Fig. 8 in New insights into the origin and relationships of blastoid echinoderms

Fig. 8. Structure of the ambulacra and brachioles in the callocystitid Pseudocrinites bifasciatus Pearce, 1843 (SM A.10192), Wenlock (Silurian), Dudley, UK. First plate (1st) in a brachiole lies directly above the adoral floor plates (grey). This suggests floor plates are the first pair of brachiolar plates modified to form the ambulacral axis. Second and subsequent brachiolar plates white. In callocystitids, floor plates are developed on the thecal surface. A. Side view showing the high profile of the ambulacral axis and rapidly tapering brachiole. B. Impressions of ambulacral floor plates on the thecal plates. Arrows point to the mouth. Redrawn and relabelled from Paul 1967a: 326, figs. 17, 18.