THE TEETH OF MAMMALS 143 



The third (and fourth, when present) are true 

 sectorial teeth (Fig. 53), and have the tubercles 

 developed still further and divided into two 

 blades, with or without notches, and the other 

 tubercles are round and blunt for crushing. The 

 principal blade is more or less deeply cleft in dif- 

 ferent species, with the prominences variously 

 modified. The principal sectorial blade below is 



Fig. 52. — Teeth of Mountain Lion. Front view. 



on the first true molar, which plays upon the in- 

 side and a little posterior of the body of the blade 

 of the second or third upper premolar. There is 

 usually no true molar above, — usually one below, 

 — or there may be a small tuberculate molar in 

 some species which are less carnivorous. The 

 lower premolars are more tuberculate, and play 

 against the inside of the tubercles or blades of the 



