422 PROCEEDINGS OF THE ACADEMY OF [1894. 



of m. 2 projecting exteriorly beyond the outer edges of their inter- 

 vening loops, forming a very irregular outline not seen in the latter 

 species. In trinotatus the inferior m. 8 is relatively large, one-aud-a- 

 half times as long as wide and made up of a more complicated series 

 of loops than in the same tooth of its allies. The coronoid process 

 is much lengthened, wide across base, blunt and distinctly notched 

 at tip. The angular process of mandible is perforated by a single 

 minute foramen; in the other forms it is multi perforate or incised by 

 two, conspicuous, oblique slits. 



Measurements of I^/P^ (in millimeters). — Total length, 234; tail 

 vertebrae, 139; hind foot, 32. (Topotype, length, 235; tail, 142; 

 foot, 32.) Skull — Total length, 24; basilar length, 17.5; zygomatic 

 width, 13; nasal length, 9.8; interorbital constriction, 4.8; height 

 of cranium, 9.8; length of mandible, 12.5; width of mandible, 6.8. 



Two males of this species were taken at Lulu Island. Another 

 from Mason Co., Washington, is referable to it. 



Zapus trinotatus is the West Cascade representative of Z. princeps. 

 Several specimens of jumping mice taken at Lac La Hache, B. C. , 

 and at Vernon, in the same province, are referable to princeps, 

 whose range will probably be found to be limited to the East Cas- 

 cade and Rocky Mountain regions of the United States and of 

 southern British America. It is probable that the range of hud- 

 sonius will be found to reach far to the west in northern British 

 America. 



I am indebted to Mr. G. S. Miller, Jr. , for the loan of specimens 

 of Z. princeps for this study. 



