A New Subspecies of Microtus montanus from Montana and Comments on Microtus canicaudus Miller — John Stuart Mill — John Shaqi
A New Subspecies of Microtus montanus from Montana and Comments on Microtus canicaudus Miller
John Stuart Mill · en
Our examination of specimens from localities in Montana east of the
range here ascribed to _M. m. pratincolus_ indicates that, among named
kinds of _Microtus_, those specimens are best referred to _M. m. nanus_.
These specimens are listed below under comparative materials. It should
be mentioned here that although Bailey (_loc. cit._) applied the name
_Microtus nanus canescens_ to Montanan specimens from Flathead Lake and
Hot Springs Creek, the subspecies _M. montanus canescens_ now is thought
to be restricted to Washington and the adjoining part of British
Columbia; _M. m. canescens_ does not occur so far east as Montana.
Grateful acknowledgment is made to those persons in charge of the
Biological Surveys collection for permission to study the specimens in
that collection, and to the Kansas Endowment Association for support of
the field work which yielded the specimens from six miles east of
Hamilton, Montana. The study here reported upon was aided also by a
contract between the Office of Naval Research, Department of the Navy,
and the University of Kansas (NR 161-791).
_Measurements._--The following measurements in millimeters are
those of the holotype and the average, maximum, and minimum,
respectively, of eleven adult males from various places in the
range of the subspecies. Except as noted below, we are unable to
detect significant morphological differences in the populations
sampled and believe that pooling of the measurements is justifiable
in this case. Measurements are: Total length, 129, 149 (156-141);
length of tail-vertebrae, 27, 37 (39-31); length of hind foot, 18,
19 (20-18) (all preceding measurements are those of the
collectors); basilar length, 22.2, 24.5 (25.7-23.4); greatest
length of nasals, 6.7, 6.9 (7.4-6.4); zygomatic breadth, 14.2, 14.6
(14.9-13.9); mastoidal breadth, 11.3, 11.8 (12.3-10.8); alveolar
length of upper molar series, 6.0, 6.2 (6.5-5.9); depth of
braincase (shortest distance from ventral surface of
basioccipito-basisphenoidal suture to the dorsal surface of the
cranium, and not perpendicular to the long axis of the skull), 7.7,
7.7 (7.9-7.5); width of rostrum, 4.7, 4.8 (5.0-4.6); interorbital
breadth, 3.2, 3.4 (3.6-3.2). Measurements of females, other than
those of the holotype, are not given owing to the lack of
sufficient material. Females, however, do not appear to differ
appreciably in measurements from males.
_Specimens examined_ (in U.S. Nat. Mus., Biol. Surv. Coll., except
as otherwise indicated).--Total, 26, all from Montana, as follows:
_Sanders Co._: Hot-springs Cr., 4. _Lake Co._: end of W arm
Flathead Lake, 5; Ravalli, 8. _Ravalli Co._: Florence, 2; 8 mi. NE
Stevensville, 4000 ft., 1; Corvallis, 4; 6 mi. E Hamilton, 3700
ft., 2(K.U.).