74 COMPARATIVE DENTAL ANATOMY 



the cusps named. The lower first deciduous 

 molar shows the gradual reduction in size of the 

 paraconid better than any other tooth of man. 



In the lower first permanent molar of man, the 

 paraconid is absent and the talonid carries three 

 cusps, — the hypoconid, the hypoconulid and the 

 entoconid. The hypoconid is the buccal cusp and 

 falls in the center of the talon of the upper molar 



FiG. 22. — Diagram to show the paraconid of the lower first deciduous 

 molar in the relation of the talonid and trigon of the upper molar. 



1. Protoconid. a. Protocone. 



2. Paraconid. b. Paracone. 



3. Metaconid. c. Metacone. 



4. Hypoconid. d. Hypocone. 



5. Hypoconulid. 



(Fig. 23). In the four-cusp molar of man, as 

 seen in the lower second molar, there is some 

 question as to which cusp is lost or fails to de- 

 velop. These forms are further complicated in 

 some of the mammals, especially in the herbivora ; 

 however, the history of the molar cusps can be 

 traced with considerable accuracy through the 

 various steps of their evolution from the early 

 geological times to the present day. 



