60 Osgood Thirty New Mice of the Genus Peromyscus. 



Skull. About as in P. allwateri ; somewhat similar to that of P. levipes 

 but smaller, with smaller teeth; lachrymal region less swollen; nasals 

 rather long and broad ; zygomata somewhat compressed anteriorly, not 

 elbowed squarely ; premaxillae usually ending beyond nasals; interpari- 

 etal rather large; audital bullpe quite small, smaller than \nlevipesor 

 eremicus. 



Measurements. Type: Total length, 210; tail vertebrae, 114; hind foot, 

 22. Average of 10 adults from various localities: 200; 112; 21.5. Skull 

 of type: Greatest length, 27; basilar length of Hensel, 19.7; zygomatic 

 width, 13.7 ; interorbital constriction, 4.2 ; nasals, 9.9 ; bony palate, 3.7 ; 

 palatine slits, 4.9 x 2; diastema, 6.3; postpalatal length, 9.4; upper 

 molar series, 3.8. 



Peromyscus attwateri eremicoides subsp. nov. 



Type .from Mapimi, Durango, Mexico. Adult male, No. 57,729, U. S. 

 National Museum, Biological Survey Collection, December 15, 1893, E. A. 

 Goldman. 



Characters. Similar to P. atlwateri, but smaller and paler; skull small 

 and light; audital bullae very small ; ears small; soles of hind feet naked. 



Color. Upper parts mixed pinkish buff and dusky, producing the gen 

 eral effect of pale broccoli brown; lateral line pinkish buff; underparts 

 pure creamy white without trace of pectoral spot; facial region between 

 eye and ear grayish; feet and ankles white; tail dusky above, white 

 below. In some specimens, doubtless the younger ones, the general 

 effect is gray, while in others a delicate shade of pinkish buff predomi 

 nates. 



Skull. Similar in general to that of attwateri but decidedly smaller ; 

 audital bullse very small ; nasals short ; interorbital constriction rela 

 tively wide; rostrum depressed. 



Measurements. Type and one topotype : Total lengths, 180 ; 195 ; tail 

 vertebrae, 102; 111; hind feet, 20; 21. Skull of type: Greatest length, 

 24; basilar length of Hensel, 18; zygomatic width, 12; interorbital con 

 striction, 3.9 ; interparietal, 8.3 x 3; nasals, 8.5 ; bony palate, 3.5; pala 

 tine slits, 4.5 x 1.5; diastema, 5.8; postpalatal length, 8.5; upper molar 

 series, 3.5. 



Remarks. This form is readily distinguishable from both attwateri and 

 pectoralis by its pale color, small ears, and very small skull. Its resem 

 blance to P. eremicus, particularly in immature and worn pelages, is re 

 markable. The only external characters by which it may be distin 

 guished are its longer, slightly more hairy tail and pure white ankles. 

 Neither of these characters, however, is to be depended upon, as the tail 

 in eremicus is often quite hairy, and the dusky on the ankle frequently so 

 little developed as to be scarcely apparent. The molar enamel pattern, 

 except in extremely worn teeth, is always diagnostic, eremicoides having 

 the small accessory cusps and eremicus being without them. 



Specimens examined. Total number 10, from localities in Mexico as 

 follows: Coahuila, Jimulco, 4; Durango, Inde, 4, Mapimi, 2. 



