A view of the peripheral rim of Hypsiclavus huntsvillensis attached to a bryozoan.

In discocystinids, the peripheral rim is composed of several circlets of plates and is relatively very small for an edrioasteroid. Typically the entire structure is less than 12 mm in diameter. Plates decrease in size proximally where they are transversely elongate to distally where they are radially elongate. Edrioasteroids use this structure to attach themselves to hard surfaces such as skeletal debris of other sea creatures such as the bryozoan pictured above.

The aboral surface of Spiraclavus nacoensis (scale is 1cm long). RZ = recumbent zone, PZ = pedunculate zone, PR = peripheral rim.