Genus Erethizon 
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covering of which is confined to the front surface; incisive 
foramina of moderate size and distinct from one another; 
fibula not articulating with the calcaneum. 
Family ERETHIZONTIDiE 
Somewhat bulky animals with subequal limbs and short 
stumpy tails with portions of the hairy covering modified 
into long sharp spines; skull short and broad, the jugal 
without inferior angle; the anteorbital foramen large; molars 
more or less completely rooted with internal and external 
enamel folds. 
This family is confined to the North American Continent. 
Genus ERETHIZON (Grk. erethizcin, to excite, irritate, in 
allusion to the quills). 
Erethizon F. Cuvier, Mem. du Mus., ix., p. 426 (1822). 
Bulky rodents of considerable size, having part of the hair modified 
FIG. 20. YELLOW-HAIRED PORCU.MNE, Erethizou epixauthvis 
Skull, showing dentition, nearly natural size 
