Female (based on 5 adults and subadults from Douglas County, Kansas): See measurements and plates 31-33; weight, 2.2 (2.0-2.4) grams; basilar length, 38.9 (37.6-40.7); zygomatic breadth less than distance between condylar foramen and M1 or than between anterior palatine foramen and anterior margin of tympanic bulla; postorbital breadth less than length of upper premolars and except in one specimen, more than width of basioccipital measured from medial margin of one foramen lacerum posterior to its opposite; least width of palate less than greatest length of P4; tympanic bulla as far posterior to foramen ovale as width of 3 to 5 upper incisors; height of tympanic bulla more or less than distance from its anterior margin to foramen ovale; length of tympanic bulla more than length of lower molar and premolar tooth-row and longer than rostrum. The skull of the female averages 41 per cent lighter than that of the male. Compared with the skull of _M. f. noveboracensis_ from Massachusetts, that of the male of _primulina_, in dorsal view, is seen to be shorter anteriorly to the postorbital processes and to have a more marked postorbital constriction. In lateral view the dorsal outline of the skull of _primulina_ is less concave in the postorbital region. In ventral view the skull of _primulina_ is seen to be wider across the mastoid processes and zygomatic arches but the most pronounced difference is in the tympanic bullae. In _noveboracensis_ each bulla is scooped out on the anterior part of the medial face and appears to be narrower anteriorly than posteriorly whereas in _primulina_ the anterior part of the medial face is not scooped out but is moderately inflated and the bulla appears to be of uniform breadth anteriorly and posteriorly. By actual measurement the breadth of the bulla averages 59 per cent of its length in _primulina_ but only 50 per cent in _noveboracensis_. Other respects in which the skull of the male of _primulina_ differs from that of _noveboracensis_ are as follows: Linear measurements of teeth more; relative to the basilar length, the length of the tooth-rows averages more, whereas the interorbital breadth and orbitonasal length are less.