CLASS MAMMALIA 



407 



The teeth of mammals generally are represented by two sets, a milk 

 dentition and a permanent dentition. The teeth are set in sockets 

 in the jaws and are generally differentiated into several types, known 

 as incisors, canines, and molars. The character of the dentition shows 

 a specialization corresponding to the character of the food and the 



Fig. 277. — Types of mammalian skulls, showing character of dentition. From speci- 

 mens. In each case the anterior part of the skull is shown from the side and one-half of 

 the same part from below, with the lower jaw removed. A, European hedgehog, an 

 insectivore. X %. B, coyote, or prairie wolf, a carnivore. X ^i- C, beaver, a rodent. 



X ^3. D, sheep, an ungulate. X 



manner of securing it. Each tooth consists largely of dentine (Fig. 278), 

 which is bony in character and derived from the dermis. The dentine 

 is covered over the crown with a layer of enamel, which is derived 

 from certain epithelial cells, and around the root by cementum, deposited 

 by the dermis after the dentine has been formed. In the center of the 

 tooth is a -pul-p cavity of soft connective tissue provided with blood vessels 

 and nerves. 



