ibuted as follows
(abbreviations for collections are given in the account of _M. m.
nanus_; localities that are not represented in Fig. 1 because
overlapping or crowding of the symbols would result are
Italicized): WYOMING: _Big Horn Co._: Medicine Wheel Ranch, 9000
ft., 28 mi. E Lovell, 30; W slope, head of Trappers Creek, 9500
ft., 2 (USBS). _Washakie Co._: 9 mi. E, 5 mi. N Tensleep, 7400 ft.,
1. _Johnson Co._: 7-1/2 mi. W, 1 mi. S Buffalo, 6500 ft., 3; Big
Horn Mountains, 3 (USBS). _Natrona Co._: Buffalo Creek, 27 mi. N, 1
mi. E Powder River, 6075 ft., 16.

=Microtus montanus fusus= Hall

_Microtus nanus_, Bailey, N. Amer. Fauna, 17:30, June 6, 1900
(part); Cary, N. Amer. Fauna 33:123, August 17, 1911.

_Microtus montanus fusus_ Hall, Proc. Biol. Soc. Washington,
51:131-134, August 23, 1938; Warren, The Mammals of Colorado, Univ.
of Okla. Press, p. 229, 1942.

_Type._--Male, adult, skin and skull; No. 61281, Museum of
Vertebrate Zoology; 2-1/2 miles east of summit of Cochetopa Pass,
Saguache County, Colorado; Sept. 21, 1933; collected by Annie M.
Alexander; original number 2568. Type not seen by me.

_Range._--Southern Colorado and northern New Mexico.

_Comparisons._--For comparison with _M. m. nanus_, the subspecies
to the northward, see the preceding account of that subspecies. For
comparison with _M. m. amosus_ the subspecies to the west see Hall
(1938) and Durrant (1952). I have not examined specimens of
_amosus_.

_Measurements._--Average and extreme measurements for 17 adults
including both males and females from several localities in
southern Colorado are as follows: total length, 160 (136-179);
length of tail, 42 (35-55); hind foot, 19.2 (17-23); condylobasilar
length of the skull, 25.2 (24.0-26.0); zygomatic breadth, 15.0
(14.1-15.5); alveolar length of upper molar tooth-row, 6.4
(6.0-6.7); prelambdoidal breadth, 8.7 (8.3-9.2); lambdoidal
breadth, 11.7 (11.1-12.6).

Average and extreme measurements of 4 adults (2 males and 2
females) from the type locality and 11 adults (4 males and 7
females) from other localities in southern Colorado are as follows:
total length, 162 (157-168), 157 (137-169); length of tail (means
only), 44.5, 40.5; hind foot, 18.8 (18-19), 18.6 (18-23);
condylobasilar length of skull, 24.5