New Mammah from Soidhern Mexico. 145 



Thomomys orizabae ,sp. nov. 



MT. ORIZABA THOMOMYS. 



Type from Mr. 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, 47-t-l). 



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 ; hijjd foot, 29. 



General Characters. — Size medium ; soot3^-plumbeous phase 

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

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

 haired. 



Color. — Plaiiibeoas phase (the t}- i)e 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, wliich 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 shoAving through in places; 

 under side of face Ijlackish ; feet and distal tliird 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. orizabx difiers from that 

 of T. peregrinns here described (the onl}- species thus far recorded 

 from southern Mexico) in the following particulars : Muzzle 

 longer and much broader ; frontals anteriorly much broader ; 

 ascending branches of premaxilla3 much broader and blunter 

 posteriorly. The breadth of muzzle acros.s ascending branches 

 of premaxilLne, and breadth of frontals anteriorly, is considerably 

 greater tlian the interorljital breadth ; \n percgriaus the contrary 

 is true. 



