MAMMALS OF THE MEXICAN BOUNDARY. 427 



portion of the hair appears to some extent. The sides are ochraceous 

 buff. Feet and under parts, white. The densely haired tail is sharply 

 bicolored ; clove brown above, white on sides and below. Whiskers 

 mostli^ colorless, but mixed with black. Soles of feet very hairy. 

 The skull measures 29 mm. in total length; basilar length (Hensel), 

 22.3 ; zygomatic breadth 15.2. It belonged to a very aged individual, 

 and is a little longer and relatively much broader than two skulls of 

 Peromyscus martirensis that we collected on the Boundary Line in a 

 pass at the summit of the Coast Range Mountains, which, though fully 

 adult, are not so mature as that of the type of P. truei. The skull of 

 P. martirensis measures: Total length (occipito-nasal), 28.2 mm.; 

 zygomatic breadth, 13.8; basilar length (Hensel), 21.2. 



Comparing these specimens with the type of P. truei, the ears appear 

 to be about the same size. The colors of P. martirensis are very much 

 darker, owing to the blackish annulation of the drab fur of the upper 

 surface. Only a narrow Une between the grayish drab upper parts 

 and the white under parts is ochraceous buff. There is a faint trace 

 of ochraceous on the breast of P. truei, and also on these specimens of 

 P. martirensis. The ears are more darkly colored, but as scantily 

 clothed as those of P. truei. The fur, though fine and soft, is coarser 

 than that of P. truei and considerably shorter, with the tail less hairy. 

 The dilBference in coloration between P. truei and P. martirensis is 

 closely paralleled by typical P. eremicus and P. eremicus fratercvlus 

 of corresponding regions. 



As would be supposed, the specimens from the Mexican Border, sev- 

 eral hundred miles north of the type-locality of Peromyscus martiren- 

 sis, depart somewhat from the typical form and approach the form to 

 the northward which Doctor Allen "^ has named Peromyscus gilherti. It 

 is not, however, exactly iutermediate, but in coloration is paler than 

 either P. martirensis or P. gilherti, and so correspond with the sub- 

 species medius of P. sonoriensis. 



PEROMYSCUS STEPHENSI Mearns. 

 FALH DESERT HOUSE . 



Peromyscus stephensi Mearns, Proo. U. S. Nat. Miis., XIX, 1897, p. 721 (original 

 description). — Miller and Rehn, Proc. Bost. Soc. Nat. Hist., XXX, No. 1, Dec. 

 27, 1901, p. 83 (Syst. Results Study N. Am. Mam. to close of 1900). 



[Peromyscus] stephensi, Elliot, Field Ck)I. Mus., Zool. Ser., II, 1901, p. 136 (Synop. 

 Mam. N. Am.); IV, 1904, p. 190 (Mam. Mid. Am.). 



Type-locality. — Lowest water, on the wagon road, in a canyon, at 

 the eastern base of the Coast Range Mountains, San Diego County, 

 California, near the Mexican Boundary Line. (Type, skin and skull. 

 Cat. No. 61026, U. S. National Museum.) 



a Bull. Am. Mus. Nat. Hist., V, Art. XII, Aug. 18, 1893, pp. 188-190- 



