162 JOURNAL OF MAMMALOGY 



Remarks. — This race is most strongly developed in the region around South 

 Yolla Bolly Mountain. A large series (in the Museum of Vertebrate Zoology) 

 from northern Trinity and southern Siskiyou counties agree in size with typical 

 mitratus, but are slightly darker; their skulls average a little longer, and narrower 

 across the zygomata, thus showing approach to trinitatis. 



Ammospermophilus leucurus pennipes subsp. nov. 



Type. — Female adult, skin and skull, No. 75683, U. S. National Museum 

 (Biological Survey collection) ; collected at Grand Junction, Colorado, November 

 11, 1895, by A. H. Howell; original number, 494. 



Subspecific characters. — Similar to Ammospermophilus I. cinnamomeus, but 

 upperparts in winter pelage more grayish (less vinaceous) and in summer pelage 

 darker and more brownish; skull slightly larger. Compared with A. leucurus 

 leucurus: Coloration in summer pelage decidedly more vinaceous (less grayish); 

 in winter pelage rather similar, but averaging more vinaceous; skull decidedly 

 larger. 



Description of type (winter pelage) : Upperparts light vinaceous-cinnamon, the 

 hairs on the median dorsal area tipped with white; flanks and hind legs vinaceous- 

 cinnamon, shading to pale pinkish buff on the hind feet; front feet similar; lateral 

 stripes creamy white; tail above, mixed black and white, the hairs showing a 

 broad, subterminal band of black; tail beneath, creamy white; underparts white, 

 the bases of the hairs plumbeous. 



Measurements. — Type (9 adult): Total length, 229; tail vertebrae, 76; hind 

 foot, 41; ear from notch (dry), 9. Average of 10 adults (4 males, 6 females) from 

 type locality: 226.6; 68.8; 39; 8.7. Skull (of type) : Greatest length, 40.8; palatal 

 length, 18.5; zygomatic breadth, 23.4; cranial breadth, 19.2; least interorbital 

 breadth, 10.1; least postorbital breadth, 14.5; length of nasals, 12.7; maxillary 

 toothrow, 6.9. 



Range. — The Colorado Valley and its tributaries (except the San Juan) in 

 western Colorado and eastern Utah; specimens examined from Grand Junction, 

 Hotchkiss, Fruita, and White River, 20 miles east of Rangely, Colorado; Vernal, 

 Thurber, and Henry Mountains, Utah. 



