MAMMALS OF THE MEXICAN BOUNDARY. 247 



Capt. C. L. Jenks, of San Bernardino, California, would be able to 

 get sheep for my collection from that region " at any time." 



Order GLIRES. 



RODENTS. 



Mamiiials with the incisor teeth | or | in number, chisel shaped, 

 adapted for gnawing; no canine teeth, a toothless space in the place 

 of canines ; molar teeth adapted for grinding ; cerebrum small, little 

 convoluted; intestinal canal elongate; ears and eyes usually well 

 developed. Food chiefly vegetable. {Jordan.) 



Suborder SIMPLICIDENTATA. 



Only one pair of upper incisors, having their enamel confined to 

 their front surfaces. Incisive foramina moderate and distinct; fib- 

 ula not articulating with the calcaneum. Testes abdominal, and 

 descending periodically only into a temporary sessile scrotum. 

 ' {Flower and Lydekker.) 



Family SCIUEID^. 



SaUIRRELS ANSHARKOTS. 



Arboreal or terrestrial forms, with cylindrical hairy tails, without 

 scales, and with twelve or thirteen pairs of ribs. Skull with distinct 

 postorbital processes; infraorbital opening small; palate broad; p\ 

 or \; first upper premolar very small or deciduous; molars rooted, 

 tubercular. {Flower and Lydekker.) 



KEY TO THE SCIUIilDiE Or THE MEXICAN BODNDAKY LINE." 



a. Without cheek pouches Sciurua (p. 248). 



00. With inljenial clieeli pouches. 

 B. Nail of pollex rudimentary. 



c. Bacli grizzled, mottled, or narrowly striped Citellus (p. 326). 



cc. Back hroadly striped. 



d. Head and neck with a mantle of rich golden color. 



GallospermopMlus (p. 309). 

 dd. Head and neck plainly colored like the back. 



AmmospermopMlus (p. 297). 

 66. Nail of pollex well developed. 



e. Upper surface plain ; body heavy and thickset ; ears rudimentary ; 



cheek pouches small Gynomys (p. 339). 



ee. Upper surface longitudinally striped ; size small ; form slender ; 

 ears long and pointed ; cheek-pouches large ; premolars f . 



Eutamias (p. 283). 



" The genus Soiuropterus, which taxinomlcally stands as the highest of the 

 Sciuridse, appears not to be represented along the Mexican line, though I have 

 heard rumors of the existence of flying-squirrels in the Mogollon Mountains 

 of central Arizona and in the Laguna and Cuyamaca Mountains of the Coast 

 Range in California. I see no reason why there should not be some of them 

 along the Rio Grande of Texas. Flying-squirrels are of common occurrence in 

 Florida and Louisiana. Mr. Samuel N. Rhoads has recently described Sciu- 

 ropterus alpinus oalifornicus from the San Bernardino Mountains. 



