THE TEETH OF MAMMALS 157 



rolled and crushed and the ends of the roll pre- 

 sented for mastication. The different densities 

 of the three tissues produce different degrees of 

 wear, so that the grinding surface is always rough 

 to be more effective for the reduction of vegetable 

 fiber. The enamel being hardest stands highest, 

 and traces the pattern of the surface; the dentin 

 being next in density stands lower, and the ce- 



FlG. 64-A. — Side view of teeth of Antelope. 



mentum being softest is most worn out. The pat- 

 terns of the arrangement of the folds of enamel 

 thus presented are very various throughout the 

 order, but each family have the same type of pat- 

 tern, and this is so constant as to have a distinct 

 diagnostic value for the distinguishing of species, 

 especially in fossil remains. Different groups of 

 the Ungulata are characterized by a distinct pat- 



