skull they are referred to _ravus_. Intergradation with _uinta_ is shown by specimens from the type locality of the latter race. The type series of _uinta_ consists of intergrades between _ravus_ and the animals to the west and south (see remarks under _uinta_). It is doubtful whether _bridgeri_ occurs in Utah. Material from Rich County and extreme northern Cache County would settle the question. Perhaps _bridgeri_ is restricted to the lower valleys in southwestern Wyoming. Two specimens from northern Cache County, from Logan Canyon, Beaver Basin, Utah-Idaho Line appear to be intergrades between _bridgeri_ and _wasatchensis_, but are referable to the latter race. _Specimens examined._--Total, 38, distributed as follows: _Summit County_: Henrys Fork, 8,300 ft., 8; E Fork, Blacks Fork, 31 mi. SSW Fort Bridger, 4 (C. M.). _Daggett County_: Vernal-Manila Road, 4 mi. W Green's Lake, 7,500 ft., 6 (C. M.); Elk Park, Uinta Mountains, 5 (B. Y. U.). _Uintah County_: Trout Creek, SE Trout Peak, 22 mi. NW Vernal, 9,300 ft., 5 (C. M.); Vernal-Manila Highway, 19 mi. N Vernal, 8,000 ft., 6 (C. M.); Taylor Peak, 17 mi. N Vernal, 4 (C. M.). =Thomomys talpoides ocius= Merriam _Thomomys clusius ocius_ Merriam, Proc. Biol. Soc. Washington, 14:114, July 19, 1901. _Thomomys clusius_ Allen, Bull. Amer. Mus. Nat. Hist., 13:246, November 25, 1896. _Thomomys ocius_ Bailey, N. Amer. Fauna, 39:107, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):83, April, 1922; Bull. Univ. Utah, 17 (No. 12):102, June, 1927. _Type._--Male, adult, skin and skull, No. 18852/25586, U. S. National Museum (Biological Surveys Collection); dry sagebrush mesas at Harveys Ranch, Smiths Fork, 6 mi. SW Fort Bridger, 6,657 ft., Uinta County, Wyoming; May 24, 1890; collected by Vernon Bailey; original number 1194 (after Bailey, type not seen). _Diagnosis._--Size small (see measurements). Color: Upper parts Tilleul Buff overlaid with Avellaneous, grading over sides and flanks to nearly white on underparts; underparts with faint wash of creamy white; postauricular patches small and dusky and completely circling the ear; nose and cheeks dusky; front feet, hind feet, throat, ventral surface of tail and distal half of tail white. Skull: Small, slender but compact; nasals rounded posteriorly; extension of premaxillae posterior to nasals very short; zygomatic arches robust, but not widely spreading, widest posteriorly; interparietal large and pentagonal in shape; extension of supraoccipital posterior to lambdoidal suture long; tympanic bullae actually as well as relatively large; basioccipital narrow; pterygoid hamulae long and ridged; upper incisors short and strongly recurved. _Comparisons._--Compared with one topotype and seven near topotypes of _Thomomys talpoides pygmaeus_, _ocius_ differs as follows: Size larger in every measurement taken. Color: Lighter throughout, grayish as opposed to brown; distal half of tail white as opposed to only a few white hairs at tip of tail. Skull: Larger in every measurement taken; skull more compact; zygomatic arches heavier and more widely spreading posteriorly; tympanic bullae larger; upper incisors larger, but equally strongly recurved; molariform teeth larger. Topotypes of ocius can be distinguished from those of _Thomomys talpoides uinta_ as follows: Color: Lighter throughout, grayish as opposed to brown. Skull: Nasals rounded posteriorly as opposed to emarginate; zygomatic arches more robust; interparietal pentagonal as opposed to subquadrangular; extension of supraoccipital posterior to lambdoidal suture markedly greater; tympanic bullae actually as well as relatively much larger; upper incisors short and strongly recurved as opposed to long and procumbent. Specimens of this subspecies can be distinguished from all other members of the species _Thomomys talpoides_ occurring in Utah by their grayish color, and by small, compact skulls with very large tympanic bullae and short strongly recurved upper incisors. _Remarks._--Two specimens from Vernal, Uintah County, are intergrades between _ocius_ and _uinta_. They resemble _uinta_ in size and dorsal color, but are slightly lighter tending toward the color of _ocius_. Ventrally they are intermediate in color but more like _ocius_. The skulls are more like those of _ocius_ in general appearance, extension of supraoccipital posterior to the lambdoidal suture, shape and thickness of the zygomatic arches, posterior tongues of premaxillae, size of tympanic bullae and recurved upper incisors. They more closely resemble _uinta_ in shape of posterior ends of nasals, basioccipital and shape of the zygomatic processes of the squamosals. In all of the above mentioned characters, they are intermediate between the two named forms, but tend towards one or the other as listed. The majority of characters are more as in _ocius_ to which they are here referred. When Goldman (1939:233, 234) listed the named subspecies of _Thomomys talpoides_, he hesitated to include _ocius_ and merely mentioned that _ocius_, _pygmaeus_ and _idahoensis_ might also belong to _talpoides_. Davis (1939:240, 241) found intergradation between _idahoensis_ and _fuscus_ and also between _idahoensis_ and _pygmaeus_, and, therefore, arranged the last two mentioned forms as subspecies of _talpoides_. This present study reveals intergradation between _ocius_ and _uinta_, and also between _ocius_ and _fossor_ (see account of _fossor_). Therefore, _ocius_ is properly to be treated as a subspecies of the series of intergrading forms of which _talpoides_ is the earliest named. All specimens of _ocius_ known from Utah are from the extreme eastern part of the northeastern corner of the state. The type locality of _ocius_ is near Fort Bridger, Wyoming, which is north of Utah. I have seen one specimen from 12 miles west of Linwood, Daggett County, Utah, on Henrys Fork in Wyoming. Additional collecting in northern Utah probably will reveal _ocius_ to inhabit also parts of northern Utah. _Specimens examined._--Total, 4, distributed as follows: _Uintah County_: Vernal, 2 (C. M.); Uncompahgre Indian Reservation, 2 (A. M. N. H.). =Thomomys talpoides moorei= Goldman _Thomomys fossor moorei_ Goldman, Journ. Washington Acad. Sci., 28:335, July 15, 1938. _Thomomys talpoides moorei_ Goldman, Journ. Mamm., 20:234, May 14, 1939. _Type._--Male, adult, skin and skull, No. 248222, U. S. National Museum (Biological Surveys Collection); 1 mi. S Fairview, 6,000 ft., Sanpete County, Utah; February 19, 1928; collected by A. W. Moore; X-catalogue number 24799 (after Goldman, type not seen). _Range._--Wasatch Plateau in Sanpete, Utah, Carbon and Emery counties, and in Wasatch Mountains south of Spanish Fork Canyon. _Diagnosis._--Size medium (see measurements). Color: Upper parts between Cinnamon and Sayal Brown, with mixture of black hairs, grading through Cinnamon on sides and flanks to Pale Pinkish Buff on underparts, clearest on inguinal and pectoral regions; nose and cheeks dusky; postauricular patches medium in size and black; ears black; chin buffy white; front and hind feet white; tail mostly white with brownish hairs on dorsal surface. Skull: Large, robust; nasals long and deeply emarginate on posterior ends, and dilated distally; zygomatic arches robust and widely spreading; zygomatic processes of maxillae heavy; interparietal comparatively small, but always wider than long; extension of premaxillae posterior to nasals short; tympanic bullae moderate in size, but markedly inflated ventrally; pterygoid hamulae long; interpterygoid space narrowly V-shaped; upper incisors long and moderately recurved; molariform teeth light. _Comparisons._--Topotypes of _moorei_ differ from topotypes and near topotypes of _Thomomys talpoides uinta_ as follows: Size slightly larger. Color: Upper parts and sides lighter; tail lighter; postauricular patches larger and darker; ears more pointed, smaller and darker. Skull: Larger, heavier and more massive; nasals longer, but deeply emarginate posteriorly as in _uinta_; rostrum wider and longer; zygomatic arches heavier and more angular; zygomatic processes of maxillae heavier; interparietal generally smaller and shorter; braincase wider; tympanic bullae more inflated ventrally; interpterygoid space more narrowly V-shaped; upper incisors longer, but not as procumbent; molariform teeth smaller. Topotypes of _moorei_ can be distinguished from those of _Thomomys talpoides oquirrhensis_ as follows: Size slightly larger; tail longer; ears larger, less pointed. Color: Lighter throughout; postauricular patches larger. Skull: More ridged and angular; nasals narrower posteriorly, but more dilated distally; posterior ends of nasals more deeply emarginate (while shallowly emarginate in _oquirrhensis_, they tend to be somewhat rounded); rostrum narrower; extension of premaxillae posterior to nasals greater; least interorbital breadth less; zygomatic arches more angular and widely spreading; zygomatic processes of maxillae heavier; interparietal smaller; tympanic bullae larger and more inflated ventrally; upper incisors generally longer. The characters that distinguish _moorei_ from _Thomomys talpoides parowanensis_ are: Color: Lighter throughout. Skull: Broader, more angular and more nearly flat; zygomatic arches more widely spreading; zygomatic processes of maxillae heavier; posterior ends of nasals emarginate rather than rounded; upper incisors longer. For comparisons of _moorei_ with _Thomomys talpoides levis_ and _wasatchensis_ see accounts of these forms. _Remarks._--Specimens from Colton, show intergradation between _moorei_, _uinta_ and _wasatchensis_, but are referable to _moorei_ in the majority of characters. Specimens from Mount Nebo, and the mouth of Reddicks Canyon, in the Wasatch and San Pitch mountains, respectively, are intergrades between _moorei_ and _wasatchensis_, but are referable to _moorei_. That part of the Wasatch Mountains south of Spanish Fork Canyon is inhabited by pocket gophers that are intergrades between _moorei_ and _wasatchensis_, but the cranial details show them to be referable to _moorei_. The range here ascribed to _moorei_ consists of the Wasatch Plateau to the east of Sanpete Valley, the San Pitch Mountains and the southern part of the Wasatch Mountains. The type locality of _moorei_ is situated in the southern end of a high valley that separates the Wasatch Plateau from the San Pitch and Wasatch mountains. Topotypical animals are larger and have more ridged, angular skulls than those from the mountains. _Specimens examined._--Total, 48, distributed as follows: _Utah County_: Near Payson Lake, 1 (R. H.); Mt. Nebo, 25 mi. SE Payson, 10,000 ft., 20; Colton, 8 (B. Y. U.). _Sanpete County_: 1 mi. S Fairview, 6,000 ft., 12 (U. S. N. M.). _Juab County_: Mouth of Reddicks Canyon, Wales Mountain (= San Pitch Mountains), 7,500 ft., 5. _Emery County_: Lake Creek, 11 mi. E Mt. Pleasant, 2 (C. M.). _Additional records._--_Sanpete County_: Ephraim, 5 (see Goldman, 1938:336). =Thomomys talpoides fossor= Allen _Thomomys fossor_ Allen, Bull. Amer. Mus. Nat. Hist., 5:51, April 28, 1893; Bailey, N. Amer. Fauna, 39:111, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):102, June, 1927; Hall, Univ. California Publ. Zoöl., 37:4, April 10, 1931. _Thomomys talpoides fossor_ Goldman, Journ. Mamm., 20:234, May 14, 1939. _Type._--Male, adult, skin and skull, No. 5240/4120, American Museum of Natural History; Florida, 7,200 ft., La Plata County, Colorado; June 25, 1892; collected by Charles P. Rowley (after Allen, type not seen). _Range._--In the mountains of San Juan and Grand counties, east of the Colorado and Green rivers. _Diagnosis._--Size medium (see measurements). Color: Upper parts Dresden Brown, grading over sides to Pale Buff on underparts; chin white; ears small, pointed, with deeply pigmented pinnae; postauricular patches grayish black; nose dusky. Skull: Long and narrow; nasals long, rounded proximally and usually simple distally; rostrum long; interparietal triangular; tympanic bullae large, and well inflated ventrally; basioccipital narrow; palate narrow; palatal pits shallow; dentition light. _Comparisons._--Near topotypes of _fossor_ can be distinguished from topotypes of _Thomomys talpoides ocius_ as follows: Size larger throughout. Color: Darker throughout, being dark brown as opposed to grayish. Skull: Longer and narrower; nasals and rostrum longer; extension of supraoccipital posterior to lambdoidal suture markedly less; tympanic bullae markedly smaller; upper incisors longer and not as strongly recurved. Among the races of _Thomomys talpoides_ occurring in Utah, _fossor_ most closely resembles _Thomomys talpoides uinta_ in color and size, but differs from it as follows: Ears smaller, more pointed and with more darkly pigmented pinnae. Skull: Longer, narrower and weaker; rostrum longer; nasals longer, and rounded proximally as opposed to markedly emarginate; interparietal triangular instead of roughly pentagonal; tympanic bullae larger and more inflated ventrally; basioccipital narrower; palate narrower, palatal pits shallower; dentition lighter. _Remarks._--Bailey (1915:111) remarked that _fossor_ was one form that held its distinctive characters over a wide range. At that time, its range was understood to include practically all of the mountainous parts of Colorado, Utah as far west as the central part of the state, and parts of New Mexico, Arizona and Wyoming. Subsequently three new forms have been named from central Utah, (Goldman 1938:334-337) thereby showing variation to be much more prevalent than formerly supposed. The range of _fossor_ in Utah, as now understood, is limited to the mountainous parts of the state south and east of the Colorado and Green rivers in Grand and San Juan counties. The Utah specimens are not typical. At first glance some differences are noted in the premaxillae and nasals. Four specimens in the collections of the Museum of Natural History, University of Kansas, three from 3 miles east of Creede, Mineral County, and one from 10 miles east of Lake City, Hinsdale County, Colorado, both of which lie north and east of the type locality of _fossor_ show the same characters as the Utah specimens. Eight specimens from Oak Spring are intergrades between _fossor_ and _ocius_. In size and color they are like _fossor_, but the skulls are intermediate. Because the animals are more like _fossor_ in the majority of characters, they are here referred to that race. As a result of these studies and due to the paucity of specimens from Utah, it is advisable, for the present, to refer all these Utah animals to _fossor_. Additional specimens may reveal characters that will merit the separation of the Utah animals from typical _fossor_; a desertlike area unfavorable to _Thomomys_ exists between the type locality and eastern Utah. _Specimens examined._--Total, 21, distributed as follows: _Grand County_: Oak Spring, Middle Fork Willow Creek, 15 mi. N Thompson, 8 (C. M.); La Sal Mountains, 1 (U. S. N. M.); Warner Ranger Station, La Sal Mountains, 3 (B. Y. U.). _San Juan County_: Geyser Pass, 18 mi. SE Moab, La Sal Mountains, 3 (1, B. Y. U.; 2, C. M.); 5 mi. W Monticello, 1 (C. M.); Cooley Pass, 8 mi. W Monticello, 2 (C. M.); Joshua Flat, Elk Ridge, 8,300 ft., 3 (M. V. Z.). =Thomomys talpoides parowanensis= Goldman _Thomomys fossor parowanensis_ Goldman, Journ. Washington Acad. Sci., 28:334, July 15, 1938. _Thomomys talpoides parowanensis_ Goldman, Journ. Mamm., 20:234, May 14, 1939; Long, Journ. Mamm., 21:176, May 14, 1940. _Thomomys fossor_ Bailey, N. Amer. Fauna, 39:112, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):102, June, 1927; Hall, Univ. California Publ. Zoöl., 37:4, April 10, 1931; Presnall, Zion-Bryce Mus. Bull., 2:14, January, 1938; Tanner, Great Basin Nat., 1:111, 1940. _Type._--Male, adult, skin and skull, No. 158072, U. S. National Museum (Biological Surveys Collection); Brian Head, Parowan Mountains, 11,000 ft., Iron County, Utah; September 8, 1908; collected by W. H. Osgood; original number 3483 (after Goldman, type not seen). _Range._--High mountains of eastern Iron and Beaver counties, and western Kane and Garfield counties. _Diagnosis._--Size medium (see measurements). Color: Upper parts Sayal Brown moderately mixed with black, lightest on head; sides lightly washed with Buff; underparts Pinkish Buff, clearest on inguinal and pectoral regions; nose and cheeks dusky; postauricular patches large and black; front feet, hind feet and distal half of tail white. Skull: Long and fairly slender; zygomatic arches not widely spreading; nasals long; rostrum long and slender; posterior ends of nasals truncate or moderately emarginate; extension of premaxillae posterior to nasals usually short; tympanic bullae relatively small; upper incisors long and narrow; molariform teeth large. _Comparisons._--Compared with _Thomomys talpoides kaibabensis_, _parowanensis_ differs as follows: Size smaller. Skull: Shorter; nasals shorter; zygomatic breadth less; nasals truncate or shallowly emarginate posteriorly as opposed to rounded; upper incisors narrower. Topotypes of _parowanensis_ differ from topotypes and near topotypes of _Thomomys talpoides uinta_ as follows: Size larger. Color: Usually lighter; postauricular patches larger and darker; ears small with pinnae deeply pigmented as opposed to large and lightly pigmented. Skull: Larger; zygomatic arches more widely spreading; nasals longer; rostrum longer; posterior ends of nasals truncate or shallowly emarginate as opposed to deeply emarginate; sides of zygomatic arches nearly parallel and not so divergent posteriorly; interparietal larger and less quadrangular; extension of premaxillae posterior to nasals less; upper incisors less procumbent; molariform teeth larger. Among named races of _Thomomys talpoides_, _parowanensis_ most closely resembles _levis_, the race nearest geographically to the east, but differs from _levis_ as follows: Size larger. Skull: Longer and wider; rostrum and nasals longer; interparietal quadrangular as opposed to roughly elliptical; upper incisors longer. For comparisons with _Thomomys talpoides moorei_ and _wasatchensis_ see accounts of those forms. _Remarks._--The mountains of south central Utah are inhabited by pocket gophers that have been designated as _Thomomys talpoides parowanensis_ and _T. t. levis_ by Goldman (1938:334, 336). They are nearly indistinguishable in color and each is variable in cranial details. The diagnostic characters of each form occasionally appear, in varying degrees, throughout the range of the other. The Sevier River Valley separates the ranges ascribed to these two forms. This valley is inhabited by pocket gophers that belong to a different species, _Thomomys bottae_. The ranges of these two races of _talpoides_ converge southward at the headwaters of the Sevier River. Specimens of _parowanensis_ from the northern limits of its range from the Beaver Mountains in eastern Beaver County and those of _levis_ from the northern limits of its range in the Fish Lake Mountains are readily distinguishable from each other. As the ranges converge to the southward, there is progressively more intergradation. The type locality of _parowanensis_ is located in the southern part of its range, while that of _levis_ is in the extreme northern part of its range. Therefore, due to the convergence of the two ranges at the south, the specimens from localities near the type locality of _parowanensis_ show the greatest amount of intergradation, if we regard specimens of _parowanensis_ from the type locality as typical of the race. Four specimens from Webster Flat, sixteen miles east of Cedar City, Iron County, and three from Duck Creek, Cedar Mountains, Kane County could equally well be assigned to either _levis_ or _parowanensis_. _Specimens examined._--Total, 24, distributed as follows: _Beaver County_: Britts Meadows, Beaver Mountains, 8,500 ft., 7 (3, M. V. Z.; 2, U. S. N. M.; 2, C. M.); Puffer Lake, Beaver Mountains, 1 (U. S. N. M.); Kents Lake, Beaver Mountains, 1 (R. H.). _Iron County_: Lava Beds, 3-1/2 mi. SW Panquitch Lake, 1 (C. M.); Brian Head, Parowan Mountains, 2 (1, U. S. N. M.; 1, C. M.); Webster Flat, 16 mi. E Cedar City, 4; Bear Valley, 2 mi. E B. V. Ranger Station, 1 (R. H.). _Garfield County_: 1/4 mi. W Sunset Point, Bryce National Park, 8,000 ft., 1 (M. V. Z.). _Kane County_: Navajo Lake, 3 (R. H.); Duck Creek, Cedar Mountains, 9,000 ft., 3 (1, R. H.). _Additional records._--_Garfield County_: Panquitch Lake, 1 (see Goldman 1938:335). _Iron County_: Beaver