376 



BULLETIN 56, UNITED STATES- NATIONAL MUSEUM. 



obtained specimens of this subspecies from the Carrizalillo Mountains 

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

 This species, including 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 

 locaUty 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 locahty 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 ramona. 



Measurements of 18 specimens of Onychomys torridus. 



Locality. 



Monument No. 40, upper comer, 100 

 miles west of the Rio Grande. 



do 



do 



do 



do 



Mosquito Springs, Monument No. 40.. 



Carrizalillo Springs, near Monument 

 No. 32. 



Monument No. 40, upper corner, 100 

 miles west of the Rio Grande. 



do 



do 



do 



do 



-do. 



La Oaa, Pima County, Arizona 



Santa Cruz River at Monument No. 

 118. 



La Osa, Pima County, Arizona 



....do 



....do 



Date. 



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... 



Dec. 13 

 Dec. 14 

 Dee. 24 



S ad. 



cfad. 

 cT ad. 

 cf ad. 

 (T ad. 

 d-ad. 

 ?ad. 



? ad. 



?ad. 

 ?ad. 

 ?ad. 

 ?ad. 



cfad. 

 »? ad. 

 «^ ad. 



Jad. 

 cT ad. 

 9 ad. 



K 



mm. 

 143 



139 

 139 

 134 

 139 

 146 

 147 



137 

 152 



140 

 146 

 146 



139 

 136 

 150 



mm 

 53 



49 

 50 

 47 

 47 

 59 

 57 



S-9 



^■- 



mm. 

 22.0 



21.0 

 21.0 

 20.0 

 21.0 

 20.0 

 21.0 



21.0 



22.0 

 20.5 

 22.0 

 21.5 



20.0 

 20.5 

 21.0 



21.0 

 24.0 

 22.0 



s 



o 



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; 

 15.0 

 13.0 



oMammse, 4 pairs (Holzner). 



