282 COMPARATIVE ANATOMY OF THE TEETH. 



The hyena has 34 teeth. In the upper jaw on either 

 side there are, incisors 3, canine 1, bicuspids 4, molar 1. 

 In the lower jaw there is one bicuspid less. The number 

 of deciduous teeth is 28, i. e. incisors 3, canine 1, molars 

 3, to each jaw on either side. 



The weasel has 34, the otter 36, the badger 30, the raccoon 

 40, the bear 42. (Fig. 77.) The deciduous teeth of the bear 

 are 22, and the seal has 34 teeth. 



MARSUPIALIA. This order, so called from having a pouch 

 for the accommodation of their young, are divided into the 

 carnivorous and herbivorous genera. 



The opossum and kangaroo are familiar examples under 

 this head. The dog-headed opossum (thylacinus) has forty- 

 six teeth. In the upper jaw, on either side, there are 

 incisors four, canine one, bicuspids three, molars four; in 

 the lower jaw are found incisors three, canine one, bicus- 

 pids three, molars four. In other varieties of the opossum 

 the teeth vary in number, being 42, 48, 50 and 54. The 

 kangaroo has twenty-eight teeth. The canines are absent. 

 The animals of this genus live on herbs. 



The dental formula is, to the upper jaw, on either side, 

 incisors three, bicuspids one, molars four ; in the lower jaw, 

 there are, molars four, incisor one, bicuspid one. Other 

 varieties have only twenty-four teeth. 



KODENTIA. This order includes the squirrel, rabbit, rat, 

 beaver, &c. 



The incisors form the distinguishing characteristic of 

 this order. There is one on either side, separated from 

 the short series of molars by a wide space. The upper 

 ones describe a large segment of a small circle, and are 

 regularly curved ; the lower ones are a smaller segment of 

 a larger circle. 



These teeth are called " scalpriform" or chisel-like. The 

 molar teeth are described as presenting numerous varieties, 

 representing, in fact, all the modifications found in the om- 

 nivorous and herbivorous genera of mammalia. In some 

 of the rodents, as the Chili rats, the molar teeth have no 

 roots. In others, as the beaver, they have short roots. 