Mountains, 9 (see Bailey, 1915:112); Buckskin Valley, 1 (see Goldman, 1938:335). =Thomomys talpoides levis= Goldman _Thomomys fossor levis_ Goldman, Journ. Washington Acad. Sci., 28:336, July 15, 1938. _Thomomys talpoides levis_ Goldman, Journ. Mamm., 20:234, May 14, 1939. _Thomomys fossor_ Bailey, N. Amer. Fauna, 39:112, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):102, June, 1927. _Type._--Female, adult, skin and skull, No. 158079, U. S. National Museum (Biological Surveys Collection); Seven Mile Flat, 5 mi. N Fish Lake, Fish Lake Plateau, 10,000 ft., Sevier County, Utah; October 1, 1908; collected by W. H. Osgood; original number 3616 (after Goldman, type not seen). _Range._--Fish Lake Mountains in Sevier County south into Garfield County, Utah. _Diagnosis._--Size medium (see measurements). Color: Upper parts near Sayal Brown, moderately mixed with black, darkest on head and middorsal region, grading to Cinnamon Buff on sides and flanks; underparts Pinkish Buff, clearest on inguinal and pectoral regions; chin, cheeks and nose dusky; postauricular patches large and black; front feet, hind feet and distal half of tail white; ears small and deeply pigmented. Skull: Slender and weak; zygomatic arches not widely spreading; posterior ends of nasals rounded; nasals moderately long and narrow; rostrum long and narrow; extension of premaxillae posterior to nasals short; interparietal usually much wider than long; pterygoid hamulae ridged; interpterygoid space usually narrowly V-shaped; upper incisors short. _Comparisons._--Compared with topotypes of _Thomomys talpoides moorei_, _levis_ differs as follows: Size smaller; tail shorter. Color: Darker throughout, especially on dorsal surface due to more black of the underfur; underparts deeper buff. Skull: Narrower, less massive; zygomatic processes of maxillae weaker and not as widely spreading; interparietal generally wider; extension of premaxillae posterior to nasals less; posterior ends of nasals rounded rather than emarginate; upper incisors shorter, less procumbent. Topotypes of _levis_ differ from near topotypes of _Thomomys talpoides uinta_ as follows: Size larger. Color: Upper parts slightly darker; postauricular patches much darker and larger; ears small and deeply pigmented as opposed to large and lightly pigmented; tail darker all around at base, with white part more extensive and with fewer buff-colored hairs. Skull: More convex dorsally; zygomatic arches more widely spreading and angular; nasals longer; rostrum longer; interparietal wider and more elliptical; posterior ends of nasals rounded as opposed to emarginate; extension of premaxillae posterior to nasals less; pterygoid hamulae more ridged; interpterygoid space more narrowly V-shaped; upper incisors shorter and less procumbent. Topotypes of _levis_ can be distinguished from those of _Thomomys talpoides kaibabensis_ by markedly smaller measurements. For comparisons with _Thomomys talpoides parowanensis_ and _wasatchensis_ see accounts of those forms. _Remarks._--Specimens from the Escalante Mountains and the Aquarius Plateau are not typical. They are of approximately the same color as _levis_, but are larger than _levis_ and have cranial details that indicate intergradation with _kaibabensis_ to the south. They resemble _kaibabensis_ in large size, long nasals and widely spreading zygomatic arches, but are like _levis_ in shape of the interparietal, extension of premaxillae posterior to the nasals, rounded posterior ends of nasals, ridged pterygoid hamulae and relatively short upper incisors. Additional material from these regions may prove these animals to merit separation and naming. _Specimens examined._--Total, 15, distributed as follows: _Sevier County_: Seven Mile Flat, 5 mi. N Fish Lake, Fish Lake Plateau, 10,000 ft., 2 (U. S. N. M.); Fish Lake Experiment Station, 2 (U. S. A. C). _Garfield County_: Posy Lake, Aquarius Plateau, 2 (B. Y. U.); 18 mi. N Escalante, 9,500 ft., 3; Steep Creek, Boulder-Teasdale Road, Boulder Mountain, 4 (B. Y. U.); Summit Birch Creek, Escalante Mountains, 2 (B. Y. U.). MEASUREMENTS OF ADULT MALES OF THOMOMYS (In millimeters) ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- _T. t. gracilis_, 4; topotypes Av. 204 53 28 31.5 13.4 21.7 18.3 6.4 7.6 1.3 15.4 7.2 Min. 194 47 27 30.3 12.9 21.1 17.8 6.3 7.3 1.0 14.7 6.7 Max. 210 63 28 33.5 14.2 22.0 19.0 6.5 7.9 1.7 16.4 7.5 _T. t. oquirrhensis_, 4; topotypes Av. 209 58 28 32.2 13.9 21.9 19.0 6.9 7.6 0.9 15.8 7.7 Min. 197 55 28 31.9 13.7 21.4 18.5 6.7 7.2 0.6 15.5 7.5 Max. 216 60 29 32.8 14.3 22.8 19.5 7.1 7.9 1.0 16.2 7.9 _T. t. wasatchensis_, 10; topotypes Av. 221 67 28 31.3 13.4 21.5 18.9 6.5 7.4 1.1 15.1 7.4 Min. 204 60 26 27.4 11.6 19.1 17.2 6.0 6.6 0.9 14.0 6.7 Max. 237 75 31 34.5 15.2 23.7 20.4 7.3 8.0 2.0 16.5 8.2 _T. t. uinta_, 5; SW slope Bald Peak, Uinta Mts. Av. 199 51 27 31.5 13.1 21.7 19.4 6.3 7.6 1.1 15.2 7.4 Min. 185 47 26 29.6 12.1 20.3 19.0 5.7 7.3 0.7 13.5 7.2 Max. 208 54 28 32.8 13.8 22.2 20.0 6.5 7.8 1.4 15.6 7.6 _T. t. moorei_, 7; topotypes Av. 216 65 29 32.4 13.9 22.9 19.2 6.5 7.7 1.5 15.9 7.3 Min. 203 52 27 31.3 13.0 21.5 18.4 6.0 7.3 0.9 14.8 6.7 Max. 236 72 31 34.7 14.5 23.7 20.0 7.0 8.2 2.0 16.3 7.7 _T. t. fossor_, 8; Cascade Creek, La Plata Co., Colo. Av. 215 61 29 31.7 13.2 21.2 18.7 5.9 7.5 0.6 15.5 7.1 Min. 202 54 27 30.5 12.0 20.5 18.2 5.5 7.0 0.0 14.5 6.9 Max. 228 70 30 33.0 14.4 23.5 19.9 6.3 7.9 1.1 16.9 7.4 _T. t. ravus_, 3; topotypes Av. 248 73 30 35.2 14.6 24.8 21.4 6.3 8.3 2.4 17.1 8.2 Min. 244 70 29 34.5 14.3 23.6 20.5 6.0 8.2 2.2 16.7 8.1 Max. 253 74 30 35.9 15.1 25.7 22.5 6.7 8.4 2.7 17.5 8.5 No. 55270 (U. S. N. M.) _T. t. pygmaeus_, 1; topotype 165 40 20 24.6 10.2 16.3 15.1 5.4 5.9 0.7 12.0 5.7 No. 177506 (U. S. N. M.) _T. t. ocius_, 1; 12 mi. W Linwood, Henrys Fork, Wyo. 200 62 26 27.5 11.5 19.9 17.8 6.2 6.8 1.0 13.5 7.0 _T. t. parowanensis_, 2; Britts Meadow, Beaver Mountains Av. 215 59 28 34.3 14.5 22.4 18.6 6.0 8.1 1.4 17.3 7.9 Min. 202 48 27 34.1 14.1 22.0 18.4 5.8 8.0 1.0 17.2 7.6 Max. 228 69 29 34.6 14.8 22.7 18.9 6.2 8.2 1.7 17.3 8.2 ---------------------------------------------------------------------- MEASUREMENTS OF ADULT FEMALES OF THOMOMYS (In millimeters) ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- _T. t. gracilis_, 2; topotypes Av. 190 58 27 29.7 12.0 19.7 17.3 6.4 7.3 1.2 14.0 6.5 Min. 185 54 27 29.5 11.9 19.7 16.9 6.3 7.2 1.1 14.0 6.4 Max. 194 61 27 29.9 12.0 19.7 17.6 6.5 7.4 1.4 14.0 6.6 _T. t. oquirrhensis_, 7; topotypes Av. 203 56 27 30.2 12.9 20.4 18.2 6.8 7.5 0.8 14.8 7.2 Min. 193 52 25 28.5 12.2 19.5 17.5 6.6 6.7 0.5 14.2 6.9 Max. 215 59 28 31.5 13.3 21.0 19.1 7.2 8.0 1.0 15.5 7.5 _T. t. wasatchensis_, 19; topotypes Av. 205 62 27 31.5 12.7 20.5 18.0 6.5 7.4 0.9 14.6 7.2 Min. 180 52 23 28.1 11.2 19.3 17.2 6.2 6.0 0.6 13.0 6.8 Max. 222 70 30 32.5 14.5 22.0 19.9 6.7 8.1 1.2 16.2 7.5 _T. t. uinta_, 2; SW slope Bald Peak, Uinta Mts. Av. 181 49 25 28.4 11.6 19.8 17.3 6.6 7.2 1.3 13.5 6.8 Min. 177 47 25 28.3 11.6 19.8 17.2 6.4 7.0 1.1 13.3 6.8 Max. 185 50 25 28.4 11.6 19.8 17.4 6.7 7.3 1.5 13.6 6.8 _T. t. moorei_, 5; topotypes Av. 206 62 26 29.9 12.8 21.5 18.4 6.6 7.3 1.3 14.6 6.8 Min. 198 55 24 29.0 12.3 21.0 18.0 6.4 7.0 1.0 14.0 6.4 Max. 213 69 28 31.2 14.1 22.5 19.1 6.8 7.5 1.6 15.6 7.0 _T. t. fossor_, 4; Cascade Creek, La Plata Co., Colo. Av. 215 57 29 32.6 14.2 22.0 19.0 6.0 7.5 0.7 16.2 7.3 Min. 204 51 28 31.3 13.6 21.5 18.0 5.7 7.1 0.5 15.9 7.0 Max. 223 63 30 34.0 14.8 22.9 19.6 6.3 7.8 1.0 16.3 7.5 No. 13684 (C. M.) _T. t. ravus_, 1; topotype 241 71 28 35.7 14.5 24.4 21.5 6.2 7.8 2.7 17.1 8.1 No. 178868 (U. S. N. M.) _T. t. pygmaeus_, 1; Fossil, Wyo. 167 52 20 24.0 10.2 16.5 14.8 5.2 5.6 0.7 11.1 5.8 _T. t. ocius_, 3; topotypes Av. 201 60 25 30.0 13.5 20.5 17.9 6.2 7.2 0.8 15.0 7.4 Min 196 57 25 29.9 13.0 19.9 17.5 6.1 7.1 0.5 14.7 7.3 Max. 205 64 25 30.1 14.0 21.5 18.6 6.3 7.3 1.0 15.3 7.5 _T. t. parowanensis_, 4; Britts Meadow, Beaver Mountains Av. 221 58 29 33.2 14.5 22.8 19.0 6.0 7.8 0.9 15.4 7.3 Min. 207 50 28 30.5 12.8 22.7 18.6 5.8 7.4 0.5 14.7 7.0 Max. 240 66 30 34.8 15.5 23.0 19.6 6.2 8.1 1.5 17.8 7.7 _T. t. levis_, 2; topotypes Av. 203 65 27 28.1 11.1 19.2 17.7 6.1 6.9 0.8 13.0 6.8 Min. 199 61 26 28.0 10.6 18.9 17.5 5.8 6.6 0.6 12.8 6.6 Max. 206 70 27 28.2 11.6 19.5 17.9 6.4 7.2 1.0 13.2 7.0 ---------------------------------------------------------------------- =Thomomys bottae= (Eydoux and Gervais) _Thomomys bottae_ is a southern species that, within the Great Basin, reaches the most northern limits of its distribution in Utah. The animals of this species inhabit the lower valleys, and with the exception of the Oquirrh Mountains, inhabit also the mountains in that part of the state west of the central mountain ranges. The specific characters are: Sphenorbital fissure present; incisive foramina posterior to infraorbital canal; anterior prism of P4 rounded; interparietal relatively small; lambdoidal suture straight in region of interparietal, in Utah specimens. =Thomomys bottae aureiventris= Hall _Thomomys perpallidus aureiventris_ Hall, Univ. California Publ. Zoöl., 32:444, July 8, 1930; Univ. California Publ. Zoöl., 37:3, April 10, 1931. _Thomomys bottae aureiventris_ Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935. _Type._--Male, adult, skin and skull, No. 43980, Museum of Vertebrate Zoölogy, University of California; Fehlman Ranch, 3 mi. N Kelton, 4,225 ft., Box Elder County, Utah; September 27, 1929; collected by Louise Kellogg; original number 451. _Range._--Northwestern Utah, and extreme western Utah as far south as the southern end of the Deep Creek Mountains. _Diagnosis._--Size medium (see measurements); claws on front feet small. Color: Near Cinnamon on dorsal and ventral surfaces; inguinal region, front and hind feet and distal third to half of tail white; nose, cheeks and postauricular patches grayish black. Skull: Moderately angular and ridged; zygomatic arches nearly parallel with sides of skull; jugals vertical; marked thickening at union of jugal and zygomatic process of maxilla; greatest zygomatic breadth at anterior part of arches; interpterygoid space lyre-shaped; ventral margin of jugal concave dorsally; nasals long and denticulate distally; parietal ridges bowed in at two places, at coronal suture and at middle of interparietal; paroccipital processes extremely well developed; dorsal frontomaxillary suture usually straight. _Comparisons._--From near topotypes of _Thomomys bottae centralis_, _aureiventris_ differs as follows: Size larger; tail shorter; hind foot longer; claws on front feet shorter. Color: Slightly darker on upper parts, but with greater extension of white on ventral surface. Skull: Zygomatic breadth greater; greatest width across zygomatic arches at anterior rather than posterior region; zygomatic arches thicker at union of jugals and zygomatic processes of maxillae; dorsal frontomaxillary suture less convex medially; mastoid breadth greater; extension of premaxillae posterior to nasals less; interpterygoid space lyre-shaped rather than V-shaped. From topotypes of _Thomomys bottae albicaudatus_, _aureiventris_ can be distinguished by: Size larger; hind foot longer. Color: Markedly lighter throughout, Cinnamon as opposed to near (13''''_n_) Black. Skull: Larger in all but three measurements taken; extension of premaxillae posterior to nasals less; alveolar length of upper molar series shorter; zygomatic arches widest anteriorly rather than posteriorly; thickening at union of jugal and zygomatic process of maxilla markedly greater; interpterygoid space lyre-shaped as opposed to V-shaped; lacrimal processes more globose at tips. _Thomomys bottae aureiventris_ can be readily distinguished from _T. b. bonnevillei_, _sevieri_, _wahwahensis_, and _convexus_ by larger size in all measurements taken and darker coloration. The same differences obtain in comparison with _T. b. tivius_ and _stansburyi_ except that _aureiventris_ is much lighter colored. See comparisons under those forms. _Remarks._--_T. b. aureiventris_ has one of the most extensive ranges of any race of _T. bottae_ occurring in Utah. The range extends from the valleys of the northwest corner of the state south along the extreme western margin of the state approximately to the southern end of the Deep Creek Mountains. This ascribed range practically bounds the northwest and western margins of the great salt desert in Box Elder and Tooele counties. As far as known, this great waste area harbors no members of the Geomyidae. Pocket gophers were available from four localities in addition to the type locality. In these four localities all of the animals were intergrades. The three specimens from Queen of Sheba Canyon, Deep Creek Mountains, although smaller than _aureiventris_ in every measurement taken, resemble it in color and general configuration of the skull. The animals from Trout Creek and Ibapah at the southern end of the range, although referred to _aureiventris_, are intermediate between it and _centralis_. In color and measurements they more closely resemble _centralis_, but the skulls closely resemble those of _aureiventris_. The skulls show some slight characteristics of _bonnevillei_, the form to the east, which indicate an early relationship between the two. Specimens from the east side of Tecoma Range, adjacent to Pilot Peak, although referred to _aureiventris_ are intergrades between it and _centralis_. Although this locality is nearer the type locality of _aureiventris_ than any of the other record stations, the animals show the maximum departure from topotypes in morphological features. In color they approach _centralis_, and agree with it in one-half of the measured characters. The general configuration of the skull and a majority of the critical diagnostic characters, for example, jugal thickening, are more nearly as in _aureiventris_. From the above remarks it is readily understood that this subspecies is extremely variable. _Specimens examined._--Total, 55, distributed as follows: _Box Elder County_: Fehlman Ranch, 3 mi. N Kelton, 4,255 ft., 8 (7, M. V. Z.); Utah-Nevada Boundary, E Side Tecoma Range, 4,300 ft., 12. _Tooele County_: Ibapah, 5,000 ft., 21. _Juab County_: Queen of Sheba Canyon, W side Deep Creek Mountains, 5,600 ft., 11. =Thomomys bottae robustus= new subspecies _Type._--Male, adult, skin and skull, No. 2726, Museum of Zoölogy, University of Utah; Orr's Ranch, Skull Valley, 4,300 ft., Tooele County, Utah; June 19, 1938; collected by S. D. Durrant; original number 1583. _Range._--Skull Valley, Tooele County, Utah. _Diagnosis._--Size medium (see measurements); tail short; hind foot short. Color: In a series of 24 animals, upper parts vary from Pale Smoke Gray (4 specimens) through Cinnamon Buff (19 specimens) to Dark Mouse Gray (1 specimen). The Cinnamon Buff color is considered to be typical. Color grading to lighter on underparts; postauricular patches small and grayish black; front and hind feet and distal part of tail white. Skull: Small, flat and heavily ridged; nasals short; zygomatic arches heavy and widely spreading, widest posteriorly at union of jugal and squamosal; union of jugal and zygomatic process of maxilla thickened, with a ventrally directed spinous process in sixty percent of the specimens; occasionally there is a second process, also directed ventrally at union of jugal and zygomatic process of squamosal; zygomatic arches convex dorsally; deep dorsal depression present in frontal bones in mature specimens; lacrimal processes prominent, projecting well above the arch at the anteromedial angle of the orbit; interpterygoid spaces V-shaped; tympanic bullae well inflated ventrally; upper incisors short, and pale; when placed on a flat plane the dorsal surface of the skull is nearly parallel to the substratum; space enclosed within the zygomatic arches nearly quadrangular. _Comparisons._--From topotypes of _Thomomys bottae aureiventris_, _robustus_ can be distinguished as follows: Size smaller; tail and hind foot shorter. Color: Lighter throughout. Skull: Smaller, more heavily ridged and more nearly flat; nasals shorter; rostrum relatively wider and shorter; zygomatic arches shorter and relatively more widely spreading with greatest width posteriorly as opposed to anteriorly; junction of jugal and zygomatic process of maxilla not as prominent; _aureiventris_ shows no spinous process at this junction; lacrimal processes larger and projecting farther dorsally; enclosed space within zygomatic arches roughly quadrangular as opposed to triangular; mastoidal part of tympanic bullae less exposed; sphenorbital fissure smaller; interpterygoid space V-shaped rather than lyre-shaped; palatal pits smaller and shallower; tympanic bullae smaller, but more inflated ventrally; basioccipital averaging relatively wider; molars smaller; upper incisors shorter, smaller and cadmium yellow as opposed to orange yellow. Comparisons of _robustus_ with topotypes of _Thomomys bottae albicaudatus_ show the following: Size smaller. Color: Lighter throughout; postauricular patches smaller and lighter. Skull: Smaller, more compact and more nearly flat; rostrum shorter and more nearly straight; lacrimal processes larger, projecting higher above the anteromedial angle of the orbit; parietal ridges uniformly heavier; mastoid width actually as well as relatively wider; zygomatic arches heavier and relatively much wider (males 76.2 percent of basilar length, females 73.8 percent as opposed to males 73.8 percent and females 73.5 percent); union of jugal and zygomatic process of maxilla uniformly more thickened; spinous process at jugal-maxillary suture present; zygomatic arches much more concave on ventral surface; uniform deep depression present in mature adults, between frontal processes of premaxillae, and anterior interorbital region of frontals; extension of premaxillae posterior to nasals less; sphenorbital fissure more constricted; tympanic bullae more inflated ventrally, extending well ventrad of basioccipital; palatal pits shallower and smaller; molars smaller; upper incisors shorter, narrower and paler (see comparison of _aureiventris_). From near topotypes of _Thomomys bottae centralis_ from 1 mile east of Garrison, Millard County, Utah, _robustus_ differs in: Size smaller; tail and hind foot shorter. Color: Lighter, terminal bands of hair cinnamon, but because more black in underfur the animals appear darker; postauricular patches smaller and lighter. Skull: Shorter, more nearly flat and much more heavily ridged; nasals shorter; rostrum shorter and wider; lacrimal processes larger and projecting higher above anteromedial angle of orbit; zygomatic arches heavier, shorter, more angular and actually as well as relatively wider; jugals thicker; angle between maxillary plate and rostrum less obtuse; spinous process at jugal-maxillary suture present; extension of premaxillae posterior to nasals less; parietal ridges much more pronounced; looked at from above, space enclosed within zygomatic arches more quadrangular in shape as opposed to roughly triangular; tympanic bullae more inflated ventrally; molars smaller; upper incisors shorter, narrower and paler. The characters that distinguish _robustus_ from topotypes of _Thomomys bottae wahwahensis_ are: Size slightly smaller. Color: Darker throughout. Skull: Rostrum longer and narrower; nasals longer; zygomatic arches wider and longer; lacrimal processes larger and projecting higher above anteromedial angle of the orbit; parietal ridges more roughened; tympanic bullae much larger and more inflated ventrally; supraoccipital higher; middorsal depression in frontals present. For comparisons with _Thomomys bottae bonnevillei_ see account of that form. The remaining forms from the Bonneville Basin, namely, _Thomomys bottae sevieri_, _convexus_, _tivius_ and _stansburyi_ are all easily distinguished from _robustus_. Specimens of _sevieri_ are paler, smaller in every measurement taken, and the skulls are weaker and less angular. All specimens of _convexus_ are paler, the skulls are more convex dorsally and narrower, with less ridging and angularity. Both _tivius_ and _stansburyi_ are small dark forms, with weak, smooth, small skulls as compared with _robustus_ which is light colored and has compact, ridged and angular skulls. _Remarks._--Twenty-three specimens were obtained at a small isolated spring. Critical study of animals taken only a few miles to the east prove them to be so different as to be referable to another subspecies, _albicaudatus_. _T. b. robustus_ is an endemic form in this desert valley. The variable color is noteworthy but difficult to explain in an isolated population as small as this one. All five of the gray animals are females of which four are lactating adults. The affinities of this subspecies are with _albicaudatus_ to the east, but enough time has elapsed since isolation to enable them to differentiate. _Specimens examined._--Total, 23, from the type locality. =Thomomys bottae minimus= Durrant _Thomomys bottae minimus_ Durrant, Proc. Biol. Soc. Washington, 52:161, October 11, 1939; Marshall, Journ. Mamm., 21:154, May 14, 1940. _Type._--Male, adult, skin and skull, No. 263942, U. S. National Museum (Biological Surveys Collection); Stansbury Island, Great Salt Lake, Tooele County, Utah; June 25, 1938; collected by William H. Marshall; original number 141. _Range._--Known only from the type locality. _Diagnosis._--Size small (see measurements); tail relatively long. Color: Upper parts Pinkish Buff, darker on head; underparts Pale Pinkish Buff; front and hind feet white; nose, chin and postauricular patches black. Skull: Long, slender and nearly devoid of ridges; braincase moderately inflated; interparietal quadrangular; zygomatic arches weak, widest in temporal region, but neither widely spreading nor angular; nasals straight and truncate posteriorly; extension of premaxillae posterior to nasals relatively great; tympanic bullae moderately inflated; palatal pits deep; rostrum short but narrow; interpterygoid space moderately lyre-shaped; upper incisors narrow; molars light. _Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _minimus_ differs as follows: Size markedly smaller; claws on front feet shorter and weaker. Color: Markedly lighter throughout, being Pinkish Buff as contrasted with near (13''''_n_) Black. Skull: Smaller in every measurement taken; slender, smooth, weak and nonangular as opposed to ridged, robust, wide and angular; zygomatic arches much weaker and not so widely spreading posteriorly; ascending processes of premaxillae much narrower; extension of premaxillae posterior to nasals less; interpterygoid space moderately lyre-shaped as opposed to V-shaped; dentition lighter. Topotypes of _minimus_ differ from those of _Thomomys bottae aureiventris_ as follows: Size markedly smaller. Color: Lighter dorsally and no "gold color" on underparts. Skull: Markedly smaller in every measurement taken; weak, smooth and slender as opposed to ridged, angular and robust; zygomatic arches weak and widest posteriorly rather than heavy and widest anteriorly; no great thickening at region of union of jugal and zygomatic process of the maxilla; jugals more nearly straight rather than concave laterally; interpterygoid space not so markedly lyre-shaped; dentition lighter. The races nearest geographically to _minimus_ are _Thomomys bottae nesophilus_ and _T. b. stansburyi_. For comparisons see accounts of those forms. _Remarks._--This subspecies is the smallest of all the races of _Thomomys bottae_ occurring in Utah. As far as known it is endemic to Stansbury Island, and since the Pleistocene Lake Bonneville attained its highest level has remained on that part of Stansbury Island that was above this high level. (See comments under _nesophilus_.) The sandy nature of the soil and the desert conditions of the area that has since been exposed at lower levels apparently do not constitute a favorable environment. Unlike _nesophilus_ from Antelope Island, this form does not have its affinities with _albicaudatus_, the valley form of the adjacent mainland, but does show affinities with _stansburyi_, the nearest mountain form on the mainland. This is easily understood when one realizes that Stansbury Island is only an isolated part of Stansbury Mountain that projects northward as a peninsula into Great Salt Lake. The history of Stansbury Island with reference to isolation of _minimus_ parallels that of _nesophilus_ on Antelope Island. See discussion under _nesophilus_. _Specimens examined._--Total, 5, as follows: _Tooele County_: Stansbury Island, Great Salt Lake, 5 (U. S. N. M.). =Thomomys bottae nesophilus= Durrant _Thomomys bottae nesophilus_ Durrant, Bull. Univ. Utah, 27 (No. 2):2, October, 1936; Marshall, Journ. Mamm., 21:156, May 14, 1940. _Type._--Male, adult, skin and skull, No. 1136, Museum of Zoölogy, University of Utah; Antelope Island, Great Salt Lake, Davis County, Utah; April 20, 1935; collected by S. D. Durrant; original number 761. _Range._--Known only from the type locality. _Diagnosis._--Size medium (see measurements); claws on front feet long. Color: Upper parts Cinnamon Buff; lighter below; sides Pinkish Buff interspersed with gray; pectoral and inguinal regions Cinnamon; nose grayish black; postauricular patches black. Skull: Interparietal wedge-shaped; tympanic bullae small; dorsal surface of lambdoidal prominence 3 mm. wide rather than developed as a crest; jugals nearly straight; zygomatic arches strongly rectangular. _Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _nesophilus_ is of approximately the same size, but differs as follows: Claws on front feet longer. Color: Lighter throughout; tail white terminally, but much darker at base; postauricular patches smaller. Skull: Interparietal wedge-shaped as opposed to roughly quadrangular; lambdoidal eminence more of a crest than a ridge; tympanic bullae smaller; jugals more nearly straight; zygomatic arches more nearly rectangular. From topotypes of _Thomomys bottae aureiventris_, _nesophilus_ differs in: Size smaller; claws on front feet longer. Color: Darker throughout; postauricular patches larger. Skull: Heavier, more massive; zygomatic arches more robust and convex laterally rather than concave; interparietal wedge-shaped rather than roughly quadrangular; braincase more nearly flat; tympanic bullae markedly smaller; upper molariform series longer; molariform teeth wider and heavier; interpterygoid space V-shaped rather than lyre-shaped. The race nearest geographically to _nesophilus_ is _T. b. minimus_ from Stansbury Island, Great Salt Lake. It can easily be distinguished from _minimus_ by the following features: Size much larger; claws on front feet longer and thicker. Color: Darker throughout; postauricular patches larger and with more admixture of buff colored hairs. Skull: Larger in every measurement taken; wide and robust as opposed to narrow and slender; zygomatic arches more widely spreading and angular; braincase more nearly flat; tympanic bullae actually larger, but relatively smaller; lambdoidal eminence flat-topped rather than a crest; interparietal wedge-shaped as opposed to quadrangular; teeth larger. _Remarks._--The affinities of _nesophilus_ of Antelope Island are unquestionably with _albicaudatus_ of the eastern and southern mainland. At the time of this writing (1945), Antelope Island is not truly an island, but only the tip of a broad peninsula projecting westward into Great Salt Lake. Nevertheless, the area of occurrence of _nesophilus_ is effectively isolated by the exposed, sandy lake bottom that is unsuited to occupancy by pocket gophers. Fluctuations in the level of the Great Salt Lake have broken and reëstablished this connection with the mainland many times. Each of the several other kinds of mammals which are known from both the island and the mainland show no differentiation on the island. These are kinds (see Marshall, 1940:156), which more freely cross the exposed, sandy lake bottom. I, myself, have noted tracks of coyotes going to and from the island. The pocket gopher, _nesophilus_, so far as known is the only mammal which has developed a subspecies endemic to the island. The beach levels of Pleistocene Lake Bonneville are well marked on both Antelope Island and Stansbury Island, which is fifteen miles west of Antelope Island. On the eastern side of Antelope Island the lower beach levels of this prehistoric lake are farmed. Although sought for elsewhere on this island, pocket gophers were found only in the farmed land. On Stansbury Island there has been no farming, and the endemic pocket gophers, _minimus_, although sought for elsewhere on that island were found only above the highest beach levels of the ancient lake. Evidently these pocket gophers still occupy only that part of Stansbury Island that projected above water during the greatest height of Lake Bonneville. Farming on Antelope Island may have developed a more favorable environment for pocket gophers, thus causing them to move down to the lower levels from that part of the island that was above water during Pleistocene times. _Specimens examined._--Total, 5, from the type locality. =Thomomys bottae stansburyi= new subspecies _Type._--Female, adult, skin and skull, No. 2045, Museum of Zoölogy, University of Utah; South Willow Creek, Stansbury Mountains, 7,500 ft., Tooele County, Utah; July 2, 1937; collected by O. S. Walsh and S. D. Durrant; original number 1257 of Durrant. _Range._--Stansbury Mountains, Tooele County, Utah. _Diagnosis._--Size small (see measurements). Color: Upper parts Saccardo's Umber, darker on head; sides and underparts Pinkish Buff; nose, chin and postauricular patches black; front and hind feet and distal third to half of tail white. Skull: Small, slender, weak and smooth; zygomatic arches light and not widely spreading; zygomatic arches actually as well as relatively short; interparietal generally quadrangular; nasals relatively long and slender; interpterygoid space narrowly V-shaped; basioccipital fairly wide; tympanic bullae moderately inflated ventrally; dentition light. _Comparisons._--Topotypical specimens of _stansburyi_ can be readily distinguished from those of _Thomomys bottae centralis_, _aureiventris_ and _albicaudatus_ by being smaller in every measurement taken, particularly those of the skull; the skull is weaker and smoother. In color _stansburyi_ is like _albicaudatus_ but is much darker throughout than _aureiventris_ and _centralis_. Comparisons of topotypes of _stansburyi_ with those of _Thomomys bottae sevieri_ show them to be of approximately the same size, but to differ as follows: Color: Darker throughout. Skull: Zygomatic arches shorter; tympanic bullae less inflated ventrally; zygomatic breadth less; mastoid breadth greater; width across alveolar processes of maxillae greater; alveolar length of upper molar series greater; molariform teeth larger. Compared with topotypes of _Thomomys bottae minimus_, _stansburyi_ is seen to be of larger size and darker color throughout, with a skull that is larger in most every measurement taken, although of the same slender, smooth, nonangular type. Among named races of _Thomomys bottae_, _stansburyi_ most closely resembles tivius, a small, dark, mountain form from central Utah. Size and color are almost the same but _stansburyi_ differs in: Tail shorter; hind foot averaging slightly longer. Skull: Generally larger in every measurement taken; zygomatic arches shorter; width across alveolar processes of maxillae greater; zygomatic arches more widely spreading, and widest in extreme posterior region rather than in region of jugal-squamosal suture. _Remarks._--The Stansbury Mountains are separated from the Oquirrh Mountains by the Stockton Bar, and from the Onaqui Mountains, which are in reality a continuation of the Stansbury Mountains, by only a low pass. Pocket gophers from Clover Creek, Onaqui Mountains and Little Valley, Sheeprock Mountains, although intergrades between _robustus_ and _albicaudatus_ are dark in color like _stansburyi_. These intergrades are large, dark colored, and have heavy, ridged, angular skulls. It appears that _stansburyi_ is a mountain subspecies derived from _albicaudatus_ of the valley. It would be instructive to artificially transplant gophers from mountains to valleys, and _vice versa_, so as to reveal what effects if any on the animals' morphology the environment might have in one or a few generations. Gophers are well known to be very plastic, and such an experiment as suggested might call for modification of the view, held here, that the differential features of gophers from South Willow Creek and, say, Bauer, are hereditary. _Specimens examined._--Total, 11, from the type locality. =Thomomys bottae albicaudatus= Hall _Thomomys perpallidus albicaudatus_ Hall, Univ. California Publ. Zoöl., 32:444, July 8, 1930; Univ. California Publ. Zoöl., 37:3, April 10, 1931. _Thomomys bottae albicaudatus_ Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Durrant, Bull. Univ. Utah, 28 (No. 4):5, August 18, 1937. _Thomomys perpallidus aureiventris_ Hall, Univ. California Publ. Zoöl., 37:3, April 10, 1931. _Type._--Male, adult, skin and skull, No. 43971, Museum of Vertebrate Zoölogy, University of California; Provo, 4,510 ft., Utah County, Utah; October 17, 1929; collected by Annie M. Alexander; original number 506. _Range._--From the area between the Great Salt Lake and the Wasatch Mountains south along the western margin of the central mountains of the state to the Sevier River, in Juab County, west into Tooele County to the Onaqui and Sheeprock mountains. _Diagnosis._--Size medium (see measurements); claws on front feet medium. Color: Upper parts near (13''''_n_) Black, grading over sides and flanks to Pinkish Cinnamon on underparts; chin, nose, top of head and postauricular patches black; front feet, hind feet and distal third to half of tail white. Skull: Angular and ridged; zygomatic arches moderately wide spreading, widest posteriorly; paroccipital processes weak; zygomatic processes of maxillae convex anteriorly; lacrimal processes small and peglike; jugals convex dorsally on ventral surface; nasals short, rounded distally and truncate proximally; parietal crests bowed in, in two places; interpterygoid space broadly V-shaped. _Comparisons._-For comparisons of _albicaudatus_ with _Thomomys bottae aureiventris_ and _centralis_ see accounts of those forms. Topotypes of _albicaudatus_ are dark colored and can be distinguished from those of _Thomomys bottae birdseyei_, _tivius_, _stansburyi_ and _contractus_ which are also dark forms, by larger size and larger, more robust skulls (see accounts of those forms). It can be distinguished from the remainder of the known subspecies of _Thomomys bottae_ in Utah by darker color and by cranial details (see accounts of those forms). _Remarks._--The range of _albicaudatus_ is larger than that of any other race of _Thomomys bottae_ limited to Utah. Specimens are available from thirty localities which represent widely varied habitats and environments. This subspecies consists of many highly variable local populations, and the marginal populations intergrade freely with adjacent races. In many populations, it is really difficult to recognize the relationships on account of the great variation, and one is frequently tempted to name some of them as distinct. Careful study of the large number of specimens has enabled me to recognize diagnostic characters common to all of these variable populations. The animals range from large and dark at the north to small and light at the south. The Jordan River bisects Salt Lake County from north to south. Pocket gophers were taken at nine places east of the river, and at three places west of it. Gophers from Salt Lake City and environs (east of the river) vary in color from almost black to dark cinnamon. Specimens from Draper, which locality is likewise east of the river, are uniformly lighter, but also vary in color. The skulls of animals from both localities are indistinguishable from each other and closely resemble those of topotypes. Specimens from the west side of the river, from Riverton, two miles west of Murray and Rose Canyon, Oquirrh Mountains, all are lighter in color than topotypes. The color varies from darkest at the north at Murray to lightest at the south at Riverton. This is exactly the reverse of what would be expected since Riverton is the locality geographically nearest to the type locality, Provo. The skulls are quite uniform and are all referable to _albicaudatus_. The Jordan River may be one factor which causes this lack of uniformity between the animals from the two sides of the river. Davis (1939:56-57) states that rivers are not barriers to movement of pocket gophers where the river completely freezes over and has the ice covered with thick snow. Although the Jordan River does occasionally freeze over, it is never frozen for more than a few days at a time, and snow in this area does not last for long periods. The material at hand indicates that the gophers from both sides of the river are referable to the same subspecies _albicaudatus_. The animals from the east side of the river are in the aggregate of characters the most typical of _albicaudatus_ of any in the entire range. Those from the west side of the river, although definitely referable to _albicaudatus_ do show some intergradation with _Thomomys bottae robustus_, the subspecies to the west. The specimens from Bauer, Tooele County, are relatively uniform in color, and are considerably lighter than topotypes of _albicaudatus_. Their upper parts vary from Sepia to Saccardo's Umber as compared with near (13''''_n_) Black of the topotypes. The sides and underparts are lighter, due primarily to much less black in the underfur. They average slightly longer in total length, but shorter in hind foot. All cranial measurements are slightly smaller than in topotypes of _albicaudatus_. The shape of the skull closely resembles that of _albicaudatus_, although the rostrum, nasals, upper incisors and posterior tongues of the premaxillae tend to be narrower. This narrowness indicates intergradation with _Thomomys bottae stansburyi_, the race nearest to the west. These animals are in the majority of characters referable to _albicaudatus_. Bauer is situated in extreme western Tooele Valley at the foot of Stockton Bar, a low pass between the Stansbury and the Oquirrh mountains. This valley lies to the west of the aforementioned Jordan River. Although these gophers are definitely referable to _albicaudatus_ they are more unlike topotypes than are the animals from Riverton. The specimens from Settlement Canyon, Oquirrh Mountains, Tooele County, show the same characteristics as those from Bauer. In a large series of animals from St. John, in Rush Valley, Tooele County, the upper parts vary from black, even darker than topotypes of _albicaudatus_, to Tawny Olive, and the underparts vary from black through Cinnamon Buff to Pinkish Buff. Most of the animals are Cinnamon Buff. Although variable they approach _albicaudatus_ in color. The total length, tail and hind foot of males are longer than in topotypes of _albicaudatus_; females differ in the same direction but only slightly. In both sexes the zygomatic breadth is less, but the mastoid breadth is greater than in _albicaudatus_. In size and shape of the lacrimal processes, and the great thickening of the jugal at the maxillo-jugal suture they approach _robustus_. They are much larger, however, and in the majority of characters are referable to _albicaudatus_. What has just been said relative to the animals from St. John applies also to those from Clover Creek in the Onaqui Mountains of Tooele County. At the latter locality the tendencies towards _robustus_ are accentuated. This is to be expected, since this locality is midway between St. John and the type locality of _robustus_. All characters considered, these animals are all referable to _albicaudatus_. The animals from Little Valley, Sheeprock Mountains, Tooele County, resemble _albicaudatus_ in color. They vary on the upper parts from near (1) Sepia to Clay Color, and ventrally from nearly black to Pinkish Buff. They are markedly smaller in every measurement taken, except zygomatic and mastoidal breadths, and extension of premaxillae posterior to nasals. This relatively greater breadth indicates intergradation with _robustus_ to the west. These gophers are smaller in most measurements than any other population referred to _albicaudatus_. This is understandable because gophers from mountains usually are smaller and have weaker, smoother skulls than animals from low lands. Although approaching _robustus_ in size and in some aforementioned cranial details, the aggregate of characters including color, make these animals referable to _albicaudatus_. The animals from Fairfield, Utah County, are closer geographically to the type locality of _albicaudatus_ than any other series, but morphologically are the least like