color, smaller and less angular skull.

From _Thomomys talpoides clusius_ (topotypes) to the northwestward, _T.
t. attenuatus_ differs in shorter body, slightly grayer color, less
width across mastoid region of skull, smaller tympanic bullae, and more
obtuse anterolateral angle on zygoma.

_Remarks._--This subspecies is of smaller size than any of the
geographically adjoining subspecies. Intergradation with _T. t.
cheyennensis_ is shown by specimens from two miles south and nine and
one-half miles east of Cheyenne, Wyoming. Intergradation with _T. t.
bullatus_ or _T. t. clusius_ or both is suggested by the larger size of
the specimen from five miles southwest of Wheatland, Wyoming. Although
large, this skull has the slender proportions of _attenuatus_ to which
the specimen is tentatively referred. Although the specimens from Avalo,
Colorado, are typical _attenuatus,_ the specimen from Pawnee Buttes,
Colorado, is somewhat larger than typical _attenuatus_ and suggests
intergradation with the subspecies to the southward, for example, at
Flagler, Colorado.

_Specimens examined._--Total number, 44, and unless otherwise indicated
in the Museum of Natural History of the University of Kansas.

=Wyoming.= _Niobrara County_: 10 mi. N Hatcreek Post Office, 5300 ft.,
1. _Platte Co._: 5 mi. SW Wheatland, 1 (U. S. B. S.). _Goshen Co._:
Little Bear Creek, 20 mi. SE Chugwater, 1 (U. S. B. S.). _Laramie Co._:
5 mi. W and 1 mi. N Horse Creek P. O., 7200 ft., 1; 3-1/2 mi. W Horse
Creek P. O., 7000 ft., 6; 2-1/5 mi. W Horse Creek P. O., 6600 ft., 1; 2
mi. W Horse Creek P. O., 6600 ft., 2; Horse Creek 6500 ft., 1; 3 mi. E
Horse Creek P. O., 6400 ft., 5; 6 mi. W Islay, 2 (U. S. B. S.); 2 mi. S
and 1/2 mi. E Pine Bluffs, 5200 ft., 1; 7 mi. W

Cheyenne, 6500 ft., 1; Cheyenne, 7 (U. S. N. M.); 1 mi. S and 4-1/2 mi.
E Cheyenne, 5200 ft., 1; 2 mi. S and 9-1/2 mi. E Cheyenne, 5200 ft., 3;
Arcola, 5200 ft., 4.

=Colorado.= _Weld Co._: Pawnee Buttes, 5300 ft., 1 (U. S. B. S.). _Logan
Co._: Chimney Canyon, 10 mi. NE Avalo, 5100 ft., 5 (U. S. B. S.).

_Museum of Natural History, University of Kansas, Lawrence. Transmitted
January 15, 1951._

TABLE 1. MEASUREMENTS, IN MILLIMETERS, OF TWO SUBSPECIES OF THOMOMYS
TALPOIDES.
______________________________________________________________________

Column A Catalogue number or number of averaged individuals
Column B Sex
Column C Total length
Column D Length of tail
Column E