178 CALIFORNIA MAMMALS. 



Family ErethizontidSB American Porcupines. 



Skull short, rug-ged, thick and strong; incisors large, prom- 

 inent, not grooved in front ; molars rooted and with complicated 

 enamel folds ; anteorbital foramen large, oval ; angular process of 

 low^er jaw joining outside of root of lower incisor; coronoid pro- 

 cess small and low ; tibia and fibula distinct ; tail prehensile in some 

 genera, short and thick in others ; toes variable in number with 

 genera; soles tuberculate; pelage containing spines; upper lip not 

 cleft ; mammae four. 



The family contains about half a dozen genera and perhaps 

 thirty species. But one genus and two^ species with several sub- 

 species occur in North America. The food is vegetable, consist- 

 ing chiefly of the fruits, twigs, leaves and bark of trees, shrubs 

 and plants. Porcupines are plantigrade, principally nocturnal and 

 more or less arboreal. 



Genus Erethizon Cuvier. (To irritate.) 



Four toes on front feet, five on hind feet, all armed with 

 long, curved, compressed claws; tail rather short, very thick, not 

 prehensile, covered above with stiff hairs and spines, and beneath 

 with bristles; pelage below short and soft, above very long and 

 mixed with sharp spines ; spines hollow through the greater part 

 of their length, small at base where they are loosely inserted in the 

 skin, points sharp and' over certain areas covered with minute flat 

 scales pointing backward, thus acting as barbs. 



Dental formula, i, i — i ; C, o — o; P, i — i ; M, 3 — 3X2=20. 



Erethizon epixanthus Brandt. (Outside — yellow.) 



WESTERN PORCUPINE. 



General effect yellowish gray, blackening on the rump, up- 

 per side of tail, face and feet ; spines one tO' twO' inches long, very 

 numerous, large creamy white with black tips ; hairs sparse, four 

 to six inches long, yellowish on the sides and on upper part of 

 head and neck, whitish at base on the back with yellowish tip and 

 black subterminal zone; face, fore legs and under parts blackish, 

 free from spines; ears small. 