topotypes. At first glance one is struck with the differences. They are uniformly Clay Color above, with Cinnamon Buff sides and flanks and Pinkish Buff underparts. Their color closely approaches that of _robustus_ to the west which has Cinnamon Buff on the upper parts. Examination of eleven measurements of males and the same number for females, shows that the animals are nearest to _robustus_ in two measurements, to _albicaudatus_ in 12, distinct in 7 and intermediate in one. The general appearance of the skull is intermediate between that of the two above mentioned forms. The differences from _albicaudatus_ in size and color may be correlated with the differences in soil at Fairfield and Provo. At Fairfield the soil is light-colored clay, but at Provo it is sandy and darker. Although they are intergrades between _robustus_ and _albicaudatus_, the animals are referred to the latter race. Utah Lake and its outlet, the Jordan River, make a partial barrier between populations at Fairfield and at the type locality at Provo. During Pleistocene times, when Lake Bonneville was present it formed a complete barrier. Enough time has evidently elapsed since the disappearance of this lake to allow _albicaudatus_, the mainland form, to expand its range to the west. Intergradation has taken place, with the result that the animals from Fairfield, although unstable, agree with the mainland form, _albicaudatus_, in a majority of their characters. Pocket gophers were taken at four localities from north to south in eastern Juab County. They range in color from Ochraceous Tawny on the upper parts and Cinnamon Buff on the underparts to shades that are slightly lighter. All are much lighter than topotypes of _albicaudatus_. The general configuration of the skull is the same as that of _albicaudatus_, and this is especially true in the females. In the narrower rostrum and weaker dentition they approach _contractus_, but are distinctly lighter colored. Hall (1931:3) referred one specimen from Nephi, Juab County, to _Thomomys bottae aureiventris_. Since that time _Thomomys bottae lenis_ which has some affinities with _aureiventris_ has been described (see account of _contractus_). The large series now available from Nephi and nearby localities do show some intergradation with _lenis_, in that four characters are more as in _lenis_ and _contractus_ and seven characters are more as in _albicaudatus_. Although differing markedly in many respects from topotypes of _albicaudatus_ they fit the aforementioned concept of this subspecies, and are being treated as a variable local population of it. Provo is the locality listed for specimens which were available to naturalists from 1875-1877. To these specimens the following names were applied: _Thomomys talpoides bulbivorus_ Coues (1875:256; 1877:627) and _Thomomys talpoides umbrinus_ Coues and Yarrow (1875:112). Possibly these names were applied to the animals currently known as _Thomomys bottae albicaudatus_ which does occur at Provo. Without the opportunity to examine the actual specimens, which so far as I know are no longer in existence, I cannot exclude the possibility that the locality designation "Provo" was used in a general sense to include pocket gophers taken a few miles to the eastward of Provo, where it is known that pocket gophers of only the species _Thomomys talpoides_ (current terminology) occur. _Specimens examined._--Total, 239, distributed as follows: _Davis County_: Bountiful, 4,500 ft., 1. _Salt Lake County_: Salt Lake City and environs, 4,300 ft., 51; 2 mi. W Murray, 4,300 ft., 6; Riverton, 4,300 ft., 11; Draper, 4,500 ft., 7; Rose Canyon, Oquirrh Mountains, 5,650 ft., 4. _Tooele County_: Bauer, 4,500 ft., 30; Settlement Creek, Oquirrh Mountains, 6,500 ft., 1; St. John, 4,300 ft., 28; Clover Creek, Onaqui Mountains, 5,500 ft., 15; Vernon, 4,300 ft., 2 (U. S. A. C.); Little Valley, Sheeprock Mountains, 5,500 ft., 20. _Utah County_: Fairfield, 4,800 ft., 24; Provo, 4,400 ft., 20 (8, B. Y. U.; 12, M. V. Z.). _Juab County_: Neff Farm, 4 mi. N Nephi, 5,000 ft., 2 (1, R. H.); Nephi, 5,000 ft., 1 (M. V. Z.); 2 mi. S Nephi, 4,700 ft., 14; 7 mi. SW Nephi, 6,000 ft., 2. =Thomomys bottae bonnevillei= new subspecies _Type._--Male, adult, skin and skull, No. 3576, Museum of Zoölogy, University of Utah; Fish Springs, 4,400 ft., Juab County, Utah; June 8, 1940; collected by S. D. Durrant; original number 1955. _Range._--Known only from the type locality. _Diagnosis._--Size medium (see measurements); claws on front feet small. Color: Entire dorsal surface Warm Buff; sides near (_e_) Cinnamon Buff, underparts near (16") Pale Pinkish Buff; inguinal region, front and hind feet and distal part of tail white: top of head, nose and cheeks grayish black; postauricular patches small and grayish black; ears small, pointed and with heavily pigmented pinnae. Skull: Angular, short and wide; nasals of medium length, narrow proximally but widely flared distally; interparietal small; lambdoidal suture concave towards the interparietal; zygomatic arches uniformly widely spreading; interpterygoid space widely V-shaped; extension of premaxillae posterior to nasals long; lambdoidal crest well developed. _Comparisons._--From topotypes of _Thomomys bottae aureiventris_, _bonnevillei_ differs as follows: Size smaller, hind foot shorter. Color: Upper parts and sides lighter; underparts pale buff rather than "gold." Skull: Shorter and relatively wider; rostrum wider and heavier; zygomatic arches relatively wider and more massive, with greatest width posteriorly instead of anteriorly; interpterygoid space widely V-shaped rather than lyre-shaped; thickening at union of jugal and zygomatic process of maxilla less developed; anterior palatine foramina larger; nasals shorter and more markedly flared distally; zygomatic breadth relatively, and mastoidal breadth actually, wider; extension of premaxillae posterior to nasals greater; tympanic bullae more inflated ventrally; upper incisors wider. From near topotypes of _Thomomys bottae centralis_, from 1 mile east of Garrison, Millard County, Utah, _bonnevillei_ differs as follows: Size smaller; hind foot and tail shorter. Color: Generally darker above and lighter below; top of head darker; postauricular patches smaller and lighter. Skull: Shorter and wider (zygomatic breadth expressed in percent of basilar length being, in males, 74.5 in _bonnevillei_ and 71.5 in _centralis_); interpterygoid space more widely V-shaped; interparietal smaller, and more triangular; nasals shorter and much more dilated distally, as well as more constricted proximally; lacrimal processes smaller and less globuse at tips; temporal fossae larger; braincase and entire dorsal surface of skull more nearly flat; lambdoidal suture convex posteriorly as opposed to nearly straight; tympanic bullae more inflated ventrally. Comparisons of _bonnevillei_ with the type and type series of _Thomomys bottae wahwahensis_ show them to be of approximately the same size, but to differ as follows: Color: Slightly darker above and lighter below; postauricular patches smaller and lighter. Skull: Larger in every measurement taken, except breadth of rostrum which is smaller; skull not as flat; tympanic bullae more inflated ventrally; nasals and rostrum longer; extension of premaxillae posterior to nasals greater; interparietal smaller and more triangular; zygomatic arches more bowed out laterally; jugals heavier; interpterygoid space more widely V-shaped; upper incisors less massive. The characters that distinguish _bonnevillei_ from _Thomomys bottae albicaudatus_ are: Size smaller. Color: Markedly lighter throughout. Skull: Shorter and wider; mastoid and zygomatic breadths greater; rostrum narrower but shorter; angle between rostrum and zygomatic processes of maxillae less; interparietal smaller and more triangular; extension of premaxillae posterior to nasals greater; upper incisors shorter, narrower and more recurved. _T. b. bonnevillei_ is indistinguishable in color from _Thomomys bottae convexus_, but differs from it in the following features: Size larger in nearly every measurement taken. Skull: Flattened dorsally as opposed to convex; zygomatic arches longer and weaker; jugals more nearly perpendicular; tympanic bullae larger; upper incisors longer; alveolar length of upper molar series the same, but molars narrower; rostrum longer but nasals shorter; extension of premaxillae posterior to nasals greater. Topotypes of _bonnevillei_ can be distinguished from those of both _Thomomys bottae tivius_ and _stansburyi_ by being larger in every measurement taken, by markedly lighter color throughout, and by ridged, massive, angular skulls rather than smooth, weak, nonangular skulls. The races closest geographically to _bonnevillei_ are _Thomomys bottae robustus_ and _T. b. sevieri_. Compared with topotypes of _robustus_, _bonnevillei_ differs in: Size larger. Color: Lighter throughout. Skull: Larger, although not as compact; zygomatic arches more widely spreading; jugals lighter; lacrimal processes not as prominent; zygomatic processes of maxillae not as robust; nasals more flared distally; extension of premaxillae posterior to nasals greater; alveolar length of upper molar series longer; molars larger; upper incisors longer, wider and darker in color; when placed ventral side down on a surface, the dorsal face of a skull of _robustus_ is approximately parallel to the surface, whereas one of _bonnevillei_ dips down in the occipital region. _T. b. sevieri_ can be easily distinguished from _bonnevillei_ by being smaller in every measurement taken, darker in color, and by small, weak, smooth skulls as opposed to large, robust, ridged skulls. _Remarks._--Fish Springs, where _bonnevillei_ occurs is a marshy area south of the barren, salt-desert country of western Utah. The source of water is springs at the base of the north end of the Fish Springs Mountains. Only the moist area supports pocket gophers. Specimens from Trout Creek, Juab County, twenty-five miles to the southwest are intergrades between _bonnevillei_ and _aureiventris_, and are referred to the latter subspecies. The country between Fish Springs and Trout Creek in 1937 and 1940 lacked pocket gophers; it was of the playa and sand type. Probably _T. b. bonnevillei_ was derived from _T. b. aureiventris_, a western mainland form of Pleistocene Lake Bonneville, through isolation and subsequent differentiation morphologically. The moist soils at Cane Springs, seven miles south of Fish Springs, had no pocket gophers when visited in 1940. _Specimens examined._--Total, 11, from the type locality. =Thomomys bottae centralis= Hall _Thomomys perpallidus centralis_ Hall, Univ. California Publ. Zoöl., 32:445, July 8, 1930. _Thomomys bottae centralis_ Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Hall and Johnson, Proc. Utah Acad. Sci. Arts and Letters, 15:121, 1938. _Type._--Male, adult, skin and skull, No. 41688, Museum of Vertebrate Zoölogy, University of California; 2-1/2 mi. E Baker (1-1/4 mi. W Nevada-Utah boundary on 39th parallel), 5,700 ft., White Pine County, Nevada; May 30, 1929; collected by E. Raymond Hall; original number 2683. _Range._--Extreme western Utah, in Millard, Beaver and Iron counties. _Diagnosis._--Size medium (see measurements); tail long; claws on front feet long. Color: Near Cinnamon Buff on upper parts, darker in middorsal region, grading to Pinkish Buff on underparts, more accentuated in pectoral and inguinal regions; nose, cheeks and postauricular patches grayish black; front and hind feet and distal half of tail white. Skull: Robust and moderately ridged; zygomatic breadth about the same for entire length of arches; jugals vertical posterior to middle; moderate thickening present at region of maxillo-jugal suture; interpterygoid space narrowly V-shaped; dorsal frontomaxillary sutures convex medially; lacrimal processes globose and well developed; nasals long and with distal denticulations; paroccipital processes well developed. _Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _centralis_ differs as follows: Size larger; tail longer; claws on front feet longer. Color: Lighter throughout, Cinnamon Buff as opposed to near (13''''_n_) Black. Skull: Basilar length and length of nasals greater; zygomatic breadth less; zygomatic arches thicker at region of maxillo-jugal sutures; interpterygoid space more broadly V-shaped; dorsal frontomaxillary sutures convex medially as opposed to straight; paroccipital processes more developed; zygomatic arches approximately the same width throughout as opposed to widest posteriorly. For comparisons with _Thomomys bottae aureiventris_ see account of that form. _T. b. centralis_ can be distinguished from _Thomomys bottae bonnevillei_, _robustus_, _sevieri_ and _convexus_ by larger size throughout and generally darker color (see accounts of those forms). From _Thomomys bottae stansburyi_ and _tivius_, _centralis_ differs in larger size throughout and lighter color (see accounts of those forms). _Remarks._--_Thomomys bottae centralis_ has one of the most extensive ranges of any of the known races of _T. bottae_. The eastern limits extend into extreme western Utah. Specimens from Utah for the most part are intergrades between _centralis_ and _aureiventris_, the race to the north. Some minor intergradation is also noted between _centralis_ and _sevieri_ and _bonnevillei_, the races to the east. Intergradation is the expected condition because the animals belonging to _centralis_ are at the extremes of their range in this area. The greater affinities of these animals with _aureiventris_ is to be expected because both _aureiventris_ and _centralis_ are forms of the western mainland of the Pleistocene Lake Bonneville; while the races to the east, although closest geographically, were isolated from the gophers of the western mainland during prehistoric times by this lake. They are still isolated and enough time has elapsed so that only vestiges of morphological intergradation exist between _centralis_ and these eastern forms. Two specimens from Cedar City, Iron County, are intergrades between _Thomomys bottae wahwahensis_, _centralis_ and _planirostris_. Their skulls are slightly convex as in _planirostris_, and the rostrum is short and wide as in _wahwahensis_. In shape of the zygomatic arches, length of the nasals, and color, they resemble _centralis_ to which they are here referred. _Specimens examined._--Total, 49, distributed as follows: _Millard County_: 1 mi. SE Gandy, 5,000 ft., 15 (M. V. Z.); White Valley (Tule Spring), 60 mi. W Delta, 4, (3 in R. W. Fautin Vertebrate Collection); Robison Ranch, 5,300 ft., (on Hendry Creek) Simonsons Ranch, 4,596 ft., 2 (M. V. Z.); 1 mi. E Garrison, 5,000 ft., 21; 5 mi. S Garrison, 5,400 ft., 5 (M. V. Z.). _Iron County_: Cedar City, 2 (M. V. Z.). =Thomomys bottae sevieri= new subspecies _Type._--Female, adult, skin and skull, No. 2530, Museum of Zoölogy, University of Utah; Swasey Spring, House Mountains, 6,500 ft., Millard County, Utah; May 16, 1938; collected by S. D. Durrant; original number 1380. _Range._--Known only from the type locality. _Diagnosis._--Size medium (see measurements); claws on front feet short and weak; ears short; tail relatively long. Color: Upper parts Pinkish Buff, grading over sides to Pale Pinkish Buff on underparts; nose, top of head, chin and cheeks grayish black; postauricular patches small and grayish black; front and hind feet and distal two-thirds of tail white. Skull: Small, weak and smooth; rostrum narrow; nasals narrow, not markedly flared distally; zygomatic arches weak, not angular, and of "graceful" contour; lacrimal processes small; characteristic dorsal depression present in region of sagitto-coronal suture; mastoid and zygomatic breadths narrow; occiput narrow and high; braincase well inflated; paroccipital processes small and smooth; interpterygoid space narrowly V-shaped; tympanic bullae small, but well inflated ventrally; alveolar length of upper molar series short; molars small; upper incisors short, but narrow. _Comparisons._--From topotypes of _Thomomys bottae aureiventris_, _sevieri_ differs as follows: Size smaller. Color: Lighter throughout, no "gold" on underparts. Skull: Much smaller in every measurement taken, less massive and not angular; zygomatic arches weaker and widest posteriorly rather than anteriorly; union of jugal and zygomatic process of maxilla not greatly thickened; interpterygoid space narrowly V-shaped rather than lyre-shaped; pterygoid hamulae shorter and weaker; tympanic bullae smaller, but markedly more inflated ventrally; dentition smaller and weaker. From near topotypes of _Thomomys bottae centralis_, _sevieri_ can be distinguished by the following features: Size markedly smaller. Color: Lighter throughout. Skull: Markedly smaller in every measurement taken, weaker and smoother; zygomatic arches weaker, less angular and more "graceful"; rostrum shorter, but narrower; lacrimal processes smaller; tympanic bullae smaller, but more inflated ventrally, being triangular in shape as opposed to ovate and with anteromedial margin decidedly pointed; pterygoid hamulae smaller and weaker; dentition smaller and weaker. _T. b. sevieri_ can readily be distinguished from _Thomomys bottae albicaudatus_ by the following features: Size smaller in every measurement taken. Color: Markedly lighter throughout. Skull: Smaller, and weaker; rostrum shorter and narrower; ascending processes of premaxillae narrower; extension of premaxillae posterior to nasals shorter; posterior tongues of premaxillae narrower; dentition much lighter. Comparisons of _sevieri_ with topotypes of _Thomomys bottae wahwahensis_ show them to be of approximately the same size, but to differ as follows: Hind foot longer; ear shorter. Color: Slightly darker. Skull: Smaller, weaker, less ridged; zygomatic breadth less; zygomatic arches markedly less angular; mastoid breadth less; rostrum much longer and narrower, not as blunt nor flattened; tympanic bullae much larger and more inflated ventrally; braincase vaulted as opposed to flattened. From topotypes of _Thomomys bottae bonnevillei_, _sevieri_ differs in: Size smaller throughout. Skull: Smaller in every measurement taken, weaker, smoother and less angular; dentition smaller and weaker. Topotypes of _sevieri_ are easily distinguished from those of _Thomomys bottae robustus_ by smaller size, and smaller, markedly weaker skull which is less angular and ridged. Among named races of _Thomomys bottae_, _sevieri_ is closest geographically to _convexus_, but differs from it as follows: Size larger; hind foot longer. Skull: Smaller in every measurement taken; nasals shorter and not so flaring distally; rostrum weaker, narrower and not so depressed; zygomatic arches markedly weaker and less angular; lacrimal processes smaller; supraoccipital narrower and higher; paroccipital processes weaker; tympanic bullae smaller; dentition markedly weaker. Topotypical specimens of _sevieri_ can be readily distinguished from those of _Thomomys bottae tivius_ by Pinkish Buff instead of Mummy Brown on upper parts. Tympanic bullae larger and markedly more inflated; nasals longer; zygomatic and mastoidal breadths greater; rostrum longer and more depressed; upper incisors longer and wider; molariform teeth smaller. The skulls of _sevieri_ resemble those of _tivius_ more closely than those of any other subspecies. _Remarks._--The House Mountains in western Millard County are surrounded by desertlike terrain that is seemingly unsuited to pocket gophers. In these mountains, gophers were sought in vain at several localities, including Antelope Springs which superficially appeared suitable for the animals. Pocket gophers were found only at the type locality, Swasey Spring, which is well above the highest level of the Pleistocene Lake Bonneville. _T. b. sevieri_, like _T. b. minimus_ on Stansbury Island, Great Salt Lake, appears to remain only on land that was an island when Lake Bonneville was at its highest level. _Specimens examined._--Total, 10, from the type locality. =Thomomys bottae convexus= Durrant _Thomomys bottae convexus_ Durrant, Proc. Biol. Soc. Washington, 52:159, October 11, 1939. _Type._--Male, adult, skin and skull, No. 2482, Museum of Zoölogy, University of Utah; E side Clear Lake, 4,600 ft., Millard County, Utah; May 20, 1938; collected by S. D. Durrant; original number 1401. _Range._--Westcentral Utah in Delta Valley. _Diagnosis._--Size medium (see measurements). Color: Upper parts and sides