THE ORKITHORYNCHUS PARADOXUS. 3S 
perfect external ear exists immediately beneath the integu- 
ments. It is extremely probable that a similar distribution 
of these parts may exist in some other animals described as 
being without external ears. 
We may now proceed from without inwards towards the 
internal ear, and briefly sum up the anatomy of the whole, 
as far as a respect for the skeleton permitted me to investi- 
gate. There is, first, the external opening, which had been 
mistaken for the simple termination of the cartilaginous 
tube of the ear, but which we have demonstrated to be the 
opening of the concha, that part of the cartilage which, in 
other animals, is in part detached from the head to form a 
true external ear, being in this animal concealed by the in- 
teguments, but in such a way as not to impede its functions. 
I need hardly mention, that the concha was situated at the 
side of the opening farthest removed from the cranium. 
From the cartilage of the concha arises a remarkably long- 
cartilaginous tube, proceeding from the upper part of the 
head, close to the eyes, over the lower jaw, as far as the 
base of the cranium ; it measures in length l-/^ths of an 
inch, and nearly ■^%ths in breadth, when opened. The tex- 
ture of the middle tunic is not quite cartilaginous ; it ter- 
minates at the root of the styloid process, and opens wide 
into the cavity of the tympanum. Near its termination in 
the tympanic cavity, a few projecting points, on its inner 
surface, mark the probable existence pf small cartilaginous 
bodies. The Eustachian tube is entirely cartilaginous, and 
is not inclosed in any osseous case ; this is owing to a defi- 
ciency of a great part of the osseous circle constituting the 
frame of the memhrana tympani. Now, in consequence of 
this deficiency, the anatomy of these parts is somewhat pe- 
culiar ; for, in addition to the Eustachian tube being sim- 
ply cartilaginous, and not inclosed in any osseous case, 
(which, so far as I know, is peculiar to this animal), the 
VOL. V. c 
