Part 5

Specimens examined: Nine, of two subspecies; Clethrionomys gapperi athabascae, British Columbia, 42922 (Indian Creek, Mile Post 234 of Alaskan Highway), 64281 (West bank Racing River, 89 mi. W Muskwa), 64287 (North bank Tetsa River, 56 mi. W, 11 mi. S Muskwa), 64290 (44 mi. W, 9 mi. S Muskwa), 64310 (32 mi. W, 2 mi. S Muskwa); Clethrionomys gapperi galei, 31 mi. N Pinedale, Sublette Co., Wyoming, 42108; Grand Mesa, Delta Co., Colorado, 60014 and 60015 (5-1/2 mi. E, 12 mi. S Collbran), 60022 (8 mi. E, 1/2 mi. S Skyway).

Clethrionomys occidentalis (Merriam)

Fig. 12

Baculum: Stalk elongate, greatest length (2.8 mm.) 2-1/2 times greatest breadth, 6 times greatest depth; three well-developed ossified processes; median process larger than lateral processes, 1/2 the length of stalk, curved, basally broad, ventrally keeled, trilobate posteriorly; lateral ossifications large, flattened distally, curved; posterior profile of stalk posteriorly slightly emarginate, thus bilobate in outline; in end-view dorsal concavity deeper than ventral, constriction less than 1/2 greatest depth, tuberosities confluent, visible in dorsal view at each side; shaft slender, especially in depth, straight; at mid-point of stalk almost twice as wide as deep, slight terminal inflation.

The general proportions of the stalk and the relatively large, uniquely shaped processes, are characteristic of most specimens of the genus Clethrionomys examined.

Specimen examined: C. occidentalis californicus, one from Mary's Peak, Benton Co., Oregon, 30, F. W. Sturges' collection.

Clethrionomys glareolus Schreber

Fig. 13

Baculum: Stalk elongate, greatest length (2.9 mm.) twice the greatest breadth in the specimen examined, flattened proximally, greatest length almost 6 times greatest depth of base; three well-developed ossified processes; median process arched in a dorsoventral plane, with basal notch and lateral lobes; lateral processes as long as median process, bowed in dorsal view, flattened distally, with ventromedial vane; basal tuberosities of stalk weakly developed, medially confluent; posterior profile in dorsal view evenly rounded; in end-view dorsal concavity shallow in comparison to most species but deeper than ventral concavity, constriction 3/4 greatest depth; shaft straight, at mid-point slightly wider than high, elongate, widest point of stalk less than 1/4 of total length from proximal end, slight lateral inflation at tip; lateral profile in dorsal view sloping at first abruptly and then gradually from widest point of stalk anteriorly onto shaft.

The specimen of Clethrionomys glareolus figured by Ognev (1950:31) in dorsal view as I interpret it, resembles my specimen in the rounded base; in the elongate, distally inflated shaft; in the initially abrupt slope of the lateral profile in dorsal view from the greatest width of stalk anteriorly; and in the presence of three well ossified processes. Ognev's specimen differs from mine in the median process being more elongate relative to its width, and rounded proximally, lacking lateral lobes and basal notch; in lateral processes being less curved; in the greater terminal inflation of the shaft; and in the closer approximation of the terminal processes to the shaft. The baculum of Clethrionomys glareolus as described and figured by Didier (1954:243-244) resembles my specimen in general proportions, but is more pointed proximally and more curved in dorsoventral plane. Didier states that the baculum is rather variable in form in this species, in different regions, but that a large number of specimens must be examined to assess the geographic nature of this variation.

Specimen examined: One from Zermatt, Valais, Switzerland, 67100.

Clethrionomys rufocanus Sundevall

Fig. 9

Baculum: Base of stalk broad but relatively flattened dorsoventrally, greatest length (3.2 mm.) less than 1-1/2 greatest width, 4 times greatest depth; three well-developed ossified processes; median process arched in dorsoventral plane, having basal notch and lateral lobes; lateral processes as long as median process, flattened distally, with ventromedial vane; basal tuberosities of stalk weakly developed, medially confluent; posterior profile in dorsal view convex with rounded posterior apex; dorsal surface of base almost flat, ventral concavity broad and shallow; constriction 3/4 greatest depth (not including an unusual irregularity on the ventral surface of the base); shaft straight, at mid-point of stalk distinctly wider than high, slender at distal end, widest point of stalk almost 1/3 of total length from proximal end, tip of shaft rounded; lateral profile in dorsal view gradually sloping from widest point anteriorly onto shaft.

The specimen of Clethrionomys rufocanus figured by Ognev (1950:97) resembles my specimen in the presence of three well ossified processes. Ognev's specimen differs however in the lack of a proximal notch on the median process, the lesser proportion of the stalk included in the basal enlargement, the more posterior position of the point of greatest width, and the presence of a concavity in the posterior profile of the stalk in dorsal view. These differences in the stalk may be owing to a difference in age (my specimen perhaps being older).

Specimen examined: One from 1 mi. NW Oho-ri, 6 M., Korea, 60438.

Phenacomys intermedius Merriam

Figs. 7 and 8

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

Baculum: In the single specimen examined, less mature than that figured by Hamilton (1946:384), the digitate processes are cartilaginous, the basal tuberosities are less well developed, and the shaft is slenderer throughout. The cartilaginous processes are of the same proportions as ossified processes in the figure mentioned. The shaft is also convex ventrally in lateral profile. The view of the side here considered to be anatomically the ventral side (adjacent to the urethra) is labelled dorsal view in Hamilton's specimen.

Specimen examined: One, from Reserve, Brown Co., Kansas, 72405.

Microtus (Herpetomys) guatemalensis Merriam

Figs. 42 and 43

Baculum: Stalk moderately elongate, greatest length (3.5 mm.) 2-1/3 times greatest breadth, spatulate, flattened throughout, greatest thickness 1/3 millimeter; three ossified processes; median process having three cornered base, curved dorsally, wider than high, 1/4 to 1/5 greatest length of stalk; each lateral process bent at middle, as long as median process, compressed laterally; base of stalk curved dorsally, tuberosities marginal, hence narrow, lateral excavations of tuberous margin not confluent medially; in end-view ventral concavity broad, no dorsal concavity, medial constriction but slightly less than greatest thickness (not depth); shaft wider than high throughout, at mid-point more than 3 times as wide as high; tip of shaft slightly inflated both laterally and dorsoventrally; lateral profile gradually sloping anteriorly from widest point of stalk.