Osgood Thirty New Mice of the Genus Peromyscus. 61 



Peromyscus polius sp. nov. 



Type from Colonia Garcia, Chihuahua, Mexico. Old female, No. 

 98,226, U. S. National Museum, Biological Survey Collection, June 26, 

 1899, E. W. Nelson and E. A. Goldman. 



Characters. Somewhat similar to P. boylei rowleyi, but decidedly larger 

 and grayer colored ; skull large and stoutly built, with large teeth and 

 relatively small audital bullse. 



Color. General color of upper parts grayish broccoli brown, produced 

 by a ground color of pinkish buff mixed with dusky ; lateral line clear 

 pinkish buff; head slightly more grayish than body, particularly on 

 cheeks ; a narrow dusky orbital ring ; lanuginous tuft at base of ear occa 

 sionally tinged with white ; under parts pure white ; feet and ankles 

 white ; tail bicolor. 



Skull. Similar in general to that of rowleyi, but larger ; molar teeth de 

 cidedly larger ; palatine slits longer ; audital bullse actually about same 

 size, relatively smaller ; otherwise not peculiar. 



Measurements. Average of 8 adult topotypes : Total length, 218.5 

 (210-234); tail vertebrae, 117 (111-120); hind foot, 25.8 (25-26). Skull 

 of type : Greatest length, 29.9 ; basilar length of Hensel, 22.9 ; zygomatic 

 width, 14.8; interorbital constriction, 4.5; interparietal, 10.5 x 2.8; 

 nasals, 11.6; bony palate, 4.4 ; palatine slits, 6 x 2 ; diastema, 7.4; post- 

 palatal length, 10 ; upper molar series, 4.7. 



Remarks. This species nearly equals P. drfficilis in size, but its shorter 

 tail and ears readily distinguish it without recourse to the skull, in which 

 the audital bullse are scarcely more than half the size of those of difficUis. 

 Its real relationship is undoubtedly with rowleyi and attwateri. It is appar 

 ently an isolated species, and is not the general Mexican representative 

 of this group, for practically typical rowleyi occurs as far south at least as 

 central Zacatecas. Its pure white ankles, as well as its large size and 

 pale color, afford convenient characters for readily recognizing it. 



Peromyscus gratus gentilis subsp. nov. 



Type from Lagos, Jalisco, Mexico. Adult male, No. 78,937, U. S. Na 

 tional Museum, Biological Survey Collection, June 27, 1896, E. W. Nelson 

 and E. A. Goldman. 



Characters. Similar to P. gratus but paler ; sides of head much more 

 fulvous; molar teeth slightly smaller. 



Color. New pelage: Upper parts pale ochraceous buff lightly mixed 

 with dusky ; middle of back with a slight concentration of dusky tipped 

 hairs ; top of head, ear tufts, etc., with a predominance of buffy ; sides 

 of head nearly clear ochraceous buff, with a slight tinge of grayish be 

 tween eye and base of ear ; eyelids black ; under parts white ; hands and 

 feet white; ankles dusky; tail bicolor, blackish above, white below. 

 Worn pelage : Upper parts varying from clear bright ochraceous buff on 

 back and rump to grayish buft about head and shoulders, sometimes with 



