376 



KULLETIN 56, 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, 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 

 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 perpaUidus), of larger size, with a larger ta'l, 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 <>f IS specimens of Onychomys torridus. 



Museum 

 number. 



2121)1 



212112 

 21197 

 21280 



21111.", 

 21201 



2121- 1 



21200 



21198 

 21199 

 21203 



212(i:, 



21428 



21429 



59210 

 59208 



:{70I2 

 37016 



37017 

 37018 

 37019 

 37011 



37013 



.:7ini 

 37015 



36289 

 59210 



1685 



1722 

 1727 

 1743 

 1747 

 179.-, 

 1669 



1699 



1718 

 1721 

 1728 

 1759 



876 

 877 



878 



2683 



2729 



Locality. 



Monument No. 40, upper corner, 100 

 miles west of the Km Grande. 



....do 



do 



....do 



do 



Mosquito Springs, Monument No. ..,.. 



Carrizalillo Springs, near Monument 

 No. 32. 



Monument No. 40, upper coiner, 100 

 mill's west of the Rio Grande. 



....do 



....do 



....do. 



....do 



.do. 



La Osa, Pima County, Arizona 



Santa Cruz River at Monument No. 

 L18. 



l.a 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 a 

 ..do.... 

 ...do... 



Dec. 13 



Dec ii 



Dee. 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 



« Mamma-, 1 pairs ( llolziier ). 



