Microtus montanus (Peale)
Figs. 19, 20 and 21
Baculum: Stalk broad, greatest length (varying with subspecies from 2.3 to 3.1 mm.) 1½ to 1¾ times greatest breadth, 31/3 to 41/3 times greatest depth; three ossified processes, median one largest, more than twice as wide and as deep as shorter, slenderer, lateral processes; median process laterally compressed distally except in one specimen in which moderately inflated distally, proximally enlarged in some specimens (Fig. 21) and 1/3 to 2/5 length of stalk; base broad, posterior profile in dorsal view evenly convex throughout, at widest point of stalk abruptly incurved; basal tuberosities moderately to strongly developed, medially confluent; in end-view base wider ventrally than dorsally, dorsal concavity slightly to much deeper than the nearly flattened ventral concavity; medial constriction 2/3 to 4/5 of greatest depth; shaft relatively slender, at mid-point of stalk slightly wider than high and ¼ as wide as base of stalk, terminally rounded or slightly inflated; lateral profile in dorsal view a gradual curve from point of greatest width anteriorly onto shaft.
The different subspecies figured show the essential characteristics of the species, differing primarily in size.
Specimens examined: Fourteen, of three subspecies; Microtus montanus amosus, ½ mi. E Soldier Summit, Wasatch Co., Utah, 62241; M. montanus fusus, La Manga Pass, Conejos Co., Colorado, 42164; 5 mi. N, 26 mi. W Saguache, 9500 ft., Saguache Co., Colorado, 42307, 42315; 5 mi. N, 27 mi. W Saguache, 9350 ft., Saguache Co., Colorado, 42308; 5 mi. N, 28 mi. W Saguache, 9325 ft., Saguache Co., Colorado, 42309; 5 mi. S, 24 mi. W Antonito, 9600 ft., Conejos Co., Colorado, 42327, 42330; Prater Canyon, Mesa Verde National Park, Montezuma Co., Colorado, 69456, 69457, 69463; Microtus montanus nanus, 2 mi. N, 2 mi. W Pocatello, Bannock Co., Idaho, 57470, 57472; ¼ mi. N, 2 mi. W Allenspark, 8400 ft., Boulder Co., Colorado, 50330.