CHAPTER IX. 



THE TEETH OF MONOTREMATA, EDENTATA, AND CETACEA. 

 MONOTBEMATA. 



THE Echidna, or Spiny Ant-eater has no teeth whatever, 

 and the strange Ornithorhyncus (duck-billed Platypus) is 

 also destitute of true calcined teeth. 



In the place of teeth its flattened bill is furnished with 

 eight horny plates, two on each side of each jaw. We 

 may therefore pass at once to the orders Edentata and 

 Cetacea, which it is convenient to take first, as their 

 dentitions are of that simple form designated by the term 

 "Homodont." 



THE TEETH OF EDENTATA (BRUT A). 



Sloths, Armadillos, Ant-eaters. 



The term Edentata was applied to the animals of this 

 order to indicate the absence of incisors (teeth in the inter- 

 maxillary bone) : though this is true of most of them, a few 

 have some upper incisors, but the central incisors are in all 

 cases wanting. 



Some of them are quite edentulous ; this is the case in 

 the Mutica, or South American Ant-eaters (Myrmecophaga 

 and Cyclothurus), in which the excessively elongated jaws 

 cannot be separated to any considerable extent, the mouth 

 being a small slit at the end of the elongated muzzle. 

 Food is taken in by the protrusion of an excessively long, 

 whip-like tongue, which is covered by the viscid secretion 



