44 FIELD MUSEUM or NATURAL HISTORY ZOOLOGY, VOL. XL 



a2. Tail not thickly haired; cheeks with large external pouch open- 

 ing outside of mouth; front of incisors 

 deeply grooved; claws on fore feet very 

 long. 



Family GEOMYID^. 

 Pocket Gophers, p. 239. 



B. Not more than 3 well developed grinding teeth on si'de of jaw; tail 



closely haired, or in some species nearly or quite naked, 

 bi. Hind feet ordinary, not greatly elongated. 



Family MURID^. Rats and Mice, p. 171. 



02. Hind feet much elongated; tail very long; size small (in one 

 species a very small premolar is present in 

 addition to the three well developed molars). 



Family ZAPODID^E. Jumping Mice, p. 246. 



SECTION 2. Upper front teeth (incisors) 4; two large incisors and 

 two very small ones directly behind them; 

 ears and hind legs noticeably long. 



Family LEPORID^E. Hares and Rabbits, p. 259. 



