| The water vascular system of the sea stars open up at the madreporite, a perforated opening in the central part of the animal. |
| The edges of adjacent paxillae meet to form a false cuticle with a water cavity beneath in which the madreporite and delicate gill structures are protected. |
| The madreporite was not visible until the juveniles were about 10 mm diameter and all the arms were of similar size. |
| One of the genital plates serves as the sieve plate, or madreporite, for the water vascular system. |
| The madreporite is usually located within one of the jaw plates, and not on the upper side of the animal as it is in starfish. |
| Water enters the system through the madreporite, a porous, often conspicuous, sieve-like ossicle on the aboral surface. |
