Baculum: Stalk broad, greatest length (2.5 to 2.7 mm.) 1-2/3 times greatest breadth, 4 times greatest depth; median process ossified, size small, 1/5 length of stalk, higher than wide, having small anterodorsal prominence in both specimens examined; lateral processes cartilaginous, relatively small, displaced posteriorly, attenuate; posterior margin in dorsal view broadly rounded, or having blunt median apex, convex throughout; basal tuberosities moderately well developed, medially confluent, barely visible in dorsal view when mature; in end-view median constriction 4/5 greatest depth, ventral concavity deeper than dorsal concavity, both comparatively shallow; stalk at mid-point 1-1/2 times as wide as deep; shaft relatively slender, bowed dorsally at tip, relatively straight otherwise; lateral profile in dorsal view a gradual concave slope from point of greatest width anteriorly to distal part of shaft. _Specimens examined_: Two, from Douglas Co., Kansas, 76834 (2 mi. N Baldwin), 68545 (1 mi. NE Pleasant Grove). Microtus (Pitymys) parvulus (Howell) Fig. 40 Baculum: Stalk broad, greatest length (2.4 mm. in specimen examined) 1-3/4 times greatest breadth, 4 times greatest depth; median process ossified, size small, less than 1/4 length of stalk, wider than high, terminally flattened; lateral processes cartilaginous, relatively small, attenuate; posterior margin in dorsal view flattened, irregularly curved with concavities medially and laterally; basal tuberosities well developed, medially confluent; visible in dorsal view; in end-view median constriction 2/3 greatest depth, ventral concavity well-formed, no dorsal concavity; stalk at mid-point twice as wide as deep; shaft relatively slender, bowed dorsally toward tip; in dorsal view lateral profile a gradual concave slope from point of greatest width anteriorly to distal part of shaft; tip of shaft enlarged. The baculum of _M. parvulus_ resembles that of _M. pinetorum_ more than it resembles the baculum of any other microtine studied, differing primarily in smaller size. _Specimen examined_: One, from 1 mi. W Micanopy, Alachua Co., Florida, Univ. Florida No. 1508. Microtus (Pitymys) quasiater (Coues) Figs. 29 and 30