1869.] THE MALLEUS AND THE INCUS OF THE MAMMALIA. 399 
outer wall of the periotic capsule, just behind the articulation of the 
quadrate bone. 
A. The auditory region, the tympanic membrane being taken away, in a Fowl. 
Qu. Quadratum.  S.Sz. Platner’s ligament. #.S¢. The extrastapedial 
cartilage, the edge of which is fixed to the tympanic membrane. 0. The 
end of the extrastapedial which is fixed to the posterior boundary of the 
tympanum. c. The ascending process. J.S¢. The infrastapedial process. 
B. The outer end of the stapes separated from the stem where the latter begins 
to be ossified. Turned round and magnified. 
I see no room for any doubt that this ascending process and the 
elastic ligament represent the suprastapedial cartilage of the Cro- 
codile. 
As in the Crocodile, the posterior end of the extrastapedial 
cartilage is closely connected by fibrous tissue with the posterior 
boundary of the tympanum and the tympanic membrane ; but I have 
been unable to discover even a rudiment of a styloid cartilage. The 
inferior, free, curved process of the stem of the stapes, which may 
be termed infrastapedial (I.St) seems at first to answer to that 
cartilage ; but its relations are quite different. 
Thus the Lizard, the Crocodile, and the Bird present a complete 
series of modifications of the parts described. In Sphenodon the 
hyoidean arch is histologically continuous throughout its entire 
length ; and in its upper part is a rod of cartilage which, at one 
point, passes into the stapes. 
In the Crocodile, the upper part of the hyoidean cornu has no 
direct connexion with the lower, and the rudimentary styloid part is 
not histologically continuous with the stapedial part. 
In the Bird the styloid part has vanished, and the suprastapedial 
is represented only by fibrous tissue. 