Pinkish Buff, purest on sides; underparts Pale Pinkish Cinnamon; inguinal and pectoral regions Pale Pinkish Buff; nearly all specimens have white on perineal region; nose grayish black; front feet, hind feet and distal third to half of tail white; postauricular patches black. Skull: Braincase moderately convex on dorsal surface; rostrum strongly depressed, giving the entire dorsal surface of the skull a "rocker-shape"; zygomatic arches heavy, short and widely spreading, widest posteriorly; upper incisors recurved, short and wide; molariform teeth large; alveolar length of upper molar series long; palatal pits deep; tympanic bullae moderately inflated ventrally; mastoidal breadth actually as well as relatively wide. _Comparisons._--Compared with topotypes of _Thomomys bottae wahwahensis_, _convexus_ is of approximately the same color, but differs as follows: Size smaller; tail, hind foot, and ear shorter. Skull: Rostrum longer, narrower and more depressed; skull convex rather than flat; nasals longer, and convex rather than flat; tympanic bullae larger; zygomatic arches shorter and more massive; molariform teeth larger. From topotypes of _Thomomys bottae centralis_, _convexus_ differs in: Size smaller; tail and hind foot shorter. Color: Uniformly lighter, more white in perineal region. Skull: Smaller, more convex; rostrum shorter, wider and more depressed; zygomatic arches shorter and heavier; mastoidal breadth actually, as well as relatively wider; tympanic bullae more inflated ventrally; upper incisors shorter and wider. Comparatively, topotypes of _convexus_ can be distinguished from those of _Thomomys bottae aureiventris_ by: Size smaller; tail and hind foot shorter. Color: Darker on upper parts; no "gold" on underparts. Skull: Smaller and more nearly flat; rostrum shorter and more depressed; zygomatic arches shorter, heavier and widest posteriorly rather than anteriorly; interpterygoid space V-shaped as opposed to lyre-shaped; upper incisors shorter, narrower and more recurved. Topotypical specimens of _convexus_ differ from those of _Thomomys bottae nesophilus_ as follows: Size smaller; tail and hind foot shorter. Color: Uniformly lighter throughout, Cinnamon Buff as opposed to Pinkish Buff. Skull: Smaller; rostrum heavier, shorter and more depressed; zygomatic arches shorter, heavier and not so widely spreading; no widening of supraoccipital as in _nesophilus_; upper incisors shorter and more recurved. When compared with topotypes of _Thomomys bottae albicaudatus_, _convexus_ shows the following differences: Size smaller; tail and hind foot shorter. Color: Markedly lighter throughout. Skull: Smaller, more convex and compact; rostrum shorter, heavier, more depressed and compact; zygomatic arches shorter and more robust; upper incisors shorter and more recurved. _Thomomys bottae tivius_ is the race closest geographically to _convexus_. From it, _convexus_ can be readily distinguished by: Size larger; tail shorter; hind foot longer. Color: Markedly lighter throughout. Skull: Much heavier and more compact, weights of skulls of males and females of the two subspecies being 2.4 grs., 1.6; 1.6, 1.2, respectively; rostrum heavier, wider and more depressed; zygomatic arches shorter, and more massive; upper incisors shorter, wider and more recurved; molariform teeth larger. For comparisons with _Thomomys bottae lenis_, _contractus_, _sevieri_, _bonnevillei_, and _robustus_ see accounts of those forms. _Remarks._--_T. b. convexus_ is limited to the area around Clear Lake in Millard County. This lake is surrounded by areas of loose, shifting sand and flat areas of barren alkali. The lake is fed by springs which flow from lava outcroppings on its eastern side. As far as discernible, the only area populated by pocket gophers (1938) was that adjacent to the lake where vegetation had trapped the sand. The factor which limits the extension of range of this subspecies probably is plant food. Also, the soil is mechanically poor for burrowing, since it caves in easily and burrows were found only in the sand where salt grass (_Distichlis stricta_) had trapped and stabilized it. Burrows were found from the edge of the water back as far as this grass persisted. _Specimens examined._--Total, 17, from the type locality. =Thomomys bottae tivius= Durrant _Thomomys bottae tivius_ Durrant, Bull. Univ. Utah, 28 (No. 4):5, August 18, 1937. _Type._--Female, adult, skin and skull, No. 1827, Museum of Zoölogy, University of Utah; Oak Creek Canyon, 6 mi. E Oak City, 6,000 ft., Millard County, Utah; September 14, 1936; collected by S. D. Durrant; original number 1100. _Range._--Limited to the Cañon Mountains, Millard County. _Diagnosis._--Size small (see measurements). Color: Upper parts Mummy Brown, grading through Cinnamon on the sides to Pale Cinnamon on the underparts; cheeks Cinnamon; postauricular patches black; distal third to half of tail white. Skull: Small, weak; zygomatic arches weak, not widely spreading, widest posteriorly; tympanic bullae large; interpterygoid space V-shaped; nasals short, usually simple distally, but with some denticulations in some specimens; palatal pits deep; palate narrow; paroccipital processes small; incisors, both upper and lower, narrow; molariform teeth small. _Comparisons._--Topotypes of _tivius_ differ from those of _Thomomys bottae albicaudatus_ as follows: Size markedly smaller in every measurement taken. Color: Lighter, Mummy Brown as opposed to near (13''''_n_) Black. Skull: Smaller, slenderer and weaker; zygomatic arches weak and not widely spreading as opposed to massive and wide spreading; nasals and rostrum narrower and shorter; extension of premaxillae posterior to nasals shorter; tympanic bullae smaller; molariform teeth smaller. For comparisons with _Thomomys bottae stansburyi_ and _T. b. contractus_ see accounts of those forms. The four subspecies _tivius_, _albicaudatus_, _stansburyi_, and _contractus_ are the darkest in color of all the _Thomomys bottae_ occurring within the state. _Remarks._--This small, dark subspecies is limited to the Cañon Mountains in eastern Millard County. Apparently it is a mountain derivative of _Thomomys bottae contractus_ which occurs in the valleys to the east and west of these mountains. Intergradation is noted with animals from the valleys on either side. For further comments on distributional problems of this type see remarks under _Thomomys bottae stansburyi_. _Specimens examined._--Total, 12, from the type locality. =Thomomys bottae contractus= new subspecies _Thomomys perpallidus albicaudatus_ Hall, Univ. California Publ. Zoöl., 37:3, April 10, 1931. _Thomomys bottae albicaudatus_ Durrant. Bull. Univ. Utah, 28 (No. 4):4, August 18, 1937. _Type._--Male, adult, skin and skull, No. 1851, Museum of Zoölogy, University of Utah; Scipio, 5,315 ft., Millard County, Utah; September 17, 1936; collected by S. D. Durrant; original number 1125. _Range._--Extreme eastern Millard and Beaver counties, Utah. _Diagnosis._--Size medium (see measurements). Color: Upper parts Cinnamon Buff, mixed with black giving a color of Dresden Brown; sides between Cinnamon Buff and Pinkish Buff; underparts Pinkish Buff, purest on inguinal and pectoral regions; postauricular patches medium in size and black; ears covered with black hairs; nose, chin, cheeks and top of head dusky; front feet, hind feet and distal third to half of tail white; proximal part of tail covered all around with buff-colored hairs. Skull: Long, slender, moderately ridged and convex transversally at proximal ends of nasals; nasals long; rostrum long and narrow; posterior ends of nasals truncate or shallowly emarginate; ascending processes of premaxillae slender; extension of premaxillae posterior to nasals long; zygomatic arches neither robust nor widely spreading; interparietal subquadrangular; supraoccipital extending horizontally well behind lambdoidal suture instead of dropping off abruptly to the foramen magnum; interpterygoid space moderately V-shaped in some specimens, but somewhat lyre-shaped in others; tympanic bullae large and truncate anteriorly; upper incisors long and narrow; molariform teeth small and light. _Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _contractus_ differs as follows: Tail longer. Color: Lighter throughout. Skull: Slenderer, less ridged and angular; rostrum narrower; zygomatic and mastoidal breadths less; ascending processes of premaxillae narrower; posterior tongues of premaxillae narrower; posterior ends of nasals less truncate; zygomatic arches weaker, less angular, and less widely spreading posteriorly; interparietal larger; paroccipital processes weaker; interpterygoid space not as widely V-shaped; upper incisors longer and narrower; molariform teeth smaller. Topotypes of _contractus_ can be distinguished from those of _Thomomys bottae convexus_ by the following: Size larger, tail longer; hind foot larger. Color: Darker throughout. Skull: Longer, narrower, and not as massive; top of skull moderately, as opposed to strongly, convex; nasals arched rather than straight; zygomatic arches neither as widely spreading, angular nor massive; space enclosed within zygomatic arches longer; interparietal larger; interpterygoid space more narrowly V-shaped; upper incisors longer and narrower; molariform teeth much lighter. Comparisons of topotypes of _contractus_ with near topotypes of _Thomomys bottae centralis_ show them to be approximately the same size, but to differ as follows: Color: Darker throughout. Skull: Shorter and slenderer; rostrum narrower; region between posterior tongues of premaxillae narrower and more convex transversally; nasals more truncate; zygomatic breadth less, but arches relatively more widely spreading posteriorly; interparietal larger; interpterygoid space generally narrower; upper incisors longer and narrower; molariform teeth smaller. Topotypes of _contractus_ differ from those of _Thomomys bottae aureiventris_ as follows: Size smaller; tail longer; hind foot shorter. Color: Darker throughout. Skull: Shorter but slenderer; rostrum narrower; nasals shorter but slenderer, and more truncate posteriorly; extension of premaxillae posterior to nasals longer; zygomatic arches weaker and less angular; zygomatic processes of maxillae weaker and with no marked thickenings at union of maxilla and jugals; interparietal larger; interpterygoid space more generally V-shaped; upper incisors longer and narrower; molariform teeth smaller. Compared with topotypes of _Thomomys bottae planirostris_, _contractus_ differs in: Size smaller throughout. Color: Darker, more black and less Cinnamon in pelage. Skull: Smaller in every measurement taken; rostrum narrower; nasals arched instead of flat; zygomatic arches neither angular, massive nor widely spreading; upper incisors narrower; molariform teeth markedly smaller and weaker. Topotypes of _contractus_ differ from those of _Thomomys bottae levidensis_ in larger size, darker color and longer, slenderer skulls. Among named races of _T. bottae_, _contractus_ is closest morphologically to _tivius_. It differs from it as follows: Size larger throughout. Color: Lighter throughout. Skull: The same general shape and proportions, but larger in every measurement taken; rostrum longer and narrower; extension of premaxillae posterior to nasals longer; posterior tongues of premaxillae narrower. _Remarks._--Fifteen animals from Oak City are intergrades between _contractus_ and _tivius_. Intergradation with _lenis_ is also shown in some specimens by the widely spreading zygomatic arches. In the majority of characters including the diagnostic long, slender, narrow rostrum they are more like _contractus_ to which they are here referred. Nine animals from Beaver were considered by Hall (1931:3) and Durrant (1937:4) to be intergrades between _Thomomys bottae albicaudatus_ and _Thomomys bottae centralis_. Restudy of these specimens in the light of additional material now shows them to be intergrades between _T. b. centralis_, _T. b. planirostris_ and _T. b. contractus_. The majority of these animals are intermediate in color between _centralis_ and _contractus_, but a few have the reddish cast of _planirostris_. The shape of the nasals is characteristic of _planirostris_, while the zygomatic arches are as in _centralis_. In the remainder of the diagnostic characters they are like _contractus_ to which they are here referred. Strong affinities exist between _albicaudatus_, _tivius_ and _contractus_. All three of these races probably stemmed from a dark form which formerly inhabited the eastern mainland of the Pleistocene Lake Bonneville. At present, _tivius_ is isolated on the Cañon Mountains in eastern Millard County, while the range of _albicaudatus_ and _contractus_ have been separated by that of _lenis_. _T. b. lenis_ has the majority of its affinities with _aureiventris_ which is an inhabitant of the western mainland of this ancient lake. An understanding of the history of the Sevier River Valley will probably clarify this distribution of pocket gophers. _Specimens examined._--Total, 39, distributed as follows: _Millard County_: Oak City, 5,000 ft., 15; Scipio, 5,315 ft., 15. _Beaver County_: Beaver, 6,000 ft., 9 (M. V. Z.). =Thomomys bottae lenis= Goldman _Thomomys townsendii lenis_ Goldman, Proc. Biol. Soc. Washington, 55:75, June 25, 1942. _Thomomys perpallidus aureus_ Moore, Journ. Mamm., 10:259; November 11, 1931. _Type._--Male, adult, skin and skull, No. 264805, U. S. National Museum (Biological Surveys Collection); Richfield, 5,308 ft., Sevier County, Utah; March 11, 1928; collected by A. W. Moore; X-catalogue number 28835 (after Goldman, type not seen). _Range._--Sevier River Valley from Piute County north to southwestern Juab and northeastern Millard counties, Utah. _Diagnosis._--Size large (see measurements). Color: Upper parts Cinnamon Buff mixed with black in middorsal region; sides, flanks, forearms, thighs and underparts Pinkish Buff; inguinal region, front feet, hind feet, underpart of tail and end of tail white; postauricular patches small and dusky; chin, cheeks, nose and top of head dusky. Skull: Largest of Utah gophers, massive and angular; nasals long and denticulate distally; rostrum long and relatively narrow; zygomatic arches widely spreading and heavy throughout; jugals nearly vertical; zygomatic processes of maxillae heavy and flaring out abruptly from base of rostrum; union of zygomatic process of maxilla and jugal greatly thickened; extension of premaxillae posterior to nasals long; posterior tongues of premaxillae relatively narrow; lacrimal processes small; pterygoid hamulae long; interpterygoid space moderately V-shaped, tending to be somewhat lyre-shaped in some specimens; tympanic bullae somewhat flattened, only moderately inflated ventrally; upper incisors long and narrow; molariform teeth actually large, but relatively small. _Comparisons._--Topotypes of _lenis_ can be distinguished from those of _Thomomys bottae tivius_, _convexus_, _contractus_, _albicaudatus_, _levidensis_, _centralis_ and _aureiventris_ by the following markedly greater average measurements of males: Total length, 250 mm.; length of nasals, 15.5; zygomatic breadth, 28.3; mastoid breadth, 22.5; and length of rostrum, 18.3. Other distinguishing characters are: Zygomatic arches more widely spreading; length of zygomatic processes of maxillae greater; and relatively longer, narrower rostrum. _Remarks._--Twenty-one animals obtained from Lynndyl, Millard County, are all intergrades between _lenis_ and _aureiventris_. They are like _aureiventris_ in the shape of the zygomatic arches, and in the bowing of the parietal crests. Slight intergradation with _centralis_ is indicated by color and the shape of the nasals. The transverse arching of the posterior part of the rostrum is indicative of some relationship with _contractus_. In six other characters studied they most closely approach _lenis_ to which they are here referred. Large size is the distinctive feature of _Thomomys bottae lenis_. The skulls are the largest of any species or subspecies of _Thomomys_ found in Utah. In total length, however, these animals are no longer than the extremes found in other named races. When Goldman (1942:75) described this race as new, he referred it to the species _Thomomys townsendii_, but remarked that the animal from Richfield was different enough from any other form then named to merit probably full specific status. I know of no character other than size to separate _Thomomys townsendii_ from _Thomomys bottae_, and since intergradation has been shown to exist between these alleged _townsendii_ from Richfield and animals from extreme western Utah known to belong to the species _bottae_, _lenis_ is here arranged as a subspecies of _Thomomys bottae_ which name has priority over _Geomys townsendii_. The range here ascribed to this race is the Sevier River Valley from Piute County as far downstream as the town of Lynndyl which is near the eastern mainland of Pleistocene Lake Bonneville. The Sevier River continues farther out into Delta Valley ultimately to empty into Sevier Lake, which at present is adjacent to the area that formerly constituted the western mainland of the aforementioned ancient lake. This watercourse may have provided a migration route in ancient times, during the fluctuations of Lake Bonneville, whereby the animals formerly of the western mainland were able to come far eastward. The animals from Lynndyl which are intergrades between _lenis_, an eastern mainland form, and _centralis_ and _aureiventris_ which are western mainland forms of Lake Bonneville lend support to this hypothesis. _Specimens examined._--Total, 26, distributed as follows: _Millard County_: Lynndyl, 4,796 ft., 21. _Juab County_: U. B. (= Yuba) Dam, 5,000 ft., 1. _Sevier County_: Salina, 4,575 ft., 1; Richfield, 5,308 ft., 3. (U. S. N. M.). =Thomomys bottae levidensis= Goldman _Thomomys bottae levidensis_ Goldman, Proc. Biol. Soc. Washington, 55:76, June 25, 1942. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--Male, adult, skin and skull, No. 191962, U. S. National Museum (Merriam Collection); Manti, 5,500 ft., Sanpete County, Utah; December 6, 1888; collected by Vernon Bailey; original number 427 (after Goldman, type not seen). _Range._--San Pitch River Valley, Sanpete County, Utah. _Diagnosis._--Size small (see measurements). Color: Upper parts and sides Cinnamon Buff, finely mixed with black along median line of back; underparts Pinkish Buff; nose, cheeks and chin grayish black; postauricular patches fairly large and grayish black; front and hind feet white (examples from type series badly stained); tail light buff but apparently white distally (the color of these specimens has apparently changed with age). Skull: Small, fairly robust; basilar length short; zygomatic arches weak, but widely spreading; tympanic bullae small; nasals short and simple distally; ventral margin of jugals convex dorsally; extension of premaxillae posterior to nasals relatively as well as actually long; posterior tongues of premaxillae relatively wide. _Comparisons._--Topotypes of _levidensis_ differ from those of _Thomomys bottae absonus_ as follows: Size smaller. Color: Lighter throughout. Skull: Shorter, weaker and less ridged and angular, but relatively wider. Compared with topotypes of _Thomomys bottae albicaudatus_, _levidensis_ differs as follows: Size smaller in every measurement taken. Color: Markedly lighter throughout. Skull: Smaller in every measurement taken; width relatively greater; skull smooth, weak and nonangular as opposed to ridged, robust and angular. For comparisons with _Thomomys bottae lenis_ and _contractus_ see accounts of those forms. _Remarks._--The range here ascribed to _levidensis_ is the San Pitch River Valley, which gradually merges southward into the Sevier River Valley. The latter valley in this area is inhabited by pocket gophers that belong to another subspecies, _lenis_. Nephi Valley to the west of San Pitch River Valley is inhabited by animals belonging to the subspecies _albicaudatus_. No known specimens show intergradation between _lenis_ and _levidensis_, but intergradation between _lenis_ and _albicaudatus_ is noted in the Nephi Valley animals (see account of _albicaudatus_). Superficially _levidensis_ resembles _absonus_ in size and color, but the skulls closely resemble those of _albicaudatus_, except for size in which they are smaller in all measurements. _T. b. albicaudatus_ is the most variable subspecies of _T. bottae_ occurring in Utah, and additional material from the Sevier River Valley between San Pitch River Valley and Nephi Valley may show _levidensis_ to be only a local variant of the highly variable subspecies, _albicaudatus_. _Specimens examined._--Total, 6, from the type locality. =Thomomys bottae osgoodi= Goldman _Thomomys perpallidus osgoodi_ Goldman, Journ. Washington Acad. Sci., 21:424, October 19, 1931. _Thomomys bottae osgoodi_ Goldman, Proc. Biol. Soc. Washington, 48:156; October 31, 1935. