Page:Descriptions of two new rodents of the genus Phenacomys.djvu/1

 PROCEEDINGS

OF THE

BIOLOGICAL SOCIETY OF WASHINGTON

DESCRIPTIONS OF TWO NEW RODENTS OF THE GENUS PHENACOMYS.

BY A. BRAZIER HOWELL.

In the course of a study of the microtine genus Phenacomys, based largely on specimens in the Biological Survey Collection, U.S. Department of Agriculture, it has been found necessary to recognize two additional races heretofore undescribed. These may be known as follows:

Phenacomys intermedius levis, subsp. nov.

Alberta Phenacomys

Type from Saint Mary’s Lake, Teton County, Montana. Male adult; No. 72,405, U.S. National Museum (Biological Survey Collection); collected by A.H. Howell, May 23, 1895; original No. 13.

Diagnosis.—Smallest race of this genus, being somewhat smaller than P. i. intermedius but indistinguishable from certain skins of the latter in color. The skull of levis is much smaller, with rostrum, which although relatively shorter, is more robust. The bullae are proportionately larger and the incisive foramina smaller.

Measurements.—Average of eight adult topotypes (collectors’ figures); Total length, 138; tail, 34; foot, 17.6. Average of seven adult skulls of topotypes: condylobasilar length, 22.5; nasals, 7.2; interorbital breadth, 3.6; zygomatic breadth, 14; lambdoidal width, 11; incisive foramina, 4.5; maxillary toothrow, 5.8; height, 8.4. Geographic distribution.—The eastern slope of the Rocky Mountains at least from central Alberta south to Teton County, Montana.

Remarks.—This race may be easily told from its neighbors by its small size. The animals from the neighborhood of Smoky River, central Alberta, are not quite typical, but are much closer to levis than to any other form.

This race seems to be confined to the easternmost part of the Rocky Mountain slopes in the range indicated, for it evidently does not penetrate for any distance into British Columbia, and is not found in western nor southern Montana. 23—Proc. Biol. Soc. Wash., Vol. 36, 1923.