Fig. 21. Oral area of the hemicosmitoid Hemicosmites pyriformis Buch, 1846, Middle Ordovician, Russia. Three ambulacra, interpreted as A, shared BC, and shared DE, converge on the mouth (M) and are surrounded by a circlet of nine radial plates (R1–R9) outside which is another circlet of nine lateral plates (L1–L9). Three wedge plates occur immediately clockwise of radial plates R3, R6, and R9. The hydropore (not shown) occurs in the adoral part of radial 9. In life, biserial cover plates would have roofed over the food grooves. Redrawn and relabelled from Bockelie 1979: 375, fig. 8b.