GENERAL CHARACTERISTICS. 



133 



living and fossil carnivores, we are led to the 

 conclusion that since the beginning of the 

 Tertiary epoch two series have been going 

 on developing, two series originally repre- 

 sented by two families now extinct. Of these 

 one, the Arctocyonida, were more omnivorous, 

 while theother,the Hyeenodontida, approached 

 the carnivorous marsupials in the form of their 

 sharp cutting molars. The genera belonging 

 to both of these families have all 44 teeth, 

 and in the Hysenodontida there were at least 

 5 premolars, the two last of which had the 

 form of carnassial teeth. Throughout the 

 whole series of the Carnivora the carnassial 

 tooth of the upper jaw appears to have 

 belonged both to the milk and the permanent 

 dentition, while the lower carnassial in most 

 cases belongs solely to the permanent set. 



It is manifest from this fact that the form 

 and origin of the teeth do not correspond 

 to one another, and that the authorities who 

 rely solely on the one or the other of these 

 characters for their determinations cannot 

 come to an agreement. 



However that may be, so much remains 

 certain, that the modifications which the Car- 

 nivora exhibit in their dental systems are due 

 primarily to the diminution in the number of 

 the teeth, which goes hand in hand with a 

 special adaptation of the structure of the 

 teeth to definite purposes. In the old families 

 the numerous premolars pass gradually over 

 into the likewise numerous molars. In the 

 families of the present day the differences in 

 form are more marked and the number of the 

 teeth is diminished, whether through the loss 

 of premolars or through that of true molars 

 or tubercled teeth. At the present day only 

 one carnivore has as many as 44 teeth, but 

 the dogs and the bears (Canida and Ursida) 

 have 42, and in this number there are as 

 many tubercled teeth as in the extinct 

 Arctocyonida. The diminution is continued 

 in the racoons, which have 40 teeth, and in 

 the badgers and kinkajous, which have 36; 

 but in all these groups the omnivorous char- 



acter indicated by the tubercled teeth is 

 preserved, even though these are reduced in 

 number. 



The Viverrida with 40 teeth have preserved 

 in their dentition manifest traces of one of 

 a marsupial type, but one which is in the 

 highest degree carnivorous in character, and 

 this character becomes more prominent in the 

 hyaenas with 34 teeth, and still more .so in 

 the members of the cat tribe (Felida), the 

 most carnivorous of all, with only 30. In 

 this series it is easy to trace the decline of 

 the tubercled teeth and the diminution in 

 number of the premolars, processes which 

 culminate in the Machairodus, that formidable 

 giant feline of Pliocene and Quaternary times, 

 in which the premolars are reduced in number 

 and size, and the dentition is almost confined 

 to the long, sharp, dagger-like canines and 

 the powerful carnassials, far back in the jaws. 



All these relations of the dentition are so 

 constant that we can only point to three ex- 

 ceptions among all the numerous carnivores. 

 The sea-otter has only 32 teeth, while the 

 other otters have 36. It is the only carnivore 

 which has only four incisors instead of six in 

 the lower jaw. The earth-wolf of the Cape 

 (Proteles), which resembles the hyaenas in so 

 many respects, has only 30 teeth, just as 

 many as the cats, but its back teeth are so 

 insignificant and ill-formed that they seem as 

 if they had been hindered in their develop- 

 ment; they stand apart from one another, 

 and one can distinguish among them neither 

 premolars, nor carnassials, nor tubercled teeth. 

 Finally, a small animal belonging to Pata- 

 gonia, having the general appearance of a 

 weasel, an animal called Lyncodon, has only 

 28 teeth, having one premolar less than the 

 Felida, whose dentition presented the smallest 

 number of highly specialized teeth known 

 before the discovery of the Lyncodon. 



The mode of life of the Carnivora is just 

 as varied as that of the animals on which 

 they feed. All live at the expense of weaker 

 animals than themselves; but their means of 



