Dicyclic crinoid cup

This is a diagram of a dicyclic cup unwrapped and flattened out. The arm bearing plates have notches called "arm facets" from where the arms extend. These plates are known as "radials", the smaller plates above the radials are the "orals", and the plates below the radials are "basals". The bottom row of plates are called the "infrabasals". The oral plate with the circlet of triangular plates is the anal pyramid. The three shaded plates are part of a series of anal plates supporting the anal pyramid, and are known as the "anal X" (the darkly shaded plate), and the "split radianals" (the two lighter plate).