Microtus mexicanus (Saussure)
Figs. 35 and 36
Baculum: Stalk attenuate, greatest breadth relatively near proximal end; greatest length (3.1 to 3.4 mm.) more or less twice greatest breadth, 4 to 5 times greatest depth; usually a single process ossified; lateral processes relatively small, cartilaginous or (in three specimens, 63094, 69453, 68019) with small ossifications; median process relatively small, sometimes appressed to tip of shaft, in length less than ¼ length of stalk; posterior profile in dorsal view rounded, flattened posteriorly, or in some specimens trilobate with angular edges; in end-view relative depths of dorsal and ventral concavities variable, dorsal usually deeper than ventral; distal end of stalk frequently bowed dorsally; shaft slender distally, sometimes slightly inflated terminally, or (in one specimen, 63085) near tip small lateral projections that are perhaps fused lateral ossifications; lateral profile in dorsal view a gradual slope anteriorly from point of greatest width to slender tip.
Specimens examined: Thirteen, of four subspecies; Microtus mexicanus mexicanus, Las Vigas, Veracruz, 30692; Nevada de Toluca, México, 63101; Valle de Bravo, México, 63094; Microtus mexicanus mogollonensis, Mt. Taylor, Valencia Co., New Mexico, 63298, 76830; Park Well, Mesa Verde National Park, Montezuma Co., Colorado, 69448, 69453; Upper Nutria, McKinley Co., New Mexico, 69997, 70000; Microtus mexicanus phaeus, Sierra Patamba, 9000 ft., Michoacán, 63085; Microtus mexicanus subsimus, 2 mi. E Mesa de Tablas, Coahuila, 58916; 13 mi. E San Antonio de las Alazanas, Coahuila, 68019, 68021.