Vibrations of the eardrum are then coupled by the middle ear ossicles , the three smallest bones in the body, to the fluid-filled cochlea.
As they grow, asteroids add new ossicles and increase size of existing ossicles .
Calcareous ossicles make up the internal skeleton.
The middle ear ossicles and tympanic membrane remained intact, so sound stimulation could be applied to the preparation through a loudspeaker connected to the external ear canal.
The calcitic ossicles of crinoids, as is typical of echinoderms, form an internal skeleton that provides support and protection.
Sound waves reaching the tympanic membrane will initiate vibrations that are transmitted through the bony ossicles of the middle ear to the oval window.
Sutural bones are usually small, irregularly shaped ossicles , often found in the sutures of the cranium, especially in the parietal bones.
Most such particles are echinoderm stem ossicles , brachiopods, bryozoans or other corals.
Internally, the mastoid is hollowed out to form the epitympanic recess to accommodate the ossicles of the middle ear.
The position of these plates on the non-rudiment side of the larva suggests that ossicles occurring on the aboral surface are extraxial.