Article: A technique for revealing the stereom structure of fossil crinoids

The stereom of fossil crinoid ossicles preserved in an argillaceous matrix can be revealed by treating them with hydrofluoric acid. The clay filling the stereom pores is dissolved and the skeletal calcite is faithfully replaced by fluorite. Features discovered in selected Lower Carboniferous crinoid ossicles prepared by this method include the following: large canals penetrating the areola in the columnals of a particular inadunate crinoid; triple aboral nerve canals, and labyrinthic stereom in the muscle fossae of distinctive inadunate brachials; and a regular arrangement of trabeculae forming a cubic structure in the stereom of flexible crinoid brachials.