THE SKELETON IN MAMMALIA. THE TEETH. 433 



They are however triangular in transverse section, not rect- 

 angular, having two antero-lateral faces covered with enamel 

 and a posterior face without enamel. Their terminations 

 are pointed, not chisel-shaped as in Rodents. The lower in- 

 cisors (fig. 83, i 1) are pectinate or partially divided by vertical 

 fissures, and the grinding teeth are of the rhinocerotic type. 



2 



6 



-h-\A 



1.1 



FIG. 83. SKULL OF Procavia (Dendrohyrax) dorsalisx%. (Camb. Mus.) 



1. nasal. 5. jugal. 



2. parietal. 6. lachrymal foramen. 



3. external auditory meatus. i 1. first incisor. 



4. paroccipital process of the 



exoccipital. 



AMBLYPODA. Two of the best known forms belonging to 

 this extinct group differ much as regards dentition. For while 

 Coryphodon has the regular dental formula, and the canines 

 of both jaws of moderate size, in Uintatherium the dentition 

 is very specialised, there are no upper incisors, and the upper 

 canines form a pair of enormous tusks. The grinding teeth 

 form a continuous series marked by V-shaped ridges and the 



01 33 



dental formula is i ^ c -- pm m total 34. 

 o 1 o o 



PROBOSCIDEA. The incisors are composed entirely of den- 

 tine and have the form of conical tusks projecting greatly 

 R. 28 



