TEETH OF DIPHYODONTS. 333 



degree, to fit that animal for the performance of its valuable 

 services to man. In no other genus of quadruped are the jaws 

 so well or so variously armed with dental organs ; notwith- 

 standing the extent of the series, the vacancies are only sufficient 

 to allow the interlocking; of the strong canines. These are effi- 



O CJ 



cient and formidable weapons for seizing, slaying, and lacerating 

 a living prey ; the incisors are well adapted, by their shape and 

 advanced position, for biting and gnawing ; the premolars, and 

 especially the sectorials, are made for cutting and coarsely 

 dividing the fibres of animal tissues, and the tuberculate molars 

 are as admirably adapted for cracking, crushing, and completing 

 the comminution of the food, whether of animal or vegetable 

 nature. 



The dentition of the Weasel tribe (Mustelida) is illustrated in 

 fig. 293 IV., Mustela : the dental formula is 



.3.3 1.1 4.4 1.1 



Z 3^ ;c n^3^ ;77l ^2 = 36 - 



The first premolar, p i, in the upper jaw, which is absent in 

 the Polecat and Weasel, is retained in the Otter, and is placed 

 on the inner side of the canine ; the sectorial premolar, p 4, has 

 its inner lobe much more developed in Lutra than in Putorius, 

 and the tubercular molar, ml, is relatively larger. Similar 

 modifications of these teeth distinguish the dentition of the lower 

 jaw of the Otter, which agrees in the number and kind of teeth 

 with that of the Polecat. The increased grinding surface relates 

 to the inferior and coarser nature of the animal diet of the Otter, 

 the back teeth being thus adapted for crushing the bones of fishes 

 before they are swallowed. 



In the Martin cats (Mustela), the little homotype of p \ above 

 is present in the lower jaw ; in the bloodthirsty Stoats and Wea- 

 sels, p i is absent in both jaws ; as it is likewise in the great Sea- 

 otter (Enhydra), in which also the two middle incisors are 

 wanting in the lower jaw. In this animal the second premo]ar, 

 p 3, has a strong obtuse conical crown, double the size of that of 

 p 2 ; the third premolar, p 4, is more than twice the size of p 3, 

 and represents the upper carnassial or sectorial strangely modified ; 

 the two lobes of the blade being hemispheric tubercles. The last 

 tooth, m i, has a larger crown than the sectorial, and is of a 

 similar broad crushing form. 



In the family Melida> is comprised the European (Meles), the 

 Indian (Arctonyx), and the American ( Taxidea) Badgers, which, 

 with respect to their dentition, stand at the opposite extreme of 

 the Mustelida to that occupied by the predaceous Weasel, and 



