OUR BEST FEATURES 



ened for the attachment of the outer layers of the 

 skin, of which they themselves formed the deeper 

 layers. In some of the recent reptiles there is a 

 small muscle at the corners of the mouth but the 

 lips are not fleshy and the tough facial mask is not 

 far below the surface. Probably the same condi- 

 tions obtained in the entire series of mammal-like 

 reptiles. 



In the most archaic mammal living today, the 

 Duckbill Platypus of Australia, the mouth is 

 surrounded by a duck-like bill consisting of leathery 

 skin well supplied with sense organs. Very 

 possibly this condition is a specialized remnant 

 of the tough skin that covered the mouth of the 

 mammal-like reptiles. In the Spiny Anteater 

 (Echidna) of Australia (Fig. 23C), the nearest 

 living relative of Ornithorhynchus, the lips, although 

 peculiarly specialized in connection with the ant- 

 catching, protrusile tongue, approach the normal 

 mammalian condition in so far as they are supplied 

 with muscles that are innervated by the seventh 

 or facial nerve and are covered with hair rather 

 than scales. 



Here we arrive at the most distinctive feature of 



the lips of mammals, in which the bony mask 



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