128 GrinneU — A New Pocket Mouse. 



middle portion of the Sonoran zone, while alticola belongs to 

 lower Transition. 



Perognathus xanthonotus sp. nov. 



Type from Freeman Canyon, 4900 feet altitude, east slope Walker Pass, 

 Kern County, California; adult <J, skin and skull, No. 16,154, Univ. 

 Calif. Mus. Vert. Zool.; collected June 27, 1911, by H. A. Carr; orig. 

 No. 111. 



General characters. — As compared with Perognathus parvus olivaceus, 

 size small, skull small, pelage fine-grained, and coloration wholly differ- 

 ent ; similar to P. alticola but pelage softer and coloration of body very 

 different. 



Colors. — Whole dorsal surface between ochraceous-buff and cream-buff, 

 almost perfectly clear on sides of body and head, and but slightly obscured 

 mid-dorsally with scanty dusky tippings to the hairs; feet and lower sur- 

 face white; ears clothed scantily with white hairs both inside and out; a 

 conspicuous spot of pure white at inferior base of ear; tail well clothed 

 with hairs, and distinctly penicillate, beneath white, above faint cream- 

 buff with a slight dusky tinge on terminal fifth. 



Skull. — Distinctly smaller than in oliraceus, mastoids and audital bullae 

 notably so; closely similar to alticola. Adult perfect skulls of both xan- 

 thonotus and alticola, however, are wanting, and are necessary to any 

 satisfactory comparison with the evidently nearest relative of these two, 

 oliraceus. 



Measurements. — Type specimen : Total length, 170 mm.; tail vertebrae, 

 85; hind foot, 22.5. Average of eight adolescents and adults: Total length, 

 165.3; tail vertebrae, 85; hind foot, 22.5. 



Occurrence. — All of the eight specimens of the new form at hand are 

 from the mountain divide east of the Kern River Valley, at the southern 

 end of the Sierra Nevada, in Kern County, California. The exact locali- 

 ties represented are : East slope Walker Pass, alt. 4000 ft., .'! ; west slope 

 Walker Pass, alt. 4(i00 ft., 2; west slope of divide at head of Kelso Valley, 

 alt, 5000 ft., 2. These localities are all in the tree yucca belt, an arid faunal 

 division about on the boundary between the Upper and bower Sonoran 

 life zones. 



'Remarks. — The coloration of xanthonotus is remarkably close to that in 

 Perognathus longimembris neglertus and P. panamintinus bangsi, these 

 being species of nearby habitats. The first-glance resemblance is striking, 

 but the former has the antitragal lobes and thick tail separating it from 

 the panamintinus group. The young of xanthonotus as compared with 

 the young of olivaceus show much of the yellowness characterizing the 

 adults, especially along the sides of the face and body ; the ears are white- 

 haired ; but the tail is much more dusky above. Xanthonotus agrees 

 with alticola in light-colored ears and tail, but differs most emphatically 

 in dorsal body color, alticola being very dark, black predominating. 



I am indebted to Mr. Frank Stephens for the loan of an adult male 

 topotype of Perognathus alticola, one of the very few specimens of this 

 rare species in collections anywhere. 



