246 FIELD MUSEUM or NATURAL HISTORY ZOOLOGY, VOL. XL 



Family ZAPODID^. Jumping Mice. 



The Zapodida* or Jumping Mice, are a semi-boreal family com- 

 prising two well marked subfamilies Zapodina and Sminthince; the 

 latter, however, is not represented in North America. The subfamily 

 Zapodince contains three genera, two of which are North American and 

 which include about 20 species and subspecies, but so far only a single 

 species, the Hudson Bay Jumping Mouse, 

 Zapus hudsonius, has been taken within our 

 limits. It is probable, however, that the 

 Woodland Jumping Mouse, Napaozapus in- 

 signis, occurs in northern Wisconsin, as it has 

 been taken in the Michigan peninsular. The 

 two genera may be briefly characterized as 

 follows : 



A small upper premolar present; tail not 

 tipped with white; teeth 18. Genus Zapus. 



Upper premolar absent; tail tipped with 

 white; teeth 16. Genus Napaozapus. 



Zapus. 

 (Much enlarged.) 



Napaozapus. 

 (Much enlarged.) 



Subfamily ZAPODIN^E. 

 Genus ZAPUS Coues. 



Zapus Coues, Bull. U. S. Geol. Surv. Terr., 2nd ser., I, 1875, p. 253. 



Type Dipus hudsonius Zimmermann. 



Tail very long and slender; hind legs greatly elongated ; antorbital 

 foramen large and oval; upper premolar present but small; crowns of 

 molars with enamel much folded ; upper incisors sulcate (grooved) and 

 brownish orange in color; hind foot with 5 toes, each with separate 

 metatarsal; fore foot with 4 functional toes with perfect claws and a 

 rudimentary thumb with a flat nail; pelage rather coarse; internal 

 cheek pouches present but small. 



Dental formula: I. 



i-i 



, C. , Pm. , M. 



o-o 



o-o 



3-3 



= 18. 



* For reasons for recognizing the family Zapodidce as distinct from Dipodidce, 

 see Lyon, Proc. U. S. Nat. Mus., XXIII, 1901, p. 659. 



