Fig. 34
Baculum: Length of stalk (2.4 mm.) 1¾, times greatest breadth, 41/3 times greatest depth; median ossified process well developed, more than 1/3 length of stalk, higher than wide, slightly bowed, closely appressed to terminus of shaft; basal tuberosities of stalk moderately developed, confluent medially, posterior profile of medial apex rounded in dorsal view, lateral indentations present, hence trilobate outline; in proximal end-view base wider ventrally, ventral concavity broader than dorsal concavity but of equal depth, medial constriction 2/3 greatest depth; shaft slender in distal part, inflated terminally, and wider than high at mid-point of stalk; lateral profile a smooth slope of gradually decreasing curvature from point of greatest width to near distal end.
The baculum of this species figured by Ognev (1950:461) differs in having lateral ossified processes, and a more rounded base of the stalk. Resemblance to the New World Stenocranius is discussed below.
Specimen examined: One from "Eastern Europe," 8059.
Microtus (Stenocranius) miurus Osgood
Figs. 32 and 33
Baculum: Length of stalk (2.8 mm.) 1½ times greatest breadth, 3½ times greatest depth; median process ossified, 2/5 to 3/5 length of stalk, laterally compressed, sometimes arched in dorsoventral plane; lateral processes cartilaginous, slender; basal tuberosities well developed, averaging less enlarged than shown in Figure 32, but more angular in lateral outline than shown in Figure 33; tuberosities confluent posteriorly; posterior profile smoothly rounded to trilobate, curvature at point of greatest breadth usually acute; in proximal end-view base wider dorsally, deep dorsal concavity, shallow ventral concavity, medial constriction 3/5 of greatest depth; shaft slender anteriorly, at mid-point of stalk twice as wide as high, at tip higher than wide, laterally inflated; lateral profile in most specimens abruptly curved anterior to point of greatest breadth.
The single specimen of the Old World M. (Stenocranius) gregalis examined resembles the New World M. (Stenocranius) miurus in the angular lateral profile at the point of greatest breadth of the stalk, slender shaft in comparison to broad base of stalk, and presence of a single well-developed laterally compressed median process. The base of the stalk in the baculum of M. gregalis is less well developed and smaller than in the baculum of M. miurus.
Specimens examined: Nine, all of the subspecies Microtus miurus muriei, from the Brooks Range, Alaska; 51077 (Lake Schrader, 145°09'50", 69°24'28", 2900 ft., Romanzof Mts.); 51151, 51152, 51154, 51164, 51166, 51169 (last 6 from Wahoo Lake, 69°08', 146°58', 2350 ft.); 51210, 51213 (last 2 from Porcupine Lake, 68°51'57", 146°29'50", 3140 ft.).