New Mammals from Southern Mexico. 145 



Thomomys orizabae sp. nov. 



MT. ORIZABA THOMOMYS. 



Type from MT. ORIZABA, STATE OF PUEBLA, MEXICO (altitude, about 

 9,500 feet). No. 53616 $ ad. United States National Museum, Depart- 

 ment of Agriculture collection. Collected April 25, 1893, by E. W. Nelson 

 (original number, 4744). 



Measurements (taken in flesh). Type specimen: Total length, 217; tail 

 vertebrae, 68; hind foot, 30. Average measurements of 13 specimens 

 from type locality : total length, 213 ; tail vertebrae, 66 ; hind foot, 29. 



General Characters. Size medium ; sooty-plumbeous phase 

 dominant ; fulvous phase resembling T. fulvus, but duller. Tail 

 longer than in T.fulvus; well haired; fore and hind feet well 

 haired. 



Color. Plumbeous phase (the type and 15 out of a total of 17 

 specimens from type locality are in this phase) : Everywhere 

 uniform slate-black (faintly paler below) except distal part 

 of fore and hind feet, distal third of tail, and inside of cheek 

 pouches, which- are white (sometimes also a few white hairs 

 about mouth and under chin). The color of the body always 

 passes down over the wrists and ankles and usually reaches half 

 way to the toes ^sometimes further. 



Fulvous phase: Upper parts dark umber-brown, becoming 

 dusky on nose and dull fulvous on sides ; under parts buffy- 

 fulvous, the plumbeous basal fur showing through in places ; 

 under side of face blackish ; feet and distal third of tail white. 

 (Only 2 specimens, one of which is very young, out of a total 

 of 17, are in this pelage.) 



Cranial Characters. The skull of T. orizabas differs from that 

 of T. peregrinus here described (the only species thus far recorded 

 from southern Mexico) in the following particulars : Muzzle 

 longer and much broader ; frontals anteriorly much broader ; 

 ascending branches of premaxillae much broader and blunter 

 posteriorly. The breadth of muzzle across ascending^ branches 

 of premaxilla3, and breadth of frontals anteriorly, is considerably 

 greater than the interorbital breadth ; in. peregrinus the contrary 

 is true. 