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--Male, adult, skin and skull, No. 158530, U. S. National Museum (Biological Surveys Collection); Hanksville, Wayne County, Utah; October 20, 1908; collected by W. H. Osgood; original number 3701 (after Goldman, type not seen). _Range._--Eastern Utah in the valleys of the drainage of the San Rafael, Dirty Devil and Price rivers. _Diagnosis._--Size medium (see measurements). Color: Upper parts near (_e_) Pale Ochraceous Buff, definitely yellow in appearance; sides Pale Ochraceous Buff; entire underparts white, with a wash of Light Buff in the pectoral and inguinal regions; top of head, nose, cheeks, and chin dusky; postauricular patches grayish black; front feet, hind feet and distal part of tail white. Skull: Fairly robust but narrow; zygomatic arches concave medially in mid-jugal region; skull moderately convex dorsally, due to swelling in region of base of rostrum; lambdoidal suture situated well ahead of posterior margin of skull, with supraoccipital forming a side shelf at posterior part of skull; interpterygoid space narrowly V-shaped; tympanic bullae well inflated ventrally; basioccipital short; nasals rounded posteriorly; molariform teeth large. _Comparisons._--Topotypes of _osgoodi_ differ from those of _Thomomys bottae absonus_ as follows: Size generally smaller. Color: Lighter throughout, more yellowish in appearance as opposed to buffy. Skull: Smaller in all measurements, except length of nasals, mastoid breadth, and alveolar length of upper molar series which are larger; rostrum shorter but relatively wider; zygomatic arches more robust and concave medially; palate wider; supraoccipital more bulging posteriorly; tympanic bullae more inflated ventrally; molariform teeth larger. For comparisons with _Thomomys bottae aureus_ and _T. b. dissimilis_ see accounts of those forms. _Remarks._--The animals here referred to _osgoodi_ are remarkably uniform in color, but vary widely in cranial details. Specimens from Carbon County are not typical and when more material becomes available it may prove that these animals from the northern part of the range of _osgoodi_ will merit separation and naming. The specimens from Emery County are not typical but resemble _osgoodi_ more than do the animals from Carbon County. The range here ascribed to _osgoodi_ is in that part of the eastern Utah desert that is bounded on the east by the Green and Colorado rivers, on the west by the high mountains of central Utah, on the north by the Book Cliffs and on the south by the Dirty Devil River. This area is an uninviting wasteland in which there are relatively few roads and little water. In addition, it is greatly cut up by washes and gullies which contain water only during a few weeks of the year. The continuation of this area of wasteland southward beyond the Dirty Devil River is inhabited by pocket gophers belonging to the subspecies _absonus_. If specimens were available they would undoubtedly show intergradation to exist between _osgoodi_ and _absonus_. _Specimens examined._--Total, 14, distributed as follows: _Carbon County_: 1-2 mi. N Spring Glen, 6,150 ft., 2; Spring Glen, 6,200 ft., 2; 2 mi. E Spring Glen, 6,200 ft., 1. _Emery County_: Price River, 2 mi. SE Woodside, 4,600 ft., 2 (C. M.); Green River, 4,080 ft., 5 (M. V. Z.). _Wayne County_: Hanksville, 2 (U. S. N. M.). =Thomomys bottae howelli= Goldman _Thomomys bottae howelli_ Goldman, Journ. Washington Acad. Sci., 26:116, March 15, 1936. _Type._--Female, adult, skin and skull, No. 25684, U. S. National Museum (Biological Surveys Collection); Grand Junction, 4,600 ft., Mesa County, Colorado; November 7, 1895; collected by A. H. Howell; original number 493 (after Goldman, type not seen). _Range._--In the valleys of eastern Utah, east of the Green River and north of the Colorado River. _Diagnosis and Comparisons._--Inasmuch as there is but one specimen, the holotype known, and as it was impossible to study it, the following diagnoses and comparisons are from Goldman, (1936:116). "_General characters._--A rather large, pallid subspecies with a broad, flattened cranium. Similar to the palest specimens of _Thomomys bottae aureus_ of the San Juan River Valley, southeastern Utah, in color, but underparts more thinly overlaid with buffy white, and cranial characters, especially the broad, flat braincase, distinctive. Approaching _Thomomys bottae osgoodi_ of the Fremont River Valley, Utah, in color, but much larger and skull widely different. "_Color._--Type (winter pelage): Upper parts in general between tilleul buff and pale olive buff (Ridgway 1912), somewhat darkened on head by a mixture of cinnamon buff and brown; a few inconspicuous dusky-tipped hairs along median line of back; muzzle dusky; ears and postauricular spots deep, contrasting black; underparts thinly overlaid with buffy white, the hairs becoming pure white to roots on inguinal region; thighs pure white to roots all around; feet white; tail buffy whitish, slightly paler below than above. "_Skull._--Similar in general to that of _T. b. aureus_, but braincase conspicuously broader and flatter; zygomata more widely spreading; nasals shorter; premaxillae more attenuate posteriorly; interparietal larger; audital bullae more rounded and fully inflated anteriorly; incisors short, as in _aureus_, but less strongly recurved. Compared with that of _T. b. osgoodi_ the skull is much larger, with flatter braincase, shorter nasals, and posteriorly narrower premaxillae." _Remarks._--Six specimens, in the Carnegie Museum from 10 miles north of Moab, Grand County, Utah, were available for this study. They are not typical of _howelli_ as it is diagnosed by Goldman (_loc. cit._). They appear to be intergrades between _howelli_ and _osgoodi_ in cranial characters, but more closely resemble _howelli_, particularly in the flat, widened, low braincase. In color, some specimens seem to intergrade toward _aureus_. The range ascribed to this form in Utah appears to be one of the most natural ones within the state since it is bounded by the Green and Colorado rivers which have formed deep rocky gorges in this region. _Specimens examined._--Total, 6, as follows: _Grand County_: 10 mi. N Moab, 6 (C. M.). =Thomomys bottae wahwahensis= Durrant _Thomomys bottae wahwahensis_ Durrant, Bull. Univ. Utah, 28 (No. 4):4, August 18, 1937. _Type._--Male, adult, skin and skull, No. 1750, Museum of Zoölogy, University of Utah, Wah Wah Springs, 30 mi. W Milford, 6,500 ft., Beaver County, Utah; July 22, 1936; collected by S. D. Durrant; original number 989. _Range._--Westcentral Utah, in Wah Wah Mountains, and Pine Valley to the west of these mountains. _Diagnosis._--Size medium (see measurements). Color: Upper parts Pinkish Buff; underparts Pale Pinkish Buff with considerable admixture of gray; inguinal and pectoral regions Pale Pinkish Buff; nose and cheeks grayish black; postauricular patches small and black; front feet, hind feet and distal one-third to one-half of tail white. Skull: Flat dorsoventrally; rostrum short and wide; premaxillae broad and heavy; nasals short and straight, with no arching as viewed laterally; tympanic bullae small; space enclosed within zygomatic arches short antero-posteriorly; alveolar length of upper molar series short; molariform teeth small. _Comparisons._--From topotypes of _Thomomys bottae centralis_, _wahwahensis_ differs as follows: Size smaller in every measurement taken. Color: Lighter, Pinkish Buff as opposed to Cinnamon Buff. Skull: Rostrum wider, shorter and more nearly flat; nasals straight as opposed to moderately convex; tympanic bullae smaller and less inflated ventrally; zygomatic arches more widely spreading and angular; molariform teeth smaller; extension of premaxillae posterior to nasals less. From topotypes of _Thomomys bottae albicaudatus_, _wahwahensis_ differs as follows: Hind foot shorter. Color: Lighter throughout, Pinkish Buff as opposed to (13''''_n_) Black. Skull: Smaller and more nearly flat; rostrum shorter, wider and more nearly flat; nasals straight as opposed to convex; zygomatic breadth less but mastoid breadth greater; tympanic bullae smaller, and less inflated ventrally; extension of premaxillae posterior to nasals less; molariform teeth smaller. From topotypes of _Thomomys bottae aureiventris_, _wahwahensis_ differs in the following features: Size smaller; hind foot shorter. Color: Lighter throughout, no "gold" on underparts. Skull: Smaller in nearly every measurement taken; rostrum shorter and relatively wider; zygomatic arches more angular and relatively more widely spreading; nasals shorter and more nearly flat; thickening at union of jugal and zygomatic process of maxilla less; interpterygoid space V-shaped as opposed to lyre-shaped; tympanic bullae much smaller, and less inflated ventrally; molariform teeth much smaller. Topotypes of _wahwahensis_ can be easily distinguished from those of _Thomomys bottae tivius_ by their markedly larger size in every measurement taken, lighter color, and larger, more robust and more nearly flat skull. For comparisons of _wahwahensis_ with _Thomomys bottae sevieri_, _robustus_, _bonnevillei_ and _convexus_ see comparisons under those forms. Among the named races of _Thomomys bottae_, _wahwahensis_ definitely has its affinities with _planirostris_ from Zion National Park. Both possess flat skulls with wide, short rostra. It differs from the latter in: Size smaller in every measurement taken. Color: Lighter throughout. Skulls: Nasals and rostrum shorter and more nearly flat; tympanic bullae markedly smaller; alveolar length of upper molar series shorter; molariform teeth markedly smaller and weaker. _Remarks._--Wah Wah Springs, the type locality of _wahwahensis_, are on the summit of a low pass in the Wah Wah Mountains in the desert of west central Utah. The surrounding valleys, for many miles, as far as my investigations show, are not inhabited by pocket gophers, except the Desert Range Experiment Station of the United States Forest Service in Pine Valley to the west of these mountains. There, pocket gophers were obtained which are intergrades between _centralis_ and _wahwahensis_. In five out of seven characters investigated these gophers resemble _wahwahensis_, to which they are here referred. Study of the topography reveals the probable means by which the animals reached this valley. The long axis of the Wah Wah Mountains is north and south, but a westward arm forms the northern boundary of Pine Valley. Around springs in this westward projecting arm workings of pocket gophers were found. With the development of water at the Desert Range Experiment Station, and subsequent improvement of forage, these animals probably came down into the valley from the springs to the north. The terrain between the Desert Range Experiment Station in Pine Valley and Snake Creek (where _centralis_ occurs) to the west is not inhabited by pocket gophers at present. This area, however, forms part of the southwest mainland of Pleistocene Lake Bonneville, which mainland in times past was probably suitable for pocket gophers. Since the close of the Pleistocene, aridity has rendered most of it unfit for pocket gophers, and they remain only in isolated areas where suitable environments still persist. _Specimens examined._--Total, 18, distributed as follows: _Millard County_: Desert Range Experiment Station, United States Forest Service, Sec. 9, T. 25 S, R. 17 W, Salt Lake Base Meridian, 6. _Beaver County_: Wah Wah Springs, Wah Wah Mountains, 30 mi. W Milford, 6,500 ft., 12 (2, M. V. Z.). =Thomomys bottae dissimilis= Goldman _Thomomys perpallidus dissimilis_ Goldman, Journ. Washington Acad. Sci., 21:425, October 19, 1931. _Thomomys bottae dissimilis_ Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--Female, adult, skin and skull, No. 158526, U. S. National Museum (Biological Surveys Collection); E slope Mount Ellen, Henry Mountains, 8,000 ft., Garfield County, Utah; October 15, 1908; collected by W. H. Osgood; original number 3677 (after Goldman, type not seen). _Range._--Known only from the type locality. _Diagnosis._--Size small (see measurements). Color: Upper parts Light Buff, grading over sides to nearly white on underparts; underparts lightly washed with Pale Buff, more marked in inguinal and pectoral regions; postauricular patches grayish black; nose, chin, cheeks and top of head dusky; front feet, hind feet and distal half of tail white. Skull: Small and weak; zygomatic arches long, but lying close to skull, giving it a slender appearance; supraoccipital markedly projecting posteriorly from lambdoidal suture; rostrum relatively long and narrow; nasals long; tympanic bullae well inflated ventrally, with a median ventral ridge; pterygoid hamulae weak; interpterygoid space narrowly V-shaped; upper incisors short and light in color; molariform teeth relatively large. _Comparisons._--Comparison of one topotype of _dissimilis_ with topotypes of _Thomomys bottae aureus_ shows it to differ as follows: Size smaller throughout. Color: Lighter dorsally and on sides, pale buff as contrasted with rich ochraceous; underparts more buffy. Skull: Smaller in every measurement taken; zygomatic arches markedly less widely spreading; braincase narrower and more vaulted; tympanic bullae with a median ventral ridge as opposed to smooth; pterygoid hamulae slenderer; interpterygoid space narrowly V-shaped as opposed to U-shaped; upper incisors smaller and lighter in color. Compared with topotypes of _Thomomys bottae absonus_, _dissimilis_ differs in the following features: Size smaller in every measurement taken. Color: Lighter throughout. Skull: Smaller in every measurement taken, except alveolar length of upper molar series which is greater; skull narrower and weaker; zygomatic arches weaker and less widely spreading; tympanic bullae more ridged on ventral surface and shorter (more rounded) in antero-posterior measurement; upper incisors shorter and narrower; molariform teeth larger. _Thomomys bottae dissimilis_ resembles _T. b. osgoodi_ more than any other subspecies but differs in: Size smaller throughout. Color: Slightly darker dorsally. Skull: Smaller in every measurement taken, and slenderer; rostrum relatively longer; zygomatic arches weaker, and less widely spreading, more converging anteriorly; tympanic bullae less rounded, more ridged medioventrally; upper incisors shorter but narrower; molariform teeth smaller. _Remarks._--The Henry Mountains, in eastern Garfield County, are in the Colorado River drainage. The surrounding country is desertlike and cut by gullies and washes with sheer escarpments and precipitous draws. The type locality of _dissimilis_ is possibly in an isolated area. Only three specimens were available to Goldman when he named _dissimilis_. He commented on the close resemblance to _osgoodi_ which inhabits the country to the north. I have examined only one of the three specimens available to Goldman. Although I can see the characters that he mentioned, I am not fully convinced that _dissimilis_ is separable from _osgoodi_. Two specimens from Escalante, Garfield County, are referred to _absonus_, but they show intergradation with _dissimilis_. _Specimens examined._--One (U. S. N. M.) from E slope Mount Ellen, Henry Mountains, 8,000 ft., Garfield County. =Thomomys bottae aureus= Allen _Thomomys aureus_ Allen, Bull. Amer. Mus. Nat. Hist., 5:49, April 28, 1893. _Thomomys bottae aureus_ Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Benson, Univ. California Publ. Zoöl., 40:450, December 31, 1935. _Thomomys fulvus aureus_ Goldman, Journ. Washington Acad. Sci., 21:417, October 19, 1931; Journ. Washington Acad. Sci., 23:464, October 15, 1933. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:74, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--No. 5243/4123. American Museum of Natural History; Bluff City, San Juan County, Utah; May 12, 1892; collected by Charles P. Rowley (after Allen, type not seen). _Range._--All of San Juan County (except extreme southwestern part) and Grand County east of the Colorado River. _Diagnosis._--Size large (see measurements). Color: Upper parts Cinnamon Buff, lighter on sides; underparts generally white, or if colored at all with only a faint wash of Light Buff; nose and chin blackish gray; top of head blackish due to admixture of black hairs; postauricular patches small and dusky; front feet and hind feet white. Skull: Long, narrow but massive; zygomatic arches not widely spreading, but heavy; jugals thick, union of jugals and zygomatic processes of maxillae thickened; rostrum long but wide; top of rostrum convex in lateral view; ascending processes of premaxillae wide and heavy; nasals thin proximally; braincase long and narrow; tympanic bullae well inflated ventrally; alveolar length of upper molar series long; molars large; pterygoid hamulae heavy; interpterygoid space U-shaped; palate arched; upper incisors long and wide. _Comparisons._--Compared with topotypes of _Thomomys bottae osgoodi_, _aureus_ differs as follows: Size larger in every measurement taken, except tail which is shorter. Color: Darker throughout except on ventral surface which is lighter. Skull: Larger, longer and wider; nasals longer; rostrum wider and longer; zygomatic arches more nearly straight and heavier; ascending processes of premaxillae wider; basioccipital longer; interpterygoid space U-shaped as opposed to V-shaped; tympanic bullae larger; upper incisors longer, wider; molars larger. Topotypical specimens of _aureus_ can be distinguished from those of _Thomomys bottae dissimilis_ by: Size larger throughout. Color: A trifle darker on dorsal surface. Skull: Larger in every measurement taken; zygomatic arches heavier and more nearly straight; tympanic bullae larger and more inflated ventrally; interpterygoid space U-shaped as opposed to V-shaped; alveolar length of upper molar series longer; molars larger; upper incisors longer and wider. Topotypes of _aureus_ differ from those of _Thomomys bottae absonus_ as follows: Size larger in every measurement taken. Color: Darker dorsally, Light Ochraceous as opposed to Cinnamon Buff; due to admixture of gray, _absonus_ has more of a grayish cast. Skull: Larger in every measurement taken, longer, narrower and more compact; zygomatic arches heavier; ascending processes of premaxillae wider; jugals heavier; tympanic bullae larger; interpterygoid space U-shaped rather than V-shaped; upper incisors longer and wider; molars larger. From topotypes of _Thomomys bottae planirostris_, _aureus_ can be distinguished as follows: Size larger; tail shorter. Color: Lighter throughout. Skull: Larger in every measurement taken except zygomatic breadth, extension of premaxillae posterior to nasals, and length of upper molariform series which are less; rostrum longer, wider and more convex; nasals slightly arched rather than straight; depression absent rather than present in posterior region of nasals; zygomatic arches not so widely spreading, but equally heavy. For comparisons with _Thomomys bottae alexandrae_, see accounts under that form. _Remarks._--Topotypes of _aureus_ are among the largest pocket gophers in the state. They are exceeded in total length only by _T. b. lenis_ and are approached by _T. b. aureiventris_ and _T. b. planirostris_. On the average they have the longest hind foot, body and ear. The length of the skull is second only to that of _lenis_ as also is the length and breadth of the rostrum relative to the basilar length. From the time of the original description of _aureus_ in 1893 until 1930, all light colored gophers from Utah were referred to that form. Barnes (1927:100) gives the range of _aureus_ as extending completely across southern Utah and on the west and east sides as far north as central Utah. Since 1930, forms named by E. R. Hall, W. H. Burt, E. A. Goldman and the writer have restricted the range of _aureus_ in Utah to that part of the state east of the Colorado River. _Specimens examined._--Total, 22, as follows: _San Juan County_: Bluff, 3,300 ft., 22 (15, M. V. Z.). =Thomomys bottae birdseyei= Goldman _Thomomys bottae birdseyei_ Goldman. Proc. Biol. Soc. Washington, 50:134, September 10, 1937. