298 Field Museum or Natural History — ZoGlogy, Vol. XI. 



I, Skull of Gray Wolf (Canis); 2, skull of Gray Fox (Urocyon); 3, skull of Red Fox (Vuipes). 



(About K nat. size.j 



KEY TO THE GENERA. 



Group 1. Postorbital process of frontal bone rounded, with end curving down- 

 ward; upper incisors with well-marked lobes or notches on sides; temporal 

 crests joining and extending in a single parietal ridge or sagittal crest (low 

 in the Prairie Wolves or Coyotes, but conspicuously high in the adults of the 

 large Timber Wolves) ; a frontal sinus present. 



Genus CANIS, Wolves, p. 313. 



Group 2. Postorbital process of frontal bone concave, with its anterior outer 

 edge turned slightly upward; some of the upper incisors very slightly lobate 

 or notched or not at all; no frontal sinus present. 



A. Temporal crests widely separated, at least .75 inch apart in adult; upper 

 incisors not notched; long hairs of tail rather coarse, with central ridge of 

 black hairs; posterior angle of under jaw abruptly emarginate below. 



Genus UROCYON, Gray Foxes, p. 300. 



B. Temporal crests much nearer together; some of the upper incisors very 

 slightly notched; hairs on tail long and soft, mixed with soft fur; posterior 

 portion of under jaw not abruptly emarginate below. 



Genus VULPES, Red Foxes, p. 305. 



