ge; color dark for the
species; zygomatic breadth large; upper molars large and upper
molar tooth-row relatively long; braincase elongate; auditory
meatus relatively small; bullae large; incisors relatively
procumbent.

_Comparisons._--From _M. p. uligocola_, the subspecies to the west,
_M. p. finitus_ differs in darker color. These subspecies resemble
each other in large size and large molar teeth. A comparison of
nine pairs of skulls by the "method of pairs" shows three features
in which _finitus_ (from at, or near, the type locality) differs
from _uligocola_ (from at, or near, the type locality); in 7 of 9
pairs _finitus_ had a relatively more elongate braincase
(Confidence Limit .60); in 9 of 9 pairs _uligocola_ had larger
auditory meatuses (C. L. .99); in 7 of 9 pairs _uligocola_ had
relatively larger bullae (C. L. .80). From _M. p. pennsylvanicus_
(Ord) from eastern Nebraska and eastern South Dakota _finitus_
differs in larger size; darker color; larger molar teeth and longer
upper molar tooth-row. Five pairs of skulls were compared; in all 5
pairs, _finitus_ had more procumbent incisor teeth (C. L. .97) and
wider first upper molars (C. L. .97); and in 4 of 5 pairs _finitus_
had a relatively more elongate braincase (C. L. .60). From _M. p.
insperatus_, the subspecies to the north, _finitus_ differs as
follows: color darker, size larger, molar teeth relatively larger
and alveolar length of the upper molar tooth-row greater. Five
pairs of skulls were compared and in all 5 pairs _finitus_ had more
procumbent upper incisors (C. L. .97) than _insperatus_; in 4 of 5
pairs _insperatus_ had a relatively more elongate braincase (C. L.
.60), narrower first upper molariform tooth (C. L. .75), and
shorter distance between the alveoli of the first upper molars (C.
L. .88).

_Remarks._--The species, _Microtus pennsylvanicus_, in Pleistocene time
ranged onto the plains of Kansas as far southward as Meade County,
Kansas (Hibbard, 1940:421). This occurrence indicates a cooler more
humid climate then than now in southwestern Kansas. _M. p. finitus_ is
more closely associated with water than _Microtus ochrogaster_, the
only other species of _Microtus_ now occupying the same region,
although both species have been captured at certain places in the same
runways. In Nebraska, a marginal part of the range of the species,