The mouth was at the summit of the theca. Radiating like flower petals from the center were five food grooves, or "ambulacra". Each ambulacrum had many long thin fine structures called "brachioles", which were used to trap food particles and bring them to the mouth. Brachioles were delicate structures, and in fossils are not usually preserved in place. A series of five spiracle plates surrounded the star-shaped mouth, which included the anus, mouth and entrances to a set of five complex, folded respiratory organs known as "hydrospires". These spiracles prevented mixing of the various fluids. Waste elimination was through the "anispiracle", an opening formed by the fusing of anus and adjacent spiracles.