MAMMALS OF THE MEXICAN BOUNDARY. 247 



('apt. C. L. Jenks, of San Bernardino, California, would be aide to 

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



Order GLIRES. 



RODENTS. 



Mammals with the incisor teeth }, or H 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 eye- usually well 

 developed. Food chiefly vegetable. (Jordan.) 



Suborder SIMPLICIDENTAT A. 



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

 their front surfaces. Incisive foramina moderate and distind : fib- 

 ula not articulating with the calcaneum. Testes abdominal, and 

 descending periodically only into a temporary sessile scrotum. 

 I Flowt r 1 1 ad Lydekki r. ) 



Family SCIURID^. 



SdUIRRELS AND MARMOTS. 



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 tipper premolar very small or deciduous; molars rooted, 

 tubercular. (Flower <ni<1 Lydekker.) 



KEY Tii THE SCIIKID.E OF THE MEXICAN BOCNDABY LINE." 



(/. Without cheek pouches Sciurus (p. 248). 



an. With internal cheek pouches. 

 b. Nail of pollex rudimentary. 



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



cc Back broadly striped. 



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



Gallospermophilus (p. 309). 

 thl. Head and neck plainly colored like the hack. 



Ammospermophilus (p. li'.'Tt. 

 ///». Nail df pnllex well developed. 



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



cheek pouches small Cynomys (p. 339). 



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

 ears long and pointed; cheek-pouches large: premolars ,. 



Eutamias i p. 283 ' . 



« The genns Sciuropterus, which taxinomically stands as the highesl of the 

 Sciurida?, appears not to he represented along the Mexican line, though I have 

 heard rumors of the existence of living-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 he some of them 

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

 Florida and Louisiana. Mr. Samuel X. Rhoads has recently described Sciur 

 ropterus alpinus californicus from the San Bernardino Mountains. 



