270 MAMMALIAN DENTITION 



forms of the teeth. We should observe that the change has 

 always been in some definite direction toward final forms which 

 are approximately the same as the latest example of series 

 drawn from other orders. Starting with the insectivorous- 

 omnivorous type the lines of progression are toward the long 

 or short jawed pure Carnivore or in another direction through 

 the omnivorous form, either to one of several varieties of pure 

 herbivorous feeder (Ungulate) or to the highly specialized 

 gnawing type (advanced Rodent). The student will have 

 recognized that the fundamental plan of progressive evolution 

 in teeth is common to all mammalian orders. 



We are studying in this volume the dentition of modern 

 Mammals, not of fossil forms and hence we do not propose 

 to carry out the suggestion put forward in the preceding para- 

 graph, but shall examine existing members of the order Carni- 

 vora in which Ave may observe the self-same facts. Why some 

 genera have retained primitive tooth forms and others, closely 

 related, have not, we are scarcely in position to state. We can 

 only say that external conditions call forth a response on the 

 part of the organism which is always along one of several 

 clearly defined directions. 



Instances cannot be multiplied on account of lack of space: 

 we will give only two examples, one from the Civets, the other 

 from the Raccoons, illustrating progression in form of teeth 

 within a single family. 



Fig. 99 contains photographs of the skulls of four Viverridae ; 

 namely the Rasse, African Civet, Fossa and Binturong. The 

 formula of all is 



I f ', C 7, P 4, M \ (Fossa --), total 40 (34). 

 o 1 4 2 [)' 



Apparent exceptions to this formula are produced in the 

 Fossa since the first premolar of each jaw in this animal is 

 shed in early life, and again in the Binturong in which the man- 

 dibular first premolar is lost in youth. The habits of all these 



