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.).