394 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Measurements of 6 specimens of Peromyscus sonoriensis rujinv^. 



o In American Museum of Natural History, New York. 



PEROMYSCUS SONORIENSIS DESERTICOLA (Mearns). 

 WESTERN DESERT PLAINS MOUSE. 



Hesperomys leucopus deserlicolus Mearns, Bull. Am. Mus. Nat. Hist., II, Art. XX, Feb. 



21, 1890, pp. 285-287 (original description). 

 Sitomys insolatus Rhoads, Proc. Acad. Nat. Sci. Phila., 1894, pp. 256-257 (type from 



Oro Grande, Mohave Desert, Kern County, southern California). 

 P\erom.yscus] t[exanus]desenicolus, Mearns, Proc. U. S. Nat. Mus , XVUI, 1896, p. 446. 

 [Peromyscus amencanus] deserlicolus, Elliot, Field Col. Mus., Zool. Ser., 11, 1901, 



p. 125 (Synop. Mam. N. Am.). 

 Peromyscus texanus deserticola, Miller and Rehn, Proc. Bost. Soc. N.H.,XXX,No. 1, 



Dec, 27, 1901, p. 85 (Syst. Results Study N. Am. Mam. to close of 1900). 

 [Peromyscus texensis] deserticola, Elliot, Field Col. Mus , Zool. Ser., IV, 1904, 



p 18 (Mam. Mid. Am.). 



Type-locality. — Mojave Desert, California. (Type, skin and skull, 

 in the American Museum of Natural History.) 



Geographical rar^ge. — Lower Sonoran Zone of the Western Desert 

 Tract. Basins of the lower Gila and Colorado rivers and head of the 

 Gulf of California, west of the Coast Range of California. 



Fig. 73.— Peromyscus sonoriensis deserticola. Anterior upper molar of three individ- 

 uals, SHOWING changes IN THE FORM OF THE ENAMEL PATTERNS DUE TO "WEAR. 



In 1890 I described the Western Desert form of Peromyscus sono- 

 riensis as a subspecies. Four years later it w^as redescribed by Mr. 

 S. N. Rhoads, from a topotype, as a species — Sitomys insolatus — and 

 the subgenei-ic name of Trinodontomys proposed for it, on account of 

 "the trefoil character of the first upper molar." Mr. Rhoads has 

 very kindly sent me the type of his Sitomys ( Trinodontomys) insolatus 

 for examination, and it proves to be exactly like the type of my Hes- 

 peromys leucopus deserticolus, which came from the same region, and 



