MAMMALS OF THE MEXICAN BOUNDARY. 



393 



Cranial and dental characters. — The skull (fig. 71) of Peromyscus so- 

 noriensis rufinus differs from that of P. leucopus in having the zygomatic 

 arches elbowed out in front in such a manner that the skull is wider 

 anteriorly than posteriorly, the reverse being true, as a rule, of P. 

 leucopus. The upper profile of the skull is less flat than that of P. 

 leucopus, being highest interorbitally, thence sloping sharply downward 

 in front and behind. There are somewhat prominent supraorbital and 



Fig. 7i.—PEE0MYSCUS aONOElENSlS RUFINUS. SKOLL. O, DOESAL VIEW, 6, VENTRAL VIEW; 



C, LATERAL VIEW. 



temporal ridges which P. leucopus lacks, and the premaxillaries are 

 narrower. The incisive foramen is longer than in P. leucopus, the 

 interpterygoid fossa longer and narrower, and the mandible has more 

 produced angular and coronoid processes, as in other members of 

 the sonoriensis group. The teeth are shown in fig. 72. 



Habits and local distribution. — This beautiful 

 mouse, which appears to intergrade with the plains 

 mice of the Austral life zone, is actually a forest 

 animal, living in great numbers in the pine, aspen, 

 and Douglas spruce woods of the Arizona moun- 

 tains. I found it in the Mogollon and San Francisco 

 mountains, frequenting camps, cabins, and every 

 part of the woods. On September 5, 1886, 1 visited 

 the ranch of Mr. Charles Ryall, in the Verde Moun- 

 tains west of Little Squaw Peak. Dozens of these 

 mice were running about the walls, rafters, and 

 thatching of thelog cabin. A pair of slender snakes 

 of the kind called "blue racers" were gliding gracefully about the 

 ceiling in the thatch and through crevices between the logs. One of 

 the snakes caught a mouse, and the pursuit had caused the excitement 

 among its companions. On the Mogollon Mountains, August 21, 

 1887, I trapped a pretty wood mouse in a "delusion" mouse trap. 

 Wishing to carry the httle beast to Fori Verde, I wrapped the trap in 

 a woolen "fascinator." Upon the road the 'woolly garment was 

 nibbled and pulled into the trap, where it was cleverly made into a 

 nice warm nest. 



Fig. 72.— PEEOinscu.s 



S0N0R1ENS13 RUFiN- 



us. Ceowns of 



MOLAR- TEETH. a, 

 LOWER SERIES, b, 

 UPPER SERIES. 



