Baculum: Stalk slender, greatest length (2.9 mm.) 2-1/4 to 2-1/2 times greatest breadth, 4 times greatest depth; three well-developed ossified processes, median one almost 1/2 length of stalk, curved, broad basally and slightly larger in all dimensions than either lateral process; lateral processes flattened distally, curved; base of stalk well developed, basal tuberosities medially confluent or separated by medial emargination, posterolateral faces flattened or rough; emarginations in the four adults examined; posterior profile in dorsal view bluntly pointed or flattened except for emargination posterially, abruptly curved at point of greatest width; shaft arising broadly from distal side of base of stalk; in end-view hour-glass shaped, medial constriction pronounced, both dorsal and ventral concavities deep; shaft having relatively straight but distally convergent sides; at mid-point of stalk, 1 to 1-1/2 times as wide as deep; tip bluntly rounded, or slightly inflated. The specimens from Quebec differ from the one from Wyoming in smaller size, relatively smaller lateral digital processes, larger more medial basal emargination, and slender shafts. The baculum of _Phenacomys intermedius_ differs much from that of _Phenacomys longicaudus_, described by Hamilton (1946:381) and by Dearden (1958:547). Dearden states that the three bacula examined by him of _Phenacomys longicaudus_ differ markedly from the specimen described by Hamilton. It seems to me that in major features the resemblance is greater between the specimens of _Phenacomys longicaudus_ examined by these two authors than between their specimens and specimens of other microtines, including _Phenacomys intermedius_. Neither Hamilton nor Dearden record the exact localities of capture, the collections in which the specimens are deposited, or the catalogue numbers of specimens. Consequently verification of identifications and observations is difficult. _Specimens examined_: Five, of two subspecies; _P. intermedius intermedius_, 5.4 mi. S Moran, Teton Co., Wyoming, 3-C-309, collection of W. B. Quay; _P. intermedius celatus_, four (including one immature specimen) from Authiernord, Abitibi-ouest Co., Quebec, specimens in collection of Bristol Foster designated by numbers 2041-2044 of S. Anderson's field catalogue. Smith and Foster (1957:107) were of the view that _Phenacomys ungava_ (including the above specimens from Quebec) may be specifically distinct from _Phenacomys intermedius_. Ondatra zibethicus (Linnaeus) Not figured