Crinoids are members of the same family as starfish, and sea urchins. Crinoids attach to the seafloor by root like structures called holdfasts. A cup-shaped head ( calix ) sits directly on top of the roots or is extended above the holdfast by means of by a long segmented stem. Arms extend upwards from the calix. The flexible segmented stem allowed crinoids to move with the ocean currents.
In the case of clematocrinus retiarus there is virtually no flexible stem and the calyx attaches directly to the roots. Two species are known from the limestones of Dudley, one with eight arms and one with sixteen arms. Both are almost always found complete on beds of very fine limestone with few other animal remains.
It has been speculated that this association reflects either a period of deeper water conditions or conversely, a time of very shallow water/emergence. The jury is still out.