THE DUCK-BILLED PLATYPUS. I67 



and the moveable part is not more than a quarter of 

 an inch. It can be drawn entirely into the mouth ; 

 and, when extended, reaches about a quarter of an 

 inch into the beak. — The organ of smell differs in 

 some measure from that of both quadrupeds and 

 birds. The external opening is placed near the end 

 of the beak ; whence are superadded to it two ca- 

 vities, extending ell the way along the beak. — The 

 beak itself is covered with a smooth black skin^ that 

 extends some way beyond the bones, both in fronts 

 and laterally ; and forms a moveable lip, so strong, 

 that wlien dried or harde:^ed in spirit, it seems to be 

 quite rigid, but when moistened is very pliant, and 

 is probably a muscular structure. The under por- 

 tion of the beak has a lip equally broad with the 

 upper. This has a serrated edge, (wanting in the 

 upper m.andible), but the serrte are mostly confined 

 to the soft part. — A curious transverse fold of the 

 external black smooth skin by which tiie beak is 

 covered, projects all round, exactly at that part 

 where it has its origin. The apparent use of this 

 is to prevent the beak from being pushed too 

 far into the soft m.ud, in which prey may he con- 

 cealed. — The nerves that supply the beak, are 

 much allied to those of birds ; and the cavity 

 of the skull has a greater resemblance to that of a 

 Duck than of a quadruped. —:- The eye is un- 

 commonly small for the size of the animal ; and 

 the external opening of the ear Is sim.ply an orifice, 

 and so minute as not to be discovered without dif- 

 ficidty. 



M 4 



