1911] Taylor: Mammah of the 1909 Nevada Expedition. 229 



is evident in all the measurements except length of tail vertebrae, 

 dimensions of interparietal, shelf of bony palate (which is pre- 

 cisely the same in both series), and maxillary tooth row (which 

 is a little longer in the animals with the smaller skulls). The 

 ratio of length of tail vertebrae to total length is greater in the 

 mountain animals. In this series, with the exception of length of 

 tail vertebrae and hind foot, and length of palatine slits (which 

 is the same in the two sexes), the females present the greater 

 dimensions in each particular. 



Old adults from localities ranging from 4100 to 9400 feet are 

 similar in color, regardless of locality. They are all in the so- 

 called pale phase of pelage (see Osgood, 1909, p. 89). From 

 the worn and faded condition of the hair the conclusion seems 

 justified that the pelage represented is the breeding coat. Descrip- 

 tion of one of these typical adult specimens (no. 8075, male), 

 follows. 



Ground color of upperparts between ochraceous buff and clay 

 color; back slightly darker than the sides, the darker tint being 

 due to an insprinkling of brown hairs; color of all the dorsal 

 parts modified by dusky hairs ; ears having a white spot present 

 at anterior base; externally anterior half seal brown, posterior 

 half lead gray, edged with white ; internally dusky gray, covered 

 with very short grayish white hairs ; a bunch of buffy-ended 

 hairs just posterior of light spot at their anterior insertion; 

 underparts of animal pure white, hairs having plumbeous bases 

 except on chin and parts of the fore leg; fore and hind feet 

 white ; tail white with a very distinct dorsal stripe nearest a van- 

 dyke brown tint. Though there are minor variations in the com- 

 parable series, they are very slight. 



The series as a whole presents the variation that would be 

 expected in any lot of Peromijscus of the same number. Fully 

 two-thirds are young animals, quite a number evid(-ntly born 

 this year. 



A few examples (notably nos. 8018, 8029) are molting into 

 the post-breeding or fresh fall pelage. 



