OF THE ORNITHOEYNCHUS TARABOXUS. l6l 
Memoir IV. 
On the Osseous, Muscular, and Nervous Sys-^ 
terns of the Ornitliorynchus paradoxus. 
I EXPERIENCED the greatest difficulty in drawing up the 
following memoir on the bones and muscles, because it is in 
these, and more particularly in the former, that the Orni- 
thorynchus deviates most from the usual structure of the 
Mammalia, and approaches nearest to the class of Reptiles. 
Moreover, in order to have examined the osteology of the 
head minutely and accurately, it was necessary to have 
suffered the head to macerate so long as to present all the 
sutures in their most distinct state. Now, this I was un- 
^villing to risk with the single specimen in my possession. 
Lastly, it is evident from the state of the bones, and more 
particularly from the o^iteration of the sutures of the cra- 
nium, that the animal had arrived at its full growth, and 
consequently was unfit, in certain respects, for the purpose 
of osteological inquiries. I was obliged, therefore, to 
content myself with a general and rather superficial view 
of these very important organs. 
From the previous description of the organs of sense, and 
from the skeleton which I have the honour to submit to 
the Society, for the inspection of the members, the general 
elongated form of the head will be readily understood. 
The extension of the superior maxillary and intermaxillary 
bones is very remarkable. The zygomatic arch is broad 
and strong ; but the osseous orbit, as in most other animals, 
is incomplete. The prolongation of the nares backwards^ 
VOL. V. L 
