A New Piñon Mouse (Peromyscus truei) from Durango, Mexico

The extensive collection of Mexican mammals made by Mr. J. R. Alcorn for the University of Kansas Museum of Natural History contains fourteen piñon mice from lava rocks eight miles northeast of the city of Durango, Mexico. These mice are all much darker than the piñon mice, Peromyscus truei gentilis , of adjoining areas in Durango and Zacatecas and show a superficial resemblance to the widespread P. t. gratus which occurs 450 miles to the southeast. Morphological differences from P. t. gratus , as well as geographic considerations (see remarks), make desirable the recognition of the lava-dwelling piñon mice from Durango as a distinct subspecies.
All specimens examined of subspecies compared with the series of piñon mice from northeast of Durango are in the University of Kansas Museum of Natural History. Capitalized color names and designators are of Maerz and Paul, A Dictionary of Color, McGraw Hill Book Co., New York, 1930.
I wish to acknowledge generous financial aid from the Kansas University Endowment Association which made possible the field work by Mr. Alcorn in Mexico.
This heretofore unknown subspecies is characterized below and may be known as:
Peromyscus truei erasmus subsp. nov.
Type. —Mus. Nat. Hist., Univ. Kansas, no. 34417, young adult female, skin and skull; from eight miles northeast of Durango, 6200 feet, Durango, Mexico; collected 16 August 1949 by J. R. Alcorn, original number 10255.
Range. —Known only from the type locality.
Diagnosis. —Upper parts dark brownish gray (Smoke Brown, 16 A 2, to Biskra, 16 A 12), darkest between ears; lower sides suffused with dull orange buff (13 H 9 to 12 H 9); dark eye ring and black spot at base of vibrissae conspicuous; ears 95 to 100 per cent as long as hind foot; bullae round, greatly inflated; interparietal large, anterior margin curved or slightly sinuous, not bulging strongly forward laterally; rostrum short; nasals broad; braincase high and full; incisive foramina slightly pointed anteriorly; molars small, as in P. t. gentilis .