. Bulletin - United States National Museum. Science. 418 BULLETIN 56, UNITED STATES NATIONAL Fig. 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, mm.; tail vertebrae, ; length of hind foot, ; ear from crown, Average of 45 adult females: length, ; tail vertebrae, ; hind foot, ; car from crown, Cranial characters.—The skull (fig. 89) is appreciably broader and lower than that of typical Pero- myscus boylii, with a much
. Bulletin - United States National Museum. Science. 418 BULLETIN 56, UNITED STATES NATIONAL Fig. 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, mm.; tail vertebrae, ; length of hind foot, ; ear from crown, Average of 45 adult females: length, ; tail vertebrae, ; hind foot, ; car from crown, 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,) 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, ) 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 wras 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 ab
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