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--Male, adult skin and skull, No. 161654. U. S. National Museum (Biological Surveys Collection); Pine Valley Mountains, 5 mi. E Pine Valley, 8,300 ft., Washington County, Utah; April 10, 1909; collected by Clarence Birdseye; original number 861 (after Goldman, type not seen). _Range._--High mountains and plateaus of southwestern Utah. _Diagnosis._--Size medium (see measurements). Color: Upper parts between Cinnamon and Sayal Brown, finely mixed with black in median dorsal region, grading over sides and flanks to Cinnamon on underparts; front feet, hind feet, and distal part of tail white; postauricular patches, chin, cheeks and top of head grayish black. Skull: Depressed along median line of frontals and posterior ends of nasals; region of nasofrontal suture concave ventrally; zygomatic arches heavy and widely spreading, widest posteriorly; posterior ends of nasals straight, tending to be somewhat rounded in some specimens; extension of premaxillae posterior to nasals moderate; tympanic bullae moderately inflated ventrally; basioccipital wide; interpterygoid space widely V-shaped. _Comparisons._--Topotypes of _birdseyei_ differ from near topotypes of _Thomomys bottae virgineus_, from Beaverdam Wash as follows: Size larger; tail and hind foot longer. Color: Darker throughout, between Cinnamon and Sayal Brown as opposed to Cinnamon Buff. Skull: Larger in every measurement taken except extension of premaxillae posterior to nasals, and length and width of rostrum which are less; skull more depressed in nasofrontal region; zygomatic arches more widely spreading; zygomatic processes of squamosals shorter; pterygoid hamulae longer; tympanic bullae smaller and less inflated ventrally. Among named races of _T. bottae_, _birdseyei_ most closely resembles _trumbullensis_ in size, but differs as follows: Hind foot and tail longer. Color: Lighter throughout; postauricular patches smaller and lighter. Skull: Larger; mastoid breadth less; zygomatic arches wider and more widely spreading posteriorly; median frontal depression more marked; extension of premaxillae posterior to nasals greater; tympanic bullae less inflated ventrally; molariform teeth larger. For comparisons with _Thomomys bottae planirostris_ see account of that form. _Remarks._--_T. b. birdseyei_ is apparently endemic to the mountainous area of southwestern Utah in Washington and Iron counties. It intergrades with _virgineus_ and with _planirostris_ as described in the account of the latter. _Specimens examined._--Total, 8, distributed as follows: _Washington County_: Pine Valley, 1 (U. S. N. M.); Pine Valley Mountains, 5 mi. E Pine Valley, 8,300 ft., 3 (U. S. N. M.); Pine Valley campground, 6,800 ft., 1 (R. H.); 3/4 mi. E town of Pine Valley, 6,500 ft., 3 (R. H.). _Additional records._--_Washington County_: Hebron, 1; Mountain Meadows, 2 (Bailey 1915:75). =Thomomys bottae virgineus= Goldman _Thomomys bottae virgineus_ Goldman, Proc. Biol. Soc. Washington, 50:133, September 10, 1937. _Type._--Male, adult, skin and skull, No. 262016, U. S. National Museum (Biological Surveys Collection); Beaverdam Creek, near confluence with Virgin River, Littlefield, 1,500 ft., Mohave County, Arizona; October 16, 1936; collected by Luther C. Goldman; original number 67 (after Goldman, type not seen). _Range._--Extreme southwestern Utah, in Beaverdam Wash, Washington County, Utah. _Diagnosis._--Size medium (see measurements). Color: Upper parts Cinnamon Buff, finely mixed with black; sides and flanks Pinkish Buff; underparts Pale Pinkish Buff; front feet, hind feet, and distal part of tail white; nose, cheeks, chin and top of head grayish black. Skull: Robust, with moderately wide zygomatic arches; zygomatic processes of maxillae wide; zygomatic processes of squamosals long; jugals concave laterally, giving the zygomatic arches the appearance of double bowing; nasals long; extension of premaxillae posterior to nasals long; tympanic bullae well inflated ventrally; pterygoid hamulae heavy; interpterygoid space widely V-shaped; molariform teeth large. _Comparisons._--For comparisons of _virgineus_ with _Thomomys bottae planirostris_ and _T. b. birdseyei_ see accounts under those forms. Topotypical specimens of _virgineus_ can be distinguished from those of _Thomomys bottae trumbullensis_ as follows: Size smaller. Color: Lighter throughout. Skull: Zygomatic arches less widely spreading; jugals more bowed medially; zygomatic processes of squamosals longer; extension of premaxillae posterior to nasals greater; tympanic bullae larger and more inflated ventrally; molariform teeth larger. Compared with topotypes of _Thomomys bottae centralis_, _virgineus_ differs in: Size smaller; tail shorter; hind foot smaller. Color: Deeper Cinnamon Buff, thus darker in overall appearance. Skull: Smaller, but relatively wider; zygomatic processes of maxillae heavier; region of maxillo-jugal sutures thicker; jugals more concave laterally; tympanic bullae more inflated ventrally; molariform teeth larger. _Remarks._--This pocket gopher occupies practically the same range in Utah as the large kangaroo rat _Dipodomys deserti deserti_ Stephens. Both are found in the Beaverdam Wash. The type locality of _virgineus_ is but a short distance down the Beaverdam Creek at Littlefield, Arizona. It intergrades with _birdseyei_, the mountain form to the north and east (see remarks under _birdseyei_). There are evidences of intergradation with _planirostris_ of the Virgin River Valley above the narrows of the Virgin River where it cuts through the Beaverdam Mountains (see the discussion under _planirostris_). There are intergradational tendencies exhibited towards _centralis_ in some specimens. Some of the animals are practically indistinguishable in color and there are intergrading cranial characters in the nasals, zygomatic arches and tympanic bullae. _Specimens examined._--Total, 20, distributed as follows: _Washington County_: Beaverdam Wash, 8 mi. N Utah-Arizona border, 7; Beaverdam Wash, 5 mi. N Utah-Arizona border, 2,600 ft., 13. =Thomomys bottae planirostris= Burt _Thomomys perpallidus planirostris_ Burt, Proc. Biol. Soc. Washington, 44:38, May 8, 1931. _Thomomys bottae planirostris_ Hall and Davis, Proc. Biol. Soc. Washington, 47:52, February 9, 1934; Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Presnall, Zion-Bryce Mus. Bull., 2:14, January, 1938; Long, Journ. Mamm., 21:176, May 14, 1940. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927; Woodbury, Ecological Monographs, 3:193, April, 1933. _Thomomys bottae centralis_ Hall and Davis, Proc. Biol. Soc. Washington, 47:52, February 9, 1934; Presnall, Zion-Bryce Mus. Bull., 2:14, January, 1938. _Thomomys perpallidus centralis_ Hall, Univ. California Publ. Zoöl., 23:445, July 8, 1930. _Thomomys bottae nicholi_ Goldman, Journ. Washington Acad. Sci., 28:337, July 15, 1938, type from Shivwits Plateau, 20 mi. S Wolf Hole (road to Parashonts), 5,000 ft., Mohave County, Arizona; Hardy, Ecological Monographs, 15:98, January, 1945. _Thomomys bottae trumbullensis_ Hall and Davis, Proc. Biol. Soc. Washington, 47:52, February 9, 1934. _Type._--Male, adult, skin and skull, No. 8395, Collection of Donald R. Dickey; Zion National Park, Washington County, Utah; May 4, 1920; collected by A. Brazier Howell; original number 2184 (after Burt, type not seen). _Range._--Valley of the Virgin River from Zion National Park west to the Beaverdam Mountains. _Diagnosis._--Size large (see measurements); tail long. Color: Upper parts Sayal Brown; underparts between Vinaceous Cinnamon and Cinnamon, grading to Pinkish Cinnamon in some specimens; nose, chin, cheeks, postauricular patches, and top of head grayish black; front feet and hind feet white; tail Pinkish Buff, with distal third white. Skull: Massive and ridged; nasals straight and flat, simple distally; dorsal surface of rostrum slightly concave at proximal end of nasals; zygomatic arches widely spreading, widest posteriorly; zygomatic processes of maxillae heavy; premaxillae broad and extending far beyond posterior end of nasals; rostrum wide and heavy; palate slightly arched; pterygoid hamulae heavy; interpterygoid space V-shaped; tympanic bullae moderately inflated ventrally, somewhat compressed laterally; upper incisors long and heavy; molariform teeth large. _Comparisons._--Compared with topotypes of _Thomomys bottae birdseyei_, _planirostris_ differs as follows: Size larger, except total length which averages slightly less in females. Color: Lighter throughout. Skull: Larger in every measurement taken; more massive; rostrum wider, longer and more nearly flat; nasals straight and not inflated dorsally on distal end; premaxillae wider at posterior ends; extension of premaxillae posterior to nasals greater; zygomatic arches heavier, especially the zygomatic processes of the maxillae; posterior ends of nasals more nearly truncate as opposed to generally rounded; tympanic bullae more nearly flat and relatively smaller; upper incisors longer and heavier; interpterygoid space more narrowly V-shaped; molariform teeth much heavier. Topotypes of _planirostris_ differ from near topotypes of _Thomomys bottae virgineus_ as follows: Size larger; tail and hind foot longer. Color: Slightly darker dorsally, but markedly darker ventrally; postauricular patches smaller and lighter. Skull: Larger in every measurement taken; skull more massive; nasals flat, neither arched nor swollen distally; rostrum wider; nasofrontal region flattened or concave as opposed to convex; premaxillae relatively narrower; zygomatic arches heavier, especially in the processes of the maxillae; tympanic bullae smaller and less inflated ventrally; interpterygoid space generally more narrowly V-shaped; upper incisors longer and heavier; molariform teeth larger. From topotypes of _Thomomys bottae trumbullensis_, _planirostris_ differs in: Size larger throughout; tail longer. Color: Much lighter throughout. Skull: More convex dorsally; rostrum wider and more depressed distally; extension of premaxillae posterior to nasals greater; zygomatic arches shorter, and not as widely spreading posteriorly; interpterygoid space more narrowly V-shaped; tympanic bullae smaller; upper incisors wider and longer; molariform teeth larger. Topotypes of _planirostris_ can be easily distinguished from those of _Thomomys bottae absonus_ by darker color throughout and markedly larger size. _Remarks._--From the synonomy at the beginning of this account one may note that the animals here ascribed to this subspecies have had nearly as many subspecific names applied to them as there have been investigators who have written about them. Although each of the previous writers had but a small amount of material upon which to base his opinion, the diversity of opinion as to subspecific status bespeaks the instability of these animals. The present study is based upon eighty animals including additional comparative material. All animals from Zion National Park have the characters pointed out by Burt (1931:38) in his description of this form. Farther down the Virgin River Valley towards St. George, however, some very perplexing problems of intergradation are encountered. St. George and environs may correctly be thought of as a "melting pot." Each of the fifty-seven animals studied from this region is an intergrade; some specimens combine the characters of three subspecies. As may be seen on the distribution map, three different subspecies of _Thomomys bottae_ occur in Washington County. Down the river, below St. George, the race _virgineus_ inhabits the Virgin River Valley below the narrows of the Beaverdam Mountains. Because these narrows are filled with water from wall to wall during periods of high runoff, they form an effective barrier at present to migration of pocket gophers. The mountains to the north of St. George are inhabited by the dark form, _birdseyei_. The type locality of _planirostris_ is on the middle reaches of the Virgin River, in Zion National Park. In addition Mount Trumbull to the south, in northern Arizona, is the locality of another subspecies, _trumbullensis_. Unquestionably the easiest route of migration into the St. George area is down the Virgin River from Zion National Park; no barrier to gophers occurs between the Park and St. George. Although the animals from St. George are all intergrades, the majority of their affinities as would be expected are with _planirostris_ from Zion National Park. The river itself is not an impassable barrier for gophers to the north and south of it, since this stream frequently changes its course, and often nearly dries up. The Virgin River Valley in Zion National Park is in the bottom of a relatively deep, narrow canyon which has sheer rock escarpments. The upper reaches of the river are inhabited by pocket gophers of another species, _Thomomys talpoides_. Two specimens from St. George, north of the Virgin River, were identified as _centralis_ by Hall and Davis (1934:52), but were stated to be intergrades between _centralis_, _trumbullensis_ and _planirostris_. Goldman (1938:338) referred twelve specimens from St. George to _nicholi_, but stated that they intergraded with _planirostris_. Twenty-six other specimens from three miles southwest of St. George on the west side of Santa Clara Creek, about one-half mile above its confluence with the Virgin River and on its north side, like the topotypes of _planirostris_ were taken in May and have complete, fresh summer pelage. With the exception of two specimens which show the ventral color of _virgineus_, these animals are indistinguishable in color from the topotypes of _planirostris_. A study of eleven measurements of the males of this series yield the following data: Like _planirostris_ in four measurements, _birdseyei_ in one, _virgineus_ in one; intergrade between _planirostris_ and _birdseyei_ in two, _planirostris_ and _virgineus_ in two and _birdseyei_ and _virgineus_ in one. Corresponding measurements of the females show the animals to be: Like _planirostris_ in four measurements, _birdseyei_ in one, _virgineus_ in two; intergrade between _planirostris_ and _birdseyei_ in two, _planirostris_ and _virgineus_ in one and _birdseyei_ and _virgineus_ in one. In eight of eleven measurements the males either are like _planirostris_ or intergrade towards it, and the females are similarly allied to _planirostris_ in seven out of eleven measurements. In none of the measurements was either sex referable to _trumbullensis_. Intergradation was noted in still other cranial details. In the heavy, relatively straight zygomatic arches, a majority of the skulls resemble those of _planirostris_, although some show the elongated zygomatic processes of the squamosals that are characteristic of _virgineus_. Some skulls show a tendency toward _birdseyei_ in the widely spreading posterior regions of the zygomatic arches. The nasals for the most part are as in _planirostris_. Intergradation between all three subspecies is shown in the extension of the premaxillae posterior to the nasals. Some skulls show the lateral concavity of the jugals which is characteristic of _virgineus_. The tympanic bullae are variable but on the average are intermediate between those of _planirostris_ and _birdseyei_, but more as in the latter. The size of the pterygoid hamulae is like that of _planirostris_, but the shape of the interpterygoid space is more like that of _birdseyei_. The size of the molariform teeth is as in _birdseyei_. The incisors are intermediate between those of _planirostris_ and _birdseyei_, but more like those of _birdseyei_. Eighteen specimens from St. George and its environs, on the north side of the Virgin River, agree with the twenty-six specimens just described, except that they show more evidence of intergradation with _birdseyei_ in slightly darker color, length of hind foot, length of nasals and alveolar length of the upper molar series. One specimen from three miles south, two from two miles southwest, another from four miles southeast of St. George, and four immature animals from Short Creek Road south of the town of Virgin, all on the south side of the Virgin River, are darker than topotypes of _planirostris_ and show intergradation with _trumbullensis_ to the south. In size they are likewise closer to the latter race. They intergrade with _trumbullensis_ in the size and shape of the zygomatic arches and tympanic bullae. In the majority of cranial details, however, they are like _planirostris_ to which they are here referred. One specimen, a skin only, from Danish Ranch, 5 miles northwest of Leeds, north of the Virgin River is an intergrade in size and color between _birdseyei_ and _planirostris_, but referable to the latter. Three specimens from the East Entrance, and three from near the east entrance to Zion National Park are much darker than topotypes of _planirostris_. All of these animals are in worn pelage, thus allowing a great amount of the black underfur to show, which gives a markedly darker color. The unworn hair is only slightly darker than that of the topotypes. The cranial details prove these animals to be intergrades between _planirostris_ and _trumbullensis_. They resemble _trumbullensis_ in size of tympanic bullae, extension of the premaxillae posterior to the nasals and shape of the nasals. The majority of the cranial details are as in _planirostris_ to which they are here referred. When Goldman (1938:337) named _Thomomys bottae nicholi_ from northern Arizona he referred twelve specimens from St. George, Washington County, Utah, to his newly named race. He noted that the animals from this region intergrade with _planirostris_. I have had occasion to study one-fourth of the material available to Goldman for his original description of _nicholi_. For his specimens listed as from St. George, the exact locality of capture, which is so essential in this distributional study, was not given. All of the specimens that I have seen from the Biological Surveys Collection are from the south side of the Virgin River, while St. George itself is on the north side. As noted earlier in this account there are differences between the gophers from the two sides of the Virgin River in this area. Those from the north side are intergrades between _birdseyei_, _planirostris_ and _virgineus_, while those from the south side are intergrades between _planirostris_ and _trumbullensis_. Goldman (_loc. cit._) mentioned several times that the skulls of nicholi were nearly indistinguishable from, or closely resembled those of, _trumbullensis_. Color was the only truly diagnostic character mentioned by Goldman. My study reveals the same differences and likenesses found by Goldman, but I consider color alone insufficient basis in this instance for establishing a new subspecies, and regard _Thomomys bottae nicholi_ as a synonym of the earlier proposed name, _Thomomys bottae trumbullensis_. The animals from the south side of the Virgin River, labelled as from St. George, Washington County, heretofore referred by Goldman to _nicholi_, are intergrades between _trumbullensis_ and _planirostris_ and along with other specimens from the same place are referable to the latter race. _Specimens examined._--Total, 68, distributed as follows: _Washington County_: Danish Ranch, 5 mi. NW Leeds, 1; Zion National Park, 2 (M. V. Z.); Grotto Camp, Zion National Park, 4,300 ft., 6 (N. H. M. S. D.); Springdale, 3,400 ft., 4 (K. U.); near Short Creek Road, S town of Virgin, 4 (R. H.); St. George, N Virgin River, 2,950 ft., 21 (4, M. V. Z.; 8, R. H.; 9, N. H. M. S. D.); Santa Clara Creek, 3 mi. SW St. George, 2,800 ft., 26; St. George, S Virgin River, 5 (2, M. V. Z.; 3, U. S. N. M.); 2 mi. SE St. George, 2,950 ft., 2 (N. H. M. S. D.); 3 mi. S St. George, 1 (C. M.); 4 mi. SE St. George, S Virgin River, 1 (R. H.); 6 mi. S St. George, 2,700 ft., 6 (K. U.). _Kane County_: East Entrance Zion National Park, 5,725 ft., 3 (N. H. M. S. D.); near East Entrance Zion National Park, 5,500 ft., 3 (N. H. M. S. D.). _Additional records._--_Washington County_: Zion National Park, 22; Washington, 7 (Burt, 1931:39); St. George, 5; Santa Clara, 2 (Bailey, 1915:75). =Thomomys bottae absonus= Goldman _Thomomys perpallidus absonus_ Goldman, Journ. Washington Acad. Sci., 21:425, October 19, 1931. _Thomomys bottae