30 . ZOOLOGY. 



a tuberculated surface, rough, with conical points, so arranged 

 as to lock into each other. In the frugivorous, living on soft 

 fruits (Fig. 24), these teeth are simply provided with rounded 



Fig. 23. Teeth of an Herbivorous 

 Animal. 



Fig. 24. Teeth of a Fru- 

 givorous Animal. 



tubercles ; in the herbivorous these teeth have a broad, rough 

 surface, resembling a millstone (Fig. 23). 



ftp! 



Fig. 25. Skull of the Narwhal.* 

 Lower surface. 



Fig. 26. Skull of the Narwhal. 



Upper surface. 

 Upper cervical vertebrae. 



* This and the two following figures illustrate the singular fact of the 

 development of only one of the incisives in the upper jaw ; the other remains 

 imbedded in the osseous tissue of the maxilla. The figures also show the re- 

 markable want of symmetry in the cranium of certain of the cetacea. K. K. 



