458 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



length, 146 (134-158) millimeters; tail vertebrae, 52 (47-60); hind 

 foot, 21.2 (20.0-22.0); ear from notch in dry skin, 14.0 (12.0-15.8). 

 Skull: Condylobasal length, 23.3 (22.7-24.7); zygomatic breadth, 

 12.7 (11.9-13.7); interorbital breadth, 4.5 (4.3-4.8) breadth of brain- 

 case, 11.5 (11.0-11.9); length of nasals, 9.7 (8.9-10.4); length of 

 mandible, 13.4 (12.6-14.1); maxillary tooth row, 3.7 (3.5-3.9). For 

 detailed measurements of specimens see page 480. 



Type-specimen. — No. 9886, United States National Museum. 

 Skin only; adult, not sexed: made up from alcohol and colors con- 

 siderately modified. Collected June 10, 1867, by Dr. Edward 

 Palmer. Catalogued January, 1872. On the label are recorded 

 the following: "Alcohohc measurements: nose to eye, .50 [hundredths 

 of inch]; nose to ear, .95; nose to occiput, 1.25; length, 3.75; tail, 

 2.00; fore foot, .40; hind foot, .80; ear, ,70 long, .50 ^vide." Ear 

 from notch in the dry skin measures 13.3 miUimeters; the hind foot, 

 19.7. 



Remarks. — A comparison of numerous examples in the same 

 pelage proves that Onychomys torridus torridus is remarkably uniform 

 in coloration over its entire range. Skins in the full mnter coat 

 from Texas can be exactly matched by comparable skins from 

 Dos Cabezos, Arizona. As noted in the description of the skuU, 

 specimens of torridus from the extreme western limits of the range 

 of the typical race show a decided approach toward perpallidus in 

 cranial characters, though retaining the coloration of torridus in 

 its extreme richness. No specimens are available from the area 

 between the northwestern limits of the distribution of torridus, as 

 mapped, and Phoenix, Arizona, where perpallidus occurs, but the 

 ranges of the two subspecies doubtless meet in this territory, as indi- 

 cated by the approach of characteristics in specimens of each. 



The type-specimen of Onycliomys torridus arenicola Mearns, col- 

 lected by Dr. Edgar A. Mearns and F. X. Holzner on the Rio Grande 

 about 6 miles above El Paso, Texas, February 29, 1892, is in the 

 collection of the United States National Museum. It is in the pale 

 spring stage of the winter pelage and exactly matches some early 

 April skins of true torridus. All late autumn and early winter skins 

 from the El Paso region and throughout western Texas are indis- 

 tinguishable in color from comparable skins of tonidus from south- 

 eastern Arizona, and there are ik) important discrepancies in measure- 

 ments or in cranial cliaracters. 



Specimens examined. — Total number, 183, from localities as follows: 



Arizona: Calabasas, 5; Camj) Grant, 1 (type); Dos Cabezos, 7; 

 Fairbank, 20 (Field Mus., Amer. Mus., and Mus. Comp. Zool.); Fort 

 TLowell, 13 (Field Mus. and Amer. Mus.); La Osa, 3; Mammoth, 2; 

 Oracle, 1; San Bernardino Ranch, 3 (Field Mus. and Amer. Mus.); 

 San Pedro River, 1; Santa Cruz River, 4; Tucson, 2; United States 



