174 CALIFORNIA MAMMALiS. 



Family Zapodidae. Jumping Mice. 



Skull of moderate size and thickness; occipetal region de- 

 pressed ; audita! bullae transverse, rather small ; anteorbital fora- 

 men very large, oval, supplemented on the lower inner side by a 

 small foramen, which transmits the second division of the fifth 

 nerve; zygomatic arch depressed, the molar part slender, except 

 anteriorly, where it widens and extends up on the maxillary 

 to meet the lachrymal ; upper incisors compressed, deeply grooved 

 in front, orange colored ; upper premolars present in one genus, 

 absent in another; lower molars absent; molars rooted; enamel 

 folds of grinding surface of molars complex; coronoid process of 

 lower jaw high, slender, curved ; angular process wide, twisted al- 

 most horizontal ; cervical vertebrae not anchylosed ; fore legs about 

 half as long as hind legs; inner toe of front foot rudimentary; 

 hind foot with five metatarsal bones and five toes, the inner toe 

 short but functional ; soles naked ; tail slender, tapering, much 

 longer than head and body ; cheeks with internal pouches. 



This small family is composed of two or three genera and 

 about twenty species and subspecies. These inhabit the wooded 

 parts of British America, northeastern Asia, Alaska and the north- 

 ern parts of the United States, reaching some of the higher south- 

 western mountains. 



Progress when hurried is by long leaps, sometimes seven or 

 eight feet, but these long leaps soon tire the animal and the leaps 

 shorten to a yard or less and the animal hides in the nearest cover. 

 The long tail is a great help in making these long le'aps and an 

 aid in going in a straight line. Jumping-Mice do not make run- 

 ways as many of the small animals are in the habit of dbling. The 

 food is vegetable, mostly seeds. 



Hiberation occurs regularly in the greater part of the range 

 of the family, but it is probably incomplete in the southern edge 

 of their range. The animals become very fat, and the fall pelage 

 is usually assumed before hibernation begins, which is when the 

 first hard frosts occur. 



Most species inhabit grassy valleys bordered by open forests 



