Conspecificity of two pocket mice, Perognathus goldmani and P. artus by Eugene Raymond Hall

_Perognathus goldmani_ Osgood and _Perognathus artus_ Osgood from southern Sonora, northern Sinaloa and adjoining parts of Chihuahua and Durango, are two named kinds of the _Perognathus intermedius_ group of pocket mice, of the subgenus _Chaetodipus_. Until now the two kinds have been treated in the literature as two species. In both _goldmani_ and _artus_ the upper parts are Ochraceous-Buff (capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) having a strong admixture of black. The lateral line is Ochraceous-Buff, and the underparts are white. _P. goldmani_ is larger than _P. artus_ (see measurements beyond) and has more inflated tympanic bullae and a relatively narrower (transverse to long axis of skull) interparietal bone.

Specimens from a transect of southeastern Sonora show intergradation between _Perognathus goldmani_ and _P. artus_. From northwest to southeast the specimens are as follows: one mile east of Buena Vista, on Rio Yaqui Reservoir, 1000 feet (2 specimens, K. U.); Alamos, 1200 feet (7, U. S. B. S.); four and a half miles southeast of Alamos, 1000 feet (5, K. U.); nine miles southeast Alamos, 1000 feet (5, K. U.). The specimens (_P. goldmani_) from Rio Yaqui Reservoir are largest. Those from nine miles southeast of Alamos (_P. artus_) are smallest. Those from Alamos proper are _P. goldmani_. Those from four and a half miles southeast of Alamos (80051-80055 K. U. collected by Robert L. Packard and here referred to _goldmani_) include two as large as _goldmani_ from Alamos, one as small as _artus_ from nine miles southeast of Alamos, and two that are intermediate in size. Features other than size, considered geographically, also suggest intergradation.