on the map for another reason;
these hills are not a barrier). The major mountainous areas higher than
approximately 8000 feet in elevation in Wyoming, Colorado and Utah are
stippled. These mountainous areas include the habitat that is most
suitable for the montane meadow mouse. The Black Hills are unoccupied by
this species but these hills seem to be ecologically suitable for the
species.]

_Measurements._--The average and the extremes for some measurements
of 34 males and females, 27 from the type locality and 7 from other
localities in the range assigned to this subspecies, are as
follows: total length, 165 (146-186); length of tail, 44.2 (35-55);
hind foot, 19.6 (17-21); condylobasilar length of the skull, 25.5
(24.0-27.5); zygomatic breadth, 15.6 (14.7-16.6); alveolar length
of upper molar tooth-row, 6.6 (6.2-7.0); prelambdoidal breadth, 8.8
(8.1-9.5); lambdoidal breadth, 12.0 (11.2-12.8). As an indication
of variability and for comparison with other series the coefficient
of variability and two times the standard error of the mean for
each measurement in this series are included in Table 1. The
averages for some measurements of 27 topotypes are as follows:
total length, 162; length of tail, 45.5; hind foot, 19.9;
condylobasilar length, 25.6; palatilar length, 14.0; molar series,
6.6; alveolobasilar length, 14.9; zygomatic breadth, 15.6;
interorbital breadth, 3.5; lambdoidal breadth, 12.1; prelambdoidal
breadth, 8.9; depth of braincase, 7.8.

_Discussion._--Three species of _Microtus_ were collected by James W.
Bee at the type locality. _Microtus montanus codiensis_, _Microtus
longicaudus mordax_, and _Microtus pennsylvanicus modestus_ were taken
in the same runways in the same meadow, at the same time. _Microtus
ochrogaster haydeni_, although not taken at this locality, occurs in the
Big Horn Basin. These four species differ in their geographic ranges,
being largely allopatric, except _M. montanus_ and _M. longicaudus_
which are sympatric. Although the different species have ecological
preferences and habits which differ, several species of _Microtus_ may
occur together in local areas such as the above. Certain of the
characteristics of _M. m. codiensis_ are intermediate between those of
the species _M. montanus_ on one hand and those of the other three
species on the other hand. Could interspecific hybridization between
"good s