M OBSERVATIONS ON THE ANATOMY OF 
ossicula of the ear are much exposed, and the tympanic 
cavity has a great portion of its parietes composed of soft 
parts, or, in other words, is placed in a great measure ex- 
ternal to the cranium. The anterior part of the malleus 
is strongly attached to the extremities of the pterygoid pro- 
cesses of the sphenoid bone. The stapes is composed of a 
single stalk and circular plate, by which it is inserted into the 
vestibular foramen of the internal ear, the foramen being 
itself also circular. The form of the stapes appeared to me 
to be that in which the ear differed most from that of the 
Mammalia, and even approached reptiles and birds ; and 
had nature preserved the same form of stapes throughout 
the whole class of Mammalia, we might have noticed the 
stapes in the Ornithorynchus as a wonderful peculiarity. 
But this is not the case, for, in the Cetacea, the stapes dif- 
fers from all other mammiferous animals ; it does not in- 
deed resemble that of the Ornithorynchus ; but it is suffi- 
cient for our present purpose, that it differs essentially from 
that type which nature has so extensively observed. " In- 
stead of the two branches," observes Cuvier, " the Cetacea 
have a solid body, compressed conically, and perforated by 
only a very small foramen.''* In the Ornithorynchus this 
perforation is wanting, (though it be present in some birds, 
as in the Owl) ; and the slender stalk and circular plate of 
the stapes bear the closest resemblance to the analogous 
ossiculum in birds and reptiles. Between the external os- 
siculum, or that connected with the membrana tympani, 
and which bears a close resemblance to the malleus in 
many of the Mammaha, and the stapes, there exists an ir- 
regular triangular-shaped bone, evidently analogous to the 
incus. It is true, that this bone may, in the Ornithorynchus, 
be merely a process of the malleus; but I am by no means 
of this opinion, for the following reasons : Ist, It is most 
j^eadily detached from the malleus ; 2dli/y It has a consider- 
