o8 Osgood — Thirty Keiv Mice of the Genus Peroinyscus. 



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. inearvsi, but with braincase averaging 

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

 corresponding. 



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

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

 zygomatic width, 13.6 ; interorbital constriction, 4 ; interparietal, 8.6 x 2. o; 

 nasals, 10.4 ; bony palate, o.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. meanm, with P. texaviis 

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

 I'otosi, are quite evidently intermediate, and a .series from Metlaltoyuca, 

 Puebla, while distinctly referable to mesomelas, shows some tendencies 

 toward mearnsl. P. me.somelas is also related to P. affinis, which is a much 

 paler form and not apt to be confused with it. ]>ike mearii.'<l and (i[fiiii.^, 

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

 most other Mexican species. 



Peromyscus texanus castaneus subsp. nov. 



I'l^pe 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. (ioldman. 



Uiaracters. — 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 upjier ])arts between 

 Front's brown and burnt umber, clearer (ju sides, darker on back ; ground 

 color rich dark fawn ; no 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 admixture and only a nari'ow line on back somewhat 

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

 grayer. 



Sknll. — Rather small and light; braincase relatively narrow; nasals 

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

 mesomelas. 



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

 169); tail vertebra?, 73 (68-79); hind foot, 21.5 (20-22). Sknll of type: 

 (ireatest length, 25.3; l)asilar length of Hensel, 19; zygomatic width, 

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

 palate, 4 ; palatine slits, 4.2 x 1.9 ; diastema, 6.2 ; i)ostpalatal length, 9.5 ; 

 upper molar series, 3.5. 



