_Characters for ready recognition (of males)._--Differs from _M. f. olivacea_ in smaller size (adult males with hind foot and basilar length less than 45), depth of skull at anterior margin of basioccipital, ignoring sagittal crest, amounting to more than 63 per cent of mastoid breadth, and greater convexity of dorsal outline of skull in longitudinal axis (see pls. 16-18); from _M. f. noveboracensis_, in males, by zygomatic breadth not less than distance between anterior palatine foramen and anterior margin of tympanic bulla and by convex dorsal outline of skull in longitudinal axis; from _M. f. primulina_ by evenly spreading zygomatic arches, lesser inflation of tympanic bullae anteromedially than posteromedially, and convex dorsal outline of skull in longitudinal axis; from _M. f. texensis_ and _M. f. frenata_ by absence of white facial markings and postorbital breadth more than distance between posterior borders of P4 and P2. _Description._--_Size._--Male: The type, a subadult male, measures (inches and quarter fractions thereof, transposed into millimeters) as follows: Total length, 390; length of tail, 113; length of hind foot, 44. Tail is 41 per cent as long as head and body. Length of hind foot less than basal length. Typical female unknown. _Externals._--Longest facial vibrissae black, or dark brown (both colors in the type) and extending beyond ear; carpal vibrissae same color as underparts and extending to within 3.5 millimeters of apical pad of fifth digit. Hairiness of foot-soles in type slightly less than shown in figure 20. _Color._--Upper parts in summer tone 4 of Burnt Umber of Oberthür and Dauthenay, pl. 304; underparts as described in _M. f. olivacea_. In winter, upper parts (based on type) near (1) Brussels Brown or grayer than tone 4 of Burnt Umber of Oberthür and Dauthenay, pl. 304, darker on top of head from nose to a line connecting posterior margins of ears. Chin and posterior third of each upper lip white. Remainder of underparts white with wash of Warm Buff. Tip of tail black. Color of underparts extends distally on posterior sides of forelegs over toes but represented on antipalmar faces of feet by only a few scattered hairs. Color of underparts extends distally on medial sides of hind limbs only to knees. Least width of color of underparts amounting to 15 per cent of greatest width of color of upper parts. Black tip of tail 50 mm. long; thus longer than hind foot and 44 per cent as long as tail-vertebrae.