iOll] Sivarth: Alaska Expedition of 1909. 127 



Evotomys phaeus, new species. 

 Dark-colored Red-backed ]\loiise. 



Tj'pe. — ^lale adult no. 8742, Univ. Calif. jMus. Vert. Zool., 

 Marten Arm, Boca de Quadra. Alaska; June 18, 1909; collected 

 by H. S. Swarth ; orig. no. 7647. 



Characters.- — Size rather large. Differs from E. wrangeli, 

 nearest it geographically, in cranial characters and in much 

 longer tail; from E. cauriiiKs. the species to the southward in 

 British Columbia, in larger size and longer tail. 



Coloration. — Dorsal stripe dark brown, between chestnut and 

 walnut brown, covering the whole back from the eyes to base of 

 tail; not very sharply defined against the color of the sides. 

 Sides and cheeks dark Isabella color. Below gray (about no. 8), 

 sharply defined against the sides. Fairly conspicuous oval 

 patches of gray hair over the hip glands. Tail bicolor. bro-vvnish 

 above, yellowish below. 



Skull. — Short and broad, with wide spreading zygomata. 

 Rostrum short. Premaxillae usually extending slightly beyond 

 posterior end of nasals. Frontals depressed. 



Measurements. — Average of nine adults : total length 155.7 

 (149-164); tail vertebrae 51 (46-58); hind foot 19.9 (19-20). 

 Skull: Average of eleven adults: length 24.8 (23-25.5); basal 

 length 21.2 (19.5-23) ; zygomatic breadth 13.8 (13-14.8) ; mastoid 

 breadth 11.1 (10.5-11.8) ; length of nasal 7.2 (6.8-7.8) ; length 

 of upper tooth row 5.1 (5-5.2). 



Remarks. — I had supposed that the red-Iiacked mouse occur- 

 ring on the mainland coast of this region would prove to be 

 E. wrangeli, but the latter appears to be purely an insular species. 

 I have had no specimens of that race for comparison, but the 

 Evotomys secured differ so widely from it in all the essential 

 peculiarities of the species as given in the published descriptions 

 that there seems little doubt of their belonging to a different 

 species. Wrangeli has a sliort tail, less than twice as long as 

 the hind foot— in adults of phaeus the tail is invariably more 

 than twice the length of the foot, frequently more than a third of 

 the entire length of the animal. From E. caurinus of southern 

 British Columbia it is distinguished by its generally larger size 



