298 Firrp Museum or Naturat History — Zoézoey, Vor. XI. 
1, Skull of Gray Wolf (Canis); 2, skull of Gray Fox (Urocyon); 3, skull of Red Fox (Vulpes). 
(About % nat. size.) 
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- 
