Mr. Home's Observations, &c. 433 



accompanying drawings will give a sufficiently correct idea of 

 the outward appearances, to answer the present purpose. 



It was not permitted to examine the head anatomically ; but a 

 smaller dried specimen, received from Sir Joseph Banks, fur- 

 nished me with the following observations. 



The beak of the Ornithorhynchus, when it is cursorily examined, 

 appears so strongly to resemble that of the duck, as to lead to 

 the belief of its being calculated for exactly the same purposes ; 

 it will however be found to differ materially from it, in a variety 

 of circumstances. 



The beak is found, upon examination, not to be the animal's 

 mouth, but a part added to the mouth, and projecting beyond it. 



The cavity of the mouth is situated as in other quadrupeds, 

 and has two grinding teeth on each side, both in the upper and 

 lower jaw ; but, instead of incisor teeth, the nasal and palate 

 bones are continued forwards, lengthening the anterior nostrils, 

 and forming the upper part of the beak ; and the two portions 

 of the lower jaw, instead of terminating at the symphisis, where 

 they join, become two thin plates, and are continued forwards, 

 forming the under portion of the beak. 



This structure differs materially from the bill of the duck, 

 and indeed from the bills of all birds, since in them, the cavi- 

 ties of the nostrils do not extend beyond the root of the bill ; 

 and, in their lower portions, which correspond to the under jaw 

 of quadrupeds, the edges are hard, to answer the purpose of 

 teeth, and the middle space is hollow, to receive the tongue. 

 But, in this animal, the two thin plates of bone are in the centre; 

 and the parts which surround them are composed of skin and 

 membrane, in which a muscular structure probably is inclosed. 



The teeth have no fangs which sink into the jaw, as in most 

 quadrupeds, but are imbedded in the gum; and have only lateral 



3 K* 



