418 



BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Fig. vi. --Pebomyscus isoylii pinalis. Skull 

 and teeth, a, skull, dorsal view; 6, 

 crowns of lower molars; c, crowns of 

 upper molars. 



Measurements. — Average of 55 adult males: length, 196.3 mm.; 

 tail vertebrae, 105.8; length of hind foot, 21.2; ear from crown, 16.3. 

 Average of 45 adult females: length, 108.1; tail vertebrae, L05.7; 

 hind foot, 21.12; car from crown, 16.2. 



Cranial characters. — The skull 

 (fig. 89) is appreciably broader and 

 lower than that of typical Pero- 

 myscus boylii, with a much shorter 

 and wider interpterygoid fossa. In 

 size and other respects they are 

 much the same, both having the 

 nasals ending in a point, (lush with 

 the premaxillaries, posteriorly. 



Remarks.— Eight specimens (Nos. 

 21531, 21594, 21605, 21602, 21586, 

 21611, 21606, and 21588, U.S.N.M.) 

 from the Huachuca Mountains have 

 white-tipped tails. The terminal 

 white portion occupies from 10 to 

 50 mm. of the end of the tail. In five of the eight the whole tip of the 

 tail is white, while the remaining three have the terminal pencil dark 

 and a subterminal band of white. I have noticed a tendency in 

 other alpine mammals, especially mice, to have white-tipped tails 

 at the highest altitudes of their range. Another specimen of the 

 present series (No. 21600, U.S.N.M.) has a small white spot on the rump, 

 showing a further tendency to albinism. The 

 white tail-tips are probably not due to freezing, 

 as some specimens having white-tipped tails 

 were too young to have experienced severe 

 frosts prior to the date of their capture in early 

 autumn. The hind foot is shown in fig. 90. 



Habits and local distribution. — The Apache 

 brush mouse w r as found, as a straggler, at 

 Mosquito Springs, Chihuahua. It was more 

 abundant on the Hachita Grande Mountains, 

 New Mexico, especially in the zone of pinon 

 pine. Some were taken at medium elevations 

 oji the San Luis Mountains. On the San Jose 

 and Huachuca Mountains it was abundant, and 

 was obtained from the lower timber line to the 

 actual summit of both ranges. Mr. Holzner obtained it in the Pata- 

 gonia Mountains, and this species was the only one obtained in the 

 Pajaritos Mountains during November and December, 1903, when it 

 was scarce. 



Fig. 90.— Peeomyscus boylii 

 pinalis. Lowed si bfai e 



<>f HINDFOOT. 



