Head of the Ornithorhynchus paradoxus. 435 



in spirit, it seems to be rigid ; but, when moistened, is very 

 pliant, and, as has been already mentioned, has probably a 

 muscular structure. The under portion of the beak has a lip 

 equally broad with the upper: this has a serrated edge ; but the 

 serrse are confined to the soft part, not extending to the mem- 

 brane covering the bone, and are not met with in the upper one. 

 The extent of the lips beyond the bones, is distinctly marked in 

 the drawings. 



There is a very curious transverse fold of the external black 

 smooth skin, by which the beak is covered, projecting all round, 

 exactly at that part where the beak has its origin. Its apparent 

 use seems to be to prevent the beak being pushed further into 

 the soft mud, in which its prey may lie concealed, than up to this 

 part, which is so broad that it must completely stop its progress. 



The nerves that supply the beak, in their general course, 

 size, and number, seem very closely to correspond with those 

 of the hill of the duck. 



The cavity of the skull bears a greater general resemblance 

 to that of the duck than of quadrupeds : there is a very un- 

 common peculiarity in it, which is, that there is a bony falx of 

 some breadth, but no bony tentorium. This is met with in no 

 quadruped that I know of: it is found in a small degree in some 

 birds, as the spoon-bill, and the parrot ; but not at all so as to 

 resemble the falx in this animal. 



The orifice of the eye lids is uncommonly small, for the size 

 of the animal; but the eye itself was not in a state to be 

 examined. 



The external opening of the ear was so small as not readily 

 to be perceived : it is simply an orifice ; but the meatus en- 

 larges considerably beyond the size of the opening, and passes 

 some way under the skin, before it reaches the organ, which in 



