Page:Descriptions of two new rodents of the genus Phenacomys.djvu/2

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Proceedings of the Biological Society of Washington

Phenacomys intermedius celsus, subsp. nov.

Sierran Phenacomys

Type from Muir Meadow at 9300 feet, Tuolumne Meadows, Yosemite National Park, California. Male adult; No. 109,103, U.S. National Museum (Biological Survey Collection); collected by J.H. Gaut, August 13, 1901; original No. 250.

Diagnosis.—A race slightly smaller and very much paler than Phenacomys intermedius olympicus, to which it is most closely related. Skull with larger braincase, stouter though no longer rostrum, and practically no indication of interorbital ridging. The incisive foramina are much smaller and the molars very much heavier. The skins are quite comparable with the paler specimens of P. i. intermedius but skulls of typical celsus may be told at a glance by their very much larger size, heavier rostra and larger bullae.

Measurements.—Average of five adults from the Yosemite Park (collectors’ figures): Total length, 148; tail, 39; foot, 18. Average of three adult skulls from the same region: condylobasilar length, 24.1; nasals, 7.8; interorbital breadth, 4; zygomatic breadth, 15.8; lambdoidal width, 11.9; incisive foramina, 4.3; maxillary toothrow, 6.2; height, 9.4.

Geographic distribution.—So far as known, the Sierra Nevada of California from the Yosemite Park north to the vicinity of Lake Tahoe.

Remarks.—This race, although considered closest in relationship to P. i. olympicus is readily distinguishable, by both external and cranial characters. Furthermore, the two races are separated by a quite different animal which ranges into the mountains of southern Oregon and northern California and whose affinities are clearly with P. i. intermedius of the Great Basin and Rocky Mountains.

Individuals from the vicinity of Lake Tahoe are not typical of celsus but are nearer this than to anything else now recognized.