CONVERGENT EVOLUTION 251 



mammals found in other parts of the world. The so-called 

 marsupial wolf of Tasmania (Thylacinus) closely resembles a 

 typical carnivore in its habits and general structure. Its teeth 

 are adapted for a predaceous life, and the entire skull (Fig. 107, B), 

 with its dentition, bears an extraordinary general resemblance to 

 that of a dog (Fig. 107, A), being distinguishable only by details 

 of structure which would hardly be noticed except by an 



FIG. 107. A. Skull of Dog, side view ; B. Skull of Thylacine, side view. 

 (From photographs.) 



anatomist. These details, however, are quite sufficient to show 

 that there is in reality no close relationship between the two. 

 Thus the dog (Fig. 108, A, AI) has in each upper jaw three 

 incisor teeth (i. 1 i. 3 ), one canine (c.), four premolars (p.m. 1 p.m. 4 ) 

 and two molars (m. 1 m. 2 ) ; and the dentition of the lower jaw is 

 the same except for the presence of a third molar (m. 3 ), which is, 

 however, in a vestigial condition. The thylacine, on the other 

 hand (Fig. 108, B, BI), has four incisors (i. 1 i. 4 ) in the upper and 