absonus_ Hall and Davis, Proc. Biol. Soc. Washington, 47:52, February 9, 1934; Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--Male, adult, skin and skull, No. 250016, U. S. National Museum (Biological Surveys Collection); Jacobs Pools, Houserock Valley, 4,000 ft., Coconino County, Arizona; June 7, 1931; collected by E. A. Goldman; original number 23569 (after Goldman, type not seen). _Range._--Southern Utah in Kane and Garfield counties, in the drainages of Kanab Creek, Johnson Creek, Paria River and Escalante River. _Diagnosis._--Size medium (see measurements). Color: Upper parts Ochraceous Buff mixed with dusky; sides and underparts Light Ochraceous Buff; chin, nose, cheeks and top of head grayish black; postauricular patches black mixed with buff; front feet, hind feet, inguinal region and distal third of tail white. Skull: Nasals relatively long; rostrum narrow; ascending processes of premaxillae narrow; extension of premaxillae posterior to nasals short; lambdoidal and sagittal crests poorly developed; zygomatic arches light; jugals nearly straight; palate narrow; molariform teeth small. _Comparisons._--Compared with topotypes of _Thomomys bottae trumbullensis_, _absonus_ differs in: Size smaller. Color: Markedly lighter throughout. Skull: Smoother, less angular; zygomatic arches weak as opposed to robust; nasals more convex as viewed laterally; extension of premaxillae posterior to nasals less; ascending processes of premaxillae narrower; palate narrower; palatal pits shallower; rostrum narrower; molariform teeth smaller. For comparisons of _absonus_ with _Thomomys bottae aureus_ see account under that form. Among named races of _Thomomys bottae_, _absonus_ most closely resembles _planirostris_, but can be distinguished from the topotypes as follows: Size markedly smaller. Color: Lighter, more buffy throughout. Skull: Smaller, less ridged and more nearly flat; nasals convex as opposed to flat; extension of premaxillae posterior to nasals less; width of ascending processes of premaxillae less; zygomatic arches weaker; palate narrower; alveolar length of upper molar series shorter; tympanic bullae more inflated ventrally; molariform teeth smaller and lighter. _Remarks._--One specimen from Kanab is an intergrade between _trumbullensis_ and _absonus_. The majority of its characters are with _absonus_ to which it is referred (see Hall and Davis, 1934:52). Two specimens from Escalante are intergrades between _absonus_ and _dissimilis_, but are referable to _absonus_. _Specimens examined._--Total, 3, distributed as follows: _Garfield County_: Escalante, 5,258 ft., 2 (B. Y. U.), _Kane County_: Kanab, 4,925 ft., 1 (M. V. Z.). =Thomomys bottae alexandrae= Goldman _Thomomys alexandrae_ Goldman, Journ. Washington Acad. Sci., 23:464, October 15, 1933. _Thomomys bottae alexandrae_ Benson, Univ. California Publ. Zoöl., 40:449, December 31, 1935. _Type._--Male, adult, skin and skull, No. 250969, U. S. National Museum (Biological Surveys Collection); 5 mi. SE Rainbow Lodge, near Navajo Mountain, Coconino County, Arizona; June 16, 1933; collected by E. A. Goldman; original number 23613 (after Goldman, type not seen). _Range._--In extreme southwestern San Juan County, Utah. Known only from Navajo Mountain, probably limited to the area enclosed on the north by the Colorado and San Juan rivers, on the east and west by Navajo and Piute canyons, respectively. _Diagnosis._--Size small (see measurements). Color: Upper parts Cinnamon Buff, grading over the sides to Pinkish Buff on underparts; nose and top of head grayish black; hind feet and tail white; postauricular patches large and dark. Skull: Small and not heavily ridged; zygomatic arches widely spreading but weak; zygomatic arches nearly parallel; tympanic bullae moderately inflated ventrally; palate not arched; interpterygoid space U-shaped; dentition light. _Comparisons._--Compared to topotypes of _Thomomys bottae absonus_, _alexandrae_ differs as follows: Size smaller in every measurement taken. Color: Upper parts Cinnamon Buff as contrasted with Light Ochraceous Buff. Skull: Smaller in every measurement taken except interorbital breadth and alveolar length of upper molar series which are larger; molariform teeth larger. Among named races of _Thomomys bottae_ occurring in Utah, _alexandrae_ most resembles _T. b. aureus_ to the northeast. It can be distinguished from topotypes of the latter by: Size smaller in every measurement taken. Color: Darker throughout. Skull: Smaller, slenderer and more nearly flat; palate nearly flat as opposed to arched; zygomatic arches weaker and not so widely spreading; interparietal narrower; tympanic bullae smaller; dentition weaker. _Remarks._--Goldman (1933:464) accorded _alexandrae_ full specific status, because he found no intergradation with other races, from which he thought _alexandrae_ had been isolated perhaps for thousands of years by the barriers of the surrounding terrain. Benson (1935:450) noted resemblances between _alexandrae_ and specimens of _latirostris_ from Keams Canyon, Zuni Well, and Winslow in Navajo County, Arizona (= _aureus_), and also between _alexandrae_ and _absonus_ from Houserock Valley, Arizona. He thought that _alexandrae_ is no more differentiated or isolated than each of several other kinds of desert pocket gophers, and, therefore, accorded _alexandrae_ only subspecific status, as I, also, am inclined to do. _Specimens examined._--One (M. V. Z.) from Soldier Spring, Navajo Mountain, 8,600 ft., San Juan County. Fourteen topotypes from Arizona also were examined. MEASUREMENTS OF ADULT MALES OF THOMOMYS (In millimeters) ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- _T. b. aureiventris_, 4; topotypes (Hall, 1930:446) Av. 243 67 32 36.4 14.7 26.5 21.5 6.6 7.9 2.4 .... ... Min. 232 59 31 35.3 14.0 25.5 20.9 6.1 7.8 1.8 .... ... Max. 253 72 33 37.1 15.3 27.3 22.3 6.9 8.0 3.4 .... ... _T. b. centralis_, 9; topotypes (Hall, 1930:446) Av. 237 75 30 36.3 14.6 25.2 20.7 6.6 8.0 3.2 .... ... Min. 215 61 29 34.5 13.9 24.6 19.7 5.8 7.5 2.2 .... ... Max. 250 83 32 38.0 15.9 26.1 21.9 7.2 8.7 4.5 .... ... _T. b. albicaudatus_, 7; topotypes (Hall, 1930:446) Av. 228 65 31 35.4 14.0 26.1 20.5 6.6 8.1 3.2 .... ... Min. 223 59 29 34.9 13.4 24.9 19.8 6.4 7.8 3.0 .... ... Max. 235 72 32 36.1 15.1 27.8 21.1 6.9 8.4 3.8 .... ... _T. b. robustus_, 9; topotypes Av. 222 65 29 34.1 13.6 26.0 20.8 6.4 7.8 2.7 15.7 8.4 Min. 214 59 28 32.6 13.0 25.2 20.0 6.1 7.3 2.0 14.7 8.1 Max. 236 70 31 35.7 14.4 26.7 21.5 6.7 8.2 3.0 17.0 8.8 _T. b. stansburyi_, 5; topotypes Av. 206 60 28 32.3 12.4 22.4 19.1 6.3 7.6 2.8 14.7 7.5 Min. 198 58 26 30.6 12.0 21.5 18.2 6.2 7.0 2.5 14.1 7.1 Max. 215 68 31 33.4 13.0 23.1 20.1 6.5 8.0 3.0 15.4 7.8 _T. b. nesophilus_, 4; topotypes Av. 230 69 32 35.3 14.4 25.5 20.4 6.8 8.4 2.5 17.1 8.2 Min. 220 60 30 33.6 14.1 24.9 19.8 6.5 8.2 2.1 16.4 7.6 Max. 242 75 33 36.5 14.8 26.2 21.1 7.1 8.7 2.9 18.4 8.6 _T. b. minimus_, 2; topotypes Av. 184 60 25 30.7 11.3 21.3 18.7 6.4 7.4 2.5 13.9 7.5 Min. 179 55 24 28.7 10.2 20.2 17.8 6.3 7.3 2.5 12.9 7.0 Max. 189 64 26 32.8 12.5 22.4 19.6 6.4 7.6 2.5 15.0 7.9 _T. b. lenis_, 2; topotypes Av. 251 80 32 39.7 16.0 28.6 22.6 6.8 8.3 3.4 18.4 8.8 Min. 248 74 31 39.4 15.8 28.4 22.4 6.6 8.2 3.0 17.9 8.6 Max. 255 86 32 29.9 16.2 28.7 22.7 6.9 8.5 3.7 18.8 8.9 _T. b. contractus_, 8; topotypes Av. 229 74 31 33.3 12.5 23.7 19.1 6.6 7.6 3.0 15.4 7.3 Min. 209 63 28 30.0 10.9 21.4 17.7 6.3 7.2 2.4 13.5 6.5 Max. 255 85 33 37.4 14.5 26.4 20.9 6.9 8.0 3.5 18.2 8.0 ---------------------------------------------------------------------- MEASUREMENTS OF ADULT MALES OF THOMOMYS--_Continued_ ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- No. 191959 (U. S. N. M.) _T. b. levidensis_, 1; topotype 222 65 28 33.3 12.7 24.5 19.0 6.5 7.6 3.3 15.1 8.0 _T. b. convexus_, 6; topotypes Av. 213 59 28 33.1 14.3 24.9 21.7 6.6 8.0 2.6 16.2 8.2 Min. 206 57 27 31.3 13.9 23.8 21.0 6.5 7.7 2.1 15.2 8.0 Max. 233 68 29 35.0 14.6 26.7 22.3 6.8 8.1 2.8 17.2 8.6 _T. b. tivius_, 7; topotypes Av. 208 69 27 31.5 12.2 22.4 18.4 6.4 7.2 2.4 14.0 7.1 Min. 199 67 25 29.3 11.9 20.6 17.1 6.0 7.0 2.1 13.2 6.5 Max. 227 70 30 34.1 12.8 25.0 19.8 6.6 7.6 3.0 15.0 7.9 _T. b. bonnevillei_, 3; topotypes Av. 228 70 30 35.4 13.9 26.4 21.8 6.6 8.1 3.7 17.6 8.5 Min. 221 62 30 33.6 13.2 25.4 20.5 6.5 8.1 3.4 16.1 8.2 Max. 236 79 30 37.4 14.9 28.0 22.5 6.7 8.1 4.3 18.1 8.7 _T. b. sevieri_, 3; topotypes Av. 216 67 30 32.7 12.9 22.9 18.7 6.4 7.2 2.5 15.3 7.6 Min. 210 66 29 31.7 11.8 22.2 18.0 6.2 7.0 1.8 14.5 7.5 Max. 222 68 31 33.5 13.5 23.4 19.3 6.7 7.2 3.0 16.4 7.7 _T. b. wahwahensis_, 4; topotypes Av. 228 66 29 34.7 13.5 25.5 20.7 6.6 7.3 2.3 15.7 8.7 Min. 210 60 26 33.0 13.1 24.6 20.1 6.5 7.0 2.2 14.9 8.5 Max. 250 78 30 37.6 14.6 27.0 21.4 6.8 8.0 2.5 17.1 9.0 _T. b. planirostris_, 8; topotypes (Burt, 1931:39) Av. 238 76 32 35.6 13.8 25.9 20.4 6.6 8.5 3.7 .... 8.8 Min. 222 66 31 33.3 12.5 24.4 19.8 6.2 8.2 3.0 .... 8.3 Max. 261 83 34 38.7 15.3 27.6 21.3 7.2 8.9 4.5 .... 9.4 _T. b. birdseyei_, 3; topotypes Av. 227 64 31 34.9 13.8 26.2 20.9 6.2 8.4 2.6 16.3 8.3 Min. 214 52 30 34.5 13.1 26.0 20.1 6.0 8.1 2.2 16.0 8.2 Max. 243 81 32 35.2 14.1 27.4 21.5 6.5 8.8 2.8 16.9 8.4 _T. b. virgineus_, 5; Beaverdam Wash, 5 mi. N Utah-Arizona Line Av. 226 68 29 34.6 13.5 25.6 20.7 6.3 8.0 3.0 16.5 8.5 Min. 216 62 27 33.5 12.8 25.0 20.0 6.1 7.6 2.4 15.3 8.3 Max. 235 70 30 34.9 14.4 26.0 21.1 6.6 8.4 3.5 17.4 8.7 _T. b. aureus_, 3; topotypes Av. 242 68 34 36.6 14.3 25.3 21.4 6.6 8.3 2.4 17.2 8.7 Min. 233 65 32 35.3 13.8 24.6 20.6 6.4 7.7 2.0 16.7 8.3 Max. 251 70 36 37.8 14.9 25.8 22.0 6.8 8.7 2.5 17.9 9.0 ---------------------------------------------------------------------- MEASUREMENTS OF ADULT MALES OF THOMOMYS--_Concluded_ ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- _T. b. howelli_, 5; 10 mi. N Moab Av. 213 67 31 33.1 13.5 23.2 20.1 6.5 8.3 2.5 16.1 8.8 Min. 205 64 30 31.8 12.8 22.8 18.9 6.4 8.0 2.3 15.1 8.1 Max. 225 68 32 35.3 14.3 24.1 20.7 6.8 8.8 2.8 17.5 9.4 No. 3094 (U. U.) _T. b. absonus_, 1; topotype 220 71 29 32.0 13.9 22.6 19.0 6.4 7.0 1.0 15.1 7.2 No. 158529 (U. S. N. M.) _T. b. osgoodi_, 1; topotype 225 70 29 33.8 13.3 22.7 19.6 6.6 8.4 3.2 16.5 8.3 _T. b. alexandrae_, 1; topotype (Benson, 1935:450) 205 59 27 33.9 13.7 24.3 19.7 6.5 8.0 ... 15.8 8.1 ---------------------------------------------------------------------- MEASUREMENTS OF ADULT FEMALES OF THOMOMYS (In millimeters) ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- _T. b. aureiventris_, 2; topotypes (Hall, 1930:446) Av. 212 62 30 32.4 12.9 22.9 19.4 6.7 7.4 2.8 .... ... Min. 208 58 29 31.8 12.6 22.5 18.9 6.6 7.0 2.7 .... ... Max. 215 65 30 33.0 13.1 23.3 19.8 6.8 7.8 3.1 .... ... _T. b. centralis_, 17; topotypes (Hall, 1930:446) Av. 214 67 29 31.8 12.6 22.1 19.0 6.6 7.6 2.7 .... ... Min. 195 55 27 30.5 11.9 21.3 18.2 5.9 7.0 2.0 .... ... Max. 229 75 30 33.0 13.8 23.1 20.1 7.1 7.8 3.4 .... ... _T. b. albicaudatus_, 4; topotypes (Hall, 1930:446) Av. 211 64 30 32.5 12.9 22.9 18.8 6.6 7.7 2.7 .... ... Min. 199 55 29 31.7 11.9 21.9 18.2 6.1 7.5 2.6 .... ... Max. 219 70 32 33.8 13.5 24.0 19.5 6.8 8.0 3.0 .... ... _T. b. robustus_, 11; topotypes Av. 199 61 27 30.6 11.7 22.6 18.8 6.4 7.6 2.6 13.9 7.4 Min. 191 56 22 29.0 10.6 21.0 18.1 6.2 7.1 2.0 12.0 7.1 Max. 207 66 29 31.6 12.2 23.6 19.8 6.7 8.0 2.9 14.7 7.9 _T. b. stansburyi_, 5; topotypes Av. 202 57 28 31.1 12.1 21.9 18.7 6.5 7.7 2.6 14.5 7.4 Min. 195 56 26 29.9 10.6 21.0 17.8 6.2 7.3 2.3 13.4 6.9 Max. 210 63 30 32.7 12.8 22.4 19.5 6.8 8.0 3.0 15.2 7.7 No. 900 (U. U.) _T. b. nesophilus_, 1; topotype 210 65 31 31.2 12.3 23.2 19.3 6.9 8.2 2.2 15.2 7.3 _T. b. minimus_, 2; topotypes Av. 178 56 25 28.2 10.6 19.7 17.4 6.1 7.0 2.3 13.1 6.7 Min. 175 54 24 28.1 10.4 19.6 17.1 6.1 7.0 2.3 13.0 6.5 Max. 181 58 25 28.2 10.8 19.7 17.7 6.1 7.0 2.3 13.2 6.8 _T. b. contractus_, 6; topotypes Av. 219 68 30 33.1 12.6 23.3 19.5 6.5 7.8 2.6 15.5 7.1 Min. 208 58 29 32.2 12.0 22.2 18.9 6.4 7.6 2.3 14.2 7.0 Max. 225 73 31 34.7 13.3 25.2 20.6 6.7 8.2 3.2 17.0 7.3 _T. b. levidensis_, 4; topotypes Av. 205 69 26 30.5 11.1 21.7 17.5 6.6 7.5 2.9 14.0 7.0 Min. 194 61 26 29.3 10.6 21.5 17.3 6.3 7.2 2.8 13.0 6.9 Max. 223 73 27 30.8 11.5 21.9 17.9 6.9 7.8 3.2 14.7 7.2 ---------------------------------------------------------------------- MEASUREMENTS OF ADULT FEMALES OF THOMOMYS--_Continued_ ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- _T. b. convexus_, 11; topotypes Av. 197 57 27 29.9 12.5 21.7 19.3 6.6 7.7 2.6 14.7 7.4 Min. 182 43 26 27.9 11.2 21.0 18.8 6.2 7.1 2.1 13.3 7.1 Max. 204 63 28 30.9 13.4 22.3 19.8 7.1 7.9 3.1 15.2 7.7 _T. b. tivius_, 5; topotypes Av. 203 68 27 29.5 11.1 21.1 17.8 6.5 7.2 2.4 13.5 6.8 Min. 192 63 26 28.0 10.5 20.1 17.3 6.3 7.1 2.0 12.7 6.4 Max. 215 74 30 31.3 11.4 22.9 19.0 6.7 7.5 3.0 14.2 7.2 _T. b. bonnevillei_, 7; topotypes Av. 199 57 28 31.7 11.8 22.2 19.3 6.6 7.7 3.2 14.9 7.3 Min. 184 50 24 29.4 10.1 20.3 18.1 6.4 7.1 2.6 13.5 6.9 Max. 216 66 29 34.3 13.6 24.3 20.3 7.0 8.5 4.1 16.6 7.7 _T. b. sevieri_, 7; topotypes Av. 205 62 28 30.2 11.8 21.6 18.0 6.4 7.0 2.7 14.2 7.1 Min. 199 54 28 29.4 11.3 20.6 17.7 6.1 6.6 2.1 13.9 6.6 Max. 212 70 29 30.7 12.6 22.1 18.6 6.8 7.4 3.0 14.7 7.6 _T. b. wahwahensis_, 8; topotypes Av. 185 56 27 28.7 11.3 20.6 17.6 6.3 7.1 2.1 12.6 7.1 Min. 180 50 26 26.3 10.2 19.0 16.5 5.8 6.9 1.1 10.8 6.4 Max. 197 62 29 30.7 12.6 22.0 19.0 6.7 7.8 2.9 14.0 7.6 _T. b. planirostris_, 8; topotypes (Burt, 1931:39) Av. 215 71 31 32.2 12.4 23.2 18.7 6.5 8.1 3.6 .... 7.9 Min. 205 61 30 31.5 11.8 22.3 18.1 6.4 7.5 2.8 .... 7.5 Max. 228 78 33 33.0 12.9 24.1 19.5 6.7 8.6 4.5 .... 8.1 _T. b. birdseyei_, 3; topotypes Av. 220 71 29 31.6 11.8 22.7 18.6 6.1 7.4 2.4 14.7 7.5 Min. 217 68 28 31.4 11.0 22.4 18.3 6.0 7.3 1.6 13.3 7.4 Max. 223 75 30 32.0 12.8 23.0 19.1 6.2 7.4 3.0 15.3 7.5 _T. b. virgineus_, 4; Beaverdam Wash, 5 mi. N Utah-Arizona Line Av. 211 64 29 31.6 12.2 22.6 19.4 5.9 7.5 3.1 15.1 7.3 Min. 202 60 27 31.3 11.3 22.4 18.8 5.8 7.3 2.4 14.4 7.2 Max. 218 68 30 32.1 12.8 22.7 20.0 6.1 7.8 3.7 15.5 7.6 _T. b. aureus_, 3; topotypes Av. 226 57 31 33.2 13.3 23.8 19.8 6.7 8.2 1.9 15.3 8.2 Min. 217 54 30 32.8 12.5 23.3 19.6 6.4 8.0 1.6 14.5 8.2 Max. 233 64 31 34.0 14.2 24.4 19.8 6.9 8.4 2.0 16.4 8.3 No. 20300 (C. M.) _T. b. howelli_, 1; 10 mi. N Moab 202 59 28 32.4 12.3 21.1 19.2 6.4 7.9 2.4 15.8 8.3 ---------------------------------------------------------------------- MEASUREMENTS OF ADULT FEMALES OF THOMOMYS--_Concluded_ ====================================================================== Total length | Length of tail | | Length of hind foot | | | Basilar length | | | | Length of nasals | | | | | Zygomatic breadth | | | | | | Mastoid breadth | | | | | | | Interorbital breadth | | | | | | | | Alveolar length of | | | | | | | | upper molar series | | | | | | | | | Extension of premax | | | | | | | | | post. to nasals | | | | | | | | | | Length of | | | | | | | | | | rostrum | | | | | | | | | | | Breadth | | | | | | | | | | | of rostrum ---------------------------------------------------------------------- No. 158524 (U. S. N. M.) _T. b. dissimilis_, 1; topotype 188 61 27 28.2 10.1 19.0 16.7 6.1 7.4 2.1 12.8 6.5 No. 158528 (U. S. N. M.) _T. b. osgoodi_, 1; topotype 203 61 27 29.6 11.5 .. 18.3 6.9 7.4 2.0 14.0 7.3 _T. b. alexandrae_, 3; topotypes Av. 205 63 28 30.9 11.8 20.8 17.9 6.4 7.6 1.8 14.1 7.5 Min. 195 57 27 28.7 11.5 20.5 17.2 6.3 7.5 1.5 13.6 7.2 Max. 215 70 29 31.5 12.1 22.2 18.6 6.5 7.7 2.0 14.7 7.7 -------------------------------------------------------------------------- LITERATURE CITED ALLEN, J. A. 1874. Notes on the mammals of portions of Kansas, Colorado, Wyoming and Utah, Part IV. On the mammals of the Great Salt Lake Valley, Utah. Bull. Essex Inst., 6:61-66, 1874. 1893. Descriptions of four new species of _Thomomys_ with remarks on other species of the genus. Bull. Amer. Mus. Nat. Hist., 5:47-68, April 28, 1893. 1893. List of mammals collected by Mr. Charles P. Rowley in the San Juan region of Colorado, New Mexico and Utah, with descriptions of new species. Bull. Amer. Mus. Nat. Hist., 5:69-84, April 28, 1893. 1896. List of mammals collected by Mr. Walter W. Granger in New Mexico, Utah, Wyoming and Nebraska, 1895-1896, with field notes by the collector. Bull. Amer. Mus. Nat. Hist., 8:241-258, November 25, 1896. 1905. Mammals from Beaver County, Utah, collected by the Museum expedition of 1904. Brooklyn Inst. Mus. Sci. Bull., 1:117-122, March 31, 1905. BAILEY, VERNON. 1915. Revision of the pocket gophers of the genus _Thomomys_. N. Amer. Fauna, 39:1-136, pls. 8, 10 figs., November 15, 1915. BARNES, CLAUDE T. 1922. Mammals of Utah. Bull. Univ. Utah, 12 (No. 15):1-176, 30 figs., April, 1922. 1927. Utah mammals. Bull. Univ. Utah, 17 (No. 12):1-183, 32 figs., June, 1927. BENSON, SETH B. 1935. A biological reconnaissance of Navajo Mountain, Utah. Univ. California Publ. Zoöl., 40:439-455, December 31, 1935. BURT, WILLIAM H. 1931. A new pocket gopher of the genus _Thomomys_ from Utah. Proc. Biol. Soc. Washington, 44:37-40, May 8, 1931. COUES, E. 1875. Abstract of results of a study of the genera _Geomys_ and _Thomomys_. Part III. Zoölogy, in explorations of the Colorado River of the West and its tributaries, explored in 1869, 1870, 1871 and 1872 under the direction of the Smithsonian Institution, reported by J. W. Powell, Gov't Printing Office, Washington, D. C., 1875. 1877. Monographs of North American Rodents, No. X, Geomyidae, pp. 601-629, U. S. Geol. Surv. of the territories, Gov't Printing Office, Washington, D. C., 1877. COUES, E., and YARROW, H. C. 1875. Report upon the collection of mammals made in portions of Nevada, Utah, California, New Mexico and Arizona during the years 1871-74. Wheeler's Rept. Expl. W of 100th Mer. vol. 5, pp. 35-129, 1875. DAVIS, WILLIAM B. 1939. The Recent mammals of Idaho. The Caxton Printers, Ltd., Caldwell, Idaho, pp. 1-400, pls. 2, 33 figs., April 5, 1939. DURRANT, STEPHEN D. 1937. Two new gophers from Utah. Bull. Univ. Utah, 28 (No. 4):1-7, August 18, 1937. 1939. A new pocket gopher of the _Thomomys quadratus_ group from the northern Great Basin region. Bull. Univ. Utah, 39 (No. 6):1-6, February 28, 1939. GOLDMAN, E. A. 1933. New mammals from Arizona, New Mexico and Colorado. Journ. Washington Acad. Sci., 23:463-473, October 15, 1933. 1936. New pocket gophers of the genus _Thomomys_. Journ. Washington Acad. Sci., 26:111-120, March 15, 1936. 1938. New pocket gophers of the genus _Thomomys_ from Arizona and Utah. Journ. Washington Acad. Sci., 28:333-343, July 15, 1938. 1939. Remarks on pocket gophers, with special reference to _Thomomys talpoides_. Journ. Mamm., 20:231-244, May 14, 1939. 1942. Three new rodents from southern Utah. Proc. Biol. Soc. Washington, 55:75-78, July 25, 1942. HALL, E. RAYMOND. 1931. Critical comments on mammals from Utah, with descriptions of new forms from Utah, Nevada and Washington. Univ. California Publ. Zoöl., 37:1-13, April 10, 1931. HALL, E. RAYMOND, and DAVIS, WILLIAM B. 1934. Notes on Arizona rodents. Proc. Biol. Soc. Washington, 47:51-56, February 9, 1934. HAYWARD, C. LYNN. 1936. A bibliography of Utah mammalogy; including references to names and type localities applied to Utah mammals. Utah Acad. Sci. Arts and Letters, 13:122-146, 1936. 1941. A bibliography of Utah mammalogy; including references to names and type localities (first supplement). Great Basin Nat., 2:125-136, December 31, 1941. MARSHALL, WILLIAM H. 1940. A survey of the mammals of the islands in Great Salt Lake, Utah. Journ. Mamm., 21:149-159, 2 pls., 1 map, May 14, 1940. MERRIAM, C. HART. 1901. Descriptions of twenty-three new pocket gophers of the genus _Thomomys_. Proc. Biol. Soc. Washington, 14:107-117, July 19, 1901. MILLER, GERRITT S., JR. 1924. List of North American Recent mammals, 1923. U. S. Nat. Mus. Bull., 128, pp. I-XVI, + 1-673, Govt. Printing Office, Washington, D. C., March 18, 1924. SVIHLA, RUTH DOWELL. 1931. Mammals of the Uinta Mountains region. Journ. Mamm., 12:256-266, pls. 1, 1 fig., August 24, 1931. 21-2786 * * * * * Transcriber's Notes Made minor punctuation corrections, and the following changes: Page 11: Changed Oquirrah Mountains to Oquirrh Mountains. Page 15: Changed interptergoid to interpterygoid. Page 25: Changed acccounts to accounts. Page 30: Changed distiguished to distinguished. Page 54: Changed hpyothesis to hypothesis. Page 57: Changed under parts to underparts. Formatted Tables to fit width guidelines. Bold text is shown within =equal signs=. Italicized text is shown within _underscores_.