PEROMYSCUS. 193 



Type locality. Providentia Mines, northwestern Sonora, Mexico. 



Gcnl. Char. Similar to P. eremicus, but tail hairy and with a 

 pencil ; sides deep orange buff instead of pale fulvous. 



Color. Upper parts mixed black and orange buff; forehead and 

 nose gray and buff mixed; sides of face, shoulders, sides, and rump 

 about base of tail deep orange buff; orbital ring black; lips and 

 entire under parts, hands, and feet pure white; tail above dusky, 

 sides and beneath white; ears brown. 



Measurements. Total length, 190.5; tail vertebrae, 101.6; hind 

 foot, 25. Skull: occipito-nasal length, 26; Hensel, 20; zygomatic 

 width, 13; interorbital constriction, 4.5; width of braincase, 12; 

 length of nasals, 10; palatal length, 10.5; length of upper tooth row, 

 4; length of mandible, angle to alveolus of incisor, 10; length of lower 

 tooth row, 4. 



155. difficilis (Vesperimus), Allen, Bull. Amer. Mus. Nat. Hist., 



1891, p. 298. 

 TROUBLESOME MOUSE. 



Type locality. Sierra de Valparaiso, State of Zacatecas, 

 Mexico. 



Geogr. Distr. State of Zacatecas, Mexico; range unknown. 



Genl. Char. Allied to P. megalotis; ears smaller; hind feet larger; 

 color darker. 



Color. Above dusky brown tinged with pale fulvous; nape and 

 shoulders ashy; sides buffy cinnamon; orbital ring blackish; under 

 parts white; tail above blackish, beneath whitish; hands and feet 

 whitish; ears large, naked, with gray edges. 



Measurements. Total length, 201; tail vertebras, 103; hind foot, 

 25.4. Skull: total length, 29.7; basal length, 24.1; zygomatic width, 

 14.7; length of mandible, 18.3. (ex Type.) 



155a. bullatus (Peromyscus} , Osgood, Proc. Biol. Soc. Wash., xvn, 



1904, p. 63. 

 PEROTE MOUSE. 



Type locality. Perote, State of Vera Cruz, Mexico. 



Genl. Char. Similar to P. truii; audital bullae greatly inflated; 

 ears very large; tail shorter than head and body. 



Color. Upper parts and sides tawny ochraceous; middle of back 

 dusky; top of head and nose broccoli brown; sides of head grayish; 

 orbital ring dusky ; under parts creamy white ; tail bicolor ; hands and 

 feet white. 



Measurements. Total length, 200; tail vertebrae, 93; hind foot, 

 23. Skull: greatest length, 28.9; Hensel, 22; zygomatic width, 14.5; 

 interorbital constriction, 4.5; interparietal, 10X3; length of nasals, 



