56 Osgood Thirty New Mice of the Genus Peromyscus. 



rich material and to whom I am indebted for much valued 

 criticism and advice. It was also my privilege to be somewhat 

 associated with Dr. Merriam during his preparation of a pre 

 liminary paper on the same group several years ago,* an expe 

 rience which is now of the utmost value to me. During the 

 work I have been greatly assisted by Mr. Nelson, and the ad 

 vantage of having at my disposal his intimate knowledge of the 

 physiographic conditions of Mexico has been much appreciated. 



Subgenus Peromyscus Gloger. 

 Peromyscus sonoriensis blandus subsp. nov. 



Type from Escalon, Chihuahua, Mexico. Adult female, No. 57,635, U. S. 

 National Museum, Biological Survey Collection, November 27, 1893, E. A. 

 Goldman. 



Characters. Similar to P. sonoriensis, f but smaller ; tail shorter ( usually 

 less than 75) ; color more vinaceous. 



Color. Type, in full winter pelage : Upper parts vinaceous buff, uni 

 formly sprinkled with dusky; a narrow lateral line of vinaceous buff ; 

 lanuginous ear tufts conspicuous, mixed white and buff; under parts 

 creamy white ; ears chiefly whitish with a wide dusky area on flexure ; 

 tail sharply bicolor ; feet white, ankles with traces of dusky and buffy. 



Skull. Similar to that of sonoriensis, but somewhat smaller ; nasals 

 averaging wider, particularly at their posterior ends. 



Measurements. Type: Total length, 145; tail vertebrae, 61; hind foot, 

 21. Average of seven adult topotypes: 161; 69; 21.4. Skull of type: 

 Greatest length, 25.4; basilar length of Hensel, 19.7; zygomatic width, 

 12.5; interorbital constriction, 4; interparietal, 8 x 1.9 ; nasals, 9.8 x 2.5 ; 

 bony palate, 3.5 ; palatine slits, 5.7 x 2 ; diastema, 6.7 ; postpalatal length, 

 9.1 ; upper molar series, 3.8. 



Remarks. This is the common short-tailed mouse of northeastern 

 Mexico. The limits of its range have not yet been thoroughly worked 

 out, but it is represented from numerous localities in Mexico east of the 

 Sierra Madre and extends north to western Texas. It is easily distin 

 guished from P. texanus of the same region by numerous characters, 

 among which may be mentioned the following : Size smaller ; tail shorter ; 

 color more vinaceous ; pelage softer; subauricular spots more prominent 

 and nearly always extensively white; nasals broader and flatter; pre- 

 maxillse less swollen laterally ; braincase smaller. Its vinaceous color 

 and small size distinguish it from sonoriensis. which is found chiefly west 

 of the Sierra Madre. 



* These Proceedings, Vol. XII, pp. 115-125, April 30, 1898. 

 tNos. fffff and f Hf U. S. N. M., from Santa Cruz River, Sonora, 

 have been used to represent P. sonoriensis. 



