Six specimens (61409-61413, 61415 K. U. collected by J. R. Alcorn), including five adults (permanent fourth premolar of full height and having cusps worn but not so much as to make a lake of dentine), from four miles north of Terrero, Sinaloa, also seem to be intergrades between _Perognathus goldmani_ and _Perognathus artus_. As compared with adults of _P. goldmani_ from 10 miles north-northwest of Los Mochis, Sinaloa, and _P. artus_ from one mile south of Pericos, Sinaloa, the specimens from four miles north of Terrero are almost exactly intermediate in length of hind foot, width of interparietal, and width of tympanic bullae. Intermediacy is shown also in total length of animal (slightly nearer that of _artus_) and length of tympanic bullae (slightly nearer that of _goldmani_). In lack of inflation laterally of the mastoidal bullae the specimens agree with _artus_. In occipitonasal length and mastoidal breadth the specimens from four miles north of Terrero average even larger than _goldmani_ from 10 miles north-northwest of Los Mochis but not so large as specimens of _goldmani_ from the type locality, which is still farther north. The uninflated mastoidal bullae "tip the balance" slightly in favor of _artus_ to which the specimens from four miles north of Terrero are here referred. The degree of inflation of the mastoidal bullae elsewhere varies geographically. For example, the mastoidal bullae of the 25 specimens of _goldmani_ from two and a half miles north of El Fuerte, Sinaloa, are intermediate in size as between those of _goldmani_ and _artus_. The morphological intermediacy of the specimens from four and a half miles southeast of Alamos and of those from four miles north of Terrero, along with the geographic intermediacy of the two localities where the specimens were obtained constitute basis for arranging _artus_ as a subspecies of _goldmani_ that has one page of priority. [Illustration: MAP 1. Geographic distribution of _Perognathus goldmani_. The black dots are known localities of occurrence. 1. _P. g. artus_ 2. _P. g. goldmani_] ~Perognathus goldmani goldmani~ Osgood _Perognathus goldmani_ Osgood, N. Amer. Fauna, 18:54, September 20, 1900, type from Sinaloa, Sinaloa. _Range._--See map 1. _Measurements._--Average of five topotypes (Osgood, _op. cit._:55): total length, 202; tail vertebrae, 112; hind foot, 28; occipitonasal length, 27.7; mastoidal breadth, 14.5; greatest width of interparietal, 7.4.