_Distribution._--The Blue Mountains of southeastern Washington, and the Pend Oreille Mountains of northeastern Washington, west to Eureka, in the Kettle River Mountains, Ferry County (Howell, 1929: 69), and south to Newport (W. W. D.). =Tamias ruficaudus simulans= (Howell) Red-tailed chipmunk _Eutamias ruficaudus simulans_ Howell, Jour. Mamm., 3:179, August 4, 1922. _Tamias ruficaudus simulans_ Ellerman, Fam. and Genera of Living Rodents, British Mus. Nat. Hist., p. 434, June 8, 1940. _Type._--Obtained at Coeur d'Alene, Kootenai County, Idaho, by C. P. Streator on June 1, 1891. _Measurements._--Six males and 3 females from northeastern Washington average: total length 234; length of tail 109; hind foot 31.6; ear 18. _Distribution._--Northeastern Washington, reported from Pend Oreille, Stevens and Ferry counties by Howell (1929: 98). _Description._--The red-tailed chipmunk closely resembles _Tamias amoenus_. From _T. a. luteiventris_ and _T. a. canicaudus_ it differs principally in larger size, wider brain case and especially in its pure white underparts. From _T. a. affinis_ it differs in richer coloration, especially the brownish rather than gray rump. The differences separating it from _amoenus_ are slight, and only adult specimens can be identified in the field. According to Howell (1929: 81) this species occurs in northern Idaho, western Montana, northeastern Washington, southeastern British Columbia and extreme southwestern Alberta. Two subspecies are recognized, only one of which occurs in Washington. A number of large, white-bellied chipmunks have been taken in northeastern Washington that answer well to the description of _ruficaudus_. Also, there are a number of specimens that I cannot definitely identify as either _amoenus_ or _ruficaudus_. Some buff-bellied chipmunks from Idaho are as large, and possess brain cases as wide, as specimens from Washington unhesitatingly called _ruficaudus_, while some white-bellied individuals match _amoenus luteiventris_ in all other characters. When all the specimens available from Pend Oreille, Stevens and Ferry counties are separated into _amoenus_ and _ruficaudus_ and the skulls are examined, it is noticeable that all the _ruficaudus_ are old, fully adult animals and that most of the _amoenus_ are younger, showing less wear on the teeth. Perhaps the buffy underparts are lost with increasing age. This leads to the suspicion that _ruficaudus_, as applied to chipmunks in Washington, is a synonym of _amoenus_. Until considerable material is collected in northeastern Washington, showing individual and age variation, it seems best to retain the name _ruficaudus_.