, respectively, in 13 adults). The
specimens from Muir Springs resemble _aztecus_ to a greater degree than
_dychei_, but are assigned to the latter because specimens from farther
west and farther south in Colorado are assignable to _dychei_. Howell
(1914:31) earlier noted that specimens from northern and central
Colorado were intergrades between the two subspecies.

The geographic range occupied by _R. m. dychei_ (from east of the
Mississippi River in Illinois and Wisconsin to the foothills of the
Rockies) is large (although not so large as that currently ascribed to
_R. m. megalotis_, which ranges from southern British Columbia to
central Mexico). Most other small rodents that occur in the same
geographic area occupied by _dychei_ are represented there by at least
two subspecies, a dark one in the east and a pale one in the west.
Eastern populations of _dychei_ have, it is true, somewhat darker upper
parts than mice from western localities, but the differences are slight;
also, judging from the literature, the "pectoral spot" is more common in
eastern mice.

It should be noted that _R. m. dychei_ probably has extended its range
both eastward and westward in the last century as a result of
agricultural practices--clearing of land in the east and irrigation in
the west.

_Specimens examined._--1145, as follows:

COLORADO. _Adams County_: South Platte River, 5 mi. N Denver, 1; 3
mi. S, 1 mi. W Simpson, 1. _El Paso County_: 5 mi. E Payton, 1; 4
mi. S maingate of Camp Carson, 1. _Larimer County_: 3 mi. N
Loveland, 1; 9-1/4 mi. W, 1/2 mi. N Loveland, 5600 ft., 1; 16 mi. W
Loveland, 6840 ft., 1; 3-1/2-4-1/2 mi. W Loveland, 5030 ft., 7; 6
mi. W, 1/2 mi. S Loveland, 5200 ft., 14; 7 mi. W, 2-1/2 mi. S
Loveland, 5370 ft., 1. _Morgan County_: Muir Springs, 2 mi. N, 2-1/2
mi. W Ft. Morgan, 21. _Washington County_: Cope, 6. _Yuma County_: 1
mi. W to 1 mi. E Laird, 6.

KANSAS. _Atchison County_: 1-1/2 mi. S Muscotah, 10; 4-1/2 mi. S
Muscotah, 2. _Barton County_: 3 mi. N, 2 mi. W Hoisington, 3. _Brown
County_: 1 mi. E Reserve, 2; 5 mi. S Hiawatha, 4. _Cheyenne County_:
23 mi. NW St. Francis, 1; 1 mi. W St. Francis, 12; 8 mi. S, 1-1/2
mi. W St. Francis, 1. _Decatur County_: 1 mi. N, 2 mi. E Oberlin, 4;
5 mi. S, 8 mi. W Oberlin, 1. _Doniphan County_: Geary, 2. _Douglas
County_: 5 mi. N, 1/2 mi. E Lawrence, 1; 1 mi. NW Midland, 1; 4-1/2
mi. N Lawrence, 2; 4 m