76 Osgood — Thirty New Mice of the Genns Peromyscus. 



Skull. — Practically as in ercmicna and anthonyi. 



Measurements. — Average of 9 adults : Total length, 189 (176-195); tail 

 vertebrae, 98 (92-103); hind foot, 21. 



Remarks. — This form is the southernmost representative of the eremicn.'' 

 group. Its range is practically continuous with that of eremicus, which 

 extends from west Texas down through Chihuahua, but it is cut off by 

 mountain ranges from anthonyi, which, curiously, it most closely resem- 

 bles. The extreme form of avtlumyi from southern Sonora occasionally 

 has the distal third of tlie tail black all around, and thus very much re- 

 sembles ^/(c'«»r».s. This is i>robably an accidental parallelism, as is also 

 shown by some specimens of fraiercidus which are strikingly like a»//(on?/i, 

 although there is even greater isolation in this case. 



Specimens examined. — Total number, 27, from localities in Mexico, as 

 follows: Coahviln, 8abinas 2, Saltillo 2; San Luis PotosI, Ahualuico, 2, 

 Hacienda la Parada, 7, Jesus Maria, 7; Nuevo Leon, Doctor Arroyo, 5; 

 Zacatecas, Canitas, 2. 



Subgenus Baiomys True. 



Peromyscus musculus nigrescens subsp. nov. 



Type from Valley of Comitan, Chiapas, Mexico. Adult female, No. 

 76,827, U. S. National Museum, Biological Survey Collection, December 

 9, 1895, E. W. Nelson and E. A. Goldman. 



Characters. — Similar to P. musculus and P. m. brunneus, but darker and 

 more sooty ; skull slightly characterized. 



Color. — Upper parts mixed vandyke brown and sooty blackish, slightly 

 more sootv on middle of back ; under parts cream buff, to roots of hairs 

 in middle of belly, on tips only at sides; tail dusky above, paler below. 



Skall. — Slightly smaller and more elongate than in P. musculus and 

 P. III. brunneus; braincase narrower ; rostrum longer ; palatine slits longer 

 and bony palate conespondingly shorter; interorbital space narrower. 



Meusureiiu'iits. — Average of 10 adult topotypes: Total length, 115.5 

 (113-120); tail vertebrae, 43 (40-45); hind foot, 15(14.5-16). Skull of 

 type: Greatest length, 20.1; basilar length of Hensel, 15.2; zygomatic 

 width, 10.5; interorbital constiiction, 3.4; nasals, 8; interparietal, 6.4 

 x2. 1 ; palatine slits, 4.3; bony palate, 2.8 ; upper molar series, 3.2. 



Remarks. — This very dark colored mouse is represented by large num- 

 bers of specimens from southern Oaxaca, Chiapas, and parts of Guatemala- 



Peromyscus allex sp. nov. 



Type from Colima, Colima, Mexico. Adult female. No. f|||f, U. S. 

 National Museum, Biological Survey Collection, March 7, 1892, E. W. 

 Nelson. 



Characters. — Color as in P. musculus; size decidedly smaller; skull 

 small, light, and slender. 



Color. — -Exactly as in P. musculus. 



