132 



THE flf:sh-eaters. 



straight, are mostly recurved, very sharp, 

 laterally compressed, with a sharp hinder 

 edge, and often notched like a saw. They 

 always overtop the crowns of the other teeth, 

 even when they are poorly developed, and 

 when the mouth is closed they fit into cor- 

 responding gaps or diastemas in the opposite 

 jaws, sliding past each other in order to do 

 so. The canine of the lower jaw, usually not 

 so powerful as that of the upper, gets inserted 

 in a diastema between the incisors and the 

 upper canine, while this upper canine fits 

 into a diastema between the lower canine 

 and the first of the lower premolars. The 

 size, strength, and sharpness of the canines 

 correspond to the greater or less degree of 

 ferocity in the disposition of the animal. 



The premolars and molars are usually close 

 enough tog-ether at the base to form a con- 



o o 



tinuous series ; but their crowns have high 

 cusps and points, and the teeth of the opposite 

 jaws usually correspond to one another in 

 such a manner that each tooth fits into the 

 interval between two teeth in the opposite 

 jaw when the mouth is closed. 



There has been much controversy as to the 

 significance of the molar teeth in the Carni- 

 vora. Many naturalists direct their attention 

 in a one-sided manner to the form of the 

 individual teeth, while others attach most 

 importance to their development from the 

 milk-teeth. It must indeed be admitted that 

 in many cases we can scarcely resort to this 

 latter character, since the milk dentition is 

 frequently unknown, especially in the case of 

 extinct types. It is clear that only very 

 rarely by some lucky accident we can become 

 acquainted with the deciduous dentition of a 

 fossil genus. 



With reference to the form alone, three 

 kinds of molars have been distinguished 

 among the carnivores still living. Behind 

 the canine come the premolars, which are 

 mostly furnished with only a single median 

 cusp, which is sometimes conical, mostly sharp, 

 and in many cases accompanied by small 



lateral cusps, which, though less prominently 

 developed, are not less sharp. The premolars 

 as well as the incisors and canines belong to 

 the milk dentition. In no living carnivore 

 does the number of these premolars exceed 

 four in each half of the jaw; but this number 

 may be reduced to two or even to one. 

 .Some of these teeth which are still present 

 in the young animal afterwards drop out, as, 

 for example, in some bears. After these 

 premolars, which usually increase in size from 

 befor*" backwards, there almost always follows 

 a peculiarly formed tooth known as the 

 sectorial or carnassial tooth. It is usually 

 the strongest tooth in the whole set, .shaped 

 like a sharp blade, divided mostly into two, 

 sometimes more, lobes, and in almost every 

 case provided with a heel or process running 

 inwards. The carnassial teeth of the upper 

 jaw close above the lower ones when the 

 mouth is shut, and these four teeth form 

 in this way the four blades of two pairs of 

 shears, which are just as shaqj as instruments 

 made of steel. If the canines are fitted by 

 their form to transfix and hold fast, if the pre- 

 molars tear the prey into fragments, the car- 

 nassial teeth cut and divide it like shears, 

 and since they are seated far back in the 

 jaws, which form single levers, they can be 

 worked with inexpressible force. Under the 

 action of the carnassial teeth the bones are 

 crunched, and the form of these teeth is all 

 the more complicated the greater the ferocity 

 of the animal to which they belong. 



Behind the carnassial tooth there is a 

 varying number ot so-called tubercled teeth, 

 never more than three, however, and some- 

 times these are altogether wanting. These 

 are broad teeth with rather flat crowns, mostly 

 studded with blunt tubercles, and often re- 

 sembling human molars. Their uneven 

 surface manifestly shows that they are in- 

 tended for crushing or bruising the food, and 

 they are more numerous and stronger the 

 more omnivorous the animal is. 



On comparing the dental systems of all 



