As far as present material permits us to judge, _Synaptomys borealis sphagnicola_ is characterized, cranially, by: Skull large; interorbital region sharply ridged (the ridges being joined for a distance of 4 mm. in the type and of 4.5 mm. in the topotype); rostrum long, tapering relatively little; nasals slightly constricted medially and unusually narrow posteriorly; interparietal narrow and rectangular. Clethrionomys occidentalis caurinus (Bailey) 1898. _Evotomys caurinus_ Bailey, Proc. Biol. Soc. Washington, 12:21, January 27, type from Lund, east shore Malaspina Inlet, British Columbia. 1935. _Clethrionomys gapperi caurinus_, Racey and Cowan, Rept. British Columbia Prov. Mus. for 1935, p. H 25. Prior to 1935 _caurinus_ was considered to be a monotypic species. In 1935 Racey and Cowan (Rept. British Columbia Provincial Museum for 1935, pp. H 25-H 26) examined material from southwestern British Columbia of _C. caurinus_, including a series of 24 specimens from Alta Lake, and compared it with _Clethrionomys gapperi occidentalis_ and _C. g. saturatus_. They found _caurinus_ to be distinct from _C. g. saturatus_ but were "not convinced that _occidentalis_ and _caurinus_ both merit systematic recognition; should they prove to be indistinguishable, as the little available material indicates, _occidentalis_ will take precedence on grounds of priority. It is our opinion that further study of the distribution of the genus in British Columbia will lead to the recognition of _occidentalis_ as the form inhabiting coast-line and _saturatus_ the interior of British Columbia" p. H 26. In the face of these opinions Racey and Cowan nevertheless recognized _caurinus_ under the name _Clethrionomys gapperi caurinus_ (Bailey). In spite of the treatment by Racey and Cowan (_op. cit._) of _occidentalis_ and _caurinus_ as subspecies of _C. gapperi_, later authors arranged _occidentalis_ as a member of the "_californicus_" group although they retained _caurinus_ in the _gapperi_ group. For example, Davis (The Recent Mammals of Idaho, The Caxton Printers, pp. 307-308, 1939) assigned _C. caurinus_ to the _gapperi_ group, although he regarded _C. caurinus_ as a species (not a subspecies). He regarded also _C. occidentalis_ as a species (not a subspecies) but assigned it to the _californicus_ group. Dalquest (Univ. Kansas Publ., Mus. Nat. Hist., 2:344, April 9, 1948) considered _occidentalis_ to be conspecific with _Clethrionomys californicus_ and wrote (_op. cit._:101): "The _californicus_ group, I feel, contains only the races of _Clethrionomys californicus_, while the _gapperi_ group contains _C. gapperi_ and its races, including _caurinus_, and possible other species." Dalquest gave no indication that he had examined any specimens of _caurinus_.