376 



BULLETIN 5(5, UNITED STATES NATIONAL MUSEUM. 



obtained specimens of this subspecies from the Carrizalillo Mountains 

 west toLaOsa (Monuments 32 to 140 of the Mexican Boundary Line.) 

 This species, inchiding its several geographic forms, ranges along the 

 Mexican line from the Pacific Ocean to the Rio Grande, at El Paso, 

 Texas, and perhaps as far eastward in Texas as the Pecos River. In 

 the north its range extends at least to St. George, Utah, from which 

 locality Doctor Merriam has described a subspecies longicaudus. On 

 the boundary strip its environmental conditions have caused it to 

 assume four well-marked geographical phases, each occupying a defi- 

 nite and considerable area. The type locality of typical Onychomys 

 torridus is old Camp Grant, Arizona. This locality is characterized 

 by the darker forms of the high interior region. To the eastward, in 

 the desert basins of the upper Rio Grande, a small, short-eared, pale 

 subspecies arenicola is found. To the westward, another desert phase 

 (subspecies perpallidus) , of larger size, with a larger tail, larger ears, 

 and still paler coloration, occupies the Colorado and Yuma deserts of 

 the lower Colorado Valley. The Pacific coast strip is the home of the 

 dark subspecies ramomi. 



Meamreuients of 18 specimens of (^hitfrhoinys torridus. 



Locality. 



Monument No. 40, upper comer, 100 

 miles west of the Rio Grande. 



do 



do 



do 



do 



Date. 



Mosquito Springs, Honumeut lio. -iJ.. 



Carrizalillo Springs, near Monument 

 No. 32. 



Moniunent No. 40, upper comer, 100 

 miles west of the Rio Grande. 



do 



do 



do 



do 



.do. 



La Osa, Pima County, Arizona 



Santa Cruz River at Monument No. 

 118. 



La Osa, Pima County, Arizona 



....do 



do 



1892. 

 Apr. 24 



May 1 



May 2 

 May 7 

 May 8 

 May 12 

 Apr. 17 



Apr. 26 



Apr. 30 



May 1 



May 2 



May 11 



1893. 

 June 5 

 ...do.... 

 ....do... 



Dee. 13 

 Dec. 14 

 Dec. 24 



mm. 

 13.5 



12.5 

 12.0 

 14.0 

 13.0 

 14.0 

 13.5 



13.5 



13.0 

 13.5 

 14.0 

 13.0 



16.5 

 17.0 



13.0 

 15.0 

 13.0 



o Mammae, 4 pairs (Holzner). 



