58 Osgood Thirty New Mice of the Genus Peromyscus. 



brownish ; tail bicolor. Immature : Similar in general to adult, but more 

 sooty; sides dark mouse gray, tinged with fawn and bordered by a nar 

 row fawn-colored lateral line; a broad stripe in median dorsal region in 

 tense black ; ankles sooty ; tail indistinctly bicolor. 



Skull. Similar to that of P. t. mearnsi, but with braincase averaging 

 slightly larger and wider ; nasals rather long and palatine slits usually 

 corresponding. 



Measurements. Type: Total length, 169; tail vertebrae, 76; hind foot, 

 23. Skull of type : Greatest length, 26.5 ; basilar length of Hensel, 20.2 ; 

 zygornatic width, 13.6 ; interorbital constriction, 4 ; interparietal, 8.6 x 2.3 ; 

 nasals, 10.4 ; bony palate, 3.8 ; palatine slits, 5.2 x 2 ; diastema, 6.9 ; post- 

 palatal length, 9.1 ; upper molar series, 3.7. 



Remarks. Although this form is very well characterized, there seems 

 to be no doubt that it is connected, through P. t. mearnsi, with P. texanus 

 and others of the same group. Specimens from Rio Verde, San Luis 

 Potosi, are quite evidently intermediate, and a series from Metlaltoyuca, 

 Puebla, while distinctly referable to mesomelas, shows some tendencies 

 toward mearnsi. P. mesomelas is also related to P. ajfinis, which is a much 

 paler form and not apt to be confused with it. Like mearnsi and affinis, 

 it has short and relatively harsh pelage somewhat different from that of 

 most other Mexican species. 



Peromyscus texanus castaneus subsp. nov. 



Type from vicinity of Yohaltun, Campeche, Peninsula of Yucatan, 

 Mexico. Adult male, No. 107,980, U. S. National Museum, Biological Sur 

 vey Collection, December 19, 1900, E. W. Nelson and E. A. Goldman. 



Characters. Similar to P. t. mesomelas, but smaller and more ferruginous 

 colored; under parts without pectoral spot; adolescents without black 

 dorsal stripe ; skull and teeth small. 



Color. Type, in fresh pelage: General color of upper parts between 

 Prout's brown and burnt umber, clearer on sides, darker on back ; ground 

 color rich dark fawn ; ho definite lateral line; under parts pure white; 

 feet white ankles brownish. Topotype No. 107,982, in slightly worn 

 pelage: Sides and upper parts nearly uniform cinnamon rufous with 

 scarcely any dusky ad mixture and only a narrow line on back somewhat 

 deeper colored than rest of upper parts. Immature: As in adult but 

 grayer. 



Skull. Rather small and light; braincase relatively narrow; nasals 

 and palatine slits short; molar teeth small; otherwise similar to P. t. 

 mesomelas. 



Measurements. Average of 10 adult topotypes : Total length, 163 (156- 

 169) ; tail vertebrae, 73 (68-79) ; hind foot, 21.5 (20-22). Skull of type: 

 Greatest length, 25.3; basMar length of Hensel, 19; zygomatic width, 

 13; interorbital constriction, 4; interparietal, 8x2.3; nasals, 9.3; bony 

 palate, 4 ; palatine slits, 4.2 x 1.9 ; diastema, 6.2 ; postpalatal length, 9.5 ; 

 upper molar series, 3.5. 



