264 ZAPUS. ERETHIZON. 



Color. Above "darker than Z. insignis; sides tawny ochraceous; 

 beneath white; amount of white on tail averaging less than in Z. in- 

 signis." 



Measurements. Total length, 220; tail vertebra?, 131; hind foot, 

 29.5. Skull: basilar length, 18.8; zygomatic breadth, 11. 7; mastoid 

 breadth, 10. i; interorbital constriction, 4.7. 



fe. — (ihietorum.. (Zapus')^ Preble, N. Am. Faun., No. 15, i8gg, p. 36. 



Type locality. Peninsula Harbor, north shore of Lake Superior, 

 Ontario. 



Geogr. Distr. Limits of range unknown. 



Genl. Char. Larger than typical Z. insignis. Comparative dif- 

 ferences in skull and that of Z. insignis; molar series longer and 

 heavier; interorbital constriction greater; ventral border of ptery- 

 goids nearly on plane of palate; maxillary process of zygoma shorter; 

 mandible heavier. 



Color. Indistinguishable from Z. insignis. 



Measurements. Total length, 225; tail vertebrae, 160; hind foot, 

 33; ear, 16.6. Skull: basilar length, 19.4; zygomatic breadth, 12.2; 

 mastoid breadth, 10.5; interorbital constriction, 4.3. 



Fam. VIII. Kretliizoiitidae. 



Form stout; long acute spines loosely attached to skin; skull 

 with facial portion short, and the jugal without inferior angle; molars 

 more or less completely rooted. 



Sub. Fam. I. Erethizontinae. 



67. Eretliizon. 



I. i=i; P. '— ; M. i=i = 20. 

 I— I I— i' .-i— 3 



Erethizon. F. Cuv. Mem. du Mus. , 1822, ix, p. 426. Type H. dor- 

 sat us, Linn. 

 Echinoprocta. Gray, Proc. Zool. Soc, 1865, p. 321. 



Four toes on fore feet, five on hind feet, all with strong claws; 

 limbs short, strong, no naked mesial line on upper lip, which is 

 covered with hair and notched above the incisors: tail short, thick, 

 non-prehensile, covered above with stiff hairs and spines, and on the 

 sides and beneath with stiff bristles. 



404. dorsatus. {Hystri.x), Linn. Syst. Nat., 1758, p. 57, and 1766, 

 I, p. 76. 

 pilosus, Richard, (nee Peale), Faun. Bor. Amer. , 1829, 214. 



