312 University of CaMfornia Publications in Zoology [Vol.12 



Thomomys monticola premaxillaris, new subspecies 

 Yolla Bolly Gopher 



Type.— J adult, no. 20242, Mus. Vert. Zool. ; two miles south of 

 South Yolla Bolly Mountain, altitude about 7500 feet, in Tehama 

 County, California; August 6, 1913; collected by G. F. Ferris; original 

 no. 166. 



Diagnosis. — A member of the monticola series of gophers; palest 

 of the forms known from California. Feet and ears .small; pre- 

 tnaxillary tongues extending far back of posterior ends of nasals; 

 interparietal relatively broad antero-posteriorly. 



Mali rial. — Twenty-five specimens (nos. 20223-20247), from three 

 localities in Tehama County, in the vicinity of South Yolla Bolly 

 Mountain: two miles south of South Yolla Bolly. about 7500 feet 

 altitude; four miles south of South Yolla Bolly, about 6000 feet alti- 

 tude; Mount Linn (South Yolla Bolly of residents of the region). 

 about 7600 feet altitude. All these localities are in Canadian or high 

 Transition Zone; semi arid in t'aunal condition; and on gravelly 

 mountain slopes in coniferous forest association. 



Measurements. — Of type (old adult male) : Total length, 215 mm.: 

 tail. 59; hind fool. 27: occipito-nasal length of cranium, 37.5: zygo- 

 matie width. 20.8; mastoid width. 18.6; height of brainea.se at bullae. 

 11.1. The hind loot averages, in thirteen adults of premaxillaris, 

 26.8 mm. 



Comparison. — From near topotypes of Thomomys monticola monti- 

 cola Allen, from the central Sierra Nevada, in Eldorado County, 

 California, the new form differs in paler coloration (above close to 

 ochraceous-tawny [of Ridgway, 1912], below Light ochraceous-buff ) , 

 in smaller ear. shorter hind foot, in slightly shorter and narrower 

 rostrum of skull, in greater development of temporal ridges and in 

 closer and more nearly parallel approximation of these, in extension 

 of premaxillary tongues far back of posterior ends of nasals, and in 

 shape of interparietal which is on an average relatively much broader 

 antero-posteriorly. From topotypes of T. monticola pinetorum Mer- 

 riam, premaxillaris differs in slightly paler coloration, in shape of 

 interparietal, which averages very slightly broader antero-posteriorly, 

 and in all other respects as from '/'. m. monticola. It may be remarked 

 that the differences distinguishing pinetorum and monticola are at besl 

 extremely slight. 



