384 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



s. Tail very hairy; color above reddisli brown, coarsely mixed with drab and 



black ; size large Peromyscus sonoriensis dementis (p. 400). 



ss. Tail moderately hairy; color above, yellowish brown, finely mixed with 

 drab and black ; size smaller. 

 i. Color dusky yellowish drab; tail vertebrse, 70 mm. 



Peromyscus sonorien^s (p. 384;. 

 it. Color wood brown, finely mixed with black; tail vertebrse 80 mm. 



Peromyscus sonoriensis medius (p. 398). 



nn. Soles of feet moderately hairy, with the metatarsal tubercles of normal size; 



pelage normal, not like that of Onychomys; tail slender, with a broad dorsal 



stripe. 



u. Pelage short; tail almost as long as head and body, nearly naked, and not 



sharply bicolor Peromyscus meamsii (p. 403). 



uu. Pelage longer; tail much shorter than head and body, hairy and sharply 

 bicolor, 

 V. Similar in proportions to Peromyscus leucopus; skull- narrow, slender and 

 lightly built, measuring less than 27 mm. in length. 



Peromyscus texanus (p. 404). 

 w. Much stouter than Peromyscus lencopus; skulj stoutly built, measuring more 

 than 27 mm. in length. - 

 w. Coloration pallid; skull squarish; intermediate subsidiary cusp of m' obso- 

 lete Peromyscus tomillo (p. 408). 



WW. Coloration darker; skull with malar arches bowed outward; interme- 

 diate subsidiary cusp of m' present Peromyscus arizonse (p. 410). 



Subgenns TRINODONTOMYS Bhoads (1894). 



PLAINS MICE. 



Trinodontomys Rhoads, Proc. Acad. Nat. Sci. Philadelphia, 1894, pp. 256, 257. — 

 Miller and Rehn, Proc. Host. Soc. Nat. Hist., XXX, No. 1, Dec. 27, 1901, 

 p. 76, footnote (Syst. Results Study N. Am. Mam. to close of 1900). 



Type. — Sitomys insolatus Rhoads { = Peromyscus sonoriensis deserti- 

 cola Mearns) from Oro Grande, Mohave Desert, Kern County, south- 

 ern California. 



Characters. — Pelage very full and soft; tail thick, hairy, sharply 

 bicolor, with a narrow dark stripe on its upper side; hind feet with 

 the tw<^ posterior tubercles small, the soles densely furred to the 

 tubercles; cheek pockets not developed as food pouches; lower jaw 

 with condyloid process shortened, with a deep notch between condy- 

 loid and angular processes, and coronoid lengthened and slightly 

 hooked^ premaxillaries narrow and laterally compressed; teeth rela- 

 tively broader than in the subgenus Peromyscus, with the tooth-rows 

 more divergent anteriorly. 



PEROMYSCUS SONORIENSIS (Le Conte). 

 SOKOBA PLAINS MOUSE. 



Hesperomys sonoriensis Le Conte, Proc. Acad. Nat. Sci. Phila., VI, No. XT, Oct. ,1853, 

 p. 413 (Santa Cruz, Sonora, Mexico; original description). — Baird, Mam. N. 

 Am., 1857, p. 474 fin part); Rep. Mex. Bound. Surv., II, Pt. 2, Mam., 1859, 

 p. 43 (in part). 



Hesperomys (Vesperimus) teucopus sonoriensis, Coues, Proc. Acad. Nat. Sci. Phila. 

 1874, p. 179 (in small part); Monogr. N. Am, Rodentia, 1877, p. 79 (Sonoran ref- 

 erences only). 



