_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.