FAMILY KRETHIZONTID^E 151 



Family ZAPODIDJE. 

 JUMPING MICE. 



Body enlarged posteriorly; hind legs and tail much, elongated, 

 the latter greatly exceeding the trunk in length, very slender and 

 scantily haired; fore legs short; upper incisors compressed, and 

 sulcate; molars rooted; ante-orbital foramen large, with an addi- 

 tional notch or foramen at its lower portion. 



Subfamily ZAPODIN/E. 



Genus Zapus Coues. 



Internal cheek pouches present, small; first digit of fore foot 

 rudimentary, nail flat and blunt; hind foot with five toes, each 

 with separate metatarsal ; anteorbital foramen large, obliquely oval ; 

 upper incisors short, stout, grooved ; orange brown in color ; upper 

 premolar present, small; crowns of molars with complex enamel 

 folds; pelage coarse. 



Dental formula^-I. 1/1; Pm. 1/0; M. 3/318. 

 Key to Subspecies of Zapus. 



Color above tawny to yellowish brown ; total length, 8.00 inches. 



Hudson Bay Jumping Mouse. 

 Zapus hudsonius hudsonius. p. 122 



Color above paler; total length, 8.75 inches. 



Prairie Jumping Mouse. 

 Zapus hudsonius campestris. p. 124 



Family ERETHIZONTIME. 

 AMERICAN PORCUPINES. 



Form short, stout; body more or less covered with sharp, stiff 

 quills which are loosely attached to the skin; molars more or less 

 completely rooted ; facial portion of skull short, the jugal lacking 

 the inferior angle. 



Subfamily ERETHIZONTIWE. 



Genus Erethizon P. Cuvier. 



Body covered with hairs intermingled with loosely attached 

 quills or spines on back and sides ; tail short, thick, non-prehensile, 

 covered above with stiff hairs and spines, below and on sides 

 with stiff bristles; limbs short, strong; four toes in front and 



