76 Osgood Thirty New Mice of the Genus Peromyscus. 



Skull. Practically as in eremicus 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 eremicm 

 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 anthonyi from southern Sonora occasionally 

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

 sembles phteurus. This is probably an accidental parallelism, as is also 

 shown by some specimens of fraterculus which are strikingly likeowtfionyi, 

 although there is even greater isolation in this case. 



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

 follows: Coahuila, Sabinas 2, Saltillo 2; San Luis Potosi, Ahualulco, 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 sooty 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 7 . 



Skull. Slightly smaller and more elongate than in P. musculus and 

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

 and bony palate correspondingly shorter; interorbital space narrower. 



Measurements. 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 constriction, 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. fffff , 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. 



