Clethrionomys rufocanus Sundevall
Fig. 9
Baculum: Base of stalk broad but relatively flattened dorsoventrally, greatest length (3.2 mm.) less than 1½ 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 ¾ 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.