PEROMYSCUS. 177 



texanus ! medius Mearns, Proc. U. S. Nat. Mus., 1895, p. 446. 



texensis medius Elliot, Syn. N. Am. Mamm., 1901, p. 130. 

 THURBER'S FIELD MOUSE. 



Type locality. San Pedro Martir Mountains, Lower California, 

 Mexico. Altitude, 7,000 feet. 



Geogr. Distr. Region of San Pedro Martir Mountains, Lower 

 California, Mexico, north into southern California to Colorado desert 

 at least. 



Genl. Char, General color pale grayish fulvous lined with black. 



Color. Upper parts grayish fulvous, darkest on dorsal line where 

 it is blackish; sides fulvous; lower sides and under parts and feet 

 white; ears dusky, at base a tuft colored like head; tail blackish 

 above, white below. 



Measurements. Total length, 177; tail vertebrae, 78; hind foot, 

 21 ; ear, 18. Skull: occipito-nasal length, 25.1; Hensel, 99.2; zygo- 

 matic width, 13; interorbital constriction, 4; length of nasals, 9.2; 

 width of braincase above roots of zygomata, 11.5; palatal length, to; 

 length of upper molar series, 4; length of lower molar series, 4. 



a. rnesonielas (Peromyscus}, Osgood, Proc. Biol. Soc. Wash., xvn, 

 1904, p. 57. 



Type locality. Orizaba, State of Vera Cruz, Mexico. 



Genl. Char. Similar to P. thurberi, darker; tail shorter; hind 

 foot larger; pectoral spot present. 



Color. Upper parts Prout's brown; under parts creamy white; 

 pectoral spot fawn; hands and feet white; ankles dusky brownish; 

 tail bicolor; ears dusky, edges whitish. 



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

 23. Skull: greatest length, 26.5; Hensel, 20.2; zygomatic width, 

 13.6; interorbital constriction, 4; interparietal, 8.6 X 2.3; length of 

 nasals, 10.4; palatal length, 3.8; palatal foramina, 5.2 x 2; postpalatal 

 length, 9.1; length of upper molar series, 3.7. 



b. castaneus (Peromyscus}, Osgood, Proc. Biol. Soc. Wash., xvn, 

 1904, p. 58. 



YOHALTUN MOUSE. 



Type locality. Yohaltun, State of Campeche, Mexico. 



Genl. Char. Similar to P. mesomelas, but smaller; no pectoral 

 spot. 



Color. Upper parts between Prout's brown and burnt umber; 

 under parts white; no lateral line; hands and feet white; ankles dusky. 



Measurements. "Total length, average of ten adults, 163 (156- 

 169); tail vertebras, 73 (68-79); nm d foot, 21.5 (20-22). Skull of 

 type: greatest length, 25.3; Hensel, 19; zygomatic breadth, 13; inter- 



