MURIDJE 125 



Evotomys obscurus Merriam. (Dusky.) 



DUSKY RED-BACKED MOUSE. 



Above olive gray with an ill-defined dorsal area of cinnamon 

 rufous obscured by black hairs; lower part of sides and face 

 clear gray ; tail bicolor, dusky above, whitish beneath. 



Length about 148 mm. (3.80 inches) ; tail vertebrje 46 

 (1.80); hind foot 17 {.6y). 



Type locality, Prospect, Upper Rogue River Valley, Ore- 

 gon. 



West slope of the northern Sierra Nevada and southern 

 Cascade Mountains. 



Evotomys mazama Merriam. 



CRATER LAKE RED-BACKED MOUSb. 



Dorsal stripe from in front of ears to base of tail cinnamon 

 rufous or hazel, shading gradually into buffy gray on sides and 

 face ; belly washed with buffy white ; tail sharply bicolor, black- 

 ish above, whitisli below. 



Length about 157 mm. (6.20 inches) ; tail vertebrae 51 

 (2) ; hind foot 19 (.75). 



Type locality, Crater Lake, Oregon. 



Higher parts of the Cascade Mountains in Oregon and 

 Mount Shasta, California, between 5,000 and 8,000 feet altitude. 



Genus Microtus Schrank. (Small — ear — mouse.) 

 Skull strong and angular ; molars rootless through life, 

 strong, with sharp outer angles ; outer and inner cusps of lower 

 molars of about the same size ; basal part of lower incisor pass- 

 ing on tongue side of the bases of first and second molars and 

 on outer side of third; feet normal; tail round, usually less than 

 half as long as head and body; form stout; size medium or 

 small. 



