52 MAMMALIAN DENTITION 



molars presents an outer and an inner cusp connected by a well 

 developed slightly concave ridge dividing the crown into a 

 posterior half which engages the corresponding maxillary tooth 

 and an anterior half which occludes with the maxillary tooth 

 next in front. The larger outer cusp fits between and internal 

 to the corresponding cusps on the two upper teeth with which 

 the lower molar occludes. In addition to the main cusps and 

 ridge each molar presents a number of small cusps on both 

 anterior and posterior margins. The crown of each maxillary 

 molar exhibits two lateral cusps of which the anterior is the 

 larger and three medial cusps decreasing in size from before 

 backwards. Some smaller cusps lie along the posterior margin. 

 From the prominent anterior lateral cusp a transverse ridge 

 connecting with a cusp on the medial aspect divides the crown 

 into two parts which occlude with the lower teeth as previously 

 indicated. It is to be observed further that the elevation of 

 the maxillary molar croAvn was probably greatest in the mid- 

 dle of the series so that from front to back of the jaw the 

 molars, as in many mammalian forms, exhibited a convex curve. 



Although at one time thought to be of herbivorous habit it 

 is now believed that Diademodon was a carrion feeder: its den- 

 tition seems to indicate a degenerate carnivorous type. The 

 temporal muscles must have been enlarged as in Carnivores 

 and the molars though worn show no such great attrition as 

 might be expected to result from a vegetable diet. But the 

 crowns are flat-topped, the cusps not very well marked and 

 the last molar smaller than the preceding tooth, all features 

 indicating departure from the primitive type. 



The features of the Cynodont dentition have been dwelt 

 upon in some detail since they show so many striking analogies 

 to the dentition of mammals and seem to illustrate a tendency 

 shared in common with the Mammalia and other mammal-like 

 creatures to develop along certain general lines. This inherent 

 tendency on the part of teeth in phylogeny to respond in some- 

 what similar fashion to similar environmental conditions will 

 frequently engage our attention in the succeeding parts of this 



