Microtus (Herpetomys) guatemalensis Merriam
Figs. 42 and 43
Baculum: Stalk moderately elongate, greatest length (3.5 mm.) 21/3 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, ¼ 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.
Specimen number 65921 (Fig. 43) differs from number 65895 (Fig. 42) described above. Terminus of shaft of number 65921 has lateral lobes from which arise lateral cartilaginous processes; median terminal ossification irregular in shape, smaller, imbedded in terminally bilobate cartilage. In the spatulate flattened stalk these two specimens are much alike. An immature specimen, number 65908, is smaller (length of stalk 2.6 mm.) also flattened and spatulate, has the terminal processes cartilaginous, the lateral processes bent medially, and proportions as in the adult.
The baculum shows no noteworthy resemblance to that of any other species of North American Microtus; on the other hand the differences between M. guatemalensis and some other species are no greater than the differences between certain species included in the subgenus Microtus. The baculum neither strengthens nor weakens the case for subgeneric rank for M. (Herpetomys) guatemalensis.
Specimens examined: Three from Guatemala; 65895 (2 mi. S San Juan Ixcoy), 65908, (3-1/2 mi. SW San Juan Ixcoy), 65921 (10 mi. E, 4 mi. S Totonicapán).