390 MAMMALIA. 



part of the Pliocene period ; and seem to have migrated along 

 the Isthmus of Panama to South America as soon as it emerged 

 at the dawn of Pliocene times. More recently they have even 

 extended their range to Australia, probably through the agency 

 of man. Yet notwithstanding this remarkable distribution 

 over all the continents, they have not undergone any important 

 change in the skeleton since their earliest occurrence in the 



O 



European area. Until the .close of the Miocene period most, if 

 not all, of the canine genera had the distal end of the humerus 

 somewhat expanded, with a bridge of bone completing an 

 entepicondylar foramen. The Pliocene and later Canidae have 

 lost this foramen and the accompanying expansion, while the 

 auconeal fossa above the trochlea is extensively pierced. There 

 is also some reason to believe that digit no. I was functional in 

 both feet in the earlier forms ; while now it is comparatively 

 small or (in the hind foot) even rudimentary. 



FIG. 219. 



Cynodictis longirostris; left half of palate, with molars and premolars, and 

 sockets for the canine and incisors, nat. size. U. Eocene (Phosphorites); 

 Quercy, France. (After Lydekker.) 



Among the remains of true Carnivora in the European 

 Upper Eocene, by far the larger proportion are referable to . the 

 Canidse ; and most of the known specimens belong to the 

 genus Cynodictis, which may not only be an ancestor of Canis, 

 but would serve almost as well for a forerunner of the 

 Mustelidse and Viverridse. The dentition of this genus (fig. 219) 

 closely resembles that of Canis, with four premolars in each 



