152 RODENTS OP IOWA 



five behind, all armed with strong, curved claws ; ears short ; p,nte- 

 orbital vacuity very large; crowns of molars with enamel folds 

 and more or less completely rooted ; mammaB four, all pectoral. 



Dental formula^-l. 1/1 ; Pm. 1/1 ; M. 3/3=20. 



A single form possibly occurs in Iowa. 



Canada Porcupine. 

 Erethizon dorsatum dorsatum. p. 126 



Suborder Duplicidentata. 



Two pairs permanent upper incisors, the second very small and 

 placed immediately behind the others; at birth three pairs of in- 

 cisors are present but the outer one on each side is soon lost; 

 enamel of incisors continuous and not confined to anterior faces 

 of teeth; incisive foramina of palate large and usually confluent; 

 bony palate narrow from before backwards; tibia and fibula united 

 and articulating with the calcaneum. 



This suborder is made up of two families, the Leporida?, con- 

 taining the true hares and rabbits, and the Oehotonidae, containing 

 the chief hares. These latter are small animals occurring in the 

 mountainous regions of western North America, arid do not occur 

 in Iowa. 



Family LEPORID. 

 HARES AND RABBITS. 



Hind legs greatly elongated ; tail short, bushy ; soles of feet cov- 

 ered with fur ; eyes large ; upper lip deeply cleft ; cheek pouches 

 wanting but inside of mouth partly furry ; skull flat ; facial sur- 

 face of maxilla perforated ; palate narrow ; rami of mandible flat ; 

 clavicles imperfect. 



Key to the Genera of Leporidae. 



Interparietal not distinct in adult; supraorbital process usually 

 more or less expanded and subtriangular, usually somewhat diver- 

 gent from skull ; hind foot five or more inches Jong Lepus 



Interparietal distinct in adult; supraorbital processes narrower, 

 the posterior notch usually narrower or wanting, owing to union 

 of postorbital process with skull; hind foot about four inches 

 long Sylvilagus 



