FAMILY ERETHIZONTID^ 151 



Family ZAPODID/E. 

 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 ; anteorbital 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^l. 1/1; Pm. 1/Q; M. 3/3=18. 



Key to Subspecies of Zapus. 



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



Hudson Bay Jumping Mouse. 

 Zapus hudsonius liudsonius. p. 122 



Color above paler; total length, 8.75 inches. 



Prairie Jumping Mouse. 

 Zapus liudsonius campestris. p. 124 



Family ERETHIZONTID/E. 



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 ERETHIZONTIN/E. 



Genus Erethizon P. Cuvier. 



Body covered with hairs intermingled with loosel}- attached 

 quills or spines on back and sides; tail sliort, 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 



