384 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



s. Tail very hairy; color above reddish 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. 

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



Peromyscus sonoriensis (p. 384^. 

 //. Color wood brown, finely mixed with black; tail vertebrae 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 tiian head and body, hairy and sharply 

 bicolor. 

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

 lightly l)uilt, measuring less than 27 mm. in length. 



Peromyscus texanus (p. 404). 

 w. Much stouter than Peromyscus leucopus; skull 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 anzonse (p. 410). 



Subgenus TRINODONTOMYS Rhoads (1894). 



PLAINS MICE. 



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

 Miller and Reiin, Proc. Bost. See. Nat. Hi.st., XXX, No. 1, Dec. 27, 1901, 

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



Type. — Sitotnij.<i insolatus Rhoads { = Peromyscus sonoriensis deserti- 

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

 ern Caliiornia. 



(liaracters. — Pelage very ftdl antl soft; tail thick, hairy, sharply 

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

 the two 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 lengtliened and slightly 

 hooked; premaxillaries narrow and laterally compressed ; teeth rela- 

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

 more divergent anteriorly. 



PEROMYSCUS SONORIENSIS ( Le Conte). 

 SONORA PLAINS MOUSE. 



Hesperomys sonoriensis Le Conte, Proc. Acad. i\at. Sci. Phila., VI, No. XI, 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) leucopus sonoriensis, Coues, Proc. Acad. Nat. Sci. Phila. 

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

 erences only). 



