182 THE MAMMALIA. 



prominent canine teeth which serve the others as 

 weapons. An early Selenodont (crescentic-toothed) 

 animal of this kind for the primeval pair-hoofed 

 group one which, like the Hyopotamus, does not 

 belong distinctly to any special type is the genus 

 Cainotherium, an animal of the most graceful shape ; 

 we have probably a correct picture of its appear- 

 ance in the living dwarf musk-animals (Fig. 30). 

 That Cainotherium and its relatives, e.g. Xipho- 

 don, Xiphodontherium, were Euminants, cannot be 

 doubted from the position and nature of the 

 tranverse ridges of their molars, also from the 

 character of the joints of the jaw upon which 

 depends the peculiar action of the grinders. The 



O -J A Q 



dental formulae is i _ c _ p -, m ~ ., and in most 

 o 1 4 a 



specimens they stand in closed rows in both jaws. 

 Now our present hollow-horned animals have no 

 incisors in the upper jaw, and no canines either in 

 the upper or lower jaw, and, moreover, they occur 

 in the upper jaw only in some species of deer. The 

 diminution of the teeth a very general pheno- 

 menon must, therefore, have taken place gradu- 

 ally in the course of ages. How and when this 

 occurred, Filhol ' has very clearly pointed out with 



1 Compare p. 64, note 2. 



