The head of the malleaus is attached to the tympanic membrane (eardrum). The incus attaches to the head of the stapes which normally sits in the oval window of the cochlea.
The smallest bone in the body is the stapes (stirrup). The head of the stapes connects to the incus and the footplate rest within the oval window of the cochlea.
In the left photo the incus has been disconnected from the head of the stapes revealing the stapedius muscle.
The bony wall of the chinchilla cochlea has been cut away revealing the fluid filled spiral chambers within. The last of the three ossicular bones, the stapes, fills the oval window of the cochlea.